Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: cwaugs on November 18, 2009, 12:50:02 AM
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I tried searching but no concrete answer. When any one of the three Viper drives E-stop the system, or hitting a limit switch, all three axes lose their green reference LED's then all three axes need to be re referenced. Why not just the one that screwed up?? P.S. Thanks again for a fantastic product as well as un-believeable support. The best! Wayne
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It will depend on how you have things set up to react to a drive fault signal. If you have one axis fault and it causes Mach to do a reset then chances are you have lost position on the other axis as well as they have stopped moving abruptly without deceleration.
Hood
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Is there a way to change the settings in Mach? Only 1 axis needs to be moving and it resets all three. Thanks again, Wayne
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How have you got the signal from the drives connected to Mach?
Hood
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The step direction and 5V from the campbell board are connected to the drives and I have the drives wired to an unused limit input, and the drives will trip the e-stop when they error but will not reset the home led's. I tried it today and without anything moving, just simply pushing any of the six limit switches un-homes all three axes on the machine. I suppose I need to go through the setup videos and try to understand more of the options settings in the configuration of Mach. I can hit a limit switch on my router and it doesn't do anything with the homing. Thanks again, Wayne
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If you have it configured in at the E-Stop then it will definitely mean you need to re-reference all axis. Why not use Input 1 and set it up as the Safety Lockout, you will find that on the lower left of the General Config page. If you do that then what happens is when that input becomes active Mach stops code running until it goes inactive. You will still need to reference any axis that was in motion when a drive faulted but not all. In fact Mach wont even force you to re-reference the axis but it will have very likely lost position so it is only wise to do so.
Having said all that it is good practice to re-reference all axis if there is even the slightest chance that they could be out of position but thats up to you and to a lesser extent the type of work you do as it may not need the accuracy.
This then brings the other question up, why are the drives faulting in the first place?
Hood
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Also meant to say, setting up soft limits should help a lot in that Mach should never let you hit the real limits unless you have lost position for some reason.
Hood
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The drives aren't faulting now because I have them tuned better than before. I was trying to run >250IPM with a big machine and even though more than that is easily possible, I need to mess with the tuning before I can crank it up. My main query is why when everything is setting still, pushing a limit switch will un home all three axes, but on my router, with soft limits disabled, hitting a limit only stops Mach from running the code. Maybe it is configured differently in that respect and that is what I am used to. I realize it would be better to re home on any out of parameter situation. Maybe I'll just stick with that mindset and continue setting up soft limits to keep that from happening, because hitting a soft limit doesn't lose home position.
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I totally agree and Thanks again for your help. Wayne
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As said above setting the fault input as Input 1 will not need re-referencing but still good to do it on any axis that was in motion at the time.
Hood
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There is little commonality between differnet servo drives. They each have their own way of behaving approaching, during and after faulting.
Some drives will fault and cut power to the motor, but continue to track the encoder and the control inputs and therefor can remain 'homed' even if the motor is stopped. Correcting the fault sends the axis back to the correct location.
You may find a review of various drive beneficial. You can find it with a search on this forum. ALL of the drives I tested do behave the same in one characteristic and that is that a reset, however initiated, causes the drive to loose 'home' and re homing is needed.
In my setup, I have the drive error lines connected individually to the Mach axis limits, but I usually have soft limits active so a limit fault means one of the servos is faulted (usually). Mach is vague about why it stops, but I have remote indicator lights on each servo drive so that I know which one faulted and I have separate reset buttons next to the indicators so I can reset each drive independently.
Still, in practice, I have to say that I agree completely with Hood in that it is safer to just re-home all axis after a fault, just to be on the safe side . . . provided, of course that your fixture setup allows this to happen conveniently. I am finally tuned up pretty well and the only faults I have these days is with stopping a program mid run that has multiple coord offsets in it or when I am debugging a program and where I sometimes have to turn soft liimts off if Mach gets confused by all the shifting around (or maybe it's me that gets confuded . . :-[)