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How to "shrink" a resin part?


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I have a Tamiya F-16 on the bench. I purchased Aires resin exhaust for it, and the part is anoyingly a little too large. Not much, just a little but enough to leave a noticeable step. Sanding is not an option because of surface details.

I've understood that resin has in some cases tendency to shrink somewhat. So my question is, is there a way to to help this tendency and try to make the part shrink a little?

Heat? Chemicals? anything?

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I think you would need to re-cast the part to make it fit, and use some tricks during the recasting:

  • first method would be to cast a condensation (tin salt) silicone rubber mold. That type of silicone rubber shrinks a bit, and keeps shrinking during its life. Typical brochure numbers are 0.1-0.4% shrinkage
  • second method would be to use a very fast resin for the recasting. Those resins heat up during the cure, depending on the ratio of (heating) volume to (cooling) surface.They solidify when they are hot, so when they cool down to room temperature they shrink. This can give you 0.5-1.0% shrinkage according to brochures

I guess this is way too much work for your part though :-)

 

Rob

 

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Resin (and RTV) 'shrink' during the curing process, when the chemical reaction occurs between the catalyst and base.  You can't make parts shrink after they have fully cured, unfortunately.

 

As Rob says, the only way to re-size your resin is to re-cast it.  Or, sand and restore details.  Or putty the fuselage, to make it match the resin.

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