Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: cornwallav8r on September 30, 2012, 03:52:33 PM
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Getting up to speed, learning how to set the home position versus limit switches, etc.
My machine consists of a 3 axis engraver table, table itself moves in Y direction, tool moves in X, and head moves up down in Z of course.
Stepper motor drives, with one limit switch at bottom left most tool position in y,one at leftmost position in x, and the z has a limit switch at top and bottom limits of travel. Total 4 switches in series.
Question 1: Not sure I am setting things up right...the z motor never references upwards properly to the switch and back off of it, like it should, it often goes up (correct direction) half an inch or so, stops as if the switch was made, then goes on to reference the x and y axes, which it ALWAYS does perfectly. The Z limit switch port pins are all identical to the other limit switches, since they all share the same line. So that is correct. What would cause the z not to go up to the switch and reference correctly? All axes are set up properly for direction and speed and acceleration and distance calibration. They all jog fine.
Question 2: I have never seen the capability to limit manual jogging to stop on limit switch. Mine just tries to plow through past the switches. I Can't find a setting for that. But I guess once I have figured out the procedure for machine limits versus soft limits versus offsets, the machine won't jog past the soft limits. ....it's all a bit confusing really.
Any assistance would be most appreciated.
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1. sounds like a bouncing switch or electrical noise, you could try adding some Debounce Interval on General Config page, try 2000 and work down to as low as you can go if it helps.
2. Config menu then Homing and limits and you can set up soft limits is what you are after, just sounds like you either dont have them turned on or they are not configured correctly.
Hood
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Thanks for the input, you might be right on the switch bounce.
Well I was depending on the wrong manual. I studied the software config manual, but now I see the larger "Install, operation and config" manual discusses these topics more in depth, lemme go read some more.
I just need to understand the setup procedure and zeroing axes better.....it's quite confusing at first. If I still can't figure it out, I will post again. Thanks
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What happens when you home is Mach sets machine coordinates. The user rarely uses or cares what machine coords are as they are really for Mach to know where it is. Normally what you do once homed is jog to where you want your parts zero position to be then zero the axis DROs. By doing that you have just set up a work offset.
There is more to it than that but that is the basic setup.
Hood
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Watch the "homing & limits" video, a couple times, it helps me figure out a lot and I really don't know what I'm doing yet. : )
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Ok I am past that learning curve, and have the machine coords versus work homing down pat.
But I am getting an intermittent problem with losing steps....for example when I jog, even though I have the speeds down to a reasonable level, in fact regardless how slow I run a particular axis, in one direction only I can hear it losing steps, verified by the VERIFY button in testing. This happens to 2 separate axes, and only on one direction. Any thoughts?
I have increased the dir and step times to 1 or 2, but it doesn't seem to change anything.
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Try changing the step pulse active state and see if that helps.
What Kernel are you running?
Hood
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Hmm....when I go into motor tuning dialog and change the dir and step us values, they don't save. Maybe that's my problem...they revert back to zero and one. Am I doing something wrong?
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They should save, can you attach your xml and I will see what happens with it here.
Hood
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Here is my xml file, thanks for looking. For reference, all i need to do is click ok, in the motor tuning dialog, and when I go back into it, the dir and step values previously chosen should show up as they were save correct?
I know it sounds obvious, but it doesn't work that way here.
I will go and change the previous step and dir settings we discussed awhile.
Thanks
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Saving fine here.
Are you using an old version of Mach? Might be worthwhile updating.
Hood
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No I just loaded it, but will write over it. You mean to say when you enter values in dir and step boxes in the motor tuning dialog, , click ok, then come back, they are what you saved previously?
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Yes they save for me.
So you have the latest version of Mach? XML seemed to be an old version.
Hood
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Ok fixed it. The software was old, updating fixed that saving issue.
The lost steps were due to a disconnected cable shield on the axis cable inside the controller box, between the motor driver card and the motor cable output jack.
Nothing like a shield disconnected, acting like an antenna. sheesh. I think all is well, thanks SO much for the quick help, much appreciated.