In case anyone is interested, these are parts for a sonic screwdriver, and the printer works so much better after all my mods, I now need to reprint all the rest of the parts before painting and assembling it.

http://home.comcast.net/~tomhorsley/har … sonic.html

I recommend the dial indicator as well.  I made a mount for mine to go on the rails.

The 0.1mm part I printed last night was quite tall - the model says it is 90.11 mm, but the printed part came out real close to 100mm (and looked very well printed with nice uniform layers, each one of which must have been slightly too thick :-). Maybe I'll print the same part at .2 and .3 to see if it really is different with different layer heights.

I'd check the z-code for the .1mm print in a text editor to see where the z-level was supposed to end up.  Maybe it didn't slice correctly.

Was the .3 print sliced from the same .stl?  Just wondering if it got accidentally scaled for some reason...

Also, note how many layers are created/called out after the slices...see if that calculated height is in line with your original CAD model height.

It is strange that 0.3 resolution comes out correct.  How many layers are the pcs you are measuring?

The 0.1mm part I printed last night was quite tall - the model says it is 90.11 mm, but the printed part came out real close to 100mm (and looked very well printed with nice uniform layers, each one of which must have been slightly too thick :-). Maybe I'll print the same part at .2 and .3 to see if it really is different with different layer heights.

If I was losing steps, I'd expect things to be shorter not taller :-).

Yep...I glossed over the the "Growing" part

It is strange that 0.3 resolution comes out correct.  How many layers are the pcs you are measuring?

Are you sure you are using the correct pitch in your calculation though?

Can't say I'm sure of anything at this point :-). Back over in the original post about switching to M3, it says the stepper is 1.8 degree per step, which is 200 steps for a full rotation, and M3 is .5mm pitch, so thats 400 steps per 1 mm, but the printrboard drivers use 16x microstepping so that 16*400 == 6400.

Anyway, I definitely need to do some test prints (when I get home later today) and see if this really does only happen when the layer height is set to 0.1mm. I'm certainly confused right now.

wardjr wrote:

Is it possible that you are just over on your steps per mm and therefor for every mm the distance compounds.

Yea, but you'd think that in Z the calculation that leads to 6400 would be exact, and I've printed 3mm layer height objects that needed to match the physical dimensions exactly, and they came out perfect (as near as I can tell).

Are you sure you are using the correct pitch in your calculation though?

Could you be losing steps because of the increased speed? Try slowing it down...since it is Z, it does not need to move that quickly.

If I was losing steps, I'd expect things to be shorter not taller :-).

But I have wondered if there are any recommendations for changes to make to Z acceleration and speed settings after switching to M3.

Is it possible that you are just over on your steps per mm and therefor for every mm the distance compounds.

Yea, but you'd think that in Z the calculation that leads to 6400 would be exact, and I've printed 3mm layer height objects that needed to match the physical dimensions exactly, and they came out perfect (as near as I can tell).