PC Injection Molding

PC Injection Molding

Polycarbonate (PC) as the only five engineering transparent plastic products, production at home and abroad is growing rapidly, in 2000 the global production capacity is about 1.85 million tons, 2001 tons, 2002 tons, 2003 tons, is expected in 2004 will increase to 2.9 million tons, 2005 tons, with an average annual growth rate of about 12%.

PC plastic molding
Our country PC capacity for many years has been small, only three companies to maintain production, capacity of less than 5000 tons/a, the annual output 2000 tons, with China’s PC demand rapid growth, at present our country a PC joint venture cooperation construction unit upsurge, bayer company and Shanghai huayi group chlor-alkali chemical company in Shanghai chemical industry park construction 200000 tons/aPC device, is expected to a period of 50000 t/a device will be in production by the end of 2004, finished at the beginning of 2006, the second phase project of 100000 tons/a, in view of our country PC huge market demand, will eventually make the PC unit capacity to 200000 t/a, plant production is mainly in optical products, used in the production of CD, DVD, car lighting system, etc.

Japanese emperor people chemical is zhejiang jiaxing construction 50000 tons/aPC device, is expected to put into production in April 2005, the main raw material bisphenol A by mitsui chemical supplies, chlorine and caustic soda were from A local enterprise, carbon monoxide their production, products for general level products, mainly supply electrical components, auto parts production, plan in 2006 will add A 50000 t/A production device; At the same time the company in Shanghai gaoqiao free trade zone construction owned 18000 tons/aPC, ABS injection molding complex device, at present has gone into operation and plan in the first half of 2005 new 20000 tons/a second line. Japan mitsubishi gas in sichuan chemical company intends to build 100000 tons/aPC device, is expected to put into production in 2007.

Plastic Molds for PC palstic parts
In addition, the domestic and some enterprises and foreign cooperation or use of the technical construction scale PC production device, so the next few years China will enter a new stage of PC production in 2006, domestic production capacity will be increased to around 250000 tons/a, 2010 will reach 50-600000 tons/a. According to China’s PC huge potential market, foreign famous PC company not only in our cooperation construction production device, but also in China, Taiwan, South Korea, Singapore, Thailand and other countries and regions construction scale device, relatively more device investment is aiming at the market.

PC production technology progress main development trend is to develop the phosgene synthesis process to replace at present the main synthesis process interfacial polycondensation phosgene method, GE plastics and bayer company are developing their non phosgene method production technology and to the industrialized production, in addition xu/chi mei, mitsubishi chemical/mitsubishi gas, emperor people company, LG chemical company are developed non phosgene technology, are building or planning to build the phosgene method PC device, the phosgene method route will become the future PC of the main production line.

Market analysis for PC injection moulding 

In the 1990 s in China since the end of the PC demand from originally of textile industry with sand tube steering electronics/electrical, CD, construction, automobile industry and other fields, demand has increased dramatically. In 1999 the domestic consumption of about 140000 tons, and in 2003 increased consumption of 380000 tons, with an average annual growth of about 28%, far higher than the average growth of the national economy and other general engineering plastics growth. Due to the domestic production minimum, our country use PC mainly imported from abroad. In 1999-2003 in China PC net imports respectively for 138000 tons, 235000 tons, 212000 tons, 342000 tons, 381000 tons, and it does not include a number of smuggled in PC, also did not consider import finished product and leftover material, so the actual domestic import and consumption data than the customs statistics to be much higher, the domestic and foreign PC world agree that our country market potential is tremendous its relative stability.

Injection mold China

In 1999-2003 in China PC market fast growth was mainly to electrical and electronic products, hollow sunshine board, CD and DVD and non one-time drinking water and food container demand, at present, China’s PC consumption structure roughly as follows: electronic electrical and computer accessories accounted for about 42%; Hollow sunshine plate accounted for about 26.3%; CD and DVD about 13.1%; Drinking water and food containers accounted for about 10.5%; Composite materials and automobile industries accounted for about 9.1%. In the next few years our country original main consumption field will continue to maintain high growth momentum, computer and household appliances sustained growth, this in the future to a PC at an average rate of about 10% – 12%; Railway, highway, airport and urban construction, the hollow sunshine plate demand remains strong, and in recent years the domestic Yangtze river and the pearl river delta area using PC processing to produce the plank enterprise economic benefits than many polymer resin production enterprise good many, is expected to hollow sunshine board for future PC demand with an average annual growth rate of 12-15%; At present our country become the world’s second big CD consumer, before all of it relies on import CD grade PC production, with bayer Shanghai CD grade PC and put into production, the next few years for the PC CD demand will still remain more than 20% high speed growth; Experts predict the future domestic PC the fastest growth in demand will be in PC as the backing material polyolefin-g-mah/kind of composite material, the automobile industry will be the main pulling power. The expected future years our country PC demand with an average annual growth rate will be 15% – 20% between, 2006 domestic PC market demand will reach 55-650000 tons/a. Domestic production is still unable to meet the domestic market demand, will from neighboring countries such as Japan, South Korea, Thailand import a large number of products in the domestic market supply.

