Printing MPCNC parts - my inner dimensions are off?

Mostly Printed CNC - MPCNC Troubleshooting
1

Hi,
I’ve just started my own MPCNC Primo build, bought every component and printed few parts but I’ve also noticed something really strange with my printed parts.
They are almost on spot when it comes to outer dimensions (± 0.1mm max) but are quite off when it comes to the inner diameter where the 25mm pipe should go (I’m in Europe so 25mm is the way to go for me). Using quite precise calipers I’m measuring anywhere between 24.78mm and 24.86mm. I’ve just checked and I’m able to force the pipe into the slot although it requires a lot of force.

Tried to calibrate my steps/mm but they where almost spot on. I could dial it in just a little bit more maybe but current issue is not the outer diameter but “inner diameter”.

  1. Will this cause any troubles when it comes to more “essential” parts with bearings? (Currently just printed feet and leg locks)
  2. What can cause such a weird issue? Horizontal material expansion? (I’m printing in PETG)
  3. Maybe the 24.9mm dimension is intended? Did anybody check it on their prints?
2

Hey Pawel.

I am currently building my LR2 *25mm using PLA.
I measured the internal diameter of the parts I have already printed and they are at 25mm with a deviation of ± 0.02 mm
Most probably you’re right about material expansion (I imagine you’re printing with fans turned off).
Maybe sanding them down a bit is the way to go in order to save the parts you printed and not waste material.