injection molding plastic deformation method

Eliminates when injection molding plastic deformation method

plastic injection molding parts

plastic injection molding parts

The causes of deformation
1) the shape of products, especially forming shrinkage relationship with product thickness caused by residual stress
2) Due to the forming conditions of residual stress in
3) parting the residual stress produced in
4) and deformation due to insufficient cooling time

2. The associated knowledge
1) the deformation of the products (warping, bending, small wrinkles) as well as the reasons of the crack.The residual internal stress in the products.Molding set conditions should be set in eliminate products of internal stress direction. Namely improve material barrel temperature and mould temperature, the material liquid get better state, the injection pressure is not too high.
2) in order to reduce the residual stress, annealing processing, namely under thermal deformation temperature of 10 degrees, more than 2 hours of heating has the effect of stress relief. But this way because of the high cost of annealing and use is not common.
3) if the mould cooling hole not to cooling homogeneity of products, also can produce residual stress, which means that the cooling hole can’t be too shallow.

Third, solution.
1) instant: sufficient cooling solidification in the mould (chronograph longer cooling time), and improve the temperature of the material, reduce the injection molding pressure.
2) short-term: make mold cooling uniformity.
3) long-term: avoid the thickness of products, where product thickness large set gate (1-1), caused by a straight line easy to warp, make it big R curve, products reversible bending die, increase the number of ejection rod, increase the draft.

Four, differences in material:
1) the crystalline materials (poly (PVC), polypropylene, pom, nylon),injection molding shrinkage rate, and easy to cause bias, non-crystalline material (polystyrene (PVC, ABS) easy to cause residual stress.

Five, the reference items:
1) use orthotics keep at room temperature after molding, to prevent deformation, slightly but not hope too much.
2) in the box forming of thin shape, bending caused by injection molding temperature, this is common thermal expansion

Injection molded products inspection methods

Injection molded products quality inspection methods
In China,Whether produced after injection products meet quality standards, must be tested, a common quality test methods are the following two way.

injection molded plastic in china

injection molded plastic in china

(1) full inspection

It was called full inspection is individually tested for injection products, we have talked about “full” refers to the number of all the plastic parts produced, rather than the entire value of the quality characteristics tested. In determining the test items,Test costs are generally low, the implementation of all product inspection is to have a higher quality requirements.

Such as plastic parts Dimensions test is easier and can be fully tested, and the requirements of the position and some plastic parts crucial, a great impact on the quality, but also the need for full inspection. Not plastic parts for each test must be carried out in full, as it cost too much time-consuming and laborious. Usually occurs when the following conditions using full inspection.

1) found that more unqualified plastic parts, plastic parts or the whole batch are unqualified, the need for follow-up products for full inspection.

High single value

2) injection products, even when a scrap will bring great losses.

3) If the product quality problems, give people life safety or safety hazard when great.

(2) Injection molded plastic sampling inspection

The so-called sampling inspection,, is from a group of randomly selected plastic part of the test conducted. By this test section of plastic parts extracted to make the evaluation of quality of these plastic parts. Compared with the full inspection sampling inspection, it tested a small number of plastic parts, low-cost test, test speed. Sampling inspection and batch size of the number of samples, volume, sample quantity; small quantities, less sampling; as long as the appropriate number of samples, the test results have a high accuracy. Usually by random checks in the following cases.

1) Some of the Injection molded plastic parts that  mechanical and physical properties need to destructive testing, this will bring damage to the plastic parts.

2) more than the mass production of plastic parts, plastic parts produced quantity particularly large, want to save test time and test costs.

3) the production of raw materials in Injection molded plastic parts, there are a lot of raw material is powdered, granular or liquid form, the raw material for these multi-use sampling. Compared with the full inspection sampling inspection, although there are a small number of test and low test cost advantages, but also the following problems: First, when the second installment of the plastic parts, even after sample testing has been considered qualified, can not believe that this batch of plastic parts plant each plastic parts are qualified, which may also exist a very small amount of non-conforming product. Second, the sample tests will inevitably appear judgmental errors, this is the vast majority of qualified products, due to sampling bias, but judged unqualified; or could have been substandard goods, has become qualified. Therefore, in order to determine the probability of error is controlled within a reasonable range, often need to coordinate the use of mathematical statistics methods.