PC/ABS injection molding  mainly used in automobile industry

Application progress

At present the global PC application has to high functionalization, specialty direction development, in view of our country PC production capacity and market demand are presents the fast development situation, especially, the domestic many sets of large-scale device of construction, with the rapid development of automobile industry pulling, the next few years PC industry in our country has entered a new stage of development, the most key is to accelerate the PC application research.

First of all domestic production enterprises should make full use of domestic production capacity increase and in plastic modified and plastic alloy accumulated experience, to speed up the PC alloy composite material development, production and application, of which the most important is:

PC/ABS alloy, PC and ABS blend can comprehensive PC and ABS fine performance, on the one hand, can improve the ABS heat resistance, impact resistance and tensile strength, on the other hand, it can reduce the cost of PC and melt viscosity, improve the processing performance and reduce products internal stress and impact strength of the sensitivity of the product thickness. At present PC/ABS alloy development is rapid, the global output of about 850000 tons/a or so, China’s demand is about 200000 tons/a or so. The world each big companies to develop out of PC/ABS alloy new varieties, such as flame retardant, glass fiber reinforced, electroplating, such as ultraviolet radiation resistant varieties, mainly for the automobile industry, computer, photocopiers and to electrical and electronic components, etc. The domestic research and production company has Shanghai jie things jie company, Chinese academy of sciences, lanzhou university (htma changchun application etc.

PBT injection molding
PC/PBT (polybutylene terephthalate) alloy, PBT and PC blend system alloy material can improve the PC liquidity and improve the processing performance and resistance to chemical resistance. Japanese researchers use PC and PBT ester exchange in the presence of catalyst, system PC/PBT blend, comprehensive performance is good, and has a good transparency; With the PC refractive index similar glass fiber reinforced PC/PBT, not only system comprehensive excellent performance, but also has the very good transparency, and can do glass instead of material. At present foreign PC/PBT alloy products are mainly used for automobile bumper, packaging film materials, auto base and seat, etc. The domestic research has just started.

In addition PC/PS (polystyrene) alloy, PC/PET (polyethylene terephthalate) alloy, liquid crystal polyester modified PC, PET/PCL (by ethylene glycol, low molecular weight polycaprolactone and terephthalic acid copolymerization a multi-block copolyester) and PC blend modification, poly (1, 4 – cyclohexane two formic acid – 1, 4 – cyclohexane two methanol) ester modified PC is worth attention and research and development.

Secondly it should keep up with the international development trend, together with PC alloy material research advances, PC application range is expanding constantly, to speed up the PC consumption field development.

Wide wave transmission of optical devices,

PC sheet especially suitable for making lens, in the PC molecular chain introducing silica group, can improve the hardness and scratch resistance. PC as high refractive index plastic, used to make resistance to high temperature optical fiber core material, if in the PC molecular chain of C – H chain for C – F chain replaced, can reduce the absorption of visible light, can effectively reduce the transmission way signal loss. Another PC good pervious to light quality, in a transparent window material, high-rise building curtain wall, airport and sports venues transparent building materials applied very common and has potential, the future is focused on the improvement of the surface hardness and antistatic property. |

Flame retardant environmental communication appliances, we should focus on developing of flame retardant PC used for communication electrical field, so no pollution flame retardant PC material become development key, bromide flame retardants due to the toxicity in reducing use and environmental protection halogen free flame retardant agent can significantly reduce the PC thermal deformation temperature and impact strength, therefore more suitable is organic silicon flame retardants. In addition with communication electrical light miniaturization of PC material put forward higher requirements, the PC/ABS alloy is especially appropriate in communication appliances and aerospace industry application.

Surface metallization of auto parts, PC surface metallization has good metal gloss and high strength, which are widely used in all kinds of auto parts, but plating process will reduce its impact toughness, and therefore the elastomer and PC for common mixing modification, contains elastomer distracted induced cracking stress, although the plating will not reduce the impact toughness, and therefore plating stage PC resin are development prospects. Another surface metallization PC can also as electromagnetic wave shielding material, the application of the computer.

