em806 Senssorless Stall Protection fault

I think I had this problem a few months back and im sure some one helped sort it however I cant for the life of me find the information any were. I thought I changed something at the time and it fixed it but the problem seam to have come back and now the z axis trips out in the same place every time on various files.

the problem is on my z axis always tripping out and giving 5 blinks on the led indicating Senssorless Stall Protection

I seam to remember it was something to do with the motor tuning and they said it was do with the axis not keeping up with each other but as I say cant find were the info I was given is.

can anyone make any suggestions on what to do?

many thanks

Is your Y axis dual-motor? Is it happening in the same physical place each time, or do you mean that the files that cause it always stop at the same line of gcode but in different physical positions?

I have a dual-motor X axis, and the only time I get the problem is when, for some reason, the gantry has gone out of square (and it doesn't seem to need to be far out). Curiously, it happens at the same place along the axis, presumably where the rails aren't quite perfectly aligned, around half-way along. The only other time it has happened was when I was tuning the system; if I pushed things too far (speed or acceleration) I could get stall events, but they don't happen now that I have settled on the parameters I am using.

Assuming no squaring problems, can you wind down speed and/or acceleration to see if that helps? If so, it might provide a pointer.

It’s a single motor, it happens on the sasme g code line anywhere on the machine it doesn’t appear to be macanical. I have had a little play with the speeds but I don’t really know what I’m doing 100%

Can you post an extract of the gcode showing an example of where it happens? One of the pairs of eyes reading this forum might spot the problem. Is it only while actually cutting, or does it also happen when "air cutting"?

Will try too tomorow it happens with both however I’m only cutting foam at the moment so it’s not exactly loaded up. It has been fine cutting one file all summer but now it’s not. Perhaps the cold has effected the motors?

would it be likely that it is the motor/driver that is giving the fault that is likely to be the problem or that its one of the others that is doing it? I have y and z axis both using a em806 and the x using a much larger kinco drive

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the problem seam to have come back and now the y axis trips out in the same place every time on various files.

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Charlie You say various files above.

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t’s a single motor, it happens on the sasme g code line anywhere on the machine it doesn’t appear to be macanical.

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But here yo are saying on the same line of gcode,

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Will try too tomorow it happens with both

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Not sure what this means.

Is it just one axis that is tripping if so can you be a bit more specific as to what is actually going on.
As Neale has suggested does it trip doing fresh air cuts?

Ok so this morning I tried the same file as yesterday which I normal run at 150% and it still faults however run at only 100% it is ok. I have a friend here who knows a little more so we have swapped the two drives over to see if the problem changed drives however now doong a rapid move on the y axis just using the keyboard trips the same driver as before which is now on the z axis.

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Originally Posted by Clive S

Charlie You say various files above.



But here yo are saying on the same line of gcode,

Not sure what this means.

Is it just one axis that is tripping if so can you be a bit more specific as to what is actually going on.
As Neale has suggested does it trip doing fresh air cuts?

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The drive is giving the same sensorless stall protection fault on the same file each time if I change the file it faults again but at a different point in the file but is repeatable if you re start the file. The fault causes a external e stop on Mach 3.

Yes the driver trips doing air cuts

Many thanks

Here are the two motor tuninging numbers for y and z that use the same driver Then the x on the junco drive

This is two different files and the lines of g code it is stoping at doing air cuts just at a random location on the machine, the third picture is the cut I was doing yesterday when the problem first arose again

Did you re-tune the drives after swapping them?

No we didn’t


However we did re tune the drives after changing back to the original settings which did not make any difference.

After that I went back to playing with the motor tuning speeds and have reduced both y and z and it has now been running for a hour or so however it does not seam quite right as it looks like it has cut some corners or not done the tool path correctly.

How do you know how to set the speeds of each motor to get the most with out problems?

Mach3 has a known issue with running at higher feedrate override settings. You're better off setting the feedrate higher in the g-code and dialing down the override. Turning it up to 150% and higher can cause issues.

cheers many thanks I was not aware of that.

I have been playing with the motor tuning and have seam to stopped the fault but im not sure its set anything like optimal

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Originally Posted by charlieuk

How do you know how to set the speeds of each motor to get the most with out problems?

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Keep increasing the settings until the motors start stalling, then reduce them to create a bit of a safety margin.

You have to find a compromise between acceleration and max velocity though. With less acceleration you can ultimately get the motors to spin faster without stalling, however if you're planning on doing things that involve lots of small moves, then sacrificing top speed for acceleration, will often result in faster machining times.

cheers well I had a go at this today and I got them all working nice and got them all a lot faster however went to run a file and when it did some very small z moves it started tripping out again so I had to massively reduce the z back down again especially with the acc. Im wondering if maybe changing the ball screw would help so the motor was spinning a little faster and the weight of the z was overcome a little more, I think its on a 1605 at the moment.

How are your motors driving the ball screws? Direct, or via belt?
What kind of speeds are you getting?

the y and z are on belts and I have the z with 20t on the motor and 50t on the ball screw. I will have to cheque the speeds tomorrow as I went through so many I have forgot. many thanks

You should be able to get a reasonable speed out the Z.

For comparison, I was tuning my Triac last night, and I was getting 2.2m/min with 500mm/sec2 acceleration on the Z, and that's with an old big round stepper driving a 5mm pitch screw with 12:30 gearing via a belt. Now I doubt your Z assembly is as heavy, and you'll be using a more modern motor.