Plastic injection molding
At Davantech, we are specialized in plastic injection molding since 2010. More specific, we are specialized in plastic injection molding and located in China. As a mold maker and manufacturer of plastic products, we state that it is still an obvious choice to have your molds made in China. One of the reasons is that the manufacturing supply is very large and efficient. As a result, we offer molds much cheaper than elsewhere in the world.
Chinese mold manufacturer.
We use steel molds for the injection molding of plastic products. A mold is a one-time investment and it allows you to produce simple as well as complex plastic parts in an fast and economic way.
The life time of a steel mold varies from 100 000 cycles to 300 000 cycles for a standard mold. However, depending on the steel grade and concept, lifetime goes up to more than 1000 000 cycles for expensive molds. Glass fiber filled plastics will reduce the lifetime of a mold, for example.
Mold production time.
The average production time of plastic injection molds in China is 35 working days. The mold maker tests the mold once the mold production is finished. It is possible that the mold needs adjustment after the first test. This is standard procedure. We will apply the surface texture or polishing after the plastic parts are accepted by our Quality department. Final samples are shipped to the customer for acceptance.
The production of series starts once the samples are accepted.
We count about 20 days for the total process. The production of each order is scheduled. Our procurement department will buy raw material in case there is no stock. One mold we can do 1500 to 2000 cycles per day. Parts are checked after injection molding. We will remove burrs and pack the goods. Ready for shipping.
Cavities in an injection mold.
Injection molding of plastic parts is a very efficient production method. Especially, when we produce large quantities. The mold in the picture above, has 12 cavities. This means we can produce 12 parts for each mold cycle. As a result we reach a far cheaper unit cost per part. The mold, however, is more expensive. Nevertheless, you will win the extra cost back in the total production cost of the plastic parts.
The plastic injection molding process.
Injection molding of plastic is an industrial process. The mold is closed with a big force and remains closed during a certain time. Next, we inject molten plastic with high pressure into a mold. . The cycle time depends on a number of factors such as plastic volume, wall thickness and type of plastic. Good to know is that a good design will reduce the cycle time.
There are 3 parameters to setup an injection molding machine :
Each different product needs different parameters. In addition, the shrinkage of each plastic type is different. To compensate the Shrinkage, the cavities in the mold are larger than the final part. A part will shrink once it is ejected from the mold. Did you know that a part made of POM can shrink up to 2%.
Products with a too big wall thickness still shrink even days later. Again, it is important to design a plastic part in a correct way.
Plastic raw materials used for injection molding.
The selection of a raw material used for injection molding depends on the use of the final product and the desired properties. Another key point is the price difference between different types of plastic. For cheaper plastic products, where the finish and looks are less important, we mostly use PP (Polypropylene). This is a strong material with good chemical resistance. It is used for outdoor furniture as well as toys and bottles and containers. However, PP is not suitable for gluing and printing. We need to do a surface treatment first.
Mostly, we make housings of electronic devices of ABS of PC-ABS. This because of its robust properties, temperature resistance and surface finish. PC or PC-ABS is more rigid and impact resistant. Strong (tough) parts and moving parts will be made of PA66 and POM (these materials are also suitable for machining). Next, we use ASA to make electronic enclosures for outdoor use which require a high impact strength, good UV resistance and transmission of signals. PVDF is a strong material that can handle high temperatures and very good chemical resistance.
The most commonly used plastic materials in injection molding are:
- Polypropylene (PP):~38% of global production
- ABS:~27% of global production
- Polyethylene (PE):~15% of global production
- Polystyrene (PS):~8% of global production
Even if we take into account all other possible manufacturing technologies, injection molding with these four materials alone accounts for more than 40% of all plastic parts produced globally every year!