Current through mill spindle. WTF?

If that's the case, how can it be resolved?

I've been hired to help get their cnc machining under control. They *want* me to find problems and address them. Fixing machines is going to be easy. Fixing personnel and methods issues is not.

Thanks for the links.

I seriously doubt that it is piezio electric in nature. Piezo electric materials are typically crystalline materials and ceramic bearings are I believe amorphous materials.

Gary H. Lucas

"Gary H. Lucas" wrote in news:hrJDg.43307$u05.31113@trnddc01:

Yup, but when that earth ground is no longer present, or degraded, then that leakage current tries to go anywhere it can find the least resistance to earth, not where, or how you wish it to to be directed (by creating a path of least resistance via the earth ground). I've seen poor grounding cause all kinds of ills, especially in a logic-controlled device.

Couple it to a transformer and sell it back to your public utility :)

If the bearings themselves are generating the voltage I would not worry about it. You could put a wiper somewhere on the spinde connected to the machine base but A couple of volts between the spindle and the machine would only hurt the bearings if they were metalic.

You might call the bearing company and check to see if this is a condition of using ceramic bearings. A conductive grease on the bearings might stop it but I would not do that unless the bearing mfgr. recommended it.

Piezo electric flow happens in the barbeque igniters,microphones, transducers and a lot of other equipment and sensors. I would highly suspect this is the cause of your problem. I wonder how it would sound if you ran it through an amplifier to a set of speakers, one for each machine? :)

John

Ceramic exhibits piezo electric properties.

After looking at these sites, it seems that even though the hard ceramics used in bearings are not very good at generating electrisity, they still do generate a little.

John

You are 90% of the way to being a big success as a consultant. Drucker and Cosby move over ....

Keep telling yourself -- "I will not attempt to solve non-technical problems with technology -- I will not attempt to solve non-technical problems with technology -- ..."

It can be exceedingly helpful to have a good working relationship with a qualified/experenced Industrial Sociologist or Group Dynamics practitioner when you encounter situations where the problems are mainly organizational/relational rather than technical. If you are close to a University, talk to the sociology and/or psychology departments. You can also find good people in the Human Resource Development programs, not so much so in the Human Resources Management programs (these tend to be a more business/finance oriented).

While not a priority item, it would most likely be worth your while (if you have not done so) to take an Abnormal Psych and Industrial Sociology classes [If you audit the classes you generally don't have to go through the enrollment/marticulation drill] so you can recognize the situation before getting "sucked in" a "no win" assignment. If possible you want the graduate seminar classes as these have the people "what been there and done that" and they are trying to figure out how they got so many knots on their head....

A place to start is Ken Kiser at Oklahoma State University. He teaches, but also does considerable consulting work. He was on my dissertation committee and is very knowledgable about the way all sizes of organizations operate. Tell him George McDuffee sent you. Email: snipped-for-privacy@okstate.edu

KEN KISER. PROF:, KEN KISER. Address:, 025 CLASSROOM BUILDING. STILLWATER, OK 74078 -4062. Phone:, 405-744-6112. Fax:,

405-744-5780 ...

I only wish that I had taken the course *BEFORE* I started consulting.....

Unka George (George McDuffee)

...and at the end of the fight is a tombstone white with the name of the late deceased, and the epitaph drear: ?A Fool lies here, who tried to hustle the East.?

Rudyard Kipling The Naulahka, ch. 5, heading (1892).

Possibly arrange a brush contact on your spindle wired to some part of the machine that is at earth pontential.

I guess if you are brave enough you could determine if this is the case by using a wire grounded at one end and touch the other end on the spindle while you are seeing this.

Wayne...

Wayne:

Much better than touching the toolholder, or creeping up on a piece of stock with the toolholder. I still think you'd create more excitement if you had the boss put one hand on the table and then touch the toolholder with the other one. LOL

Or his tongue...

