Z-Axis Calibration

Trying to dial in my Z-Axis calibration
Here is what I did using pronterface to move the Z-Axis Up by 1 each time
I measured from the bed to the head (fixed points)

124.22
1 125.45 1.23 mm
2 126.56 1.11 mm
3 126.89 0.33 mm
4 128.14 1.25 mm
5 129.28 1.14 mm
6 130.23 0.95 mm
7 131.18 0.95 mm
8 132.42 1.24 mm
9 132.59 0.17 mm
10 133.01 0.42 mm
11 133.87 0.86 mm
12 140.18 6.31 mm
13 141.31 1.13 mm

My question is what could be causes for the inconsistency
M201 Z = 60
M203 Z = 450
M92 Z = 200 <<-- this I know adjusts the movement as a whole

You can't hear the motors so I know my current is right, but you can hear a "loud" squeal as thread twists through the holding mechanism on the Z-Axis assembly


Any thoughts

Thanks in advance

What printer setup do you have? Prusa I2? Prusa I3?

If you are using threaded rod for the z axis, calibration should not be necessary. You just plug in the numbers. My steps per mm for z axis are 3200/1.25 because I am using M8 threaded rod and standard 1.8 degree steppers with 1/16th microstepping. Also, if you are hearing a sqealing sound, you should add lubricant to the threaded rod so that it turns smoothly.

If you provide more info about your printer I should be able to help

Eric

If your Z axis max feedrate is indeed 450 (mm/s? mm/min? the setting in Marlin is mm/s, but I'm not sure if M203 reports in mm/min or mm/s. The RepRap wiki is somewhat conflicting on this, though I believe it is supposed to be in mm/s. What setting do you actually have in firmware?), that is way too fast. Try limiting it to 3 mm/s or even less. What feedrate do you have set for the Z axis in your host software, Pronterface or Repetier Host or whatever? The acceleration rate for your Z axis looks reasonable, so that's likely not the problem.

RP Iron Man is correct, you should not be adjusting your steps per unit for your Z axis. Set it to the correct calculated value in your firmware (use [calculator.josefprusa.cz] if you need to) and leave it there.

Thanks Guys

First off this is a repstrap my own piece together very similar to a Prusa 3i with bits taken from a 3D drag

I used 1/4-20 threaded rod from Lowes and tapped a 1/4 - 20 hole in the aluminum that connects the X-Z axis (head) to the Z-axis threaded rod

The M201 M203 and M92 numbers are direct from Pronterface and I believe are what is set in the firmware but I can change any of them

The mm/min Z: in Pronterface (Top Left Corner) is set to 300

Using the website

Motor step angle 1.8 200 per revolution (I know this is right it is on the motor)
Leadscrew pitch 1.5875 mm/rev I have found that this might be 1.27mm 1/4-20
Presets 1/4-16 Acme 1.5876mm per rotation
Desired layer height 0.3mm I know this is what is set in Slic3r and is my nozzle size
Z axis gear ratio 1 : 1 Direct drive I know this is right

0.2937 0mm 37 0.0079375mm
0.3 +0.5353670572424599mm 37.79765654529419 0.0079375mm
0.3016 0mm 38 0.0079375mm

Do I then set M92 Z to 37.8 ? Is that correct ?


I found this at [www.buildlog.net]
!!! For 1/4-20 Threaded Rod !!!
Lead Screw pitch (p) = #1/4-20 = 20 threads/in = 0.05 inch = 1.27 mm
Resolution = 200steps/rev * 16microsteps / 1.27mm/thread = 2519.68


FYI setting M92 Z to 2519.68 just very high pitch whines and hardly moves at all


Also it would appear now that after I have moved up or down
The motor does not wish to turn but you can hear this humm click humm click humm click humm click humm click humm click very very softly

Does this help

Thanks again

Edited 2 time(s). Last edit at 03/05/2014 06:34PM by TheBearF8.

Are you using 1/4-20 or 1/4-16? You say you are using 1/4-20 but the calculator copy/paste text say 1/4-16. 1/4-20 is normal threaded rod while 1/4-16 I think is acme lead screw usually. The lead screw is better for what it's being used for, but you probably don't have a lead screw since you picked it up at Lowes. Use the 2519.68 number for M92.

Lower M203 to 60 (for 60 mm/min). Try to move it via 1 and 10mm increments. That should be 1 and 6 seconds of movement respectively. If that is working going up and down, set M203 up by 30. Rinse, repeat until you have problems, then back it off. Eventually you'll get to a point where it's just trying to move too fast and starts to skip steps.

I had a similar issue with the default z-axis rate of 240 for my printer with the squealing. Through starting off low and going up, I found that 230 was the magic maximum speed for the x-axis. I went with 210 as that was 3-1/2 times 1mm/sec (more just a "round number") and gave me some cushion, and it only resulted in a 10 seconds extra when homing the z-axis.