CN110654007A - PP foaming injection molding process for inner plate of rear door of automobile - Google Patents
PP foaming injection molding process for inner plate of rear door of automobile Download PDFInfo
- Publication number
- CN110654007A CN110654007A CN201910805164.4A CN201910805164A CN110654007A CN 110654007 A CN110654007 A CN 110654007A CN 201910805164 A CN201910805164 A CN 201910805164A CN 110654007 A CN110654007 A CN 110654007A
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- injection molding
- pressure
- foaming
- molding process
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
- B29C45/77—Measuring, controlling or regulating of velocity or pressure of moulding material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/76—Measuring, controlling or regulating
- B29C45/78—Measuring, controlling or regulating of temperature
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76494—Controlled parameter
- B29C2945/76498—Pressure
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
- B29C2945/76—Measuring, controlling or regulating
- B29C2945/76494—Controlled parameter
- B29C2945/76531—Temperature
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
The invention discloses a PP foaming injection molding process for an inner plate of a rear door of an automobile, which specifically comprises the following steps: performing mold closing operation, namely closing the movable mold cavity and the static mold cavity on an injection molding machine; step two: injection molding, wherein the injection molding machine injects a PP modified material with 75-85% of the volume of the mold cavity into the mold cavity, wherein 0.4% of foaming agent is added into the PP modified material; the injection pressure is divided into six zones, a low-medium-high increasing mode is adopted, the pressure controls the screw feeding section to be 30-40bar, the screw compression section to be 50-60bar and the screw metering section to be 70-80 bar; the injection molding speed corresponds to the injection molding pressure, a descending mode of high, medium and low is adopted, the pressure controls the screw feeding section to be 12-15mm/s, the screw compression section to be 8-10mm/s and the screw metering section to be 5-6 mm/s; step three: maintaining the pressure at 10-15bar for 15-18 s; step four: opening the mold and taking out the part; the process problem that the performance requirement of parts is damaged due to the uneven appearance of the foamed product is solved.
Description
Technical Field
The invention belongs to the technical field of polypropylene injection molding, and particularly relates to a PP foaming injection molding process for an inner plate of a rear door of an automobile.
Background
The polypropylene (PP) resin has the characteristics of rich raw material sources, light weight, superior cost performance, excellent heat resistance, chemical corrosion resistance, easy recovery and the like, and is one of the resins with wide world application and fast yield increase. At present, most researchers in the industry concentrate on the field of medium-high ratio foaming, and in reality, injection molding of large or thick-walled products using PP as a base material is always a difficult problem, because of the high crystallinity of PP, it is difficult to avoid various problems such as shrinkage and flow marks when manufacturing the large products.
The properties of foamed PP depend on the relative density and cell structure characteristics of the foamed material. Uniformity of cell distribution and reduction of cell size are key factors for enhancing the performance of the hair foam article with respect to cell structure.
The study of scholars finds that: under the same density condition, the smaller the cell size, the more uniform the distribution, and the higher the tensile property of the foam material; the weight reduction range of the material is increased, and the tensile property is reduced; the impact strength of the foamed product is greatly related to the relative density and the thickness of the skin layer.
For injection molding foaming PP, the foaming appearance is influenced by multiple factors such as temperature, shearing force, cavity pressure and the like.
With the increasing complexity of products, the tolerance requirements and the surface appearance quality requirements of parts are higher and higher, and the quality or cost requirements are difficult to achieve by adopting the traditional injection molding processing technology. Especially, the foaming material is controlled by constant air pressure, especially the sensitivity of the foaming agent to temperature is high, and if the temperature gradient is not properly controlled, excessive flatness of the foaming or insufficient foaming rate can be generated, the foaming efficiency is affected, and the expected weight reduction effect cannot be achieved.
Disclosure of Invention
The invention provides a PP foaming injection molding process for an inner plate of a rear door of an automobile, which solves the problems in the background technology.
In order to achieve the purpose, the invention adopts the technical scheme that: a PP foaming injection molding process for an inner plate of a rear door of an automobile specifically comprises the following steps,
the method comprises the following steps: performing mold closing operation, namely closing the movable mold cavity and the static mold cavity on an injection molding machine;
step two: injection molding, wherein the injection molding machine injects a PP modified material with 75-85% of the volume of the mold cavity into the mold cavity, wherein 0.4% of foaming agent is added into the PP modified material;
the injection pressure is divided into six zones, a low-medium-high increasing mode is adopted, the pressure controls the screw feeding section to be 30-40bar, the screw compression section to be 50-60bar and the screw metering section to be 70-80 bar;
the injection molding speed corresponds to the injection molding pressure, a 'high, medium and low' decreasing mode is adopted, the pressure controls the screw feeding section to be 12-15mm/s, the screw compression section to be 8-10mm/s and the screw metering section to be 5-6 mm/s;
step three: maintaining the pressure at 10-15bar for 15-18 s;
step four: and opening the mold to take out the part.
