Interesting mistake with no initial consequences

[Questor]

So, I was setting in several cabinet doors to mortise in some hinge recesses. 2 small toolpaths for each door, 2 bits, easy as it goes.

Of course, each time I swapped out a bit, I would zero the z axis. I would tap the plate to the bit to make sure the input lights up on the screen, then run the process.

I ran the program as usual. The bit touched, moved up, retouched again, and set the z zero just fine.

As I removed the zero plate, I noticed that I had forgotten to hook up the grounding clip to the spindle. Oh ****...

But, as is my habit, I keep the grounding clip attached to the leg of the bot when not in use. Keeps it out of the way, yet firmly in place.

I tested things a few times, and found that this is in fact a ground location. Removing the clip from the leg and touching the zero plate to the bit does not light up the indicator on the screen.

Now, I do not plan on using this again, as I can hear a slight hum through the system when the bit is touching the zero plate. I will hook up the clip to the spindle as directed.

But, nice to know I didn't break a bit from being absent minded.

Just passing the info along.

[scottp55]

Steve, Kirk and I have NEVER clipped to collet and now we both use the leg, I noticed Kyle and others use the leg as well. Now Bill Y says he ALWAYS has to use the collet nut on his Desktop. I was told when I started that it doesn't matter too much where it is, SO LONG as when you tap the plate to bit you get the Green Input 1 light. VERY important to ALWAYS check for that continuity green light though. Dislodged clips/broken wires/corroded or loose connections can Really bite you in the A--.
Funny, Kirks has that mild buzzing sound and mine doesn't? Anybody know what or why that might be?
scott

[Chazz]

I have used the collet but never tapped the bit to verify the connectivity. It just never occurred to me. I understand there are some non-conductive bits and that would make sense on new bits. I have the router rather than the spindle. Does this make a difference? I will have to check....

[scottp55]

Chazz, not positive, but some bit coatings are non-conductive (diamond-like or possibly Ti-Gold but not sure) or other coatings or possible lubricants. Always Tap bit every single time. Cheap insurance. Better safe than sorry, Just heard last week of another set of bearings lost to that type of thrust load(Not Shopbot-NOT spindle- but, consider close acquaintance -NOT =friend of a friend -who heard of). Ouch!.

[dana_swift]

"I can hear a slight hum through the system".. gulp.

A change like clipping the ground clip to something else thats grounded should never cause a hum in anything. If it does it is a clear indication something is wrong. No current should flow though the collet clip wire, it's just a signal wire and when contact is made with the bit the current should be just a milliamp or two. Nothing that should cause hum in anything.

That means something isn't grounded that needs to be. I fear possible problems in the future from ground issues. I don't have a desktop bot, so I cant recommend a solution, but there must be users on here who can chime in and help. Save yourself some broken bits later from comm errors and unexpected shutdowns, both symptoms of improper grounding.

Static buildup is another big issue, this is a warning.. take heed.

Of course - that is just my opinion.

D

[Chazz]

So, how do you Z-zero with a non-conductive bit?

[jerry_stanek]

So, how do you Z-zero with a non-conductive bit?

By eye using the keypad. put a piece of paper on the table and bring the bit down to it just touches it and do a zz

[scottp55]

Like Jerry said Chazz, but when you get close, go into "Fixed Mode" like maybe .01" and keep tapping down while CONSTANTLY moving the paper.
DANA, I don't have the "slight hum", but how would an idiot with a volt meter start to trace down the "hum", if there was a significant difference between leg and collet grounding. Just curious for Steve and Kirks machine. If it's very involved don't bother yourself.
Thanks
Oh! Steve, moving Gantry and creating surge is page 65.
Darn, won't upload .pdf, too large even Zipped or .rar.
I'll e-mail direct to you.
For others it is SBG00142080923 UserGuide.pdf maybe Google search? but grabbed it from Shopbot store initially I think. E-mail if you'd like it, but kinda old.

[adrianm]

Should be able to get all the latest documentation from here - http://www.shopbottools.com/ShopBotDocs/

[dana_swift]

Scott- the voltmeter test is simple. The voltage between the alligator clip and any point on the frame should be 0. If its not, then connecting it to the frame will cause a short circuit for that voltage- which will show up as the hum.

If the voltage on the frame at some point is not zero, that is a grounding problem!

Its not rocket surgery-



D