Anthony, Again I'll say what I have said before. If removing or installing a ground affects the way a machine operates then the machine is wired WRONG! Properly wired systems do NOT change operation due to grounding. The grounding is only for electrical safety. When you drive a ground rod next to a machine you have in fact compromised the electrical safety of the whole building, not just this one machine. Electrical inspectors ought to be on the lookout for this kind of "fix" and order the offending machines shut down until the proper repairs are made and the ground rod is removed.

Gary H. Lucas

Gary,

There are times in some area's of the states where ground rods solve problems.

As long as the ground rod shares a common connection to the building ground it poses no safety hazard.

It is not something to do unless you understand your "Specific: buildings ground and what the oem has to say.

Supplemental ground rods are permitted under the National Electrical Code ® (NEC), but they should only be installed, if at all, after a careful analysis of the building's entire electrical, grounding and lightning protection systems.

'grounding%20rodsmachine%20tools') I know your an expert on the subject, maybe you can read the links and present some comments as to where they are wrong.

Regards ' Regards Daveb

Driving a supplemental ground rod is a practice that many in the industry either don't recognize or don't support. The NEC doesn't consider the practice because it's not a matter of life safety. Manufacturers of electronic equipment like computers and electronic motor drives don't subscribe to the theory because it's unnecessary. And IEEE standard 1100 (The Emerald book), which focuses on powering and grounding sensitive electronic equipment, doesn't recommend it. Instead it recommends a single-point ground, from individual electronic cabinets, be individually bonded to a local ground grid.

Some CNC machine manufacturers recommend, or even require, the addition of a supplemental ground rod at the CNC machine. (?CNC Machine Manufacturers Speak Out? on page 24). In most cases, this is an 8-foot copper rod driven next to the machine, often through the concrete floor, and bonded to the machine's ground plate. The NEC does permit such an installation, as long as the ground rod is bonded to the building electrode grounding system. However, you must realize that this installation may still invite stray ground currents.

Best

Daveb

Maybe you could try calling the tech support of the company that built the machine. Shoudn't cost anything.

Rocky

Had a similar situation with large laser. Everytime gantry came close to job support, small spark!

Checked all wiring within machine, then moved (with forklift) machine away from wall - found +- 15meters of mains cable coiled up in neat, tight coil behind machine. Replaced with short mains lead - bye-bye spark . .. .

Cool dry air is great for building up static. Is the air system grounded anywhere? Should an air system be grounded? Is this question going to- no, I won't even go there.

Try Parameters/Tool/Edit, and the length offsets should appear in the left column, and the diameters will be in the right column. As you tab through the numbers with the arrow buttons, the current offset for each one will appear next to itself. You can then type an equation and look at it next to the original number before pressing Enter. Is it a Centurion6 control?

Later,

Charlie

holy cow.

So I guess you have a hybrid VMC/EDM machine! Does that mean your tools will never wear out? So now that the secret is out, where did you buy the machine?

put a voltmeter across the table and the tool and see what you get. you might also be getting a static charge built up somehow. Is this a belt driven spindle? Sounds to me like you've got a grounding problem. The resisitance between the spindle and the table is going to be nill, so any voltage differential between the two points is going to cause a significant amount of current. Which translates to a high potential for arcing.

ca

Black Drag> At new $employer I've spent the past couple weeks doing light

The machine is a month or two old and under warranty. Allegedly all the Miltronics techs are busy at some shop that has about 40 of their machines and got flooded with four feet or so of water.

A factory tech is going to be in some time this week to address a squareness problem, and the entire purpose of my original post was so I could have a bit of understanding about what could possibly cause electrical current to flow through a machine spindle. I fully admit to being clue impaired when it comes to electricity.

I don't have time to reply to all the most excellent posts on the subject, but thanks much guys.

George... me a consultant? Meheh. I definitely would make a better insultant, don't you think?

FWIW, I measured the voltage of the rotating spindle again while it was cutting. When the tool was engaged in the cut the voltage fluctuated between .5 and 1.5 volts, and when the tool exited the cut on a entry / exit arc move it jumped up to around 10 volts, then back down to .5 /

1.5 when back in the material.

Oh, I see their in NO last yr .