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Author Topic: Alright fellow campers...a frankenstein moment!!  (Read 6367 times)

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #20 on: November 15, 2017, 12:27:47 PM »
Tweakie, thank you for the suggestion, I need to order things better.  when I first started I knew nothing about cnc electronics, so of course I am making all the typical beginners mistakes...so its been quite a learning curve and it continues.
Re: Alright fellow campers...a frankenstein moment!!
« Reply #21 on: November 15, 2017, 12:34:59 PM »
Rich HI

I took your radio idea to locate the heavier sources of noise in the system.  The inverter itself produced very little static on the radio.  The control box of course produced a lot of noise, but nothing produce static as much as the spindle itself... it was very strong around the junction where the shielded cable inserts into the built in plug on the spindle motor.  The shielded cable itself had no static along its length.  I purchased an 8 foot copper grounding rod and will drive it into the ground today or tomorrow and then "earthground" the spindle, control box, the base is alumn., and anything else I can ground it to--as you suggested.
Re: Alright fellow campers...a frankenstein moment!!
« Reply #22 on: November 15, 2017, 01:02:41 PM »
Hi,
that might work but may also cause problems.

Your household electrical installation will have an earth rod somewhere. If you go and put in another somewhere near your machine an hook it to the frame of the machine
you will have created an earth loop. By earth loop I mean: frame of your machine to new earth rod, through earth to existing earth rod, to the earth conductor of household
wiring, to the socket you have your machine plugged into, to the metalwork of your machine, a loop. Any alternating magnetic field passing through that loop ill induce
a voltage in the loop potentially causing problems.

You are working the strategy that you wish to reduce the sensitivity of your installation from radiated and/or conducted electrical noise, its a worthy strategy and lots of little
things you can do to make it effective.....BUT there is an even better way.....stop the electrical noise from being generated in the first place. If you never turn your
spindle on then you get no interference....not very helpful. Why is your spindle motor so noisy? Is it a DC motor and if so are the brushes in good order? Are the brush
springs providing the require engagement force?. Are they the right brushes, not some that you found and filed down to fit your motor (yes I've done it)? Is there a RF choke
in series with each brush or could you put one there? Is there suppression capacitors on the motor or have they broken off? If they've been replaced have they ben replaced
with ceramic or silver mica caps? It may be as simple as correcting a fault with your spindle motor and all the noise issues recede into the distance.

Craig
My wife left with my best friend...
     and I miss him!
Re: Alright fellow campers...a frankenstein moment!!
« Reply #23 on: November 15, 2017, 02:24:44 PM »
Thanks Craig for the loop information... the spindle is brand new and has less than 2 hours of actual running time.

I guess if I installed a new ground rod some distance from the house and then if after grounding the spindle to the rod, and then of the lathe didn't turn on by itself anymore, then we would have fixed the situation.  So I will try your suggestions.  But an earth ground loop at this point seems unlikely as the rod is grounding to the whole earth which would seem to offer much less resistance than the loop... you disagree??? bob
Re: Alright fellow campers...a frankenstein moment!!
« Reply #24 on: November 15, 2017, 02:31:38 PM »
Hi,
to have a second earth stake is to have an earth loop...thats pyhsics.

It may be troublesome but then again it may not. My experience is that earth loops can cause control circuit faults
particularly in industrial situations where large machines can produce large magnetic fields and work on earth loops.

Craig
My wife left with my best friend...
     and I miss him!
Re: Alright fellow campers...a frankenstein moment!!
« Reply #25 on: November 15, 2017, 03:17:13 PM »
I now follow your thinking. I will let you know how the experiment works out... I don't think a 1.5kw spindle can compete with big industrial machinery.

bob
Re: Alright fellow campers...a frankenstein moment!!
« Reply #26 on: November 15, 2017, 03:59:19 PM »
Hi,
it does seem unlikely that an earth loop will cause you any issues in a home situation.

If you ever talk to an Audio engineer or a sound technician for a band...ask about earth loops and they will give you chapter
and verse. Don't overlook earth loops they WILLl cause grief and are hard to solve if you don't keep your eyes/mind
open.

Craig
My wife left with my best friend...
     and I miss him!

Offline RICH

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #27 on: November 15, 2017, 06:23:13 PM »
ECHO.......
"Only do one change at a time and see if it solves the problem"
That includes the earth grounding also. Then if there is a connection at the spindle wrap some wire mesh/ braid  around the
the connection and attach the wire to the mesh. The mesh acts as a shield.   

I must add "makes progress" to improving the situation.
See if  a fix can be improved.
Then add another fix in addition to the original.
Ideally one would quantify any fix, or analyze the field, but, unfortunately most don't have the equipment or knowledge to do that.

Note that once a signal is mixed with another it may be impossible to resolve the matter, simply.

RICH
« Last Edit: November 15, 2017, 06:35:04 PM by RICH »
Re: Alright fellow campers...a frankenstein moment!!
« Reply #28 on: November 15, 2017, 07:27:54 PM »
Rich,  thanks, good points... step by step, record all experiments.  bob
Re: Alright fellow campers...a frankenstein moment!!
« Reply #29 on: November 15, 2017, 07:30:03 PM »
I have a variable speed wood lathe... a small one... at last resort I can simply use that and have the Cnc spindle do the millings in conjunction with that... but I would like to be able to do indexing... so I will take the time to figure this out.