EP4107224A1 - Process for adding surface enhancement to thermoplastic article - Google Patents

Process for adding surface enhancement to thermoplastic article

Info

Publication number
EP4107224A1
EP4107224A1 EP21757525.7A EP21757525A EP4107224A1 EP 4107224 A1 EP4107224 A1 EP 4107224A1 EP 21757525 A EP21757525 A EP 21757525A EP 4107224 A1 EP4107224 A1 EP 4107224A1
Authority
EP
European Patent Office
Prior art keywords
additive material
thermoplastic
thermoplastic part
melted
applying
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21757525.7A
Other languages
German (de)
French (fr)
Inventor
John SPADAVECCHIA
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Polymer Solutions International Inc
Original Assignee
Polymer Solutions International Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Polymer Solutions International Inc filed Critical Polymer Solutions International Inc
Publication of EP4107224A1 publication Critical patent/EP4107224A1/en
Pending legal-status Critical Current

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C35/0266Local curing
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00Moulds or cores; Details thereof or accessories therefor
    • B29C33/38Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
    • B29C33/3842Manufacturing moulds, e.g. shaping the mould surface by machining
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00Moulds or cores; Details thereof or accessories therefor
    • B29C33/42Moulds or cores; Details thereof or accessories therefor characterised by the shape of the moulding surface, e.g. ribs or grooves
    • B29C33/424Moulding surfaces provided with means for marking or patterning
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17Component parts, details or accessories; Auxiliary operations
    • B29C45/26Moulds
    • B29C45/37Mould cavity walls, i.e. the inner surface forming the mould cavity, e.g. linings
    • B29C45/372Mould cavity walls, i.e. the inner surface forming the mould cavity, e.g. linings provided with means for marking or patterning, e.g. numbering articles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C59/00Surface shaping of articles, e.g. embossing; Apparatus therefor
    • B29C59/02Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C35/00Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C35/08Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
    • B29C35/0805Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
    • B29C2035/0822Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using IR radiation
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C59/00Surface shaping of articles, e.g. embossing; Apparatus therefor
    • B29C59/02Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
    • B29C2059/028Incorporating particles by impact in the surface, e.g. using fluid jets or explosive forces to implant particles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C59/00Surface shaping of articles, e.g. embossing; Apparatus therefor
    • B29C59/02Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
    • B29C59/04Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing using rollers or endless belts
    • B29C59/046Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing using rollers or endless belts for layered or coated substantially flat surfaces
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0037Other properties
    • B29K2995/0072Roughness, e.g. anti-slip
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29LINDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00Other particular articles
    • B29L2031/712Containers; Packaging elements or accessories, Packages
    • B29L2031/7178Pallets

Definitions

  • the present disclosure relates generally to thermoplastic products, and more specifically to processes for permanently adding a surface enhancement to a previously manufactured thermoplastic article.
  • Injection molding is a commonly used process to reproduce thermoplastic articles used in a wide variety of applications. Molds used in injection molding must be built according to desired specifications in order to provide the desired part geometry.
  • Some injection molded products require features that are not feasible to produce in an injection mold. Other injection molded products require complex designs that can make the cost of the tooling cost prohibitive, particularly for larger parts. Product designs are often made more complicated when special surface features are required. For example, some thermoplastic products require the addition of an anti-slip surface to prevent items from sliding or slipping on the surface of the product. Other thermoplastic products require the addition of a shock absorbing cushion and/or scratch-resistant covering to reduce damage to the product and/or to items that come in contact with the product.
  • injected molded products can require customized changes or refinements that are requested by a customer or end user based on a specific need. These changes or refinements may require the attachment of material to change the geometry or surface of the finished thermoplastic product.
  • thermoplastic articles There are many known methods for changing the surface geometry of a thermoplastic article. These methods have many drawbacks, particularly methods that assemble materials to surfaces of thermoplastic articles. Many methods result in a relatively weak attachment that can break down over time. Other methods are incapable of attaching materials to the thermoplastic part at precise locations or in specific arrangements, particularly in applications where high production speed is required. Methods that are capable of attaching materials with precision and speed can often be too costly where limited production volumes dictate a lower cost application method.
  • Anti-slip surfaces present a particular challenge, particularly in areas such as bulk handling and storage where thermoplastic pallets, and totes are used. Some plastic articles are injection molded with small pointed projections to reduce product slippage on the articles. Other plastic articles have surfaces that are scuffed or sanded in a secondary operation. These surfaces do not create a sufficient amount of friction to prevent slippage of heavy items, and are completely ineffective in wet environments.
  • thermoplastic articles include the attachment of pre-fabricated "add-on" products, such as strips or grommets made of anti-slip material.
  • add-on products are designed to be heat welded onto the surface of the thermoplastic article.
  • Other add-on products are press fitted or snapped into recesses in the surface. Heat welding and press fitting are not sufficient to withstand shear forces under heavy loads. Therefore, many add-on products can easily separate and dislodge from the surface when loaded with heavy items.
  • prefabricated strips and grommets have a fixed shape, limiting how they can be arranged to fit on articles.
  • specially designed add-on products typically have a high unit cost.
  • FIG. 1 is a flow diagram of a process according to one example
  • FIG. 2 is a flow diagram of a process according to another example
  • FIG. 3 is a schematic side view of an apparatus for forming a modified surface on a thermoplastic article according to another example
  • FIG. 4A is a perspective view of a thermoplastic article with a retention void formed according to a first surface modification profile
  • FIG. 4B is a perspective view of a thermoplastic article with retention voids formed according to a second surface modification profile
  • FIG. 4C is a perspective view of a thermoplastic article with retention voids formed according to a third surface modification profile
  • FIG. 5 is a perspective view of a thermoplastic article with a modified surface formed in the retention void shown in FIG. 4A;
  • FIG. 6 is an enlarged and truncated cross section view of the modified surface shown in FIG. 5;
  • FIG. 7 is an enlarged and truncated cross section view of the retention void shown in FIG. 4A;
  • FIG. 8 is an enlarged and truncated view of a mold used in forming a retention void according the present disclosure;
  • FIG. 9 is an enlarged and truncated view of the mold in FIG. 8 after a thermoplastic material is injected into the mold.
  • FIG. 10 is an enlarged and truncated view of the mold and thermoplastic material in FIG. 9 after the thermoplastic part has cured, and while the thermoplastic part is being separated from the mold.
  • thermoplastic part refers to a product, apparatus, component or other article of manufacture that has at least one surface made of thermoplastic material.
  • thermoplastic parts include but are not limited to material handling products such as thermoplastic pallets, trays, slip sheets, top frames, totes, and dollies.
  • Other examples of thermoplastic parts that are contemplated include but are not limited to structural parts used in fabricating boat decks, stairs and ramps.
