Warp Analysis using SOLIDWORKS Plastics

What is Warpage?

Warpage is the deformation that occurs when there is an uneven shrinkage in different areas of the molded component. The result is a twisted, uneven, or bent shape which was not intended. It is a cosmetic and structural defect which can be easily identified by naked eye.

When the plastic gets heated at high temperature and cooled again, there are a lot of changes happening at the molecular level. Warping is usually caused by non-uniform cooling of the mold material. Different cooling rates in different parts of the mold cause the plastic to cool differently and thus create internal stresses. These stresses, when released, lead to warping.

If the shrinkage is uniform, then you get a perfect product which is smaller than the original. This condition can be controlled by scaling up the CAD model while designing the mold. But if the shrinkage is non-uniform then it causes the part to bend from one side which can cause fitment issues or just look ugly.

SOLIDWORKS Plastics can help you predict shrinkage and warpage at a very early stage of design. This helps you to modify the part design, choose the best gate locations and design a better mold which will result in a better product quality.

For understanding warpage of a component in a better way, a cooling channel is required. Moulds are usually built with cooling channels. These channels are usually connected in series with one inlet and one outlet for water/coolant flow.

Designing a cooling channel is pretty easy is SOLIDWORKS Plastics. You just need to specify the cooling channel by creating a 2D or 3D sketch.

Once the sketch is complete, you can specify the type of coolant, inlet and outlet points, flow rate and temperature as well. Furthermore you can specify the type of polymer, injection pressure, gate location, etc.

Once the cooling channel is designed properly, we can proceed to run the warp analysis. Unlike Flow and Pack simulation which are based on Finite Volume Method, Warp analysis is based on Finite Element method to give the results.

The results which we receive is the stress displacement in direction X,Y,Z or resultant of all of them. This gives you a clear indication of the bending behaviour of the part.

How can we avoid Warpage?

Avoiding warpage completely is very difficult, but certain measures can be taken to make the shrinkage more uniform throughout the part. Some measures which can be taken to control warpage are:

• Ensure that the cooling time is sufficiently long and that it is slow enough to avoid the development of residual stresses being locked into the part.
• Design the mold with uniform wall thickness and so that the plastic flows in a single direction.
• Select plastic materials that are less likely to shrink and deform. Semi-crystalline materials are generally more prone to warping.

Note: Cooling channel design and Warpage analysis can be performed using SOLIDWORKS Plastics Premium.

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