simple Z axis re calibrating resulting in problems

Hi all now that I have got my prusa i3 home made clone to work, that is to say print the 20mm test cube I find that the X and Y sizes are spot on 20mm but the Z axis is only 15 mm undersized by 25% and so I thought the answer was simple increase the working step count that is re calculate M5 screws at 0.8 pitch so 1.8 deg stepper motor =200 steps per 360 degrees with 16 micro stepping =3200 multiply this by 1.25 calculates to 4000 steps per mm movement. My problem is that when the printer is connected by usb to pronterface all axis work fine and move correctly that is in 0.1mm 1.0mm and 10mm moves but when being moved by the rotary encoder and viewed on the LCD as a standalone machine the X and Y axis work fine in all incroments but the Z axis will only move up or down in the 0.1mm incroments the 1.00 mm simply makes the stepper motor hum loudly and also when the Zaxis lifts during printing moves it hums and misses steps I have slowed the acceleration and max speed down to 50 mm but I cannot make it work but If I reduce the step count to under 3200, 1 complete revolution say 3175 steps per mm all works fine except it is inaccurate measurement can someone please tell me why

You're probably trying to drive the motor too fast for the controller board. If you're using an A/R controller, you can produce maximum 40k steps per sec. If you try to drive the Z axis faster than 10 mm/sec the controller can't produce the pulses fast enough.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Sounds like you need to adjust you Stepper motor current.

You can search on you-tube how to adjust the stepper motor current for your controller type

here is one for ramps [www.youtube.com]

here is a Reprap calculator [www.prusaprinters.org]

Edited 1 time(s). Last edit at 08/14/2017 04:32PM by Roberts_Clif.

If you are using Marlin firmware

In config.h find this line #define DEFAULT_MAX_FEEDRATE { 300, 300, 5, 25 } change the 5 to a 2
5 is normally too fast for printers when using the M5 rods

4000 is correct steps/mm for M5 rods
200*16/0.8=4000

Edited 2 time(s). Last edit at 08/14/2017 07:01PM by obewan.

Thanks guys, all your comments have been taken on board, check driver voltage, 1.56v reduce Configuration.h max speed 2 done all these things but still have problem. My logic says that as the G 28 command and the commands from pronterface move the axis fine i.e. homing feed rate is set at (3*60) and working well and smoothly so pulses are being generated fast enough, so have I missed some setting for the rotary encoder, is it trying to work at a higher speed or in a different way that the steppers can not cope with ? I have tried changing values on the two options that I found in configuration.h but ended up reverting to default as they made no difference to the problem. A second thought as I had to reduce the SD card spi speed to get the machine to work, could it be a speed of the smart controller connection ??? my brain cannot see that far!!!

Edited 1 time(s). Last edit at 08/16/2017 05:03AM by papakel.

If you have EEPROM enabled in firmware, make sure you send M502 to load the settings from your configuration.h and then M500 to store them to EEPROM. I had that same problem with the speed not being obeyed until I remembered that.