  • modified surface refers to a surface of a previously manufactured thermoplastic part that is changed, or the act of changing the geometry of a surface of a previously manufactured thermoplastic part.
  • the phrase can refer to adding material onto the surface of an injection molded part.
  • the added material can be formed of a thermoplastic elastomer, and can define one or more raised surfaces on the surface of the thermoplastic part.
  • the added material can be added into a void to become flush with the surrounding surface of the thermoplastic part and/or recessed beneath the surrounding surface of the thermoplastic part.
  • the phrases are to be distinguished from objects that are built from scratch by laying down successive layers of material one on top of another (e.g. 3D printed objects), and processes that build objects from scratch by laying down successive layers of material, one on top of another, until the object is created (e.g. 3D printing).
  • surface modification profile refers to any programmable pattern, shape, template, or design used as the basis for forming a modified surface.
  • Modified surfaces according to the present disclosure include but are not limited to “functional surfaces”, “ornamental surfaces”, and “indicia”.
  • functional surface refers to a surface having one or more properties that provide or enhance a utilitarian purpose or benefit.
  • functional surfaces include, but are not limited to, anti-slip surfaces, shock absorbing surfaces and scratch-resistant surfaces on the surface of a thermoplastic part.
  • Anti slip surfaces can be formed by adding material that exhibits a coefficient of friction after cooling that is higher than the coefficient of friction on the surface of the thermoplastic part.
  • ornamental surface refers to a surface, finish, design element, or other surface characteristic that is applied to or on the thermoplastic article to achieve a desired aesthetic appearance or effect.
  • indicia refers to letters, numbers, symbols, logos, trademarks, tradenames, rulings, and other markings that convey information.
  • Apparatuses and processes according to the present disclosure include those that use conventional or customized computer numerical control (CNC) machines and pellet extruders as described in U.S. Provisional Application Serial No. 62/928,617, the contents of which is incorporated by reference herein in its entirety.
  • CNC computer numerical control
  • Apparatuses and processes according to the present disclosure utilize specifically chosen materials to form the modified surface.
  • the material applied to a thermoplastic part to form a modified surfaced must be compatible with the material that forms the thermoplastic part to ensure proper fusion of materials.
  • the following Table contains a partial list of examples of compatible materials.
  • the present disclosure also includes processes and apparatuses that apply surface enhancements to melted surfaces.
  • a surface enhancement is applied to a thermoplastic part using a tunnel apparatus operated by a controller.
  • the part can be moved on a movable conveyor that passes through a stationary tunnel apparatus.
  • the tunnel apparatus can be moved over or around a stationary part.
  • both the tunnel apparatus and part can be moving, but at different speeds and/or different directions, such that the part moves relative to the tunnel.
  • FIG. 1 shows one possible set of steps for applying a surface enhancement to a thermoplastic part.
  • a first step 1000 the controller is programmed with a surface modification profile.
  • a focused infrared (IR) heater produces a heat flux adequate to melt the top skin or surface of the thermoplastic part as the part is moved relative to the IR heater.
  • the top surface is melted to a desired depth.
  • the depth of melting is controlled based on one or more parameters, including but not limited to intensity setting of the IR heater, the spacing between the heater and the part, and the velocity at which the part is moved relative to the heater.
  • the entire top surface can be melted. Alternatively, only the area(s) of the top surface corresponding to the surface modification profile is(are) melted.
  • an applicator immediately applies additive material onto the melted surface of the part.
  • the additive material may be in the form of particles, pellets, flakes, regrind, powders or may be sheet fed from one or more rolls.
  • the applicator can move relative to the surface of the thermoplastic part to apply additive material to different areas on the melted surface.
  • the controller controls the movement of the applicator and/or the thermoplastic part so as to apply additive material according to the surface modification profile.
  • the additive material can be a thermoplastic elastomer (TPE).
  • the TPE can be one of a variety of thermoplastic materials, including but not limited to thermoplastic vulcanizate (TPV), styrene- ethylene-butylene-styrene (SEBS), and linear low-density polyethylene (LLDPE).
  • TPV thermoplastic vulcanizate
  • SEBS styrene- ethylene-butylene-styrene
  • LLDPE linear low-density polyethylene
  • a calender roll compresses and shears the additive material.
  • the calender roll can be chilled. Alternatively, the calender roll can be heated.
  • the calendar roll can also be textured. Compression by the calendar roller creates entanglement of the additive material with the substrate that creates adhesion, and flattens the top surface. Parameters can also be adjusted so that compression induces shear to additive particles and causes them to flow. If the roll is chilled, the roll cools the heated additive material and top surface.
  • a fifth step 1400 the part exits the tunnel.
  • exit can refer to a moving part being conveyed out of a stationary tunnel, a moving tunnel moving past a stationary part, or a moving part moving out of a moving tunnel traveling at a different speed and/or different direction than the moving part.
  • steps can be used to add a functional surface, ornamental surface, or indicia to the surface of a thermoplastic part.
  • the steps can be the only steps used, or used in combination with other steps.
  • an optional heating step can be performed between the third step and fourth step.
  • additional heat is applied to the newly deposited elastomer material.
  • the additional heat can be applied with the same IR heater, a different IR heater located downstream, or another heat source.
  • the additional heat can be focused on areas of the surface corresponding to the surface modification profile.
  • the additional heat can be applied to melt the surface of the part and/or the additive material deposited on the surface of the part, to help incorporate the additive material into the part surface.
  • a surface enhancement is applied to a thermoplastic part using a tunnel apparatus operated by a controller, similar to the first process.
  • the part can be moved on a movable conveyor that passes through a stationary tunnel apparatus.
  • the tunnel apparatus can be moved over or around a stationary part.
  • both the tunnel apparatus and part can be moving, but at different speeds and/or different directions, such that the part moves relative to the tunnel.
  • FIG. 2 shows one possible set of steps for applying a surface enhancement to a thermoplastic part using this alternate process.
  • the controller is programmed with a surface modification profile.
  • a focused IR heater produces a heat flux adequate to melt the top skin or surface of the thermoplastic part as the part is moved relative to the IR heater.
  • the top surface is melted to a desired depth.
  • the depth of melting is controlled based on one or more parameters, including but not limited to intensity setting of the IR heater, the spacing between the heater and the part, and the velocity at which the part is moved relative to the heater.
  • the entire top surface can be melted. Alternatively, only the area(s) of the top surface corresponding to the surface modification profile is(are) melted.
  • an applicator immediately applies additive material onto the melted surface of the part.
  • the applicator moves relative to the surface of the thermoplastic part to apply additive material to different areas on the melted surface.
  • the controller controls the movement of the applicator and/or the thermoplastic part so as to apply additive material according to the surface modification profile.
