Problem Calibrating RAMPS 1.4

Hi. I'm rebuilding my old Makerbot Cupcake. I've replaced the old-n-busted with RAMPS 1.4 and an E3D v6 hot end.

I'm using the Repetier Host (on a Win Vista box) and the 0.91 Rev 8 firmware on my RAMPS.

I've tried following Triffid Hunter's guides for calibration here: http://reprap.org/wiki/Triffid_Hunter%27s_Calibration_Guide

But I've not been able to get the X, Y and Z to move the distances that I'm requesting them to, using the manual controls in Repetier Host.

X & Y move 42mm when I ask for 50mm. Z moves a mere 0.5mm when I request 10mm! Can someone please have a look at my calculations and let me know where I've goofed?

X & Y Axis Stepper Motor Resolution Calculation
steps_per_mm = (motor_steps_per_rev * driver_microstep) / (belt_pitch * pulley_number_of_teeth)

motor steps / rev: 200 (step angle 1.8°)
driver microstep: 16
belt pitch: 2 (mm between teeth)
pulley number of teeth: 17

steps / mm = (200 * 16) / (2 * 17)
steps / mm = 3200 / 34
x/y-steps / mm = 94.1176


Z Axis Stepper Motor Resolution Calculation
steps_per_mm = (motor_steps_per_rev * driver_microstep) / thread_pitch

motor steps / rev: 200 (step angle 1.8°)
driver microstep: 16
thread pitch: 0.9 mm / rev

steps / mm = (200 * 16) / 0.9
steps / mm = 3200 / 0.9
z-steps / mm = 3555.556

Thank you.

-[a]-

Your maths looks good, but never heard of a 17 tooth pulley

If we take you’re results, requested 50, got 42 we get 112.04 steps/mm are you 100% sure you have 17 tooth pulleys?

If we calculate for 14 teeth we get 114.28 steps/mm

but im guessing your acceleration or feed rate is to high for Z, so the stepper is just skipping

Try the moves really slowly eg g1 x50 f300 or g1 z10 f60

The other thought is that cupcakes came with 1/2-10 acme is 10 threads per inch .1" per rev = 2.54mm per rev unless you have replaced that too...

I quadruple checked the pulley, and it does indeed have 17 teeth. I guess they chose some unusual parts for the early Makerbots, eh? After some additional reading in the Repetier documentation I realized what the problem is: I was failing to set the EEPROM_MODE to a different number, and the result was that the settings were not actually getting updated on the printer.

My printer's X and Y stages are moving correctly now! \o/ The Z is greatly improved, but needs some fine tuning. You're probably right about the thread pitch, I'll try using that as a basis for recalculating the z-steps.

Thank you for your insight, Dust.

-[a]-

Edited 1 time(s). Last edit at 10/06/2014 09:24PM by andr01dm.

.9mm is not a standard metric thread lead. Are you sure on that measurement? A 28 tpi threaded rod would have almost that same lead. It doesn't explain the huge difference, but you might want to double check.

I've solved the Z-Axis issue. The z-rods on my printer are M8 with a 1.25 thread pitch.

steps_per_mm = (motor_steps_per_rev * driver_microstep) / thread_pitch

motor steps / rev: 200 (step angle 1.8°)
driver microstep: 16
thread pitch: 1.25 mm / rev

steps / mm = (200 * 16) / 1.25
steps / mm = 3200 / 1.25
z-steps / mm = 2560

Now I just need to sort out the plastruder.

Thank you again for your help, cdru & Dust.

Edited 1 time(s). Last edit at 10/10/2014 10:58PM by andr01dm.