In short, the full inspection and sampling test has its own characteristics, and applications and problems also vary, depending on the circumstances test methods should be chosen to adapt. Mostly due to the injection mold products for mass production, it is more to take sample tests

Precision injection molding process flow

Process flow of Precision injection molding and the common plastic molding difference

The characteristics of precision injection molding is: the size of the injection molded parts with high precision, small tolerance.

precision injection molding

precision injection molding

To achieve the requirements of precision injection conditions must be met:

(1) the mold material is better, rigid, cavity dimension precision and template between positioning accuracy is higher, lower surface roughness.

(2) to adopt precision plastic molding machine.

(3) to adopt precision molding process.

4) to choose suitable for precision injection molding process of the material. Commonly used precision molding materials have several: POM, POM = CF (carbon fiber), PNM = GF (glass fiber), PA \ FRPA66 (enhanced PA), PC, etc.

Precision injection process can ensure the size precision injection molding is the important way to control the shrinkage of injection molded parts, including: thermal contraction, disguised contraction of molded parts, orientation and compressed contraction and elastic recovery.

Common injection molding features are: precision is not high, the size of injection molded parts are typically can be assembled into standard, requirements for the appearance of the injection molded parts is relatively high, if necessary, may use the second processing (oil, for example) to improve the appearance of defects. Ordinary injection molding don’t need to use special precision injection molding machine, also do not need to specially designated materials, general common thermoplastics can be used to production. So ordinary injection molding technology is widely used in modern plastic industry.

Custom injection molding -RIM technology

Custom injection molding in china

Custom injection molding in china

Custom Injection Molding in china for RIM

RIM (reaction injection molding), Chinese commonly known as reaction injection molding , is the late 1970s, first developed in Europe and America . Is different from the traditional injection molding and other molding process is a special process .
The principle is:
The two reaction materials ( polyurethane component and resin mixture ) with a stirrer were placed in a temperature-controlled feed tank , through accurate measurement , at high pressure into the mixing head at the start of injection , the mixing head of the valve to open , the reactants into the mixing chamber under pressure , speed fierce collision , near the atmospheric pressure and then flows into the mold , the exothermic chemical reaction in the mold to form a polyurethane polymer . This process can be simplified to : Store → Measurement → mixing → filling → curing → top out → post-processing.
RIM molding process is particularly suitable for large-scale ( large ) housing member .

PU resin first by Bayer (Bayer) (PU industry founder ) , Professor invented in 1937 , has been 70 years old .
Polyurethane with high strength, abrasion resistance , tear resistance, flex resistance, low temperature resistance and oil resistance, excellent chemical resistance and good blood compatibility , etc. , etc. . Polyurethane foam products made of resin , elastomers, coatings, adhesives , fibers, synthetic leather and other varieties of auxiliary surface material , which is widely used in transportation, electronics, shipbuilding , civil engineering , light industry and textile and other sectors , products and varieties yearly basis, in the material industry occupies important proportion of the current usage of the PU after PP, ABS, PVC. since the late 1930s since the advent of its applications continue to expand , production increased year by year , is developing very rapidly .
RIM process has the advantage ( own summary , we hope to supplement ) :
1 , shorten product development cycles , reduce product development costs
RIM technology to make product design becomes more free, more casual , and its expression on the product to better reflect the designer’s whim , and because of the low viscosity of the reaction material , good fluidity , can be very small in the case of pressure under molding complex parts ; due process of low pressure injection of RIM , low requirements of the mold , the mold is usually done using epoxy or aluminum material , so the cost is only a fraction of the equivalent injection mold , the processing cycle more is the injection mold can not match, the process is particularly suitable for short production and prototype production, can greatly shorten the product development cycle and saving development costs and speed to market share opportunities ;
2, can be molded article of a large area of good quality and the appearance and structure of the