  • the additive material can be a thermoplastic elastomer (TPE).
  • TPE thermoplastic elastomer
  • the TPE can be one of a variety of thermoplastic materials, including but not limited to thermoplastic vulcanizate (TPV), styrene-ethylene-butylene-styrene (SEBS), and linear low-density polyethylene (LLDPE).
  • TPV thermoplastic vulcanizate
  • SEBS styrene-ethylene-butylene-styrene
  • LLDPE linear low-density polyethylene
  • the TPE can be applied in various physical forms, including but not limited to pellets, flakes, or particles.
  • a laser is moved relative to the molten surface of the thermoplastic part and the additive material to sinter the additive material with particle deposition.
  • the controller controls the relative movement of the laser so as to sinter additive material according to the programmed surface modification profile.
  • This step can also include a secondary heat flux application as an alternative to laser sintering.
  • a calender roll flattens and intimately mates the additive material into the thermoplastic part.
  • a sixth step 2500 the part exits the tunnel.
  • exit can refer to a moving part being conveyed out of a stationary tunnel, a moving tunnel moving past a stationary part, or a moving part moving out of a moving tunnel traveling at a different speed and/or different direction than the moving part.
  • steps can be used to add a functional surface, ornamental surface, or indicia to the surface of a thermoplastic part.
  • the steps can be the only steps used, or used in combination with other steps.
  • FIG. 3 shows an apparatus 100 for applying a functional surface to a thermoplastic article.
  • Thermoplastic articles enter apparatus 100 through a first end 102 and exit the apparatus through a second end 104.
  • Apparatus 100 includes a conveyor belt 110 for moving a thermoplastic part past a number of stations.
  • a controller 115 controls relative movement of the conveyor belt and thermoplastic part.
  • Thermoplastic articles are moved past a first station 120 which comprises a heat source 122 in the form of a first IR heater 124.
  • a thermoplastic article As a thermoplastic article enters apparatus 100, it moves past IR heater 124 at a controlled rate established by controller 115.
  • IR heater 124 is configured to melt the top surface of the thermoplastic article at a controlled heat flux, which is also controlled by controller 115.
  • thermoplastic article moves to a second station 130 comprising an applicator 132.
  • Applicator 132 is configured to immediately apply additive material in the form of particles P to the heated top surface of the thermoplastic article while the surface is still melted.
  • Particles P can comprise or consist of thermoplastic pellets, regrinds, or irregularly shaped non-thermoplastic material, including but not limited to sand, marble dust, granite dust, crumb rubber or other material.
  • thermoplastic article moves with conveyor belt 110 to a third station 140 comprising a second heat source 142 in the form of a second IR heater 144.
  • Third station 140 is an optional station that can apply supplemental heat as needed to maintain or change the temperature of the surface of the thermoplastic article and of the additive material. Apparatuses in accordance with this disclosure can be used with the third station disabled, or omit the third station entirely if supplemental heating is not needed.
  • thermoplastic article with additive material then moves past a fourth station 150 comprising a roll 152.
  • Rolls according to the present disclosure can be heated rolls, chilled rolls and/or textured rolls.
  • Roll 152 is configured to compress and shear particles of additive material on the top surface of the thermoplastic article to embed and bond the material to the top surface. If roll 152 is cooled, the roll further serves to cool down and begin curing the top surface and additive material. If roll 152 is textured, the roll can impart a modified surface texture to the top surface and additive material.
  • conveyor belt 110 is configured to move the thermoplastic article with modified surface out of apparatus 100 through second end 104.
  • a retention void is formed on a surface of the thermoplastic part.
  • An additive material is subsequently deposited or applied in the retention void to fill and completely seal the void so that no gaps or enclosed spaces are formed in the void.
  • a first portion of the additive material fills the void to a level aligned with the surface of the thermoplastic part.
  • a second portion of the additive material projects out of the retention void and above the surface to form a functional surface on the surface of the thermoplastic part.
  • the retention void enhances the bonding of the additive material to the thermoplastic part by holding a portion of the additive material beneath the surface.
  • the retention void provides more surface area on the thermoplastic part for attaching to the additive material than would be provided if the thermoplastic material is simply applied to a flat surface on the thermoplastic part with no void.
  • the retention void can be designed to protect the additive material from shear damage from a unit load on the thermoplastic part, as will be explained.
  • FIG. 4A shows one example of an article with a retention void for receiving additive material.
  • the article is a pallet 3000, but it could also be any other thermoplastic article to which an additive material is applied.
  • Pallet 3000 includes a substrate or base 3100.
  • Base 3100 has an upper surface 3110 designed to support a load, for example one or more containers for bulk transport and/or storage.
  • a retention void 3120 is formed in the upper surface 3110 of pallet 3000.
  • retention void 3120 is shown as a shallow cylindrical shaped void extending into the upper surface 3110 of pallet 3000.
  • thermoplastic articles in accordance with the present disclosure can have any number of voids, and the void(s) can have any geometric shape, which may all be the same shape or one or more different shapes, in order to form an anti-slip feature or features on the pallet.
  • a plurality of retention voids can be formed in a series of stripes, a polka-dot pattern, or in concentric shapes, including but not limited to concentric circles, ovals, squares, rectangles or other shapes.
  • FIG. 4B shows an example in which retention voids 3120' are formed in a series of linear stripes.
  • FIG. 4C shows an alternate example in which retention voids 3120" are formed in a plurality of concentric circles.
  • retention void 3120 is configured to receive an additive material to form a functional surface on upper surface 3110.
  • FIG. 5 shows retention void 3120 filled with an additive material 3140 consisting of thermoplastic elastomer 3142.
  • Thermoplastic elastomer 3142 exhibits a higher coefficient of friction than upper surface 3110 of pallet 3000, thereby providing a functional surface 3150 in the form of an anti-slip feature 3152 on the pallet.
  • additive material 3140 completely fills and completely seals retention void 3120 by fusing with the interior of the void, leaving no seams or enclosed spaces that can collect contaminants. This makes pallet 3000 easy to keep clean and suitable for use in applications requiring sanitization.
  • FIG. 6 a cross section view of pallet 3000 is shown in the area of retention void 3120 and anti-slip feature 3152. It will be understood that other retention void configurations, including but not limited to those shown in FIGS. 4B and 4C, can be formed with the same cross section. Thus, the following cross-section description is not limited exclusively to cylindrical-shaped retention voids, but is also applicable to retention voids having other shapes and patterns on the surface of a thermoplastic article.
  • Additive material 3140 has a first portion 3140a below upper surface 3110 and a second portion 3140b above the upper surface. For delineation purposes, first portion 3140a and second portion 3140b are divided by a dashed line in FIG. 6.
