This blog is translated from German with DeepL.
KNOW HOW
When manufacturing injection molded parts, one or the other challenge arises. A few things need to be considered as early as the design stage. Almost all everyday objects are produced primarily from plastic. Most of these parts, in turn, are manufactured using the injection molding process. But what exactly is injection molding, or injection molding? In this process, hot, liquid plastic is injected into a mold at high pressure. After the plastic has solidified, the mold can be opened and the finished part removed. And where does it make sense to produce a part by injection molding? Injection-molded parts are used wherever large quantities are required. The cost-effectiveness depends on the complexity of the part and the size of the series. What are the advantages of injection molding over mechanical production?
3 RULES
As is well known, many roads lead to Rome. But by observing a few rules, namely 3, the goal is best achieved and no mistakes are made. For larger quantities, production costs and production time can be extremely reduced, since only one mold needs to be built. After that, complex parts can be produced in a matter of minutes. In addition, there are practically no limits to the shape and design of the part. Free forms can be realized without any problem.
Despite the above advantages, there are some points that must be taken into account when designing an injection molded part. The most important ones are explained here:
1. demoldability:
Since the plastic solidifies in the closed mold (tool) after injection, care must be taken to ensure that it is possible to open the mold again. Usually a mold is used which consists of 2 halves. When the mold is opened, one half is lifted off the other half in a certain direction (opening direction). It must therefore be ensured that neither half of the mold hooks onto the other half of the mold or onto the injection-molded part. If it is not possible to design a part so that it can be demolded with only one opening direction, it is possible to use sliders. These sliders can be used to demold individual geometries, for example a screw dome, in a different direction. However, the sliders make the mold considerably more expensive.
2. chamfering:
To prevent surfaces of the part and the mold from rubbing against each other when the mold is opened, which reduces the surface quality, it is necessary to apply draft bevels. This means that all surfaces that are parallel to the demolding direction must be sloped. Depending on the material and surface, an angle of approx. 0.5° to 1.5° is recommended.
3. wall thickness:
Suppose we pour liquid plastic into a drinking glass and fill it to the top. What happens? While the plastic on the outside of the glass has already cooled down completely and solidified, it is still warm on the inside. But after some time, the plastic inside also cools down. As the material contracts during cooling, stresses are created. These cause the part to warp and not have the desired shape. The plastic behaves in the same way in the mold. For this reason, care is taken not to design “filled” parts, but to build up the part from walls and ribs.
Would you like to learn more about injection molding and its advantages and also use this manufacturing process for your own products? The Gimelli Engineering AG team will be happy to advise you and will get the maximum out of your product!
