The Dreaded X axis stepper error using UC400ETH and UCCNC !!!

**dachopper** · 10-08-2017

Originally Posted by Clive S

Ok First make sure the machine frame is earthed to the star point in the control box, make sure the screen on the spindle cable is earthed at one end only (solder a wire to the screen and ground it to the spindle body)

Are all your other cable screens grounded to the star point (In the control box you should have only one point where everything is grounded to)

In the control box, I have main 220Volt house power earthed to the corner of the mounting plate, The Stepper Drivers are bolted to the plate, and the Torroidal Transformer is also bolted to the plate.
Then I have a single earth wire coming off that same corner to a small ACDC transformer, and another single wire that goes off then splits to 4 and is the AC earth for my woodchip / 2 x pond pumps and Spindle power inverter.

So I should earth the spindle + Spindle sleeve to earth in the inverter? or back to star?

From DC transformer - all that suff plugs directly into the stepper drivers etc....

**m_c** · 10-08-2017

Try downloading some manuals for good quality VFDs to see how they recommend grounding.

Typically the screen would be connected to the earth point at the VFD. Then the VFD earth connected to the star point.
Whether the screen gets connected to the motor varies. I'd be inclined to try it with and see how things run, as having the spindle well grounded is recommended from a safety point.

Ideally you want to avoid ground loops, however sometime they're unavoidable. Having them in the screen of a power cable isn't likely to cause problems. The problems occur when you get a ground loop in signal wire screen, as that's when you start introducing noise into control circuits.

**Clive S** · 10-08-2017

Originally Posted by dachopper

In the control box, I have main 220Volt house power earthed to the corner of the mounting plate, The Stepper Drivers are bolted to the plate, and the Torroidal Transformer is also bolted to the plate.
Then I have a single earth wire coming off that same corner to a small ACDC transformer, and another single wire that goes off then splits to 4 and is the AC earth for my woodchip / 2 x pond pumps and Spindle power inverter.

So I should earth the spindle + Spindle sleeve to earth in the inverter? or back to star?

From DC transformer - all that suff plugs directly into the stepper drivers etc....

OK some decent picture of your control box would be good.
You need to earth the screen at one end only.
Do you have screens on the stepper wiring?
Do you have the machine frame grounded?

**dachopper** · 11-08-2017

Ok , Thanks Clive / M_C

I ended up running a separate ground from the spindle all the way back to the star, and from the sleeve all the way back , and another from the inverter power feed all the way back

The shock I was getting on the Z axis has moved to a different area of the frame ..... WTF !

I don't really understand how AC voltage is detected, but what I noticed is that I seem to have 12 Volt AC between my machine and the workshop floor, although the freq jumps. When I power up the anxillary devices, ( water pumps, spindle powered but not turning, and woodchip extractor on but not turning, the A/C jumps up to a constant 105-110 Volts 60Hz. I get a tingle touching the machine frame bearfoot after that.

Does this seem like an earth leak in the shed somewhere?

The machine frame was earthed to the same star point as the inverter / Dc transformer / spindle / spindle sleeve. I tried discnnecting it as I'm trying to figure out where the zapping is coming from.

All I know is that with the machine on and the DC steppers motoring, there is no problem and no zapping.

With the spindle relay on..... and spindle turning there was big zapping when the spindle rotated.... that is fixed , but now there is a smaller underlying zap that is on when the A/C power is on regardless if the devices are turning or not.

Should my stepper motor power sleeves also go to the same A/C ground? they are currently not connected? ( insulated both ends )

**Clive S** · 11-08-2017

Ok First from what you have said are you sure that you have a good earth into your shop (is it actually connected)?

Where are the pictures?

It is beneficial to wire steppers with 4 core screened cable with the control box end of the screen connected to the star point.

Personally I would keep the vfd mains wiring on its own socket.
If you have grounded the screen on the spindle cable at the vfd end. then don't connect the screen at the other end.

Have you grounded the machine frame? to the star point. (the purpose of the star point is to avoid ground loops)

I take it that the electricity supplier give you an earth connection and that you are not using an earth rod in the ground.

**dachopper** · 11-08-2017

Originally Posted by Clive S

Ok First from what you have said are you sure that you have a good earth into your shop (is it actually connected)?

Where are the pictures?

It is beneficial to wire steppers with 4 core screened cable with the control box end of the screen connected to the star point.

Personally I would keep the vfd mains wiring on its own socket.
If you have grounded the screen on the spindle cable at the vfd end. then don't connect the screen at the other end.

Have you grounded the machine frame? to the star point. (the purpose of the star point is to avoid ground loops)

I take it that the electricity supplier give you an earth connection and that you are not using an earth rod in the ground.

Hi clive....

So this is what I'm at now.

I checked all the stepper motor shielded cables, made sure they were insulated at the stepper motor end and touching nothing, then at the control box end they all go to the star point.

The VFD spindle/Z axis block is now earthed direct to the star point. ( No other frame earth, just the one on the Z block )

The VFD cable shield is earthed separately onto the same star block, and it's insulated at spindle end ( not touching the spindle )

The other AC appliances ( VFD + Wood chip motor + 2 x pumps ) are all earthed at the same star point where applicable.

On the earth side - I'm using the house common earth..... how can I test if this is faulty?

I was a little concerned about the cable shielding pushing an AC signal back into the stepper motor shielding, but it seems to be going ok, 40 minutes into a cut now

**Clive S** · 11-08-2017

The VFD spindle/Z axis block is now earthed direct to the star point. ( No other frame earth, just the one on the Z block )

Personally I would just earth the main frame not the Z block ( if you want to earth the Z block connect that to the main frame)

was a little concerned about the cable shielding pushing an AC signal back into the stepper motor shielding, but it seems to be going ok, 40 minutes into a cut now

Let us know how you get on.

Still no pics of the control box !!