RIM Procedure — Custom injection molding

RIM molding procedure of product size and stability , aesthetically pleasing ( up to Class A surfaces ) , impact resistance and good corrosion resistance ( up to PC / ABS performance ) , for forming a larger area of housing has unparalleled advantages, RIM product thickness range is very large, the same cross-section of molded parts,it  can vary between from 6mm to 28mm , which is the other process can not be compared , it can be integrally molded article thickness variations, in order to improve the quality of products reliability , good performance surface coating , which can meet different process requirements , formulated by adjusting the ratio of raw materials,it  can be made into a hard surface, such as density polyurethane foam structures of different products, to meet the diverse needs of customers ;

the product package inserts simple process
A variety of inserts can be placed in the injection mold before the RIM material , so that the RIM material in the molding process to complete the package insert , steel or aluminum structural frame , electronic sensors , circuit boards, batteries, antennas, magnets, glass, metal parts so you can use RIM technology package, thereby reducing or even eliminating secondary processing sectors , so you can : Protect your important and sensitive components from dust, oil , corrosive chemicals pollution ; make your product You can work in wet or even water ; increased intensity of your product and protect critical components from impact damage from impact or slow ; way so your products can be in more extreme environments.

Easy to mold paint spraying
In the RIM process, prior to injection can be coated with polyurethane paint and gel-coat in the mold . Gel-coat or polyurethane paint in the custom injection molding process and polyurethane materials combined into one, resulting in mold decoration finished parts , greatly reducing the cost and increasing the secondary painting after processing efficiency.
RIM technology because of its superior product performance are widely used in automotive parts and modification parts, engineering machinery covering parts , medical equipment , instrumentation , electronics, machinery and equipment covering parts , industrial parts , chemical components , sports and other fields, as alternative materials such as metal , has incomparable advantages and prospects .

want to know more for custom injection molding in china or custom plastic injection molding in china, visit our website or video at

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Plastic Injection Moulding material —-PEI

Plastic Injection Moulding Product

Plastic Injection Moulding Product

PEI Characteristics  and application of plastic products

PEI: poly-ether imide with excellent mechanical properties, electric insulation properties, high radiation resistant, good resistance to low temperature and wear resistance, which is accessible via microwave.

As PEI both excellent high-temperature mechanical properties and wear resistance, steering valves can be used in the manufacture of water pipe valves and fittings. Due to its high flexibility and strength, heat resistance, is an excellent coating and film-forming material, and they can apply in the electronics industry coatings and thin films.

Main characteristics of continuous operating temperature range (long-term exercise -200–170) glass transition temperatures and thermal denaturation temperature close, up to 330 degrees at low/high temperature melting point has maintained high mechanical strength, high hardness, high outstanding resistance to creep resistance, good toughness of precipitation.

So PEI widely used, mainly used in the electronics industry: Shell connectors, General and micro-relays, circuit boards, coils, soft circuits, secret mirror, high precision optical components, high-temperature insulating Board. Automotive industry: connectors, high power lights and indicator lights, control of vehicle cabin external temperature sensors, control of air and fuel mixture temperature sensor, medical equipment and so on.

This our company’s production of PEI products :

Our company specialized in plastic injection moulding mold design, production and plastic injection molding production.
Materials include not only the commonly used ABS,PP,PC,PA and so on, but also covers special plastics such as PPEK,POM,PPT,PEI and so on.

China Forefront Plastic Injection Moulding Company

If you are looking for a company offering quality and precision manufacturing in the field of plastic injection moulding, Cnmoulding is at your disposal. Being at the forefront of the China market for plastic mouldings, we have developed our experience in the design, creation, innovation, manufacturing and delivery of plastic injection mouldings for a variety of purposes.

Our precision manufactured plastic parts and components are used throughout a host of industry sectors.

Our efforts as a team in the field of initial concept design and in the manufacturing stage are the guarantee of quality injection moulding, and we can offer you quality in the preparation of CAD drawings, research and design, tooling, etc – all your needs for plastic injection moulding. With more than twenty years experience we are able to deal with all volumes, sizes and shapes

panels for cars, mechanical parts, as well as small plastic mouldings such as bottle caps, spools, combs, etc.
In special plastic injection moulding materials if you face any technical problems in product development, Reference at for solution

