Centroid Community CNC Support Forum

Folks,

I'm in the middle of refitting a used Techno Isel lathe. I've started posting videos to my you tube channel. Please take a look if interested.

https://www.youtube.com/playlist?list=P ... ut0dRy_u85

Some topics addressed on the channel:
Overview
Rip out and Acorn install
VFD integration
Motor integration and tuning
Ball screw rebuild, unbend, and reinstall (future)
Alignment (future)

For a functional test, I ran the packaged pawn program.

Enjoy,
Mike

Looks like you are doing a nice job on your conversion.

I have one that I am working on as well.

So far, I have it working with dmm drives and servos. Right now I am working on cleaning up the install and the alignment of the machine. Some of the issues mine has is the fit of the carriage gibs to the bed and my cross slide was so bad it barely moved.

To fix the carriage I designed new gib plates that utilize a tapered style adjustable gib. I am experimenting with delrin gibs and they seem to work wonderfully.

As for the cross slide I've been experimenting with linear bearings and rails. I have it working pretty well but it's not ideal. I just made use of some stuff I had on hand. I'd like to redesign the cross slide utilizing hiwin low profile trucks and rails. Sort of a sub plate that bolts to the carriage.

I am looking forward to seeing your progress.

-Adam

Nice! thanks for posting!
everyone should watch your excellent test for EMI noise before and after good cable with shielding.

Adam,

I am interested in seeing your linear rail and gib solutios for your lathe. Got pictures or videos you posted?

Mike

I'm in the middle of refitting a used Techno Isel lathe. I've started posting videos to my you tube channel. Please take a look if interested.

https://www.youtube.com/playlist?list=P ... ut0dRy_u85

Some topics addressed on the channel:
Overview
Rip out and Acorn install
VFD integration
Motor integration and tuning
Ball screw rebuild, unbend, and reinstall (future)
Alignment (future)

For a functional test, I ran the packaged pawn program.

Mike, I watched your EMI video and you show the shield wire ungrounded? I've built recording studios in the past and many automation systems with over 30,00 points in them, and this seems odd to me as we grounded all wires at one end but not the other so as to take any stray signals to a common single point ground. I'm wondering how a shield could do anything if it has no ground potential?

Dave C.

Dave,

You are correct, I currently do not have the shield grounded at this time on either end. Building code in my area requires GFCI outlets in the garage and I've had issues with shield grounds from 3-phase motors with VFD's producing enough conducted emissions to trip the breakers. Additionally, grounding this signal to the machine increases conducted emissions into the Acorn which can cause sporadic issues.

Now it is important to note that real source of the EMI is the VFD's which produces high voltage chopped 3-phase signals in the KHz to MHz range causing radiated emissions in the cable and conducted emissions in the motor. The motors emissions get conducted through both the frame and through the rotor. The rotor's signal generally gets conducted through the bearings, which if large enough, can lead to bearing scoring and shorten the life of the motor. Depending on the length of the motor cable, the captured radiated emissions from the cable shield can be 10x that of the motor. And by the way, once its on the ground, you can put a scope on the ground anywhere in your house and measure the VFD noise.

I've made many attempts to run the shield through the GFCI ground using blocking capacitors, chokes, and ferrite cores with limited success. There are other types of GFCI outlets out there that provide some additional immunity, but are quite pricey. The best recommendation I've received, and one I intend to enact, is to run the shield ground either through a dedicated earth ground path or by-passing the GFCI ground (just for the shield of course). The former seems to make the most sense to me, the later technically exposes the Acorn to conducted emissions ( as well as other house hold items potentially).

Hope this helps,

Mike

Dave,

You are correct, I currently do not have the shield grounded at this time. Building code in my area requires GFCI outlets in the garage and I've had issuues with shield grounds from 3-phase motors producing enough conducted emissions to trip the breakers. Additionally, grounding this signal to the machine increases conducted emissions into the Acorn which can cause sporadic issues.

I've made many attempts to run the shield through the GFCI ground using blocking capacitors, chokes, and ferrite cores with limited success. There are other types of GFCI outlets out there that provide some additional immunity, but are quite pricey. The best recommendation I've received, and one I intend to enact, is to run the shield ground either through a dedicated earth ground path or by-passing the GFCI ground (just for the shield of course). The former seems to make the most sense, the later technically exposes the Acorn to conducted emissions.

Mike

Interesting issue! I've never had a three phase motor installed on a GFCI. Our code for GFCI's is only for single phase circuits like bathrooms and kitchens or outdoor receptacles.

Your installation may be a bit more unique as well because your control cabinet is part of your lathe. All of my installations have separate cabinets on the wall so the grounding scheme is a bit different.

I would guess that you motor is grounded to the lathe, which would make it common to the cabinet as well?

That being the case, a good electrical earth ground should be applicable just like any other good machine installation. That is one of the reasons for the whole 4 wire thing for 240 volt single phase. Two wires for the 240 legs, one for neutral and one for ground.

That was supposed to get ride of floating voltages on the neutral!

I would not, I repeat NOT, run a dedicated earth ground as that will give you a different potential to ground from the rest of your electrical system. If you have a way to use the same ground that you breaker panel uses, the one that has the earth ground wire, that should solve your issues.

Let us know what you come up with as there are others here who can benefit from your experience.

Also, I assume you are using 240 volt single phase in the garage and the drive converts to three phase. So does your code require you to have a GFCI on a 240 volt outlet? (using two 120 volt GFCI's for a 240 Volt circuit does not work as the return potential is not the same and they will trip)

Dave C.

Dave,

Yes, if I do run a separate earth ground, it will only be for the shield and will be isolated from the rest of the machine ground.

Mike

Dave,

I'm running on 120V single phase. The motor is 1 HP. Any more and I would have to consider 240V.

Mike

i upgraded our in house Techno Lathe to Clearpath as well!
here are some quick first impression videos...



test part run wtih 3/4-20 thread





demo of X and Z tool offset automatic measurement cycle.