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Author Topic: X and Y axes jump when reversing directions  (Read 2374 times)

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X and Y axes jump when reversing directions
« on: March 31, 2013, 12:56:19 AM »
Hi everyone.  This is my first post, so glad to be in good company

In the last few weeks I've got my BlackTow 2x4 running smoothly with Mach3 - until today.  I've only had a short time to actually play with it, but managed to have the simple g-code spiral drill example on page 3-10 of the Using Mach3Mill manual run smoothly.

This evening though, when I went to run it again - or when moving the gantry with the keyboard arrow keys - the gantry jumps every time it changes direction in either X or Y;  Z remains smooth as silk.  I've checked that motor tuning is correct and inverted drive signals are selected as with my original setup, but it appears that I have managed to mess up some configuration somewhere and I have no idea where to look.  When I slowed the drive speed way down so the gantry moves at a crawl, it still jolts at each axis change of direction.  It acts as if there are a fixed number of steps introduced at the start of each direction change - then it runs smoothly again until the next direction change when it jumps (in the new direction) and then continues on smoothly.  The jump is very short, but rather more violent than makes any rational sense - and as I mentioned earlier, this is not the action I saw initially.  All the drive shafts and chains appear to be tight and well adjusted, and I don't believe its clocking - surely not in Y since there's only one drive.

I was looking at a bunch of configuration stuff last time I used the machine, so am afraid I've set something wrong.   

Anyone have any suggestions?



Offline alenz

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Re: X and Y axes jump when reversing directions
« Reply #1 on: March 31, 2013, 02:05:45 AM »
You might try going to Config>Backlash and see if  ‘Backlash Enabled’  is checked. If so uncheck it.
Just a thought.
Re: X and Y axes jump when reversing directions
« Reply #2 on: March 31, 2013, 02:32:58 PM »
Thanks Al

That did the trick!!  Guess I was touching knobs I shouldn't have before knowing what they might do.

Great help - really appreciate it.