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Author Topic: Motion from XHC shuttle mpg pendant  (Read 2443 times)

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Motion from XHC shuttle mpg pendant
« on: February 10, 2015, 02:15:33 PM »
I have a wireless XHC mpg:

http://www.ebay.com/itm/Wireless-Mach3-MPG-Pendant-Handwheel-for-CNC-Mac-Mach-3-4-axis-Wholesale-Price-/140918851970?pt=LH_DefaultDomain_0&hash=item20cf6b0982

It's pretty much a godsend on my 4x8 router.  The terminal's too far away to mess with the keys.  I guess a wireless keyboard would be nice too, but this fits in the hand.  And it's cheap, and has a DRO on the pendant.

What I'm bummed about is the handwheel motion.  It's a single speed, which means it's really not different than pressing a button.  That is, there's a"fast" setting where it moves in about 1/2" increments at a constant speed.  There's also a "slow" setting which moves in small incremental steps, like 0.02".  However, spinning the handwheel faster in either mode doesn't actually move the axis faster.  Rather, it just stays in motion at the same speed for as long as you're turning the handwheel. So it's not acting like a handwheel, it's not a handwheel if the speed you turn it has no effect.  Also that means it "loses" steps when turned quickly, so rotating 3 turns clockwise quickly and then 3x counterclockwise slowly will not return the axis to the same position even though the handwheel is in the same position, so there's no direct relationship between handwheel position and axis position.

I was wondering if there's any way to change that?  The XHC documentation's real limited here.

What I want is for it to
1) go slowly if the handwheel's turning slowly
2) go quickly if the handwheel's spun quickly and
3) make a consistent relationship between the handwheel position and axis position.  

Number 3) there, that does have a danger, that if you spin it faster than the axis moves, it'll cache the motion and may take some time to catch up so it will stay in motion after the handwheel is stopped, in order to get to that position.  

I guess that also means I'd want:

4) be able to change back the target on-the-fly.  That is, say the axis is slow and you've spun the wheel clockwise so it's been commanded to move 10" further than it actually has gone at this moment.  But you decide that's too far and turn the handwheel back CCW 2".  It need to go 8" and stop, not cache the moves where it goes to 10" and back to 8".

And I know that one seems difficult.  If I'm using the MDI and enter "G0 X10" and then enter "G0 X8", it can't possibly modify the X10 move and stop at X8.
« Last Edit: February 10, 2015, 02:23:39 PM by MechanoMan »