Preferably, in the second step, 79% of the volume of the mold cavity of the PP modifying material is injected into the mold cavity.
Preferably, the injection molding temperature in the second step is controlled to be 1.2-1.3 times of the melting point of the PP modified material.
Preferably, the injection pressures of the six zones in the second step are respectively as follows: 35bar, 40bar, 55bar, 58bar, 68bar and 75 bar.
Preferably, the injection molding temperatures corresponding to the injection molding pressures of the six zones in the second step are respectively as follows: 180 ℃, 190 ℃, 210 ℃, 220 ℃, 200 ℃ and 190 ℃.
Preferably, the pressure value of the pressure maintaining in the third step is 14bar, and the pressure maintaining time is 17 s.
The beneficial effect of adopting above technical scheme is:
1. according to the PP foaming injection molding process for the inner plate of the rear tail door of the automobile, the actual foaming rate state is considered, the injection volume filling amount is controlled to be 75-85% of the volume of the mold cavity, the volume expansion rate after being pressed is 17-33%, and in the specific step II, a PP modified material with 79% of the volume of the mold cavity is injected into the mold cavity, so that the weight of the inner plate of the rear tail door of the automobile is reduced by 21%; 0.4% foaming agent is added into the PP modified material, so that the foaming efficiency is ensured.
Dividing the injection pressure into six zones, adopting a low-medium-high increasing mode, controlling the pressure to control the screw feeding section to be 30-40bar, the screw compression section to be 50-60bar, and the screw metering section to be 70-80bar, wherein the injection pressure of the six zones in the specific step II is respectively as follows: 35bar, 40bar, 55bar, 58bar, 68bar and 75bar, the injection speed corresponds to the injection pressure, a descending mode of high and medium, and the pressure control screw is provided with a feeding section of 12-15mm/s, a compression section of 8-10mm/s and a metering section of 5-6mm/s, so that the injection molding product with larger size, for example: the injection molding pressure and the injection molding temperature of different injection molding sections of the inner plate of the automobile back tail door are properly adjusted, so that the consistency of the viscosity of the PP modified material and the foaming uniformity are ensured, namely the uniformity of the foam cell distribution and the uniformity of the foam cell size are ensured.
2. The injection molding temperature in the second step is controlled to be 1.2-1.3 times of the melting point of the PP modified material, and the injection molding temperatures corresponding to the injection molding pressures of the six zones in the second step are respectively as follows: the temperature of 180 ℃, 190 ℃, 210 ℃, 220 ℃, 200 ℃ and 190 ℃ ensure the viscosity state of the PP modified material under the corresponding injection pressure, thereby ensuring the foaming saturation state.
3. And in the third step, the pressure maintaining value is 10-15bar, the pressure maintaining time is 15-18s, the pressure maintaining value is 14bar, the pressure maintaining time is 17s, a lower pressure maintaining value and a longer pressure maintaining time are adopted, the PP modified material is convenient to rapidly expand in volume in the die cavity, the foaming rate is increased, and the lightweight requirement is met.
Detailed Description
The following examples are included to provide further detailed description of the embodiments of the invention and to provide those skilled in the art with a more complete, concise and complete understanding of the principles and spirit of the invention, and to facilitate its practice.
The invention relates to a PP foaming injection molding process for an inner plate of a rear door of an automobile, which solves the process problem that the performance requirement of parts is damaged due to the uneven appearance of a foamed product.
The following specific working modes are illustrated by specific examples:
example 1:
in order to improve the injection foaming efficiency, 0.4 percent of foaming agent is added into the high-viscosity PP modified material for mixing. The temperature setting of the feeding section of the pressure control screw is low, and the foaming agent and the PP modified material are mixed and begin to melt. The temperature in the compression section of the screw is set to be high, generally 15-25 ℃ higher than that in the feeding section of the pressure control screw, so that the foaming agent mainly obtains more heat, and the foaming agent is decomposed to generate a large amount of gas which is uniformly distributed in the plastic melt of the PP modified material. The temperature of the metering section of the screw is generally 10-15 ℃ lower than that of the compression section of the screw, and the pressure of a melt and gas is increased during injection and melt of glue, so that the gas is forced to be higher in the melt. We set the injection temperature at 180 deg.C, 190 deg.C, 205 deg.C, 210 deg.C, 200 deg.C and 190 deg.C. The pressure value of the pressure maintaining is 12bar, the pressure maintaining time is 12s, and the volume filling amount of the injected glue is 81 percent. The product appearance can meet the requirement of the lining, the cross section is cut open at a plurality of positions, and the size of the foaming foam pores is between 40 and 50 mu m and is uniform. And (4) taking a sample plate with uniform thickness for tensile strength test, wherein the average value is more than or equal to 14 MPa. The weight of the inner plate of the rear tail door of the automobile is reduced by about 18 percent compared with that of the inner plate of the rear tail door of the automobile in an unfoamed state.
