We've got drawings for a prototype that we're trying to mimic by altering an original mold of the product. For us to mold it would be quite expensive to just test it to see if it works or not. We're trying to see if there's way to cut the Food Grade Silicone in a uniform way that would leave the edges smooth? This would allows us to test our drawing in the real world and get feedback.

We haven't had any success so far. I'm not a materials guy so this is new to me. Looking for any advice.

  • $\begingroup$ I'm just guessing and if you try, ventilate well, but would a hot wire cut? We used to make them when I was a kid to cut shapes in polystyrene : ventilation H&S.... just open the window a bit :) $\endgroup$
    – Solar Mike
    Jan 12, 2018 at 22:37
  • $\begingroup$ are molds made of silicon flexible? $\endgroup$
    – Solar Mike
    Jan 13, 2018 at 8:48
  • $\begingroup$ @SolarMike This one is yes. It is quite flexible. And it's silicone pardon my grammar. It's a cone shaped piece of flexible, food grade, silicone. $\endgroup$
    – M Purry
    Jan 15, 2018 at 17:24
  • $\begingroup$ @SolarMike I'm not sure how hot it'd have to be. I tried my soldering iron and all it did was char it. $\endgroup$
    – M Purry
    Jan 15, 2018 at 17:25
  • 2
    $\begingroup$ @SolarMike Silicone doesn't melt like thermoplastics do so I don't think a hot wire is helpful. $\endgroup$
    – Eric S
    Sep 19, 2019 at 16:42

2 Answers 2


A laser would be the best method followed by repetitive razor slicing in ever deeper cuts to avoid frictional deformation. Another method would be cold cuts by freezing the silicone and using a regular mechanical saw.

The key to doing it properly is removing deformation from the property of silicone when pressure is applied.

  • $\begingroup$ Best I can tell, silicone freezes at -55C so you're not going to get it frozen in a normal freezer. $\endgroup$
    – Eric S
    Sep 19, 2019 at 16:46
  • $\begingroup$ Who has a can of liquid nitrogen ? LOL $\endgroup$ Sep 20, 2019 at 3:22
  • $\begingroup$ Nitrogen is a bit extreme. Hospital grade freezers go to - 100°C $\endgroup$
    – Rhodie
    Sep 20, 2019 at 20:57

Here is a trick you can try. Cut the silicone edge so that the edge dimension (for lack of a better term) is a little smaller than you final finished dimension. Now make a temporary casting mold for the cut edge such that the inside edge of the mold adjacent to the cut edge forms a wall , the gap between the cut edge and the smooth mold wall is sized correctly. Now just cast in some silicone molding compound, the same silicone as your prototype. Because silicone bonds to silicone, you will have a perfectly smooth new edge.


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