Percent of shrinkage when casting resin?

[f5guy]

Hi everyone,

     I'm thinking of having some 3D items printed up, and am considering using them to cast up some resin clones. I know that resin shrinks slightly when cast, so I'm considering having the originals made slightly larger to compensate for this. But how much larger? Any ideas? Thanks, Fred K.

      

Edited February 10, 2023 by f5guy

[arnobiz]

It totally depends on the resin you use, and on the parts geometry. Larger parts will generate more heat and likely more shrinkage. Small parts with properly mixed low-shrinkage resin will have negligible shrinkage.

[f5guy]

8 hours ago, arnobiz said:

It totally depends on the resin you use, and on the parts geometry. Larger parts will generate more heat and likely more shrinkage. Small parts with properly mixed low-shrinkage resin will have negligible shrinkage.

 

I'm thinking about doing some 72nd scale airliner wheels, so they'd be big for wheels, but not necessarily big overall.

[arnobiz]

This would qualify as small, I wouldn't worry about shrinkage at all 😉

 

Arnaud

[ElectroSoldier]

Each and every resin has its own shrink rate. That is usually published on its data sheet.

 

 

[Rob de Bie]

Generally speaking, the slower the resin, the lower the shrinkage. It has to do mainly with the temperature that the resin reaches during the cure. Most of the shrinkage is thermal shrinkage. This data from Smooth-On clearly shows the relation:

 

                                    potlife (min) shrinkage (%)
Smooth Cast 300Q    0.5                1
Smooth Cast 300        3                  0.5
Smooth Cast 305        7                   0.35
Smooth Cast 310        15-20           0.025

 

The shrinkage listed is dimensional, not volumetric. So with 300Q your parts would be ~1% smaller.

 

Rob