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Countering shrinkage in FDM prints with wavy lines

Posted by aarond10 
Countering shrinkage in FDM prints with wavy lines
January 20, 2023 02:19AM
Has anyone tried post-processing gcode to intentionally add waves to long, straight extrusions to counter expected shrinkage?

I've never tried editing G-code before so before I go and give this a try, I was wondering if anyone knows of existing attempts at this.
I've used notches in the past to fight shrinkage but if PLA shrinks by 2%, why not add 2% to the path length of extruded strands in the first N layers of the print by turning straight lines into slightly sinusoidal lines and letting the shrinkage stretch them back.
Would that not work for some reason? Would the required deviation be too high or something?
Re: Countering shrinkage in FDM prints with wavy lines
January 20, 2023 08:31AM
Bulk shrinkage numbers don't directly apply to 3D printing in layers which is why you can design a part to be 100x100 mm and the print comes out 100x100 mm. If you laid down a line of molten plastic and the whole thing was molten and cooling all at once, it would shrink, but when we print the plastic comes out of a nozzle and solidifies/shrinks continuously just a few mm away behind the nozzle.

I've never heard of anyone having a problem with PLA shrinking, except in the context of annealing (baking it in an oven to somehow improve the strength) a print. The reason people print with PLA is because it is easy to print, partially because it doesn't shrink enough to cause prints to warp.

ABS is often considered difficult to print material because of the tendency of prints to warp if you try to print in a room temperature chamber. I have found that breaking up long straight lines into wavy lines or zigzag segments reduces the tendency of ABS prints to warp, but if you want to print ABS, do it in a heated chamber (at least 50C) and warping isn't going to be a problem.

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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