CN109514795B - Cambered surface workpiece and control method and application of warping degree thereof - Google Patents
Cambered surface workpiece and control method and application of warping degree thereof Download PDFInfo
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- CN109514795B CN109514795B CN201811517337.4A CN201811517337A CN109514795B CN 109514795 B CN109514795 B CN 109514795B CN 201811517337 A CN201811517337 A CN 201811517337A CN 109514795 B CN109514795 B CN 109514795B
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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
- B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
- B29C45/14778—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles the article consisting of a material with particular properties, e.g. porous, brittle
- B29C45/14786—Fibrous material or fibre containing material, e.g. fibre mats or fibre reinforced material
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Abstract
The invention discloses a cambered surface workpiece and a control method and application of the warping degree of the cambered surface workpiece, wherein the control method of the warping degree of the cambered surface workpiece comprises the following steps: step 1: placing the continuous fiber reinforced thermoplastic composite material sheet at the bottom of an injection mold with a flat-plate-shaped cavity; step 2: injecting the injection molding material into an injection mold, and naturally cooling after injection molding to obtain a cambered surface workpiece; the total thickness of the cambered surface workpiece is 2-4 mm, and the continuous fiber reinforced thermoplastic composite material sheet accounts for 10-50% of the total thickness of the cambered surface workpiece. According to the invention, the control on the warping degree of the cambered surface workpiece is realized through the formula design, the warping degree does not need to be corrected by auxiliary equipment, the production procedures are reduced, and the production efficiency of the product is improved. And the prepared product has excellent mechanical property.
Description
Technical Field
The invention relates to the field of manufacturing of arc-shaped workpieces, in particular to an arc-shaped workpiece and a control method and application of warping degree of the arc-shaped workpiece.
Background
The continuous fiber reinforced thermoplastic composite material (CFRT) is a novel high-strength, high-rigidity, high-toughness and recyclable thermoplastic composite material which is formed by using thermoplastic resin as a matrix and continuous fibers as a reinforcing material through resin melting impregnation, extrusion and other processes. Because the fibers in CFRT are continuous and the resin impregnates the fiber filaments more fully than conventional thermoplastic composites (e.g., GMT, LFT). The mechanical properties, in particular tensile and flexural, impact properties, are therefore also much higher than in the conventional thermoplastic composites described above.
The traditional forming process of CFRT mainly comprises the following steps: the hand lay-up molding has the defects of loose texture, low density, low product strength, manual dependence, unstable quality and low production efficiency; secondly, the injection molding improves the working efficiency to a certain extent, but still cannot meet the requirement of mass production, and is used for manufacturing transition layers of automobile bodies, ship bodies, bathtubs and storage tanks; thirdly, lamination molding is carried out, and the method has the characteristics of high mechanization and automation degree, stable product quality and the like, but the equipment investment is large at one time; winding and molding, wherein the product has a single structure and is only used for manufacturing cylinders, spheres and certain positive curvature rotary bodies or cylindrical fiber products; fifthly, pultrusion is carried out, and the process is suitable for producing section bars with various section shapes, such as I-shaped section bars, angle-shaped section bars, groove-shaped section bars, special-shaped section bar bars and combined section bar sections formed by the sections; liquid forming, the application of the process is based on accurate pipeline conveying and metering and automatic temperature and pressure control, belongs to the cross category of high polymer materials and modern high and new scientific technologies, and is not very wide at present; and seventhly, compression molding is carried out, the early-stage mold is complex to manufacture, the investment is high, and the size of a workpiece is limited by the size of a press.
Compared with the traditional forming process, for CFRT, injection molding is a novel forming process, the forming process is to put a semi-finished blank into an injection mold and adopt glass fiber reinforced thermoplastic material for injection molding, and the manufacturing adopts a reinjection technology. The CFRT and the non-continuous fiber reinforced plastic can be fully combined, the part with a simple structure takes the prepreg tape sheet as a main support, and the part with a complex structure adopts an injection molding mode. The forming process has wide application of foreign products, and Lanxess has a plurality of application cases on automobile parts. In recent years, the demand for lightweight in the domestic automobile industry is higher and higher, products made of plastics instead of steel are more and more abundant, and CFRT has excellent characteristics such as high strength, high rigidity and high toughness, and is widely favored. In addition, the injection molding greatly reduces the whole production process, shortens the whole period, enhances the environmental protection flexibility, adds the personalized design, improves the safety, and is the application integrating light weight, high rigidity and strength, fatigue resistance, energy absorption and functions. The injection molding compounding of CFRT and non-continuous fiber reinforced plastics is a great trend, and the application market of CFRT can be greatly expanded.