Gas assistant injection molding china

Gas assistant injection molding china

Gas assistant injection molding technology

Application prospect  gas assistant injection molding china 

Gas-assisted injection molding china technology is widely developed . Since 1990, as a new type of technology, in order to overcome the limitations of traditional injection molding, plastic injection engineering community is of general concern. The use of gas-assisted technology, improve product accuracy, surface quality, to solve large size and wall thickness varied deformation of the product, improve product strength, reduce stress, save plastic materials and greatly simplify mold design, widely used in automotive, household appliances, office supplies , household products and many other fields. It is called the second revolution of the plastic injection molding china industrial. Process simulation of gas assisted injection molding with CAE software, help us to understand the melt filling in injection molding process, the gas-assisted filling, gas protection pressure molding process, to avoid the injection melt insufficient, the gas pressure is too large, cavitation, blowing wear surface depression occur to determine the the melt gate, gas inlet position, the runner dimensions airway size optimization and airway reasonable arrangement, material selection, process conditions set, And through the analysis of the calculation results, determine a set of the best program to ensure the test model success. In recent years We have successfully passed CAE analysis software to assist injection molding of home appliances and automotive parts, and achieved good results.

Gas-assisted  control 2 ways of injection molding china company

Gas assisted injection molding molten resin injection, gas injection, gas holding pressure, gas recovery, part ejection, and several major steps.The molten resin is injected into the mold cavity through the gate , and then inject a constant pressure of an inert gas (usually nitrogen), The resin is produced by the gas pressure, and is filled to the various parts of the mold cavity. So that the plastic part to finally form a hollow section while maintaining the full shape. And from the interior of the resin packing, the gas pressure becomes the holding pressure. Gas emissions occur at the end of the cooling mold. Compared with the conventional injection molding process, a gas-assisted filling stage, and the packing stage holding pressure by air pressure. Holding pressure, can reduce stress and prevent Warp products. Due to the pressure exerted by the gas can effectively pass, The internal surface of the product can be ensured during the cooling process to compensate for the volume shrinkage. And also to avoid the deformation when part ejection. Using gas assisted injection molding, is controlled by the amount of plastic to control the injection cavity articles the hollow ratio and the shape of the airway. Gas-assisted injection molding pressure control method and volume control method are two ways.

2 gas-assisted for china injection molding and china mold maker technology features

  • 2.1 is capable of forming wall thickness difference larger products and complex three-dimensional hollow products

Gas-assisted technology into the airway wall thickness at the hollowed design, thus ensuring the thickness difference the larger molding quality of the products, the use of gas-assisted technology, but also to simplify the structure of the products. Parts due to the large wall thickness difference had to be divided into several parts, molding and then together, forming one gas-assisted technology.

  • 2.2 injection pressure is low

Gas from the gate to the end of the current to form a continuous flow passage, no pressure loss can be realized in low-pressure injection molding, therefore, the residual stress is smaller parts, warpage deformation is small, dimensionally stable.

  • 2.3 to eliminate sink marks, improve the quality of the product surface

In the the gas packing process, the contraction of the plastic secondary penetration by the gas to be compensated, so that the parts will not sag In addition, the use of gas-assisted injection molding, the thicker part of the products can be hollowed out to reduce or even eliminate sink marks.

In addition, to enhance the strength and stiffness, but also save materials, shorten the molding cycle.

Custom injection moulding process

custom injection molding
Custom injection moulding  is a process of shaping plastic by melting it and injecting it into a predesigned mold. The process was first designed in the 1930s and was originally based on metal die casting designs. It offers many advantages to alternative manufacturing methods, including minimal losses from scrap (since scrap pieces can be melted and recycled), and minimal finishing requirements. This process differs from metal die casting in that molten metals can simply be poured; plastic resins must be injected with force.

The china custom injection moulding process uses large injection molding machines, which advance the resins through six major processes to produce everything from computer parts to plastic Halloween spiders. Although this machine is a complex piece of equipment, custom injection moulding will consists of two basic elements: the injection unit and the clamping unit. The process starts with a mold, which is clamped under pressure to accommodate the injection and cooling process. Then, pelletized resins are fed into the machine, followed by the appropriate colorants. The resins then fall into an injection barrel, where they are heated to a melting point, and then injected into the mold through either a screw or ramming device.Then comes the dwelling phase, in which the molten plastics are contained within the mold, and hydraulic or mechanical pressure is applied to make sure all of the cavities within the mold are filled. The plastics are then allowed to cool within the mold, which is then opened by separating the two halves of the mold. In the final step, the plastic part is ejected from the mold with ejecting pins. The completed part may contain extraneous bits called runners, which are trimmed off and recycled. The entire process is cyclical, with cycle times ranging from between ten and 100 seconds, depending on the required cooling time.