  • Retention void 3120 is defined by a bottom wall 3122 and a side wall 3124. Bottom wall 3122 and side wall 3124 provide increased surface area for attachment of additive material 3140 to base 3100.
  • the combined surface area in retention void 3120 i.e. the total area of the bottom wall and side wall
  • retention void 3120 provides a superior bonding surface and improved subsurface foundation that enhances the attachment between base 3100 and additive material 3140.
  • Second portion 3140b of additive material 3140 extends above upper surface 3110 of base 3100. Moreover, second portion 3140b projects above side wall 3124 in an exposed position. In this exposed position, the second portion 3140b functions as the aforementioned anti-slip feature 3152.
  • retention voids can be manufactured with one or more protective walls or guards that are adjacent the retention void and at least partially surround the second portion of the additive material extending above the surface.
  • base 3100 includes a raised wall 3160 that surrounds the circumference of retention void 3120.
  • Raised wall 3160 extends above upper surface 3110 and encloses a substantial section of second portion 3140b, thus shielding that section from lateral collision with objects, and reducing the effects of shear when an object rubs against anti-slip feature 3152.
  • retention voids can have various cross section geometries that can further strengthen the attachment between the base and additive material. Referring to FIG.
  • retention void 3120 is shown without additive material 3140.
  • Retention void 3120 has an undercut 3121 that further prevents anti-slip feature 3152 from being separated and pulled out of base 3100.
  • the diameter DB at the bottom of retention void 3120 is smaller than the diameter DT at the top of the retention void. This forms a tapered geometry or constriction that prevents first portion 3140a of additive material 3140 from slipping or pulling out of retention void 3120.
  • Retention voids can have shapes other than cylindrical, as noted above. When other shapes and configurations for the retention void are used, an undercut can still be provided, for example by making the cross-sectional width at the bottom of the retention void wider than the cross-sectional width at the top of the retention void.
  • the retention void can be in the form of a channel having a trapezoidal cross section.
  • FIG. 8 schematically shows a portion of an empty mold M.
  • Mold M includes a planar inner wall I adjacent a chamber C where the base is formed.
  • a circular projection or plug PL extends from inner wall I.
  • Plug PL has a base portion BP having a first diameter D1 and a free end portion FE having a second diameter D2.
  • Second diameter D2 is larger than first diameter Dl.
  • the diameter of plug PL increases at a constant rate or uniform manner from base portion BP to free end portion FE.
  • plug PL has a dovetail-shaped cross section.
  • FIG. 9 schematically shows mold M after a thermoplastic material T is injected into the mold.
  • thermoplastic material T flows into chamber C around plug PL and into contact with inner wall I.
  • inner wall I forms the upper surface 3110 of base 3100
  • plug PL forms retention void 3120 that extends into the upper surface.
  • Retention void 3120 has an undercut geometry due to the dove-tail shaped geometry of plug PL.
  • FIG. 10 schematically shows base 3100 in the process of being removed from mold M after thermoplastic material T has cured.
  • the dove-tailed geometry of plug PL interlocks with sidewall 3124 around the retention void 3120, creating an interference. Therefore, a certain amount of force must be applied to overcome the interference.
  • plug PL bears against sidewall 3124 of retention void 3120.
  • Plug PL is much more rigid than the cured thermoplastic material around sidewall 3124. Therefore, sidewall 3124 around retention void 3120 will yield under stress as plug PL is pulled out of the retention void, as shown. This creates plastic deformation that permanently changes the shape of sidewall 3124 around retention void 3120.
  • thermoplastic material T should have adequate elasticity and elongation so as to allow for plastic deformation without fracturing during demolding.
  • base 3100 is shown after being removed from mold M.
  • Plastic deformation of sidewall 3124 around retention void 3120 results in a top edge 3126 being pulled outwardly and upwardly from upper surface 3110 of base 3100.
  • Raised wall 3160 forms a rim 3162 with a sharp edge 3164.
  • Raised wall 3160 and rim 3162 are adapted to protect at least part of anti slip feature 3152 that projects from retention void 3120.
  • Raised wall 3160 can also provide an anti-slip function on its own, without an additive material applied or otherwise deposited into retention void 3120. Edge 3164 of raised wall 3160 can increase surface roughness of upper surface 3110 and reduce the occurrence of slippage on base 3110.
  • a functional surface, ornamental surface or indicia is formed on a surface of a thermoplastic part using an additive material that is UV cured.
  • the additive material is a roll-on rubber ink.
  • the additive material is a coating that is silk screened onto the top surface of the thermoplastic part and then conveyed below one or more UV lamps for curing.
  • a functional surface, ornamental surface or indicia is formed on a surface of a thermoplastic part using an additive material that is pad printed or sprayed onto the thermoplastic part.
  • the additive material is ink or paint.
  • the present disclosure encompasses all of the foregoing possibilities.
  • the present disclosure encompasses apparatuses and processes that include or carry out any combination of features or steps described in the present disclosure, whether presented in the same example or presented in separate examples. It is further intended that the appended claims cover all such variations as fall within the scope of the present disclosure.

Abstract

A process for modifying a surface geometry of a thermoplastic part using a tunnel apparatus operated by a controller is provided. The process includes the steps of: programming the controller with a surface modification profile; moving a thermoplastic part relative to a heat source to form a melted surface on the thermoplastic part; and depositing an additive material onto the melted surface according to the surface modification profile.

Description

PROCESS FOR ADDING SURFACE ENHANCEMENT TO THERMOPLASTIC ARTICLE
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority to U.S. Provisional Patent Application No. 62/977,963, filed February 18, 2020, entitled "PROCESS FOR ADDING SURFACE ENHANCEMENT TO THERMOPLASTIC ARTICLE" the contents of which are incorporated herein by reference in their entirety.
FIELD
The present disclosure relates generally to thermoplastic products, and more specifically to processes for permanently adding a surface enhancement to a previously manufactured thermoplastic article.
BACKGROUND
Injection molding is a commonly used process to reproduce thermoplastic articles used in a wide variety of applications. Molds used in injection molding must be built according to desired specifications in order to provide the desired part geometry.
Some injection molded products require features that are not feasible to produce in an injection mold. Other injection molded products require complex designs that can make the cost of the tooling cost prohibitive, particularly for larger parts. Product designs are often made more complicated when special surface features are required. For example, some thermoplastic products require the addition of an anti-slip surface to prevent items from sliding or slipping on the surface of the product. Other thermoplastic products require the addition of a shock absorbing cushion and/or scratch-resistant covering to reduce damage to the product and/or to items that come in contact with the product.
Other injected molded products can require customized changes or refinements that are requested by a customer or end user based on a specific need. These changes or refinements may require the attachment of material to change the geometry or surface of the finished thermoplastic product.