For injection molded parts, warpage is one of the important quality indicators, and affects not only product assembly and service performance, but also product appearance quality. As the shrinkage rates of CFRT and non-continuous fiber reinforced plastics are greatly different, the sensitivity to temperature is different, the finished piece can be warped and deformed after injection molding, and the product percent of pass is directly influenced.
Therefore, in the prior research and application, warpage is regarded as a defect of the plastic product, and needs to be avoided or improved as much as possible. This knowledge is also present in the manufacturing process of the preforms. Cambered surface finished piece, like curved surface cell-phone shell, curved surface LED display back lid etc. during its production, at first must design the mould of a pair of cambered surface shape die cavity, secondly to shaping back warpage problem, still need rectify adjustment warpage to obtain qualified product, so not only increase many mould processing expenses, increased expenses such as auxiliary forming equipment, manual work moreover, lengthened production cycle.
Disclosure of Invention
In order to solve the technical problems, the invention provides a control method of the camber of the cambered surface workpiece, which realizes the control of the camber of the cambered surface workpiece through formula design without correcting the camber by auxiliary equipment, reduces the production procedures and improves the production efficiency of products. And the prepared product has excellent mechanical property.
The specific technical scheme is as follows:
a method for controlling the warp degree of a cambered surface workpiece comprises the following steps:
step 1: placing the continuous fiber reinforced thermoplastic composite material sheet at the bottom of an injection mold with a flat-plate-shaped cavity;
step 2: injecting the injection molding material into an injection mold, and naturally cooling after injection molding to obtain a cambered surface workpiece;
the total thickness of the cambered surface workpiece is 2-4 mm, and the continuous fiber reinforced thermoplastic composite material sheet accounts for 10-50% of the total thickness of the cambered surface workpiece.
The invention overcomes the technical prejudice that the 'warping' is regarded as a defect of plastic products in the prior art, and utilizes the warping deformation by compounding the continuous fiber reinforced thermoplastic composite material and the fiber reinforced thermoplastic material and regulating the thickness range of the continuous fiber reinforced thermoplastic composite material to regulate the warping degree of the cambered surface workpiece. The technical scheme has the advantages that: the different warping degree workpieces can be realized only by one group of plane dies, namely, the workpieces are not required to be designed into arcs, and the dies with different radians are not required to be respectively designed according to the warping degree requirements of the different arc surface workpieces; the cambered surface workpiece with a certain warping degree can be obtained by controlling the thickness of the continuous fiber reinforced thermoplastic composite material, namely, the cambered surface workpiece starts from the raw materials of the formula without correcting the warping by auxiliary equipment, so that the production procedures are further reduced, and the production efficiency of the product is improved.
Preferably, the shape of the continuous fiber reinforced thermoplastic composite sheet is adapted to the shape of the cavity of the injection mold. The term "conformable" means that the shape of the continuous fiber-reinforced thermoplastic composite sheet is the same as the shape of the cavity of the injection mold, and both are sheet-like. However, the size of the continuous fiber reinforced thermoplastic composite material sheet is slightly smaller than that of the cavity of the injection mold, and a space reserved at the edge can prevent the continuous fiber reinforced thermoplastic composite material sheet from being deformed due to expansion at high temperature, and can enable the injection molding material to be coated on the edge of the continuous fiber reinforced thermoplastic composite material sheet for modification, so that the appearance of the final cambered surface part is more attractive. Preferably, the distance between the edges of the continuous fiber reinforced thermoplastic composite material sheets and the corresponding edges of the injection mold is 5-10 mm.
Preferably, the base material of the continuous fiber reinforced thermoplastic composite material sheet is selected from polypropylene, the continuous fiber is selected from continuous glass fiber, and the content of the continuous fiber in percentage by weight is 50-70% based on the total weight of the raw materials. Further preferably 60%.