Custom injection moulding process requires some complex calculations. Every different type of resin has a shrinkage value that must be factored in, and the injection molds must compensate for it. If this value is not precisely determined, the final product will be incorrectly sized or may contain flaws. Typically, this is compensated for by first filling the mold with resin, holding it under pressure, and then adding more resin to compensate for contraction. Other complications may include burned parts resulting from the melt temperature being set too high, warpage resulting from an uneven surface temperature, or incomplete filling due to a too slow of an injection stroke.

China custom injection moulding can be surprisingly expensive, sometimes upward of $100,000 US Dollars (USD). If the desired part quantity is great enough, however, the mold cost becomes relatively insignificant, and the resulting plastic parts are very reasonably priced. Some molds are made with more than one cavity; these multicavity molds cost more than their single cavity counterparts, but due to increased production efficiency, the cost per part is minimized.

China custom injection moulding method can be used with a variety of plastic resins. The most popular resins for this type of molding include polypropylene (PP), polyethylene (PE), and ABS. Each has its own set of advantages and disadvantages, and they are chosen based on the desired characteristics of the final part.


China mold company designe slider

Overview of China mold company  design slider

china mold maker technology with slider

Injection molder design slider

When the side wall of the plastic molding products with a hole recess boss, plastic injection molding products not directly emerge from the injection molds forming holes, grooves and bosses molded parts must be made of the activities, known as core activities. Completion of the activity type out and reset mechanism called pumping institutions.

(A) China mold company -Classification of core-pulling mechanism

  1. China mold motor core pulling , rely on the action of the inspection injection mold, core-pulling machine with the active core, the core extraction. Core pulling motor with large ejection force, labor intensity, high productivity and easy to operate, widely used in production. Their transmission mechanism can be divided into the following categories: bevel pillar core oblique block core pulling, rack and pinion core pulling.
  2. Manual pumping core mold, relying on human to extract core activities either directly or through pass parts. The disadvantage is that production, labor-intensive, and restricted, it is difficult to get a large core pulling force, the advantage of the mold structure is simple, easy to manufacture, manufacturing mold cycle is short, suitable for the trial and small batch production of plastic products. Characteristics of plastic parts limitations, can not use the motor core pulling, you must manually pumping the core. Manual core pulling their transmission mechanism can be divided into the following categories: a screw mechanism core pulling, rack and pinion core pulling activities insert core, core-pulling.
  3. Hydraulic pumping the core of the core activities, relying on the hydraulic cylinder, and its advantages can be replaced according to the size of the ejection force and the length of the core-pulling distance the core hydraulics, to get a larger ejection force and longer pulling distance , due to the use of high-pressure liquid as the driving force transfer smooth. The disadvantage is that the operation process, but also the whole set of hydraulic core pulling device, therefore, its use is limited in scope, it seldom used.

(B) China mold company — core-pulling distance and the calculation of the ejection force

Core from the plastic molding monk pumped without prejudice to the plastic products prolapse of the monk, that core pulls in the direction of the distance, called core-pulling distance. Pulling distance should be equal to the molding hole depth plus 2-3 mm.

A. Pulling distance calculation as shown in Figure 3-102.

Calculated as follows:

To S = Htgθ (3-26)


S —— pulling distance (MM)

The H —— oblique guide posts required to complete the core pulling stroke (MM)

theta —– oblique angle of inclination of the guide post, and generally 15 · 20 ·

the calculation of the ejection force plastic products in the cooling package tight core, resulting in the force of the package tight, To the core extracted must overcome the resistance of the friction caused by the package tight force, this force is called the ejection force at the beginning of core pulling the moment required release force.