There are many known methods for changing the surface geometry of a thermoplastic article. These methods have many drawbacks, particularly methods that assemble materials to surfaces of thermoplastic articles. Many methods result in a relatively weak attachment that can break down over time. Other methods are incapable of attaching materials to the thermoplastic part at precise locations or in specific arrangements, particularly in applications where high production speed is required. Methods that are capable of attaching materials with precision and speed can often be too costly where limited production volumes dictate a lower cost application method. Anti-slip surfaces present a particular challenge, particularly in areas such as bulk handling and storage where thermoplastic pallets, and totes are used. Some plastic articles are injection molded with small pointed projections to reduce product slippage on the articles. Other plastic articles have surfaces that are scuffed or sanded in a secondary operation. These surfaces do not create a sufficient amount of friction to prevent slippage of heavy items, and are completely ineffective in wet environments.
Other techniques for providing anti-slip surfaces on thermoplastic articles include the attachment of pre-fabricated "add-on" products, such as strips or grommets made of anti-slip material. Some add-on products are designed to be heat welded onto the surface of the thermoplastic article. Other add-on products are press fitted or snapped into recesses in the surface. Heat welding and press fitting are not sufficient to withstand shear forces under heavy loads. Therefore, many add-on products can easily separate and dislodge from the surface when loaded with heavy items. In addition, prefabricated strips and grommets have a fixed shape, limiting how they can be arranged to fit on articles. Moreover, specially designed add-on products typically have a high unit cost.
In addition to durability problems and cost, add-on products present concerns in applications that require sanitized environments, such as the food and pharmaceutical industries. Strips, grommets and other add-on products that are assembled to a pallet, for example, can create seams and enclosed spaces in the pallet surface. These seams and enclosed spaces easily collect residues, dust, grime and other contaminants. Contaminants that become trapped in the seams and enclosed spaces increase the risk of contaminating products that come in contact with the pallets, making those pallets very difficult to clean, and therefore unsuitable for use in many applications. It is possible to mold parts with functional surfaces using a multi component mold. Building a multi component mold and running it in a machine is extremely expensive, however, and is generally cost prohibitive in low volume production. A multi component mold may be a viable option for extremely high volume production, but typically is only suitable for small sized products. The foregoing drawbacks are addressed in several respects by apparatuses and processes described in the next sections.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
The following detailed description section will be better understood in conjunction with non-limiting examples shown in the drawing figures, of which: FIG. 1 is a flow diagram of a process according to one example;
FIG. 2 is a flow diagram of a process according to another example; FIG. 3 is a schematic side view of an apparatus for forming a modified surface on a thermoplastic article according to another example;
FIG. 4A is a perspective view of a thermoplastic article with a retention void formed according to a first surface modification profile; FIG. 4B is a perspective view of a thermoplastic article with retention voids formed according to a second surface modification profile;
FIG. 4C is a perspective view of a thermoplastic article with retention voids formed according to a third surface modification profile;
FIG. 5 is a perspective view of a thermoplastic article with a modified surface formed in the retention void shown in FIG. 4A;
FIG. 6 is an enlarged and truncated cross section view of the modified surface shown in FIG. 5;
FIG. 7 is an enlarged and truncated cross section view of the retention void shown in FIG. 4A; FIG. 8 is an enlarged and truncated view of a mold used in forming a retention void according the present disclosure;
FIG. 9 is an enlarged and truncated view of the mold in FIG. 8 after a thermoplastic material is injected into the mold; and
FIG. 10 is an enlarged and truncated view of the mold and thermoplastic material in FIG. 9 after the thermoplastic part has cured, and while the thermoplastic part is being separated from the mold.
DESCRIPTION
The challenges with thermoplastic articles described in the Background section are addressed in many respects by processes and apparatuses described herein. The processes and apparatuses described herein are described using terminology defined as set forth below.
The term "thermoplastic part", as used herein, refers to a product, apparatus, component or other article of manufacture that has at least one surface made of thermoplastic material. Examples of thermoplastic parts that are contemplated include but are not limited to material handling products such as thermoplastic pallets, trays, slip sheets, top frames, totes, and dollies. Other examples of thermoplastic parts that are contemplated include but are not limited to structural parts used in fabricating boat decks, stairs and ramps.
The phrases "modified surface", "modifying surface" and the like, as used herein, refer to a surface of a previously manufactured thermoplastic part that is changed, or the act of changing the geometry of a surface of a previously manufactured thermoplastic part. For example, the phrase can refer to adding material onto the surface of an injection molded part. The added material can be formed of a thermoplastic elastomer, and can define one or more raised surfaces on the surface of the thermoplastic part. Alternatively, the added material can be added into a void to become flush with the surrounding surface of the thermoplastic part and/or recessed beneath the surrounding surface of the thermoplastic part. The phrases are to be distinguished from objects that are built from scratch by laying down successive layers of material one on top of another (e.g. 3D printed objects), and processes that build objects from scratch by laying down successive layers of material, one on top of another, until the object is created (e.g. 3D printing).
The phrase "surface modification profile" as used herein refers to any programmable pattern, shape, template, or design used as the basis for forming a modified surface.
Modified surfaces according to the present disclosure include but are not limited to "functional surfaces", "ornamental surfaces", and "indicia".
The term "functional surface", as used herein, refers to a surface having one or more properties that provide or enhance a utilitarian purpose or benefit. Examples of functional surfaces include, but are not limited to, anti-slip surfaces, shock absorbing surfaces and scratch-resistant surfaces on the surface of a thermoplastic part. "Anti slip surfaces" can be formed by adding material that exhibits a coefficient of friction after cooling that is higher than the coefficient of friction on the surface of the thermoplastic part.
The term "ornamental surface", as used herein, refers to a surface, finish, design element, or other surface characteristic that is applied to or on the thermoplastic article to achieve a desired aesthetic appearance or effect.
The term "indicia", as used herein, refers to letters, numbers, symbols, logos, trademarks, tradenames, rulings, and other markings that convey information.
Apparatuses and processes according to the present disclosure include those that use conventional or customized computer numerical control (CNC) machines and pellet extruders as described in U.S. Provisional Application Serial No. 62/928,617, the contents of which is incorporated by reference herein in its entirety.
Apparatuses and processes according to the present disclosure utilize specifically chosen materials to form the modified surface. The material applied to a thermoplastic part to form a modified surfaced must be compatible with the material that forms the thermoplastic part to ensure proper fusion of materials. The following Table contains a partial list of examples of compatible materials.