The continuous fiber reinforced thermoplastic composite material sheet is prepared by die pressing, and the die pressing process comprises the following steps:
sheet → ply design → heat → compression molding.
Preferably, the injection mold is a two-plate mold, so as to enclose a flat-plate-shaped cavity.
Preferably, a positioning column is arranged in the cavity of the injection mold, a positioning hole is formed in the continuous fiber reinforced thermoplastic composite material sheet, and the positioning column is matched with the positioning hole in size and used for fixing the continuous fiber reinforced thermoplastic composite material sheet to the bottom of the injection mold. Further preferably, the number of the positioning columns is two.
Preferably, the injection molding material is a long glass fiber reinforced polypropylene material, and the weight percentage content of the long glass fiber is 20-40%, and more preferably 30% based on the total weight of the raw materials.
The continuous glass fiber reinforced PP has high specific rigidity and specific strength, so that the comprehensive performance is excellent; the long glass fiber reinforced PP has small specific gravity and is easy to form, and an injection molding product has good appearance quality. The two are combined for use, so that the requirements of high performance and appearance quality of the product can be met, the product is easy to uniformly recover, and the reutilization rate is high.
The injection molding machine is a horizontal injection molding machine, the injection molding mold is adopted, and the injection molding comprises five processes of mold closing, filling, pressure maintaining, cooling and mold opening. Preferably, the injection molding process is as follows:
the melt temperature is 200-220 ℃, the injection speed is 20-40 mm/s, the injection pressure is 30-50 MPa, and the cooling time is 8-12 s.
And taking out the workpiece, and naturally cooling the workpiece, wherein the temperature range of the natural cooling condition is 20-26 ℃.
Further preferably, the total thickness of the cambered surface workpiece is 3mm, and the continuous fiber reinforced thermoplastic composite material sheet accounts for 10% -50% of the total thickness of the cambered surface workpiece.
The invention also discloses the cambered surface workpiece prepared by the method, and the adjustment range of the warping degree is 0.015-0.035.
The invention also discloses application of the cambered surface workpiece in preparation of a curved mobile phone shell, a curved LED display rear cover and the like.
Compared with the prior art, the invention has the beneficial effects that:
the invention overcomes the technical prejudice of plastic products, utilizes the 'warping' as the defect, and utilizes the warping deformation by compounding the continuous fiber reinforced thermoplastic composite material and the fiber reinforced thermoplastic material and regulating the thickness range of the continuous fiber reinforced thermoplastic composite material to regulate the warping degree of the cambered surface part. The technical scheme has the advantages that: the different warping degree workpieces can be realized only by one group of plane dies, namely, the workpieces are not required to be designed into arcs, and the dies with different radians are not required to be respectively designed according to the warping degree requirements of the different arc surface workpieces; the cambered surface workpiece with a certain warping degree can be obtained by controlling the thickness of the continuous fiber reinforced thermoplastic composite material, namely, the cambered surface workpiece starts from the raw materials of the formula without correcting the warping by auxiliary equipment, so that the production procedures are further reduced, and the production efficiency of the product is improved.
Drawings
FIG. 1 is a schematic view of the invention for preparing a cambered surface part;
in the figure, 1-injection mold, 2-positioning column, 3-CFRT sheet and 4-injection sheet.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention.
In the following examples and comparative examples, the same injection mold 1 is used, the cavity of which is flat, the length of which is 210mm, the width of which is 140mm, and the thickness of which is 3mm, and two positioning columns 2 are symmetrically designed in the cavity, as shown in the attached drawings.
The raw material composition of the CFRT sheet and the injection molding compound used in each example and comparative example, respectively, was as follows:
the raw material composition of the CFRT sheet is as follows:
the injection molding material comprises the following raw materials:
the test standards used in the examples and comparative examples are as follows:
the tensile strength is tested according to ISO 527-4 standard;
the bending strength is tested according to the ISO 14125 standard;
the flexural modulus is tested with reference to ISO 14125 standard;
the formula for calculating the warping degree is as follows:
wherein h is the warping amount, and l is the projection length of the evaluation target in the specific direction.
Example 1
Step 1, preparing a CFRT sheet 3 with the thickness of 0.3mm by adopting the raw material formula of the CFRT sheet through mould pressing;
step 2, cutting two positioning holes at the positions, corresponding to the positioning columns in the injection mold, on the CFRT sheet, and then placing the CFRT sheet in the injection mold;
and 4, taking out the workpiece, and naturally cooling to obtain the final cambered surface workpiece.
