When a plastic design, most of the product designers consider less about the manufacturing process, like mold making and injection molding. So it will be easy to get trouble when injection molding if you don’t look the process carefully.
While clients transfer their design drawing to a injection mold factory, their drawing should be optimized before mold making. Here below are some common optimization work we are working for our customers.
The thickness of wall is to make the plastic part flowing smoothly without any shrinkage issue. When we take over a project from our clients, we always check out the material filling by moldflow software. And it’s easy to find out some features that existing uneven wall, which are not good for resin filling, as well result in shrinkage problem. So we will either advise our clients to modify the 3D drawing or we update from clients.
Draft angle is a very common design for plastic parts. However lots of product designer forgot to add some draft on the part. It will directly affect the part to be ejected from the mold.
Normally for a part size within 100mm, we advise a 0.5~1.0 degree draft, for a part size 100mm~300mm, we should make it 1.0~3.0 degree of draft. However if a part size is bigger than 300mm, we have to suggest it at least 5 degree as possible. The bigger draft angle, the easier for injection molding.
A draft angle should be added on the 3D model at the very beginning of a product design. If you ignored this concern, you have to re-create your 3D drawing, even adjust other relative parts. All in one, you will waste your time to remake drawings.
Fitting feature defined by tolerance
We saw a lots customers make a 3D drawing with zero to zero tolerance, which is a terrible tolerance policy for product design, especially for product with precision fitting features. For example, if you design a shaft with diameter of 5.0mm while the assembly hole diameter is also 5.0mm, it’s a big problem to get the shaft and hole assembled together, since there are some dimensional deviation from any manufacturing process. In this case, we suggest customers either set the shaft 5.0mm and the hole 4.9mm, or create a 2D drawing to define the tolerance as properly as you needed.
You should know, when mold making process, the mold maker only follow the 3D drawing for CAM manufacturing system. (if they received a 2D drawing, they might be change the nominal dimension for 3D drawing. We should always pay attention to this issue.
Aestetics line is actually a tolerance design for manufacturing, since the line will absorb any dimensional deviation or part deformation. When a product design, we strongly recommend to add this aestetics line to your 3D drawing. Otherwise the assembly will be a big problem.