MODELS SUBJECT TO PRESSURE (35-42PSi) SHRINK

[jamado]

I´m producing my dental models for making dental aligners on my UM2+ wich by the way works perfect. I use PLA spool and infill of 25-30% but when trying to make the aliogners on the vacuum machine they shrink. Shoul I increase the infill? or any other change in the process to avoid this ?

[dorsai3d]

What temperatures are you using with the vacuum machine? I would think that PLA would hold up okay to 40PSI external, but if it's at elevated temperatures (45°C+) then it could well be weakened enough to deform. This would be a good case to look into using HTPLA and annealing or switching to a higher temperature material altogether.

[jamado]

Thanks for your reply an yes the vacuum is above 60C in temperature. Do you know a HTPLA brand ? One you've used? Thanks again

[zemlin]

Is there a reason you want to stick with PLA, or can you consider other materials with better thermal stability?

[dorsai3d]

I don't have direct experience with elevated temperatures with this, but I'd recommend looking into something like this: https://www.proto-pasta.com/products/high-temp-pla-v2-0. Make sure that you heat treat it before using it in service, though.

Alternatively, you might be able to print a negative and cast it in another material (thermoset? plaster?) that holds up better.