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Z axis going negative

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I am having a problem with my z axis it was alway working fine. Then one ny next print i did auto home like i normally do it did that little bounce and set itself correctly.

I waited for everything to heat up the when the temp was right and the gcodes kicked in (checking the g28)

x and y was good but the z did not do the bounce instead it continues to go negative squishing the z endstop till it can go no more then it tries to print. pressing and scrapping the glass.

I have swapped out the step drivers same issue i also swapped out the endstop. it works fine if i hit auto home on my lcd. it's when it starts to print the second autohome from the gcode it messes up. any ideas?

It not the endstop u can do auto home all day and every day and it will stop on a dime, it only with cura where it continues sqaushing down on the endstop till it cant go any futher.,



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Must be UM Original if he swapped stepper drivers.

I have several ideas. I guess the most likely is that the DIR signal from the arduino to the Z driver is either always stuck or intermittently stuck so that even if the firmware commands the Z down, it still goes up.

Connect the UM to a PC through USB, then use print window in cura to move the Z 1mm at a time in both directions (actually first spin the Z screw so that you won't smash nozzle into bed).

Try moving up and down. If it always moves the same direction then the DIR signal is bad for the Z axis. This is 90% fixed by soldering the 2 or 3 solder joints involved on the PCB. I would probe the DIR signal with a voltmeter at various spots while you command the Z axis up and then down.

The circuit diagram, and board layout are here:


There is a zip file at the top. It contains the "brd" file which is the layout. Also the "sch" file which is the schematic.

Both files can be opened by eagle software which is free:




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Ok sorry been away first it a prusa i3. With ramps 1.4 home built.

I have tried it with pronterface and no problems

I found a older profile which I loaded up now and the older profile it can print but still on occasions it will continue the same past issues so what I do now is a bit of a pain but I do it to use cura.

Load old profile configure old profile

Is auto home level bed then raise z .9 mm set temp hit print.


I had tried doing a "new machine" redid all settings but that did not work.

My auto home starts at left corner nearest to you.. How can I set it up manually so that I don't need to use the z end stop?

Oh is there also a way to use m modes like m119 or m220 beer or during the print?



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Do you have Marlin firmware? The Marlin gcodes are explained here:


Cura expects Marlin for most modes but Daid is trying to make Cura work for other firmwares. If you have a specific request for example "change all G1 to G0 for prusa printer" or something like that, he will usually make changes like that. Daid wants cura to work for all open source printers.

From above link:

M119 - Output Endstop status to serial port

M220 S- set speed factor override percentage

M119 doesn't make sense during a print but M220 will work - you can edit it right into the gcode if you are using marlin.


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Yes m119 was trying to test out my end stops before printing

Yes I am using marlin I was pronterface today I want to see how well my calibration I have to use pronter just to be able to have live code input. But I was test to see how fast my printer could go.. Started with m220 s100 then s150 s175 s200 I was around s280 I did not want to really push it but my print was clean edges sharp I was doing a 40 mm fan mount adapter the had sharp corners circles hole infill a Jump to the second part horizontal holes all the things for real world test.

So I went to cura to input speed 200 it said it was not possible to print at that speed so I will not let you put those numbers in. ...what is up with that?

What I would like to see is a way I can manually put my gcode in a command line like pronterface I can heat up my bed faster, turn fans off and on, speed up print in certain section or slow then down using m220 etc.

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Marlin only lets you do a certain range for M220. Something like 10% to 200%. It's better to just set the speed directly in the slicer. Setting this override percentage is a little dangerous as it overrides for instance the minimum layer time setting which I keep at 5 seconds. With M220 S200 it will only do 2.5 Seconds when it gets to very small layers and you will get crappy looking print.

Anyway - why not just set the speed on the first page of Cura settings? You can set to 10mm/sec or 200mm/sec or 300mm/sec or whatever you want. Set it close to a speed you think will be the actual speed and you can double it with M220 (but no more than 200%). or you can cut it way back to maybe 10%.


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