Sorry for the late reply...
I should have added that I have sepparate switches on each axis to
enable or disable them independently. That makes a whole lot of
difference. Even relatively slow cranking with the driver "off"
can generate enough back EMF to semi-power driver and make cranking
really hard. Disabling them makes quite a difference.
True, moving the steppers manually can put you off by as much as two
steps when you switch the drivers back on. But on average it's more
like 1 step. Given 200 step per rev steppers on my .050 per rev
screw that's (theoretically) .00025 per step and a deviation of
at most a half thou, more likely much less, which for most work is
silly talk anyway. Though that would be different if you're using
5 TPI screws...
I suppose I shouldn't have said "micro-position." That's misleading.
What I meant was I'm a lot more comfortable delicately sneaking up on
locations slowly, carefully and manually and by feel. My "finger
memory" for turning the hand wheels is very reliable and the tactile
feedback helps. My "finger memory" for those shift-alt-control cursor
keys is much les reliable. Which is, o course, my own fault. Slowing
things down doesn't help much because once you've hit the wrong key
(or the right one with the wrong modifier) the part or tool is likely
ruined before realize there's a problem, let alone hit the E-stop.
MDI is the other thorn in my side. I still use it all the time. Love
it. But if I had a dime for every time I pressed "cursor up" to scroll
back through the history and moved the table instead... Sigh.
No pleasing some people, eh? :)
Anyway I see where you're coming from. My point was simply that
some people really do use the hand wheels on CNC'd machines for
any number of reasons.
On Mon, March 25, 2013 8:02 pm, Thayer Syme wrote:
> I used to have the same problem with jogging until I decided to leave
> it set to .001 increments. My rapids are set at 75 ipm so I get that
> with <shift> plus arrow keys. I have the actual motion rate set to 5%
> I think, or there about, so with just the arrow keys I have a feed
> rate of maybe 5 ipm. I can then switch to .001 jogging quickly with
> <ctrl> plus arrow keys. I find this combination works very well for
> me and I can find edges quite quickly working that way. I used to
> change the micro positioning scale to then accurately move for the
> offset, but then I learned how to drive with the MDI screen.
> I do have cranks on all three axes and use them for rough positioning
> but never fine tuning. My understanding is that the motors can move a
> step or two as you press the reset button which would likely negate
> the accuracy of manual edge finding.
> My setup is the A2Z CNC Monster Mill, Sherline 10k spindle, Keling
> steppers and power supply, a Gecko G540 driver and Mach 3.