Example 2:
to increase the foaming size, 0.6% of a foaming agent is added to the high viscosity PP-modified material and mixed. When the melt is foamed and expanded in the mould, the expansion pressure of the melt is lower than the holding pressure, if the holding pressure is adopted, the melt is not foamed and expanded, so that the holding pressure can be omitted or smaller holding pressure can be used during foaming injection, and the implementation process scheme is controlled without using the holding pressure. The influence of the injection rate mainly aims at the foam holes formed in the filled mold, when the cavity is not filled and is just filled, the increase of the injection rate is beneficial to the increase of the number of the foam holes, the injection rate is adjusted, the pressure control screw feeding section is 10mm/s, the screw compression section is 8mm/s, and the screw metering section is 5 mm/s. We set the injection molding temperatures at 180 deg.C, 190 deg.C, 205 deg.C, 210 deg.C, 200 deg.C and 190 deg.C. The volume filling amount of the injected gel is 77%. The product has slight defects in appearance, the cross sections are cut open at multiple positions, and the sizes of foaming cells are between 60 and 70 mu m and are uniform. And (3) taking a sample plate with uniform thickness for tensile strength test, wherein the average value is lower, and the tensile strength range is 11-12 MPa. The weight of the inner plate of the rear tail door of the automobile is reduced by about 23.5 percent compared with that of the inner plate of the rear tail door of the automobile in an unfoamed state.
The present invention has been described in an illustrative manner, and it is to be understood that the invention is not limited to the precise construction and arrangement of parts so described, and that various insubstantial modifications can be made without departing from the spirit and scope of the invention; the present invention is not limited to the above embodiments, and can be applied to various fields without modification.
Claims (6)
1. The PP foaming injection molding process for the inner plate of the rear door of the automobile is characterized by comprising the following steps of: the method specifically comprises the following steps of,
the method comprises the following steps: performing mold closing operation, namely closing the movable mold cavity and the static mold cavity on an injection molding machine;
step two: injection molding, wherein the injection molding machine injects a PP modified material with 75-85% of the volume of the mold cavity into the mold cavity, wherein 0.4% of foaming agent is added into the PP modified material;
the injection pressure is divided into six zones, a low-medium-high increasing mode is adopted, the pressure controls the screw feeding section to be 30-40bar, the screw compression section to be 50-60bar and the screw metering section to be 70-80 bar;
the injection molding speed corresponds to the injection molding pressure, a descending mode of high, medium and low is adopted, the pressure controls the screw feeding section to be 12-15mm/s, the screw compression section to be 8-10mm/s and the screw metering section to be 5-6 mm/s;
step three: maintaining the pressure at 10-15bar for 15-18 s;
step four: and opening the mold to take out the part.
2. The PP foaming injection molding process of the automobile rear tail door inner plate as claimed in claim 1, wherein the PP foaming injection molding process comprises the following steps: and in the second step, 79% of PP modified material of the volume of the mold cavity is injected into the mold cavity.
3. The PP foaming injection molding process of the automobile rear tail door inner plate as claimed in claim 1, wherein the PP foaming injection molding process comprises the following steps: and the injection molding temperature in the second step is controlled to be 1.2-1.3 times of the melting point of the PP modified material.
4. The PP foaming injection molding process of the automobile rear tail door inner plate as claimed in claim 1, wherein the PP foaming injection molding process comprises the following steps: and in the second step, the injection molding pressures of the six areas are respectively as follows: 35bar, 40bar, 55bar, 58bar, 68bar and 75 bar.
5. The PP foaming injection molding process of the automobile rear tail door inner plate is characterized in that: and in the second step, the injection molding temperatures corresponding to the injection molding pressures of the six zones are respectively as follows: 180 ℃, 190 ℃, 210 ℃, 220 ℃, 200 ℃ and 190 ℃.
6. The PP foaming injection molding process of the automobile rear tail door inner plate as claimed in claim 1, wherein the PP foaming injection molding process comprises the following steps: and in the third step, the pressure maintaining pressure value is 14bar, and the pressure maintaining time is 17 s.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910805164.4A CN110654007B (en) | 2019-08-29 | 2019-08-29 | PP foaming injection molding process for inner plate of rear door of automobile |
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| CN201910805164.4A CN110654007B (en) | 2019-08-29 | 2019-08-29 | PP foaming injection molding process for inner plate of rear door of automobile |
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| CN110654007A true CN110654007A (en) | 2020-01-07 |
| CN110654007B CN110654007B (en) | 2021-05-21 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113787668A (en) * | 2021-09-14 | 2021-12-14 | 深圳创维－Rgb电子有限公司 | Injection molding process, display and molding equipment |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113787668A (en) * | 2021-09-14 | 2021-12-14 | 深圳创维－Rgb电子有限公司 | Injection molding process, display and molding equipment |
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