The performance parameters of the finished arc prepared in this example are listed in table 1 below.
Example 2
Step 1, preparing a CFRT sheet with the thickness of 0.5mm by adopting the raw material formula of the CFRT sheet through mould pressing;
step 2, cutting two positioning holes at the positions, corresponding to the positioning columns in the injection mold, on the CFRT sheet, and then placing the CFRT sheet in the injection mold;
and 4, taking out the workpiece, and naturally cooling to obtain the final cambered surface workpiece.
The performance parameters of the finished arc prepared in this example are listed in table 1 below.
Example 3
Step 1, preparing a CFRT sheet with the thickness of 0.8mm by adopting the raw material formula of the CFRT sheet through mould pressing;
step 2, cutting two positioning holes at the positions, corresponding to the positioning columns in the injection mold, on the CFRT sheet, and then placing the CFRT sheet in the injection mold;
and 4, taking out the workpiece, and naturally cooling to obtain the final cambered surface workpiece.
The performance parameters of the finished arc prepared in this example are listed in table 1 below.
Example 4
Step 1, preparing a CFRT sheet with the thickness of 1.2mm by adopting the raw material formula of the CFRT sheet through mould pressing;
step 2, cutting two positioning holes at the positions, corresponding to the positioning columns in the injection mold, on the CFRT sheet, and then placing the CFRT sheet in the injection mold;
and 4, taking out the workpiece, and naturally cooling to obtain the final cambered surface workpiece.
The performance parameters of the finished arc prepared in this example are listed in table 1 below.
Example 5
Step 1, preparing a CFRT sheet with the thickness of 1.5mm by adopting the raw material formula of the CFRT sheet through mould pressing;
step 2, cutting two positioning holes at the positions, corresponding to the positioning columns in the injection mold, on the CFRT sheet, and then placing the CFRT sheet in the injection mold;
and 4, taking out the workpiece, and naturally cooling to obtain the final cambered surface workpiece.
The performance parameters of the finished arc prepared in this example are listed in table 1 below.
Comparative example 1
Step 1, mixing the raw materials of the injection molding material, melting, injecting into an injection mold, and cooling and solidifying to obtain a finished piece, wherein the melt temperature is 210 ℃, the injection speed is 30mm/s, the injection pressure is 40MPa, and the cooling time is 10 s;
and 2, taking out the workpiece and then naturally cooling the workpiece.
The performance parameters of the fabricated shoe for this comparative example are listed in table 1 below.
TABLE 1
By analyzing the data of the above embodiments and comparative examples, it is not easy to find that by using the method of the present invention, the camber of the arc-shaped part prepared in embodiments 1 to 5 shows a certain regular change, different arc-shaped parts can be obtained by different CFRT sheet thicknesses, the thickness of the arc-shaped part can be controlled to obtain a camber-specific arc-shaped part, and for different product structures, prepreg tape sheets with different thicknesses are selected for injection molding compounding, so that the result of local reinforcement and warpage deformation can be utilized, and the controllable range of camber in the present invention is 0.015 to 0.035.
Comparing example 5 with comparative example 1, the CFRT sheet thickness in example 5 was 1.5mm, whereas in comparative example 1 there was no CFRT sheet, and the tensile strength, flexural modulus of example 5 were significantly better than comparative example 1.
Comparing example 5 with example 1, the thickness of the CFRT sheet in example 1 is only 0.3mm, the tensile strength, bending strength, and bending modulus are lower than those of example 5, and the warp of the deformation is large. According to different requirements of different application occasions on strength and shapes of parts, the thickness of the CFRT sheet can be selected to meet the requirements of products.
The method disclosed by the invention has the advantages of simple equipment, easiness in implementation and operation, reduction in production procedures, great improvement on production efficiency and wide application prospect.
Claims (9)
1. A method for controlling the warp degree of a cambered surface workpiece is characterized by comprising the following steps:
step 1: placing the continuous fiber reinforced thermoplastic composite material sheet at the bottom of an injection mold with a flat-plate-shaped cavity;
step 2: injecting the injection molding material into an injection mold, and naturally cooling after injection molding to obtain a cambered surface workpiece;
the total thickness of the cambered surface workpiece is 2-4 mm, and the continuous fiber reinforced thermoplastic composite material sheet accounts for 10-50% of the total thickness of the cambered surface workpiece.
