Vertical hole dimensions

[Gooz74 0]

Hi,

 

I'm using Cura 4.5 on a Ender 3 and I'm trying to make a test print for this test plug (attached).

Now my dimensions of everything is correct (20mm base, 10mm pole) but the dimension of the hole is only 9.6mm

 

The testprint doesn't fit if I want to put it together.

I've read that you can use horizontal alignment but that would effect my base and pole too and those are correct.

 

Any help is appreciated.

test_plug.stl

[gr5 2,069]

This is normal for all 3d printers.  PLA is like snot when melted - it sticks to itself and is stretchy.  As it comes out of the nozzle it cools slightly and shrinks and is like a liquid rubber band.  When wrapping around that hole it is pulling inward and the final dimensions of vertical holes are typically 0.4 to 0.5mm smaller than in CAD.  This is VERY Hard to fix in the slicer as the possible geometries are infinite.  Not everyone prints flat plates with vertical holes.  Note that horizontal holes don't have this problem.

 

Anyway the normal fix is to add around 0.4 to 0.5mm to the diameter of every vertical hole in CAD.  This is not the only technology where you have to "fudge" things like this.  It's much worse with injection molding - there you can't even let 90 degree corners be 90 degrees!

 

Unfortunately there is no magic fix with cura settings (e.g. negative horizontal expansion and scaling) unless your part is extremely simple.

[Gooz74 0]

Thank you for the answer but that is not good for me since I don't create the files in CAD myself (i'm a beginner).

The things I want to print are coming from the internet (thingiverse) and I can't change them myself.

 

Even so, thank you for the answer

[gr5 2,069]

Then I suggest you drill the holes out.  That is actually a really good solution for a lot of people.  The good news is they are printed too small.  If they were too large then you'd be in trouble.  🙂

 

You can do other - much worse hacks depending on the part shape - you can add a negative horizontal expansion: -0.2mm will work out to .4mm larger holes - but your entire part will be .2mm smaller in X and Y dimensions all over the place.  You can the compensate that by scaling your part bigger (don't scale Z direction!).  But now the holes are the wrong distance apart.  So depending what you care about (part overall size versus hole spacing versus hole size) you can fix one or 2 of the overall issues.

 

I also recommend you learn a CAD - it's a valuable life skill.  Like touch typing.  Here's a guide to help you pick one:

https://www.gliffy.com/go/publish/5271448

[geert_2 556]

I also drill out the holes, with this tool. It only costs a couple of euro/dollar in any tool shop. This gives good feeling and control. Do it manually, not electrically, otherwise everything melts (don't ask how I know).