Volumetric Shrinkage
Volumetric shrinkage is worked out by comparing the density of the resin before and after it has cured. We usually print a disc with a hole in the centre in a clear resin to ensure no internal air bubbles are present (that will change the measured density). The density of the solid is measured by weighing in air then water 5 times to get an average (http://www.gcamerica.com/products/operatory/KALORE/Kalore_2009%20IADR_FF.pdf).
Resin Density
The resin density is then measured by measuring the mass of a glass buoy of known mass within the resin (http://hyperphysics.phy-astr.gsu.edu/hbase/Class/PhSciLab/dens.html equation 3). Resin density changes with temperature so I made sure all measurements are made at the same time so any temp error was averaged over them all. (these values aren’t exact due to temp variations but are equivalent to each other)
Sample |
Liquid Density |
Solid Density |
Volumetric Shrinkage |
PC Hard |
1.114 |
1.194 |
6.7 |
PC Firm |
1.069 |
1.139 |
6.1 |
Formlabs Clear |
1.10 |
1.179 |
6.3 |
Formlabs Tough |
1.086 |
1.187 |
8.5 |
Fun to Do Industrial |
1.076 |
1.185 |
9.1 |
Fun to Do Deep Black |
1.071 |
1.177 |
8.9 |