Examples of Compatible Part Materials and Added Materials
The present disclosure also includes processes and apparatuses that apply surface enhancements to melted surfaces. In one process, a surface enhancement is applied to a thermoplastic part using a tunnel apparatus operated by a controller. The part can be moved on a movable conveyor that passes through a stationary tunnel apparatus. Alternatively, the tunnel apparatus can be moved over or around a stationary part. In addition, both the tunnel apparatus and part can be moving, but at different speeds and/or different directions, such that the part moves relative to the tunnel. FIG. 1 shows one possible set of steps for applying a surface enhancement to a thermoplastic part.
In a first step 1000, the controller is programmed with a surface modification profile.
In a second step 1100, a focused infrared (IR) heater produces a heat flux adequate to melt the top skin or surface of the thermoplastic part as the part is moved relative to the IR heater. The top surface is melted to a desired depth. The depth of melting is controlled based on one or more parameters, including but not limited to intensity setting of the IR heater, the spacing between the heater and the part, and the velocity at which the part is moved relative to the heater. The entire top surface can be melted. Alternatively, only the area(s) of the top surface corresponding to the surface modification profile is(are) melted.
In a third step 1200, an applicator immediately applies additive material onto the melted surface of the part. The additive material may be in the form of particles, pellets, flakes, regrind, powders or may be sheet fed from one or more rolls. The applicator can move relative to the surface of the thermoplastic part to apply additive material to different areas on the melted surface. The controller controls the movement of the applicator and/or the thermoplastic part so as to apply additive material according to the surface modification profile. The additive material can be a thermoplastic elastomer (TPE). The TPE can be one of a variety of thermoplastic materials, including but not limited to thermoplastic vulcanizate (TPV), styrene- ethylene-butylene-styrene (SEBS), and linear low-density polyethylene (LLDPE). The additive material adheres to the sticky, molten surface of the part after it is applied.
In a fourth step 1300, a calender roll compresses and shears the additive material. The calender roll can be chilled. Alternatively, the calender roll can be heated. The calendar roll can also be textured. Compression by the calendar roller creates entanglement of the additive material with the substrate that creates adhesion, and flattens the top surface. Parameters can also be adjusted so that compression induces shear to additive particles and causes them to flow. If the roll is chilled, the roll cools the heated additive material and top surface.
In a fifth step 1400, the part exits the tunnel. The term "exit" as used herein can refer to a moving part being conveyed out of a stationary tunnel, a moving tunnel moving past a stationary part, or a moving part moving out of a moving tunnel traveling at a different speed and/or different direction than the moving part.
The foregoing steps can be used to add a functional surface, ornamental surface, or indicia to the surface of a thermoplastic part. The steps can be the only steps used, or used in combination with other steps.
For example, an optional heating step can be performed between the third step and fourth step. In such a step, additional heat is applied to the newly deposited elastomer material. The additional heat can be applied with the same IR heater, a different IR heater located downstream, or another heat source. In addition, the additional heat can be focused on areas of the surface corresponding to the surface modification profile. The additional heat can be applied to melt the surface of the part and/or the additive material deposited on the surface of the part, to help incorporate the additive material into the part surface.
In another process, a surface enhancement is applied to a thermoplastic part using a tunnel apparatus operated by a controller, similar to the first process. The part can be moved on a movable conveyor that passes through a stationary tunnel apparatus. Alternatively, the tunnel apparatus can be moved over or around a stationary part. In addition, both the tunnel apparatus and part can be moving, but at different speeds and/or different directions, such that the part moves relative to the tunnel. FIG. 2 shows one possible set of steps for applying a surface enhancement to a thermoplastic part using this alternate process.
In a first step 2000, the controller is programmed with a surface modification profile.
In a second step 2100, a focused IR heater produces a heat flux adequate to melt the top skin or surface of the thermoplastic part as the part is moved relative to the IR heater. The top surface is melted to a desired depth. The depth of melting is controlled based on one or more parameters, including but not limited to intensity setting of the IR heater, the spacing between the heater and the part, and the velocity at which the part is moved relative to the heater. The entire top surface can be melted. Alternatively, only the area(s) of the top surface corresponding to the surface modification profile is(are) melted.
In a third step 2200, an applicator immediately applies additive material onto the melted surface of the part. The applicator moves relative to the surface of the thermoplastic part to apply additive material to different areas on the melted surface. The controller controls the movement of the applicator and/or the thermoplastic part so as to apply additive material according to the surface modification profile. The additive material can be a thermoplastic elastomer (TPE). The TPE can be one of a variety of thermoplastic materials, including but not limited to thermoplastic vulcanizate (TPV), styrene-ethylene-butylene-styrene (SEBS), and linear low-density polyethylene (LLDPE). Moreover, the TPE can be applied in various physical forms, including but not limited to pellets, flakes, or particles. The additive material adheres to the sticky, molten surface of the part after it is applied.
In a fourth step 2300, a laser is moved relative to the molten surface of the thermoplastic part and the additive material to sinter the additive material with particle deposition. The controller controls the relative movement of the laser so as to sinter additive material according to the programmed surface modification profile. This step can also include a secondary heat flux application as an alternative to laser sintering.
In a fifth step 2400, a calender roll flattens and intimately mates the additive material into the thermoplastic part.
In a sixth step 2500, the part exits the tunnel. As noted above, the term "exit" can refer to a moving part being conveyed out of a stationary tunnel, a moving tunnel moving past a stationary part, or a moving part moving out of a moving tunnel traveling at a different speed and/or different direction than the moving part.
The foregoing steps can be used to add a functional surface, ornamental surface, or indicia to the surface of a thermoplastic part. The steps can be the only steps used, or used in combination with other steps.
FIG. 3 shows an apparatus 100 for applying a functional surface to a thermoplastic article. Thermoplastic articles enter apparatus 100 through a first end 102 and exit the apparatus through a second end 104. Apparatus 100 includes a conveyor belt 110 for moving a thermoplastic part past a number of stations. A controller 115 controls relative movement of the conveyor belt and thermoplastic part.
Thermoplastic articles are moved past a first station 120 which comprises a heat source 122 in the form of a first IR heater 124. As a thermoplastic article enters apparatus 100, it moves past IR heater 124 at a controlled rate established by controller 115. IR heater 124 is configured to melt the top surface of the thermoplastic article at a controlled heat flux, which is also controlled by controller 115.
After being heated at the first station, the thermoplastic article moves to a second station 130 comprising an applicator 132. Applicator 132 is configured to immediately apply additive material in the form of particles P to the heated top surface of the thermoplastic article while the surface is still melted. Particles P can comprise or consist of thermoplastic pellets, regrinds, or irregularly shaped non-thermoplastic material, including but not limited to sand, marble dust, granite dust, crumb rubber or other material.
