Z-axis slow

mebj

When using a Z Acme screw with 400 steps/mm the Z movement is extremely slow. Initially I made a mistake and did set it to 1600 steps/mm and then it works at speeds I am used to see (I have another printer working with M8 screws for years now). This behaviour is repeatable, whenever I set it back to 1600 steps/mm z speed is normal.Changing max z speed, accelerations and othe suggested changes or using development version makes no noticeable difference (and yes - I have changed eeprom parameter between changes).I can find no reason why firmware set much lower speed at 400 steps/mm compared to 1600 steps/mm. To me it would be natural to get same speed for whatever number of steps/mm while now there seems to be some type of set time involved to comlete a movement.This item has been discussed several times before but none of the suggestions/explanations I have found have improved or explained the extremely slow z speed. I am sure a change to an M8 standard screw would speed up things but the preloaded T8 screw should be a technically better solution I would like to keep.

MartinH

If you mean the manual move buttons in repetier host, there is a speed adjustment in RH/config/printer tab- Z axis feed rate.
There is allso a Z max feedrate and Z homing feedrate in the software tool under
Z axis stepper motor section under 'mechanics tab'.
currently i have mine set at 30 and 12 respectively, with a 400 step/mm lead screw which gives decent Z speed.

mebj

Glad to hear that speed could be OK at 400 steps/mm, remains to find the reason why mine behaves differently.Speed seems to be the same/similar whether movement initiated from controller, from host buttons or with a G-command.I already have tried changing Z max feedrate and Z homing feedrate without noticing any major change in z speed. Will try again to verify.Still I can not see any logic in that speed changes when using different settings of steps/mm.

Roko

"Still I can not see any logic in that speed changes when using different settings of steps/mm."

It seems to me that, If it moves 1 mm in 400 steps and is changed to 1 mm in 1600 steps it would have to turn 4 times faster at any given set speed to move that 1 mm.

Repetier

Please check also eeprom. There the max. speed for z is stored as well as z homing speed. Changing in configuration.h is not enough.

mebj

Roko said:

"Still I can not see any logic in that speed changes when using different settings of steps/mm."

It seems to me that, If it moves 1 mm in 400 steps and is changed to 1 mm in 1600 steps it would have to turn 4 times faster at any given set speed to move that 1 mm.

You are right, of course, but that also means that the time is the fixed variable and not the speed. If speed is constant then time would be 4 times longer for 1600 steps, right?

mebj

Repetier said:

Please check also eeprom. There the max. speed for z is stored as well as z homing speed. Changing in configuration.h is not enough.

Thank's, that might be the root of the problem. I have changed the eeprom param between trials but might have missed it. Or are there values which are not changed between compiles even if eeprom mode is changed?

MartinH

eeprom change should update the eeeprom afaik.
However i allways prefer to do a
M502
M500

this will read the config.h and store values into eeprom.

mebj

When checking the eeprom values I found that these were not correct at all for max speed and homing speed. I do not know what happened because values were not in line with any value I ever did set nor the "standard" values coming from the config tool. After changing them manually with the host software z-speed became OK also for 400 steps/mm. Guess I should have cleared the eeprom before upload of the firmware.Thank's a lot to everybody contributing to the solution.