Re: [CAD_CAM_EDM_DRO]How to pick up an edge accurately
Posted by
Marcus & Eva
on 2002-02-17 22:20:52 UTC
Hi Ray:
This method actually works really well and is a LOT more sensitive than
an edge finder.
I gave up on those about a decade ago because I was finding that they were
inconsistent for accurate positioning.
You know what the culprit turned out to be? Magnetism in the workpiece!!
I do a lot with toolsteels that have been hardened and ground and they
retain some magnetism even after I run them over the demagnetizer.
So the workpiece will pull the edge finder toward it and read wrong, often
by up to 0.002"
Drove me nuts until I figured out the problem.
With the 3/4 pin and the 1/8 gauge block I can pick up a part center faster
and to closer tolerance than I can with a tenths clock.
Don't forget, I'm using the gauge block as a feeler, so the pin doesn't get
traversed right up against the job, it is stopped roughly 1/8" away.
Actually I run up a bit closer, and then push the gauge block into the gap
while jogging away again at the 0.0001 setting, but just spinning the
handwheel.
When the block slips through the gap, I stop and then go back toward the job
in 0.0001 increments, gaging after each jog increment, until the block has
the right feel as it slides through the gap.
You can easily position to 0.0001 this way, and it's super quick; way
quicker than farting about with a clock.
Give it a try, you'll like it!!!
Cheers
Marcus
This method actually works really well and is a LOT more sensitive than
an edge finder.
I gave up on those about a decade ago because I was finding that they were
inconsistent for accurate positioning.
You know what the culprit turned out to be? Magnetism in the workpiece!!
I do a lot with toolsteels that have been hardened and ground and they
retain some magnetism even after I run them over the demagnetizer.
So the workpiece will pull the edge finder toward it and read wrong, often
by up to 0.002"
Drove me nuts until I figured out the problem.
With the 3/4 pin and the 1/8 gauge block I can pick up a part center faster
and to closer tolerance than I can with a tenths clock.
Don't forget, I'm using the gauge block as a feeler, so the pin doesn't get
traversed right up against the job, it is stopped roughly 1/8" away.
Actually I run up a bit closer, and then push the gauge block into the gap
while jogging away again at the 0.0001 setting, but just spinning the
handwheel.
When the block slips through the gap, I stop and then go back toward the job
in 0.0001 increments, gaging after each jog increment, until the block has
the right feel as it slides through the gap.
You can easily position to 0.0001 this way, and it's super quick; way
quicker than farting about with a clock.
Give it a try, you'll like it!!!
Cheers
Marcus
----- Original Message -----
From: "Raymond Heckert" <jnr@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, February 17, 2002 5:08 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: OK, I've got a detent encoder... What
now?
> Was I was you, I'd use an edge-finder! They tolerate up to .050 of "oops,
> too much" movement. I can get an edge finder to "repeat" within about
> 0.0002".
> I'd really worry about bending something by jumpin' at it .01" at a time,
> by the eyeball.
>
> RayHex