After receiving additive material at second station 130, the thermoplastic article moves with conveyor belt 110 to a third station 140 comprising a second heat source 142 in the form of a second IR heater 144. Third station 140 is an optional station that can apply supplemental heat as needed to maintain or change the temperature of the surface of the thermoplastic article and of the additive material. Apparatuses in accordance with this disclosure can be used with the third station disabled, or omit the third station entirely if supplemental heating is not needed.
The thermoplastic article with additive material then moves past a fourth station 150 comprising a roll 152. Rolls according to the present disclosure can be heated rolls, chilled rolls and/or textured rolls. Roll 152 is configured to compress and shear particles of additive material on the top surface of the thermoplastic article to embed and bond the material to the top surface. If roll 152 is cooled, the roll further serves to cool down and begin curing the top surface and additive material. If roll 152 is textured, the roll can impart a modified surface texture to the top surface and additive material. After passing roll 152, conveyor belt 110 is configured to move the thermoplastic article with modified surface out of apparatus 100 through second end 104.
In another process, a retention void is formed on a surface of the thermoplastic part. An additive material is subsequently deposited or applied in the retention void to fill and completely seal the void so that no gaps or enclosed spaces are formed in the void. A first portion of the additive material fills the void to a level aligned with the surface of the thermoplastic part. A second portion of the additive material projects out of the retention void and above the surface to form a functional surface on the surface of the thermoplastic part. The retention void enhances the bonding of the additive material to the thermoplastic part by holding a portion of the additive material beneath the surface. In particular, the retention void provides more surface area on the thermoplastic part for attaching to the additive material than would be provided if the thermoplastic material is simply applied to a flat surface on the thermoplastic part with no void. In some embodiments, the retention void can be designed to protect the additive material from shear damage from a unit load on the thermoplastic part, as will be explained.
FIG. 4A shows one example of an article with a retention void for receiving additive material. In the present example, the article is a pallet 3000, but it could also be any other thermoplastic article to which an additive material is applied. Pallet 3000 includes a substrate or base 3100. Base 3100 has an upper surface 3110 designed to support a load, for example one or more containers for bulk transport and/or storage.
A retention void 3120 is formed in the upper surface 3110 of pallet 3000. To simplify the present example, retention void 3120 is shown as a shallow cylindrical shaped void extending into the upper surface 3110 of pallet 3000. It will be understood that thermoplastic articles in accordance with the present disclosure can have any number of voids, and the void(s) can have any geometric shape, which may all be the same shape or one or more different shapes, in order to form an anti-slip feature or features on the pallet. For example, a plurality of retention voids can be formed in a series of stripes, a polka-dot pattern, or in concentric shapes, including but not limited to concentric circles, ovals, squares, rectangles or other shapes. FIG. 4B shows an example in which retention voids 3120' are formed in a series of linear stripes. FIG. 4C shows an alternate example in which retention voids 3120" are formed in a plurality of concentric circles.
Referring back to FIG. 4A, retention void 3120 is configured to receive an additive material to form a functional surface on upper surface 3110. FIG. 5 shows retention void 3120 filled with an additive material 3140 consisting of thermoplastic elastomer 3142. Thermoplastic elastomer 3142 exhibits a higher coefficient of friction than upper surface 3110 of pallet 3000, thereby providing a functional surface 3150 in the form of an anti-slip feature 3152 on the pallet. Unlike prior techniques that assemble a grommet or strip into a recess, additive material 3140 completely fills and completely seals retention void 3120 by fusing with the interior of the void, leaving no seams or enclosed spaces that can collect contaminants. This makes pallet 3000 easy to keep clean and suitable for use in applications requiring sanitization.
Referring to FIG. 6, a cross section view of pallet 3000 is shown in the area of retention void 3120 and anti-slip feature 3152. It will be understood that other retention void configurations, including but not limited to those shown in FIGS. 4B and 4C, can be formed with the same cross section. Thus, the following cross-section description is not limited exclusively to cylindrical-shaped retention voids, but is also applicable to retention voids having other shapes and patterns on the surface of a thermoplastic article.
Additive material 3140 has a first portion 3140a below upper surface 3110 and a second portion 3140b above the upper surface. For delineation purposes, first portion 3140a and second portion 3140b are divided by a dashed line in FIG. 6. Retention void 3120 is defined by a bottom wall 3122 and a side wall 3124. Bottom wall 3122 and side wall 3124 provide increased surface area for attachment of additive material 3140 to base 3100. The combined surface area in retention void 3120 (i.e. the total area of the bottom wall and side wall) is larger than the surface area that would be provided for attachment to upper surface 3110 if the upper surface were simply flat without a void. Therefore, retention void 3120 provides a superior bonding surface and improved subsurface foundation that enhances the attachment between base 3100 and additive material 3140.
Second portion 3140b of additive material 3140 extends above upper surface 3110 of base 3100. Moreover, second portion 3140b projects above side wall 3124 in an exposed position. In this exposed position, the second portion 3140b functions as the aforementioned anti-slip feature 3152.
In some applications, it is possible that the exposed second portion 3140b can become damaged by shear when an article on pallet 3000 comes into contact with anti slip feature 3152. To protect an anti-slip feature from shear damage, retention voids can be manufactured with one or more protective walls or guards that are adjacent the retention void and at least partially surround the second portion of the additive material extending above the surface.
In the example shown, base 3100 includes a raised wall 3160 that surrounds the circumference of retention void 3120. Raised wall 3160 extends above upper surface 3110 and encloses a substantial section of second portion 3140b, thus shielding that section from lateral collision with objects, and reducing the effects of shear when an object rubs against anti-slip feature 3152.
The fusion between the additive material and retention void is quite strong, and unlikely to be overcome by mechanical force. Nevertheless, retention voids according to the present disclosure can have various cross section geometries that can further strengthen the attachment between the base and additive material. Referring to FIG.
7, retention void 3120 is shown without additive material 3140. Retention void 3120 has an undercut 3121 that further prevents anti-slip feature 3152 from being separated and pulled out of base 3100. In particular, the diameter DB at the bottom of retention void 3120 is smaller than the diameter DT at the top of the retention void. This forms a tapered geometry or constriction that prevents first portion 3140a of additive material 3140 from slipping or pulling out of retention void 3120.
Retention voids can have shapes other than cylindrical, as noted above. When other shapes and configurations for the retention void are used, an undercut can still be provided, for example by making the cross-sectional width at the bottom of the retention void wider than the cross-sectional width at the top of the retention void. For example, the retention void can be in the form of a channel having a trapezoidal cross section.
Referring to FIGS. 8-10, one technique is shown for forming base 3100 with retention void 3120. FIG. 8 schematically shows a portion of an empty mold M. Mold M includes a planar inner wall I adjacent a chamber C where the base is formed. A circular projection or plug PL extends from inner wall I. Plug PL has a base portion BP having a first diameter D1 and a free end portion FE having a second diameter D2. Second diameter D2 is larger than first diameter Dl. The diameter of plug PL increases at a constant rate or uniform manner from base portion BP to free end portion FE. In this arrangement, plug PL has a dovetail-shaped cross section.