2. The method for controlling the camber of the arc-shaped workpiece according to claim 1, wherein the shape of the continuous fiber reinforced thermoplastic composite material sheet is adapted to the shape of the cavity of the injection mold, and the distance between the edges of the continuous fiber reinforced thermoplastic composite material sheet and the corresponding edge of the injection mold is 5-10 mm.
3. The method for controlling camber of an arc-shaped object according to claim 1, wherein the continuous fiber-reinforced thermoplastic composite sheet material comprises a base material selected from polypropylene, the continuous fiber is selected from continuous glass fiber, and the weight percentage of the continuous fiber is 50-70% based on the total weight of the raw materials.
4. The method for controlling the camber of an arc-shaped workpiece according to claim 1, wherein a positioning post is arranged in the cavity of the injection mold, a positioning hole is formed in the continuous fiber reinforced thermoplastic composite material sheet, and the positioning post is matched with the positioning hole in size and used for fixing the continuous fiber reinforced thermoplastic composite material sheet to the bottom of the injection mold.
5. The method for controlling camber of an arc-shaped object according to claim 1, wherein the injection molding material is a long glass fiber reinforced polypropylene material, and the long glass fiber accounts for 20 to 40 wt% of the total weight of the raw materials.
6. The method for controlling camber of an arc-shaped workpiece according to claim 1, wherein the injection molding process comprises:
the melt temperature is 200-220 ℃, the injection speed is 20-40 mm/s, the injection pressure is 30-50 MPa, and the cooling time is 8-12 s.
7. The method for controlling the camber of the cambered surface workpiece according to any one of claims 1 to 6, wherein the total thickness of the cambered surface workpiece is 3mm, and the continuous fiber reinforced thermoplastic composite material sheet accounts for 10-50% of the total thickness of the cambered surface workpiece.
8. The cambered surface workpiece prepared by the method according to any one of claims 1 to 7, wherein the adjustment range of the warping degree is 0.015 to 0.035;
the formula for calculating the warping degree is as follows:
wherein h is the warping amount, and l is the projection length of the evaluation target in the specific direction.
9. Use of the arc-shaped object of claim 8 in the preparation of curved mobile phone shells and curved LED display back covers.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03278921A (en) * | 1990-03-29 | 1991-12-10 | Nec Home Electron Ltd | Injection molding method |
| JPH0760785A (en) * | 1993-08-25 | 1995-03-07 | Mitsubishi Gas Chem Co Inc | Synthetic resin molded product and its manufacture |
| JPH07299840A (en) * | 1994-05-09 | 1995-11-14 | Tokuyama Corp | Production of thin-walled molded product |
| CN107118437A (en) * | 2017-05-18 | 2017-09-01 | 中广核俊尔新材料有限公司 | Lower shrinkage, Long Glass Fiber Reinforced PP Composite of low warpage and its preparation method and application |
| CN107567375A (en) * | 2015-05-08 | 2018-01-09 | 乐金华奥斯有限公司 | Using fibre reinforced composites insert injection molding method and utilize its injection-molded article |
-
2018
- 2018-12-12 CN CN201811517337.4A patent/CN109514795B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03278921A (en) * | 1990-03-29 | 1991-12-10 | Nec Home Electron Ltd | Injection molding method |
| JPH0760785A (en) * | 1993-08-25 | 1995-03-07 | Mitsubishi Gas Chem Co Inc | Synthetic resin molded product and its manufacture |
| JPH07299840A (en) * | 1994-05-09 | 1995-11-14 | Tokuyama Corp | Production of thin-walled molded product |
| CN107567375A (en) * | 2015-05-08 | 2018-01-09 | 乐金华奥斯有限公司 | Using fibre reinforced composites insert injection molding method and utilize its injection-molded article |
| CN107118437A (en) * | 2017-05-18 | 2017-09-01 | 中广核俊尔新材料有限公司 | Lower shrinkage, Long Glass Fiber Reinforced PP Composite of low warpage and its preparation method and application |
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