Top ten tips for designing the hottest plastic pro

2022-08-24
  • Detail

Ten tips for plastic product design

in the design process of plastic products, there are some basic considerations that cannot be ignored. Raw material manufacturers can be said to be an important promoter of plastic product design. This paper introduces the basic skills and principles of plastic product design from the aspects of raw material selection, processing process selection, strength consideration, mold design, etc

design checklist

the goal of new product development or product improvement is to make the product have excellent performance and obtain low production cost at the same time. The design tasks mainly include the selection of raw materials, processing methods, strength calculation and mold design

only when these factors are considered comprehensively and followed up systematically can we produce high-quality and commercial molds. It must be emphasized that the practicality and cost efficiency of plastics are not inevitable. Designers must pay great attention to the selection of raw materials and the correct solution of the processing process

raw material comparison

compared with other traditional raw materials, special attention should be paid to the design of plastic raw material parts

the properties of plastics can vary in a wide range. By adding fillers, reinforcing materials and modifiers, their properties will be greatly transformed

sometimes under the same operating conditions, plastic will show completely different performance from metal. Therefore, the cost-effective functional design of cast metal will easily fail if it is used in plastic in a hurry

when the temperature of the material is closer to its melting point, the temperature and time will directly affect the deformation performance of the raw material

the properties of plastics are not only the properties of pure raw materials. If the raw materials are processed within the inapplicable range, the best design will fail. Similarly, products cannot be processed to solve design weaknesses. Therefore, the quality of plastic parts can be guaranteed only by optimizing the process taking into account all factors

cost saving design

designers bear most of the ultimate cost of plastic parts. His decision predetermines the cost of production, mold making and assembly. Later revision and optimization are usually expensive and infeasible

giving full play to the advantages of the characteristics of plastic raw materials can save costs in many aspects. Multi function integrated design, the use of low-cost assembly technology (such as buckle, welding device, fixed device, double material injection molding technology, etc.), the use of lubrication characteristics that have become a best seller in Mongolia, and the elimination of surface treatment procedures. Paying attention to wall thickness, mold, tolerance, raw materials, etc. can further save costs

gate position

the designer must not only carry out the design and calculation of plastic products, but also pay special attention to the gate design of the mold. They must choose the right gate system and the number and location of pouring points. Different types and positions of gates will have a great impact on the quality of products

the choice of gate location will determine the following properties of plastic products:

filling behavior

final dimension (tolerance) of products

shrinkage behavior, warpage

mechanical property level

surface quality (appearance)

if the designer chooses the wrong gate, it is almost impossible to correct the consequences from optimizing processing parameters during molding processing

basic design principle:

do not place the gate in the high pressure area

try to avoid or reduce the fusion line

try to keep the fusion line away from the high pressure area

for reinforced plastics, the position of gate determines the warpage performance of parts

provide sufficient exhaust ports to avoid air accumulation

basic assembly technology

some simple assembly technologies recognized by all designers, such as snap assembly, press assembly and thread assembly, can greatly save production costs by simply and quickly assembling components

the biggest advantage of buckle assembly is that there is no need to add additional assembly parts. In the buckle design, the designer must ensure the geometric dimensions of the accessories to avoid the loosening of assembly parts caused by stress relaxation

pressure part assembly can enable plastic components to be assembled with high strength at the lowest cost

thread assembly consists of the application of separate screw, combined screw or integral screw insert. In order to avoid the generation of unqualified components, ensuring the correct bushing size is the key. Screw manufacturers can make many suggestions in this regard

material selection

generally speaking, there are no bad materials, only the wrong materials are used in specific fields

thermoplastic is the most commonly used in injection molding. It can also be divided into amorphous plastics and semi crystalline plastics. Generally speaking, semi crystalline thermoplastics are mainly used for parts with high mechanical strength, while amorphous thermoplastics are often used for shells because they are not easy to bend

thermoplastics include unreinforced, glass fiber reinforced, mineral and glass filled products. Glass fiber is mainly used to increase strength, firmness and application temperature; Mineral and glass fiber have a lower strengthening effect, which is mainly used to reduce warpage

a series of reinforcing materials, fillers and modifiers are added to some thermoplastics to change their properties

some thermoplastic materials, especially PA6 and PA66, have strong moisture absorption. This may have a great impact on their mechanical properties and dimensional stability. Special attention should be paid to this performance when carrying out

reinforcing rib

generally speaking, the rigidity of components can be enhanced by the following methods:

increase the wall thickness

increase the elastic modulus (such as increasing the content of reinforcing fiber)