Affect the ejection force of many factors, broadly summarized as follows;

  • Core forming part of the surface area and cross-sectional geometry: a core molding part of the area is large, wrap-tightening force, the mold clamping force; product shape of the cross-sectional area of the core, including the tightening force is small, and also its releasing; core cross-sectional shape is rectangular or curved, package shipping force, the release force is also large.
  • The plastic shrinkage, coefficient of friction and rigidity: The plastic shrinkage, large clamping force on the core package, the release force is also large; good surface lubricity performance plastics, the release force is small; soft plastic, hard plastic required ejection force small.
  • The wall thickness of the plastic products: inclusive area of the same size plastic products, thin-walled plastic products shrinkage, the ejection force is also small shrinkage; captured wall plastic products, mold release force.
  • Plastic products the same side at the same time the number of core-pulling: When plastic products have more than two hole slot on the same side of the pumping mechanism pulls into plastic products have more than two of the same side of the hole slot, the use of sampling World institutions at the same time pulls, due to the contraction of plastic products Pitch, the ejection force.
  • The active core molding surface roughness: the active core molding surface of the contact surface of the plastic article Pulling relative friction against the release force, have a great impact, therefore, the injection molder surface should be smaller roughness (usually Rα0.4um), processing of grain to the requirements and pulls in the same direction.
  • China mold company process; injection pressure, dwell time, cooling time for the ejection force. When the injection size, dwell time is short, the ejection force. Long cooling time, condensing contraction of plastic products is substantially complete, the package tight force, ejection force.

Under the influence of various factors, the ejection force computing power formula is as follows:

F = Lhp (u * cosα-sinα)

Wherein F —- ejection force (N)

The L — core activities are cross-sectional shape of the plastic products package tight perimeter (MM)

H — forming part of the depth (MM)

P — unit area packet clamping force, and generally … 12Pa;

u — friction slope (°)

Plastic injection molding product with chrome plated

Chrome-plated plastic, high-quality surface finish can be comparable with the metal surface to its light weight, ease of processing and use of broad characteristics, prompting the chrome-plated plastic is widely used in the automotive industry, as well as a variety of industrial production and daily life, our injection molding plastics technology can deal difference kind of chrome plated plastic molding parts with enough experience .


Plastic Injection Molding, Plastic Molded Parts

We combine plastic injection molding design, engineering and manufacturing in shanghai with engineering and tool making operations , Cnmoulding capability that cuts lead times and allows for competitive baseline pricing. we added plastic injection molding design and engineering associates to implement “follow the sun engineering.” Our engineering counterparts in China start work on projects as we’re winding down for the day here in shanghai. The workflow doesn’t stop, because each group turns its progress over to the other at the end of the day.
Our plastic injection molding engineers and toolmakers are trained and certified on our UG-NX system, so they’re an integral part of our concurrent engineering capabilities and can interface with customer ERP systems.

To discuss your plastic injection molding and plastics tooling manufacturing requirements—and how our global resources, process engineering and emphasis on continuous improvement can support them—contact kennyhan, at 0086-13061707408 or email us.



China plastic injection molders produce transparent parts

China plastic injection molders experience of transparent part

Today , let us talk about plastic injection molders transparent parts, with our 20 years experince, following article that hope can give you more help

you can visit youtube for china plastic injection molders

transparent product by china plastic injection molders

The plastic has the advantages of light weight, good toughness, easy to injection molding, low cost, in modern industrial and consumer products, more and more use of plastic instead of glass, especially used in optical instruments and packaging industry developing rapidly. However, due to the transparency and better wear resistance higher impact firmware is better, and therefore the composition of the china plastic injection molders whole process, equipment, molds, have to do a lot of work, to ensure that these used in place of glass plastic (hereinafter referred to as transparent plastic), the surface quality is good, so as to achieve the requirements of use.
Generally on the market use a transparent plastic or polymethyl methacrylate (PMMA, i.e., commonly known as acrylic or perspex,), polycarbonate (PC), polyethylene terephthalate (PET), transparent nylon, acrylonitrile-styrene copolymer (AS), polysulfone (PSF), wherein contact is PMMA, PC and PET three plastic, the following three kinds of plastic, for example, discussion of a transparent plastic material characteristics and the china plastic injection molder process.

The performance of a transparent plastic

Transparent plastic must first have a high transparency, to have a certain strength and abrasion resistance, high impact, heat resistance, better chemical resistance are superior absorb water small, the only way able to meet the transparency requirements over the long term, are listed in Table 1 below, compare the performance of PMMA, PC, and PET.
Table 1: The transparent plastic Performance Comparison
Performance Density
(G/am2) tensile strength
(MPa) Notched Impact
(J/m2) transparency
(%) Distortion temperature
(° C) allows moisture shrinkage abrasion chemical resistance
PMMA 1.18 75 1200 92 95 0.04 0.5 difference benign
PC 1.20 66 1900 90 137 0.02 0.6 in benign
PET 1.37 165 1030 86 120 0.03 2 Good Excellent

Note: (1) because of the variety, this is only averaging, actual different varieties of data vary.
(2) PET data (mechanical) for the data after stretching.
From the data in Table 1 shows that the PC is the ideal choice, but the master of its expensive price of raw materials and injection molding process is difficult, so is still used PMMA-based products, (general requirements), and RET to go through the stretch to get good mechanical properties, multi-use in packaging, containers.

