Stepper Tuning / Print Size Error

[shawnrw]

Gents,

I have searched and cannot seem to find what I'm looking for, please point me in the right direction if I missed it...

Just got my M2 setup and finished some test prints. Everything comes out with correct shape/proportions and no axis drift, but the parts are smaller by .15mm on all dimensions than the model. I have some experience with larger CNC machines and this can be generally be corrected with stepper tunning, but I can't seem to find any info in regards to this.

Please let me know your thoughts on how to correct this or if I should be looking another direction..

Regards,
Shawn

[jsc]

Did you run through the recent new user's guide by Jules on the tips forum? That covers most of the necessary tuning procedures. Most likely you will want to at least run an extruder calibration.

If that is not the issue, then be aware that different plastics shrink from cooling by different amounts.

[ednisley]

the parts are smaller by .15mm on all dimensions than the model

Unlike a CNC milling machine, where you can tweak the cutter diameter offset and come out dead on, a 3D printer produces an object by squeezing molten goo out of a hole: it's not nearly as precise a process as you might expect.

In addition to having the plastic shrink by maybe half a percent (varies with material / isn't isotropic), round holes become smaller due to geometric issues (the nozzle drags material toward the center) and the overall size can vary depending on what order the nozzle lays down the threads (inside-out or outside-in).

In round numbers, I can expect ±0.2 mm overall without any preparation and, on a good day with a fair wind in the sails, ±0.1 mm after tweaking the model and running off a sizing protoype or two. Mostly, anything in that range suffices for my simple needs, so I generally don't fuss with tighter tolerances.

By and large, you're already there. [grin]

Do the Extrusion Multiplier calibration dance and things may get slightly better (and possibly more consistent), but the final dimensions will never be dead on.

If you really care, you can get seriously crazy about platform alignment...
http://softsolder.com/2015/09/04/thinwa ... er-images/



But that way lies madness...

Welcome to the M2 crew!

[billhunter]

If you want correct sizes inside you need to use a different program like Kisslicer.