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Hole dimension smaller than STL cad file


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Posted · Hole dimension smaller than STL cad file

Hi all,

I find ALL my hole dimension are approx. 0.3mm smaller than the cad stl file.

I printed 3, 5, 10, 20, 30, 40, 50 in ABS and PETG

I used CURA 3.2.1 for my print and both materials had the same results for the holes, the outside dimension on the PETG was nearer to the stl cad size.

If I use the scale option in Cura it just scales the outside and NOT the hole dimensions.

Is there a plugin to fix this or have I to just increase Hole diameters to compensate, which is OK if I am to print my own design/drawn models.

Awkward if I have to pass on information to 3rd parties about how they should adjust their hole sizes.


Thanks for any ideas.

hole size check.stl

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    Posted · Hole dimension smaller than STL cad file

    Yes unfortunately you will have to change your hole diameters to compensate. 3D FDM printers do not draw circles they draw straight lines, obviously  lots of small lines. The line cuts across the apex of the circumference and you end up with  a slightly smaller diameter; which if dimensional accuracy is important for a part is a pain. Some trial and error will get you to where you want to be. Printing slow and cool all help to reach dimensional accuracy too. A long time since I have needed to do this but I think I used to increase the diameter between 0.2 to 0.4mm. It could be that it varies on size of diameter but I never needed to investigate that.

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    Posted · Hole dimension smaller than STL cad file

    Also, when depositing molten filament in a circle, it is pulled inwards towards the center of the circle, before it has time to solidify. Like syrup would be pulled inwards.


    If the holes need to be accurate, a simple solution is to carefully go through them with a hand drill. No electric drills: they will melt the model if it is PLA.


    I bought a separate drill chuck for this, so I have a good grip on it, and I use that as manual drill. This gives enough power, and gives you a good feeling for what is going on.




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