Low residual harmful food container, industrial synthetic PC is bisphenol A type, because when synthetic trace unreacted monomer bisphenol A residue in the resin, in as drinking water and food containers, easy to be dissolve out so as to influence people in healthy body, therefore to develop health level PC resin, used as A water bucket and other food container production and use, as A water bucket and other food packaging materials and containers PC in the domestic application prospect is very good.

Anti cracking embrittlement of medical devices, PC has many excellent properties, at present has been used medical instrument, because of its resistance to chemical character is poorer, in the presence of chemical easy cause internal stress cracking, such as PC in artificial dialyser, artificial lung medical equipment application to solve high temperature disinfection lead to crack aging phenomenon, if overcome these disadvantages, PC in medical instrument can be applied in rapid expansion.

Food packaging materials and containers PC in the domestic application has a good prospect

Concluding remarks

At present our country PC industrial production, consumption and application into a rapid deplastic injection mouldvelopment in the new period, in view of the present situation in our country in addition to speed up the PC application study outABside, but also speed up the localization technology industrialization process, after many years of hard work our country – ester exchange method PC production technology mature, become very promising green production process, the domestic should collaborative promote industrialization process.

In addition the domestic production enterprises should avoid blind construction of introduction and PC device, can avoid competition hot, speeds up the PC materials such as bisphenol A and other production, future domestic bisphenol A great gap, from another point of promoting China’s PC industry development, but also effective to avoid market risks. At present the domestic technology level compared with foreign there is still a large gap, the existing small and medium-sized production device should speed up the technology introduction, digestion, absorption edge production side, and constantly bigger and stronger, and at the same time supporting production some PC composite material, set up the sales network, forming characteristic PC processing application enterprise.

Injection Mold Design

Plastic injection molding for producing plastic products

Plastic injection molding is the principal process for producing plastic products or parts of products. Plastic is acknowledged to be a very flexible and cost-effective material that is used in many applications. Although the tooling can be expensive, the cost, per part is very low. Intricate geometries are limited only to the abiltiy to create the injection mold. Things you use everyday, such as the case that houses your monitor, the keyboard on which you type or the mouse on your desk were produced with plastic injection molding.

Plastic injection molding involves the transformation of a plastic solid, usually in the form of granules or pellets, and heating the plastic resin to a specific temperature until it melts. The melt is then forced into a mold made up of two or more dies, where it is forced to “cool”, resulting in producing the desired shape. A specific amount of time passes, usually a few seconds, and the mold is then opened and the part is released. This cycle then repeats continuously until the desired quantity is reached.

Considerations of  Injection Mold Design

The design of the part, and therefore the mold, needs to include draft features (angled surfaces) to make possible the removal of the part from the mold. Typical draft angles are about 1 to 2 degrees for part surfaces which do not exceed five inches. Dimensional tolerance specification will dictate the final cost of the part as well as its ability to be manufactured. If there is a small section of the part which needs higher tolerances, such as the location of a critical feature used for alignment,do not specify a tight tolerance, as an alternative, plan and design for post molding processes such as machining to achieve the desired results.

Radii and Corners

It is very important that uniform wall thickness be maintained at the corners. The internal and external radius need to share the same center point. External radii = internal radii + wall thickness. The minimum radii should not be less than ¼ of the minimum wall thickness. Design for radii to be ½ to ¾ of the nominal wall thickness. When a large amount of stress is going to be present, it is very important to design in larger radius as this will distribute the stress much more evenly.

Wall Thickness

The production of thin wall items such as a clamshell for retail packaging are possible with today’s technology. Products with thick walls are also easily produced. However, parts which require uneven wall thickness present a challenge to the plastic molder manufacturer. Creating a part with a uniform wall thickness and cross section will abridge manufacturing and reduce costs. One issue to be aware of is sinking. Wherever an intersection or “tee” occurs, there will be some degree of sinking. This occurs because thicker walls cool at a slower rate and therefore create this problem.


Ribbing should be ½ to two thirds of the nominal wall thickness and less than 3 times the thickness in height.A taper of 1° is usual. Note: as mentioned above, excess thickness can result in shrinkage.An excess in rib height combined with a taper will produce thin areas requiring extra fill time at the mold.

Weld (Part) lines

The location of weld lines needs to be considered by designer before a injection mold is created. Weld lines are formed by the joining of the flow fronts of the plastic during molding. One issue of concern is the that the weld line area is more susceptible to cracks and stress failure.


  • Diameter = (Outside Diameter) \ (Inside Diameter) = 2 to 3
  • Thickness = 1/2 to 2/3 nominal wall thickness
  • Gusset Height = 2/3 Height
  • Height = Fastener minimum requirements
  • Taper = 1 deg. all around
  • Diameter Ratio should be minimum ratio of 2., this will reduce risk of failure.


