Any plastic part designer knows that one of the biggest worries in an injection molding process is a mold that won’t properly fill- commonly known as a “short shot.” While there are a handful of machine parameters that a molder can tweak to fix this, it’s always preferable to find such issues early in the design process- perhaps even when there’s still time to change the design of a part.

Sometimes, short shots are also intentionally run on a mold to try and visualize the filing process- something I had the opportunity to do at the injection molding lab at California State University at Chico. While the real-world part matched our simulation fairly well, SOLIDWORKS Plastics 2018 provides a great chance to examine the short-shot prediction more closely. To predict the filling pattern and compare it to a real-world short shot, we simply need to take a solid-body .SLDPRT file, such as the container handle below, and create a mesh with SOLIDWORKS Plastics:

Previous versions of SOLIDWORKS Plastics would predict a short-shot phenomenon with an easy-to-compute criteria: as the molten plastic cooled and the flow rate of the melt into the mold fell below a certain % of the maximum (by default, 1%), the part would be assumed “frozen” and the short-shot warning would be triggered.

In reality, we know that the actual shape of a part, regardless of whether there’s a short shot, results from where and when the plastic cools and solidifies. So, in SOLIDWORKS 2018, there’s a new “Temperature Criteria for Short Shots” option, which is enabled by default with the Glass Transition Temperature automatically pulled from the SOLIDWORKS Plastics material database. This means that the actual shape of the flow front will be based on where the molten plastic has cooled over time, providing for better realism.
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