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Mr_Asa
Mr_Asa PowerDork
11/25/21 10:36 a.m.

In reply to Azryael :

I don't worry about shrinkage either.  Unless I'm making something that is all 3D printed then I'm going to end up doing post processing in order to get stuff to fit anyways.

Also, shrinkage is not necessarily something I concern myself with as shrinkage is not a uniform thing.  Skinnier parts are going to cool faster than other parts and can result in more shrinkage.  Its not as bad as you'd get with cast parts, but its difficult to plan for

Azryael
Azryael Reader
11/25/21 11:02 a.m.

Makes sense. A PETG piece I made for an outdoor application had 60% infill, and a bi-cubic fill pattern, and experienced no shrinkage whatsoever.

It's skinny/hollow PLA that seems to shrink the most aggressive for me when it does. I printed a tank from the Warhammer 40K universe out of PLA that experienced no shrinking either.

I hadn't actually noticed any shrinkage until two things I just recently printed. The fact that it's far cooler in my office now could be a contributing factor in it cooling too quickly.

JFW75
JFW75 New Reader
11/25/21 11:00 p.m.
Azryael said:

apparently has a 2% shrinkage rate. The final will probably be printed out of PETG, but I'm curious if you guys scale up a certain percentage before slicing to make up for any shrinkage?

If you calibrate your printer it should print to the exact size. Check "Teaching Tech" on YouTube for a tutorial. 

Holes usually come out an extruder width narrower due to how they interpolate them. I just bump them up 2x nozzle width in CAD before slicing. 

Azryael
Azryael Reader
11/26/21 2:21 p.m.

I'll have to look into it.

Honestly, I've never had an issue with it not printing to the exact size I've specified, it's just that some smaller/more hollow parts seem to experience shrinkage.

As an example, I printed some donuts to test fit the hole for a pivoting rod for an outdoor umbrella in the following ID sizes: .775", .785", .795", and .798", and with my Mutitoyo calipers, they measure out accurately within .0001-0002", and never experienced any shrinkage with these.

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