FIG. 9 schematically shows mold M after a thermoplastic material T is injected into the mold. During injection, thermoplastic material T flows into chamber C around plug PL and into contact with inner wall I. As thermoplastic material T cures, inner wall I forms the upper surface 3110 of base 3100, and plug PL forms retention void 3120 that extends into the upper surface. Retention void 3120 has an undercut geometry due to the dove-tail shaped geometry of plug PL.
FIG. 10 schematically shows base 3100 in the process of being removed from mold M after thermoplastic material T has cured. As force is applied to remove base 3100 from mold M, the dove-tailed geometry of plug PL interlocks with sidewall 3124 around the retention void 3120, creating an interference. Therefore, a certain amount of force must be applied to overcome the interference. As this force is applied, plug PL bears against sidewall 3124 of retention void 3120. Plug PL is much more rigid than the cured thermoplastic material around sidewall 3124. Therefore, sidewall 3124 around retention void 3120 will yield under stress as plug PL is pulled out of the retention void, as shown. This creates plastic deformation that permanently changes the shape of sidewall 3124 around retention void 3120. For best results, thermoplastic material T should have adequate elasticity and elongation so as to allow for plastic deformation without fracturing during demolding.
Referring back to FIG. 7, base 3100 is shown after being removed from mold M. Plastic deformation of sidewall 3124 around retention void 3120 results in a top edge 3126 being pulled outwardly and upwardly from upper surface 3110 of base 3100. This creates raised wall 3160 that surrounds the circumference of retention void 3120 and projects above upper surface 3110. Raised wall 3160 forms a rim 3162 with a sharp edge 3164. Raised wall 3160 and rim 3162 are adapted to protect at least part of anti slip feature 3152 that projects from retention void 3120.
Raised wall 3160 can also provide an anti-slip function on its own, without an additive material applied or otherwise deposited into retention void 3120. Edge 3164 of raised wall 3160 can increase surface roughness of upper surface 3110 and reduce the occurrence of slippage on base 3110.
In another process, a functional surface, ornamental surface or indicia is formed on a surface of a thermoplastic part using an additive material that is UV cured. In one example, the additive material is a roll-on rubber ink. In another example, the additive material is a coating that is silk screened onto the top surface of the thermoplastic part and then conveyed below one or more UV lamps for curing.
In another process, a functional surface, ornamental surface or indicia is formed on a surface of a thermoplastic part using an additive material that is pad printed or sprayed onto the thermoplastic part. In one example, the additive material is ink or paint.
Accordingly, the present disclosure encompasses all of the foregoing possibilities. In addition, the present disclosure encompasses apparatuses and processes that include or carry out any combination of features or steps described in the present disclosure, whether presented in the same example or presented in separate examples. It is further intended that the appended claims cover all such variations as fall within the scope of the present disclosure.

Claims

CLAIMS What is Claimed:
1. A process for modifying a surface geometry of a thermoplastic part using a tunnel apparatus operated by a controller, the process comprising the steps of:
A. programming the controller with a surface modification profile;
B. moving a thermoplastic part relative to a heat source to form a melted surface on the thermoplastic part; and
C. depositing an additive material onto the melted surface according to the surface modification profile.
2. The process of claim 1, further comprising the steps of:
D. entangling the additive material with the melted surface; and
E. cooling the melted surface.
3. The process of claim 1, wherein the step of moving the thermoplastic part relative to the heat source comprises moving the thermoplastic part relative to a tunnel apparatus.
4. The process of claim 3, wherein the tunnel apparatus is stationary, and the thermoplastic part is moved on a movable conveyor that passes through the tunnel apparatus.
5. The process of claim 3, wherein the thermoplastic part is stationary, and the tunnel apparatus is moved over or around the thermoplastic part.
6. The process of claim 3, wherein the tunnel apparatus and the thermoplastic part are moving at different speeds and/or different directions.
7. The process of claim 1 further comprising the step of applying heat to the additive material and melted surface after the step of depositing the additive material onto the melted surface.
8. The process of claim 1, further comprising the step of passing a laser over the melted surface and the additive material to sinter the additive material.
9. The process of claim 8, further comprising the step of flattening and mating the additive material with the melted surface.
10. The process of claim 1, wherein the step of cooling the melted surface comprises compressing the additive material with a roller.
11. A process for modifying a surface geometry of a thermoplastic part, the process comprising the step of rolling an additive material onto a surface of the thermoplastic part.
12. The process of claim 11, wherein the additive material is a roll-on coating.
13. The process of claim 11, wherein the additive material is an ink or a paint.
14. The process of claim 11, further comprising the step of UV curing the additive material on the thermoplastic part.
15. A process for modifying a surface geometry of a thermoplastic part, the process comprising the step of applying an additive material onto a surface of the thermoplastic part.
16. The process of claim 15, wherein the step of applying the additive material comprises printing the additive material onto the surface.
17. The process of claim 15, wherein the step of applying the additive material comprises silk-screening the additive material onto the surface.
18. The process of claim 15, wherein the step of applying the additive material comprises pad printing the additive material onto the surface.
19. The process of claim 15, wherein the step of applying the additive material comprises spraying the additive material onto the surface.
20. The process of claim 15, wherein the step of applying the additive material comprises moving an applicator containing the additive material over the surface.
21. The process of claim 20, wherein the applicator is part of a CNC machine having a controller.
22. The process of claim 21, wherein the CNC machine is a Cartesian printer.
23. The process of claim 21, wherein the CNC machine is a CNC controlled robotic arm.
24. An apparatus for carrying out the process according to any one of the preceding claims.
25. An apparatus for carrying out the process according to any one of the examples in the Description.
EP21757525.7A 2020-02-18 2021-02-18 Process for adding surface enhancement to thermoplastic article Pending EP4107224A1 (en)

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GB1157312A (en) * 1966-04-07 1969-07-09 Valley Printing Company Ltd Improvements in or Relating to Printing Processes
DE10042566A1 (en) * 2000-08-22 2002-03-14 Inst Polymerforschung Dresden Process for modifying plastic surfaces
EP1356152A2 (en) * 2001-01-30 2003-10-29 The Procter & Gamble Company Coating compositions for modifying surfaces
US8557349B2 (en) * 2009-06-12 2013-10-15 Apex Materials Corporation Elastomeric paint with protective coating upon styrenic block copolymer articles
US9573024B2 (en) * 2013-12-31 2017-02-21 Nike, Inc. 3D printed golf ball core

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