DWP611 Continuity for Z-axis Probing

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TonyB
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DWP611 Continuity for Z-axis Probing

Post by TonyB » Tue Jun 07, 2016 9:15 pm

I apologize if this question has been asked before.

When it comes to Z-axis probing, a lot of people use a something like this:
http://tinyurl.com/zo6xtvn

I have something similar that I built. Manually attaching an alligator clip to the end mill is not only annoying but somewhat dangerous.

What I'm wondering is, is there a way to connect a ground wire to some part of the DWP611 to get continuity to the endmill/collet? If so, then you would only need to bring the touch plate to the end mill; which is half as much work.

Thanks,
Tony
MegaSquirted 62mm 7m @ 20psi on 91 octane
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CastIrony
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Re: DWP611 Continuity for Z-axis Probing

Post by CastIrony » Tue Jun 07, 2016 10:58 pm

I'll check tonight, but I'm not super optimistic.
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CastIrony
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Location: Portland, OR

Re: DWP611 Continuity for Z-axis Probing

Post by CastIrony » Wed Jun 08, 2016 5:10 am

Yeah, I'm not measuring any continuity between the bit/collet and the metal on the outside.

If you open it up, you might be able to solder a wire to the outside of the bearing, but I don't think those are meant to maintain reliable electrical continuity even if it usually works. You *really* don't want your probe connection to be unreliable.
Shapeoko 3 #192 - Complete! Needs limit switches.

cvoinescu
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Re: DWP611 Continuity for Z-axis Probing

Post by cvoinescu » Wed Jun 08, 2016 10:17 am

I don't have a solution for making the spindle conductive, but I have one for making the alligator clip safe.

Rig your spindle speed controller (or add a relay) so that it's energized only when a certain input is grounded. Connect that input to an otherwise insulated metal part (e.g. a post or a loop), to be used as a parking position for the alligator clip. This way, the spindle can not start unless the clip is off the endmill and parked on its metal loop.

With a couple of diodes, you can also make that connection short the probe input to ground, which will make the probing operation fail if the alligator clip is still parked -- so you also avoid the situation where you forgot to put the clip on the endmill and the probing movement does not stop and destroys the endmill and/or the touchplate.

Probing can still fail in a number of ways (e.g. you don't place the touchplate under the endmill, or you take the clip off its parking position but forget to attach it to the endmill), but you've got the two most important cases covered.
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