Another factor in the design will be the clamping pressure required to produce the part while the plastic is being injected. Smaller cavities can result in high pressures being required to force the plastic or rubber material to fully fill the mold cavity. This will, in turn, determine the thickness of the mold material, usually steel) as well as the type of machine in which can be used.


Many factors must be taken into account when designing a mold for the creation of plastic injection molded parts. Factors such as draft angles, wall thickness, ribbing (not the kidding kind), bosses and weld lines and clamping pressure all come into play when designing a mold that will be used in a plastic injection mold machine. Each facet is important in and of itself, but as a whole, each one affects the others. Therefore the design of a mold for plastic molding can be quite involved. When done correctly, the result will be a mold which will yield thousands, hundreds of thousands, or even millions of parts over it’s lifetime.

Injection Molding Process

Process of Injection Molding

The process of injection molding process is best explained as heating up a type of plastic and under a forced type or pressure is poured into a predesigned mold, after the hot liquid is poured into the mold the mold is clamped shut to prevent any air from getting in. After the initial work is done, the mold hardens and takes the shape of the mold.

Then the next step in the process is when the resin (hard plastic) which is now in the shape of a small pellets are poured into the feed hopper, the hopper is a large open bottomed contained and what it does is that is filters the pellets into the screw.

As the screws turn the resin pellets are moved into the screw and then they go through a very intense pressure. Then friction is created and when that happens heat is generated to melt the pellets. There are heaters on both sides of the screws and there is temperature control during the melting process.

The oil gets pumped from the tank to the injection molded parts that run along the tie bar equipment, then that’s when the liquid plastic gets injected into the mold. Then the water-cooling technique is applied in assist in cooling off the mold. The process is complete when the mold is pulled from the pre-designed mold.

Used Injection Molding Machines

Used Injection Molding Machines

There are constantly new techniques and new technology in the industrial world of injection molding. New machines, new plastics, new equipment. There are some companies that keep up with other companies by buying a lot of expensive equipment the second it comes out.

But these are the companies that cost so much because they have to charge more to pay for the price of the new equipment they just bought. But then you have the companies that like to keep using used machinery because they are just as good as new and as the old saying goes if it isn’t broke don’t fix it. Not every company wants to be the fancy company with all new machines.

Some companies want to just be known as the company that did my job in the most outstanding way. They want the recognition for a job well done rather than for the company who spend a lot of money on a piece of new machinery.

Companies that keep using used machinery don’t have to increase their prices and customers like to see that and they will keep coming back to the company that does great work for a great price.

How Injection Molding Works

How Injection Molding Works

In this post I’m going to explain how injection molding works. Creating polymers is an amazing process. Then there is the question of forming the plastic or rubber into useful objects….another fantastic discipline. One of the most common methods of forming rubber or plastic resins is a process called injection molding. Injection molding is made possible by large machines called injection molding machines.

Material, either rubber or plastic resin is fed to the machine. This can be in the form of a hopper for plastic pellets or an auger for thicker, heavier compounds. Colorants are usually fed to the machine directly after the hopper. The resins enter the injection barrel by gravity though the feed throat. Upon introduction into the barrel, the resin is heated to the appropriate temperature to make it melt.

This now viscous material is injected into the mold by a reciprocating screw or a ram injector. A reciprocating screw provides the advantage of being able to inject a smaller percentage of the total shot1. The ram injector on the other hand, must typically inject at least 20% of the total shot. A screw injector can inject as little as 5% of the total shot. Many factors also come into play such as the type of mold, how the material is injected, etc., effect the shot.

The Plastic mold is a cavity in the machine that receives the material and shapes it accordingly. In order to make the injected material solidify, the mold is cooled constantly to a temperature which makes the solidification possible. The mold plates are forced together, usually by hydraulic force. The clamping force is defined as the injection pressure multiplied by the total cavity projected area. Molds are typically over-designed with regard to the pressures they must endure depending on the material to be cast. In addition, each injectionable material has a calculated shrinkage value associated with that has to be accounted for as well.

Some Typical Complications

Burned or Scorched Parts: Melt temperature may be too high. Polymer may be becoming trapped and degrading in the injection nozzle. Cycle time may be too long allowing the resin to overheat.

Warpage of Parts: Uneven surface temperature of the molds. Non-uniform wall thickness of mold design.

Surface Imperfections: Melt temperature may be too high causing resin decomposition and gas evolution (bubbles). Excessive moisture in the resin. Low pressure causing incomplete filling of mold.

Incomplete Cavity Filling: Injection stroke may be too small for mold (ie. not enough resin is being injected). Injection speed may be too slow causing freezing before mold is filled.