Second,china plastic injection molders build transparent process should be noted the common problem.
Higher transmittance, transparent plastic inevitable requirement plastic products strict quality surface, can not have any markings, porosity, white, fog halo, black spots, discoloration, poor gloss and other defects, thus the entire plastic injection molder  process of raw materials, equipment, molds, and even the design of the product, should pay great attention to strict and even special demands. Both full Second, because of the transparent plastic, mostly high melting point, poor mobility, so as to ensure the surface quality of the product, often at higher temperature, injection pressure, injection speed and other parameters for minor adjustments, the plastic injection molders will produce internal stress caused deformation and cracking.
Here in the preparation of raw materials, equipment and tooling requirements, injection molding process and raw materials processing aspects, should pay attention to talk about the matter.

(A) the preparation and drying of raw plastics containing any point impurities may affect the transparency of the product, and storage, transportation, feeding process, you must pay attention to sealing to ensure a clean raw materials. Raw materials containing water, heating cause material deterioration, so be sure to dry injection, feeding must use the drying hopper. Also note that the drying process, the input air should preferably by filtration, dehumidified, in order to ensure that no contamination of raw materials. The drying process is as shown in Table 2.
Table 2: The transparent plastic material drying process:
The the process drying temperature (℃) Drying time (h) the material layer thickness (mm) Remarks
PMMA 70 ~ 80 2 ~ 4 30 ~ 40 hot air circulation drying
PC 120 ~ 130 greater than 6 less than 30 hot air circulation drying
PET 140 ~ 180 3 ~ 4 by continuous drying feeding device preferably

(B) of the barrel, screw and its attachments clean
To prevent the contamination of raw materials and the depression in the screw and accessories there are old materials or impurities, particularly thermal stability of the resin is present before use, after the shutdown applications screw cleaning agent to clean, it may not stick with impurities cleaning screw screw cleaning agent, available PE, PS and other resins. Temporary shutdown to prevent raw stay a long time at a high temperature, causing the lower solution should reduce the temperature of dryer and barrel, such as PC, PMMA cylinder temperature should be reduced to 160 ℃. For PC (hopper temperature should be reduced to less than 100 ℃)

(C) should pay attention to the problem of mold design (including product design)
In order to prevent back flow of poor or uneven cooling caused by bad plastic molding, surface defects and deterioration, generally in the design of the mold, you should be aware of the following points.
a) wall thickness should be uniform, and the the stripping slope be large enough;
b) the transition section should gradually. Smooth transition and prevent any sharp corners. Sharp edges, especially the PC product must not have a gap;
c) gate. Flow channel as much as possible large, chunky, and the location of the gate should be set according to the contraction of the condensation process, necessary, add cold slug well;
d) the mold surface should be smooth, low roughness (preferably less than 0.8);
e) vent. The slots must be sufficient, and when the exhaust air and the gas in the melt;
f) In addition to PET, the wall thickness of not too thin, generally not less than lmm.

(D)china plastic injection molders process should pay attention to the issues (including the requirements of the plastic injection molders machine)
In order to reduce the internal stress and surface quality defects, in the injection molding process should pay attention to the following aspects of the problem.
a) should use special screws, with separate thermostat nozzle injection molding machine;
b) injection temperature of the plastic resin is not decomposed under the premise, suitably higher injection humidity;
c) injection pressure: generally higher, in order to overcome the defects of melt viscosity, but the pressure is too high internal stresses stripping difficulties caused and deformation;
d) the injection speed: the meet filling the case, generally should be low, much better to use slow – fast – slow multi-stage injection;
e) dwell time and the molding cycle: meet the product to fill the mold does not produce depression bubble; should be as short as possible, to minimize the melt in the barrel residence time;
f) screw speed and back pressure: under the premise that meet the quality of plastics should be as low as possible, to prevent the generation of the solution down the possible;
g) mold temperature: cooling products, good or bad, on the quality of a great impact, mold temperature must accurately control its process may mold temperature should be high.

