Injection Molding Service
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Design Guidelines
ProtoFlow® Fill Analysis

Select ProtoQuote® interactive quotes include a
ProtoFlow® fill analysis to predict potential mold
fill issues. The following video clips demonstrate
ProtoFlow® in action:



ProtoFlow® Fill Analysis FAQs

ProtoFlow® is the name of a patented proprietary software package developed by Protomold®. ProtoFlow works by simulating the injection process using your part geometry and a set of resins. The output of ProtoFlow is a 3D animation of the fill phase of the injection molding process showing fill pressure or fill temperature for your part and your resin.

Selected Protomold ProtoQuotes® include an animated issue (moldability advisory) for your part. This simple animation will assist you in seeing where knit lines will likely occur; seeing potential gas trapping issues; and seeing where higher-than-normal fill pressures may occur. ProtoFlow can help you understand where problems may occur based on fundamental design-for-injection-molding rules, such as using uniform wall thicknesses and proper draft.


What does ProtoFlow show us?

Injection pressure – Protomold needs expected molding pressures to be under 15,000 PSI in most cases.  We consider geometry such as wall thickness, number of shut-offs and thin-to-thick transitions among many other variables with your selected resin.  The higher the pressure, the more difficult the fill, which translates to greater concern about weak knit lines (contributing to poor part integrity), flash, sink and shorts.

The color coding gets “hotter” as the pressure goes up. Gold and Yellow are bad colors, showing high pressure and reduced flow. Blue and Green are cool colors showing flow is good and the parts will have a wide process window to work with.


Isobars – Just like reading an elevation map, the closer the isobars are to each other, the higher the pressure gradient and the higher the injection pressure required. High pressure gradients often result in weaker knit lines, more flash on shut offs, and gas trapping.

Fill Temperature – ProtoFlow shows how your part will cool, which can give an experienced analyst insight into potential issues such as warping. If our analysts determine that ProtoFLow is indicating a possible warp problem, they will include a separate warp warning on your quote.

What do I do when ProtoFlow indicates excessive fill pressure? – The number one thing to do when trying to reduce fill pressure is increase the nominal wall thickness.  Even 15-20% extra wall thickness can produce a significant change in fill quality. A Protomold Customer Service engineer at 877.479.3680 may also be able to make other specific recommendations on modifying your part.

What happens if Protomold can’t fill my part? – Protomold may not be able to fill your part using your preferred part geometry and selected resin .  If you cannot change your part design you may need to consider one of multiple alternatives:



  • You can try a different material with a higher flow rate.

  • You can ask Protomold to attempt to mold your part as designed, understanding that there is a risk and Protomold may not be able to fill your part.  If we cannot, you may need to consider a mold modification after we make an attempt.


Is a “good” ProtoFlow simulation a guarantee that my part will fill free of knit lines, sink marks, and voids? – No, this is a predicted fill pressure assuming perfect venting.  As with any molding project, your geometry and the way the resin behaves in that geometry will be crucial to the success of the part.  ProtoFlow is a useful tool that helps us select a gate location while also animating potential fill issues, but it is not a crystal ball showing all possible issues.

Is a ProtoFlow analysis run on every part? – No, Protomold only initiates a flow analysis when there is a concern based on geometry and resin.  However, Protomold Customer Service Engineers are happy to run a flow analysis on any part and attach the result to your ProtoQuote. Please call them at 877.479.3680 and ask.






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