Z height issues and the need for strange steps per mm

Milesy · 21 Jan 2018, 19:47

So I have spent the weekend setting up my new Duetwifi board, mostly straight forward but I have one issue I cannot solve.

When printing the second and third layer are smooshed by the hotend. I have checked all the axis movements are correct and have had to change what the configurator suggested (M92 X100 Y100 Z400 E420 ; Set steps per mm) to get the correct distance travelled.

Is this where my problem originates or should i be looking elsewhere. I have also tried various settings in Slic3r but nothing seems to make a difference?

Any Ideas?

Link to Image of smooshed print.

number40fan · 22 Jan 2018, 14:01

Is the Z in your M92 correct now? If you use DWC and command the Z movement 100mm, how far does it move?

kraegar · 22 Jan 2018, 14:11

That can happen if your steps / mm aren't easily divisible by your layer height.

For example, we had a 16T pulley on our Z stepper, belt driven to a 30T pulley. Since the math came out funny, every third layer or so was smooshed. We switched to a 16T / 32T pulley, our steps/mm are now 1 step = 0.01mm, and everything's happy.

Milesy · 22 Jan 2018, 21:27

Thanks for the reply's.

Is the Z in your M92 correct now? If you use DWC and command the Z movement 100mm, how far does it move?

Yes I am pretty sure it is but I will double check that it moves 100mm when commanded.

That can happen if your steps / mm aren't easily divisible by your layer height.

For example, we had a 16T pulley on our Z stepper, belt driven to a 30T pulley. Since the math came out funny, every third layer or so was smooshed. We switched to a 16T / 32T pulley, our steps/mm are now 1 step = 0.01mm, and everything's happy.

I don't think this is an issue as the the leadscrews are T8's and should give me increments of 0.04mm (if my maths is correct).

Would print speed make a big difference on a small test print?