(E) other aspects of the problem
General injection should guard against the deterioration of the surface quality, as little as possible with a release agent; nor greater than 20% when using regrind.
In addition to PET, the products should be post-processed to eliminate the internal stress, PMMA 70-80T hot air circulation drying for 4 hours; PC should be clean air, glycerol. Such as liquid paraffin is heated to 110-135 ℃, time products, the highest need more than 10 hours. While the PET must go through the step of biaxial stretching, in order to obtain good mechanical properties.

3, transparent plastic injection molders in china process
(A) transparent plastic process characteristics: In addition to the above common problem, clear plastic and have some process characteristics are described as follows:
1, PMMA process characteristics

PMMA viscosity, mobility somewhat less, and therefore must be high material temperature, the job of the high injection pressure injection molding, injection temperature is greater than the injection pressure, injection pressure increases, will help to improve the shrinkage of the product. The wider range of injection temperature and a melting temperature of 160 ° C, while the decomposition temperature of 270 ° C, therefore the wide adjustment range of the material temperature, the process is better. Therefore, to improve the liquidity, proceed from the injection temperature. Poor impact resistance, abrasion resistance and bad, easy to draw flowers, easy to rattle, it should raise the mold temperature, improve the condensation process, to overcome these deficiencies.
2, PC process characteristics
PC viscosity, high temperature of the melt material, poor mobility, back to this must be the injection of the higher temperature (270-320T), is relatively narrow adjustment range of the material temperature, process is better of PMMA. The injection pressure on liquidity, but the viscosity still larger injection pressure accordingly in order to prevent the internal stress generated, dwell time should be as short as possible. Shrinkage, dimensional stability, but the stress within the product, easy to crack, so it is appropriate to raise the temperature rather than the pressure to improve liquidity and increasing the mold temperature, to improve mold structure and post-processing to reduce the possibility of cracking. When the injection speed is low, the gate at prone corrugated and other defects alone control the temperature of the radiation Tsui, mold temperature is higher, the runner, gate resistance is smaller.
3 the PET A process characteristics
PET molding temperature and material temperature adjustment range is narrow (260-300 ° C), but after melting, good liquidity, so the process is poor, and often in the nozzle to increase the anti-extension of flow control devices. Mechanical strength and performance are not high, after injection must be through the stretching step and modified in order to improve performance. Mold temperature is accurately controlled, is to prevent warping. The deformation of the important factors, so we recommend using hot runner mold. High mold temperature, otherwise it will cause the surface luster poor and stripping difficulties.

4, transparent plastic defects
Due to space constraints, only discuss defects affecting product transparency, and other defects, please refer to the product manual or other information. Its defects about the following:

Transparent product defects and overcome:

(A) crazes: filling and condensation processes, internal stress anisotropy affects the stress generated by the vertical direction, so that the resin flow orientation, refractive index and non-current orientation of different raw flash silk pattern when After its expansion, may make the product cracks. In addition to the attention on the injection molding process and the mold (see Table, the best products for the annealing treatment. Pc material can be heated to more than 160 ℃ maintained for 3 to 5 minutes, and then can be cooled naturally.

(B) the bubble: the main resin, water vapor and other gases row does not go out, mold condensation process or inadequate due to filling the condensing surface excessive condensation and the formation of a “vacuum bubble”. Them overcome the method are shown in Table.

(C) poor surface gloss: Master injection mold large roughness, on the other hand condensate prematurely, so that the resin can not copying the state of the surface of the mold, all the tiny irregularities of its surface cows, leaving the products lose luster. Then overcome the method are shown in Table.

(D) shock pattern: from the sprue intensive corrugated reason for the melt viscosity is too large, front-end material has been condensed in the cavity, and later material and break through this condensation surface, leaving the surface of the shock pattern . Then overcome the method are shown in Table.

(E) whitened. The fog Halo: mainly due to fall into the raw material or feedstock moisture content is too large due to dust in the air. Then overcome the method are shown in Table.

(Vi) white smoke. Black spots: mainly due to decomposition or deterioration of resin plastic drum machine, leaving the barrel due to local overheating