reinforcing ribs are considered in the design

if the material used in the design cannot meet the required rigidity, the material with a larger elastic modulus should be selected. Large moment of inertia can be easily achieved by setting thick and high reinforcing ribs. However, for thermoplastic engineering plastics, this method often produces problems such as surface dents, internal voids and warps. Moreover, if the height of the reinforcing rib is too high, the structure may expand under load. In view of this consideration, the size of the reinforcing rib must be maintained within a reasonable proportion

in order to ensure that the products with reinforcing ribs and good ventilation of the electric cabinet are easy to eject, an appropriate demoulding taper must be designed

the size of components with very high surface requirements, such as automobile wheel covers, is very important. The correct design of reinforcing rib can reduce the possibility of forming surface dents of components, so as to improve the quality of components

in plastic design, the cross structure is the best, because it can cope with many different load arrangement changes. A properly designed cross structure that can withstand the expected stress can ensure the uniform distribution of stress on the whole product

tolerance

injection molded products cannot have the same tolerance as machined products. Although most people are aware of this, they often specify inaccessible tolerances or make cost-effective production impossible

injection molding is generally divided into three quality levels, namely, general-purpose injection molding, the cooperation between China and Asian and European countries is in the best period in history, technical injection molding and high-precision injection molding. Din16901 standard points out that they are divided according to the tolerance and size of injection molded products within the allowable range

general purpose injection molding requires a low level of quality control, which is characterized by low return rate and fast production cycle

technology injection molding will be more expensive, because it has higher requirements for mold and production process, requires frequent quality inspection, and thus increases the return rate

the third kind, high-precision injection molding, requires accurate molds, the best production conditions and 100% continuous production monitoring. This will affect the production cycle and increase the unit production cost and quality control cost

designers play a key role in determining the cost of injection mold products. They must determine commercially feasible tolerances. Although the selected tolerances need not be as strict as possible, they must be sufficiently strict

in order not to set too strict tolerance range for plastic parts, we must pay attention to some factors that affect the dimensional accuracy of injection molded products

The tolerance of mold manufacturing must be strictly observed. Designers should keep in mind that the importance of demoulding slope is that it can make demoulding easy and prevent warping

a problem related to tolerance is that the shape is made of different materials or different wall thicknesses. The shrinkage value after die is related to direction and thickness. This property of glass reinforcement is more obvious. The orientation of glass fibers can produce significant shrinkage in the horizontal and vertical directions, resulting in inaccurate size

the geometry of plastic products also has an impact on shrinkage, which in turn affects tolerances. If the tolerance requirements of complex molding are very strict, it is necessary to obtain accurate data about the shrinkage value and warpage behavior of the mold prototype

when using semi crystalline plastics, post mold shrinkage must be considered

there is no need to carry out quality control immediately after demoulding. Din16901 standard points out that quality control can be carried out only after storage for 16h under standard climatic conditions (23 ℃, 50% relative humidity) or after appropriate pretreatment

wall thickness

in the design of engineering plastic parts, experience shows that there are some design points that must be considered, one of which is the design of wall thickness

changing the wall thickness of a part will have a significant impact on the following main properties:

part weight

the flow length that can be obtained in molding

production cycle of parts

rigidity of molded parts

tolerance

part quality, such as surface finish, warpage and voids

at the initial stage of design, it is necessary to consider whether the materials used can obtain the required wall thickness. The ratio of process flow to wall thickness has a great influence on the filling of mold cavity in injection molding process. If in the injection molding process, in order to obtain a long process and thin wall thickness, it is very necessary that the polymer should have a considerable low melting viscosity (easy to flow and melt)

if the wall thickness is increased without considering the consequences, the material and production costs will increase, but the rigidity will not increase

increasing the wall thickness not only determines the mechanical properties, but also determines the quality of finished products. In the design of plastic parts, it is very important to make the wall thickness as uniform as possible. The different wall thickness of the same part can cause different shrinkage of the part. According to the different rigidity of the part, it will lead to serious warpage and dimensional accuracy problems. In order to obtain uniform wall thickness, the thick wall part of the molded product should be set with a mold center. This prevents the formation of voids and reduces internal pressure, thereby minimizing distortion. The voids and micropores formed in the parts will narrow the cross section, increase the internal stress, and sometimes there is a notch effect, which greatly reduces its mechanical properties

welding technology

the most commonly used welding methods for plastic engineering parts are: high temperature tool welding, rotary welding, vibration welding, ultrasonic welding, and other methods are: high frequency welding, induction welding, hot gas welding, laser welding, etc

in order to obtain high-quality and repeatable welding quality, it is necessary to select a suitable welding method to optimize the welding parameters and ensure that the parts to be welded are designed correctly and match the selected welding method

before deciding to choose a welding method, compare with the design

Copyright © 2011 JIN SHI