PDA

View Full Version : Why doesn't my knee mill run?



krems
02-27-2015, 08:48 PM
Imagine my surprise when I powered up the knee mill and it doesn't run. I just finished moving the Webb 3 hp EVS head from one room into another - maybe 30 feet max. The mill runs on 220 volt single phase power. ( it ran great before I unhooked the machine just 3 days ago. I had an electrician run the 220v wire directly from the electrical panel on the house into the same room using the same electrical panel from the other room. The power checks out good at the electrical panel. My Monarch ee lathe runs fine on 220 v single phase power. I have the power cord running directly from the inverter box on the mill to the electrical panel. Now I am no electrician but could they have wired this wrong on the electrical panel because of the inverter box and single phase power? .... I hit the start button and get a buzzing sound and the RPM digital readout is very dim and no error code. The spindle won't turn. I am not getting power from the inverter box to the motor. I don't think it matters but I still have the head tilted towards me and to the side from the move. Any thoughts on what I should check?......could both legs be wired backwards or something? It looks like the white-black-green -red wires are all connected to the electrical panel.

lakeside53
02-27-2015, 09:54 PM
Measure the incoming voltage and make sure you have 240 volts (red to black) to the inverter, and from the red and black leads, 120v to the white (neutral) and ground. Why no error codes on the vfd - maybe it's faulty... no matter what it should show codes if it's working.

Jim Hubbell
02-27-2015, 10:09 PM
For start, try plugging in a machine that runs elsewhere into the new outlet. Go nogo?
I am not clear what an inverter box is in this setup. Have you any way to test for voltage which you are comfortable with?
More info may be helpful.

J Tiers
02-27-2015, 11:03 PM
So you have a VFD on the mill? Should be no problem if the thing ran before.

I would say you have low voltage... perhaps the sparkys wired it for 120V.

USUALLY the VFD will either run or not run, though. The internal power supply in most is an SMPS that works fine off a wide range of voltage, and shuts off if not high enough.

BUT, a few of the cheaper ones use a regular line frequency transformer type supply for the display and logic inside. If yours is that type, then it might easily sort of half-work on low voltage, which is generally in agreement with your description.

lakeside53
02-28-2015, 12:28 AM
He might have wired the wall plug wrong, or at least different to the mill.... What type are you using for the 4 wire connection?

macona
02-28-2015, 01:11 AM
Bet you have the ground and a hot swapped.

PStechPaul
02-28-2015, 01:21 AM
You can't run on a bad knee... :rolleyes:

krems
02-28-2015, 09:14 AM
I am not able to plug in another machine since the mill is wired directly to the electrical panel. I must have low voltage somehow because the fan comes on and the digital rpm display light seems dim. The spindle doesn't turn in either direction when turned on. I need to get a picture posted on how it is wired in. Sparky pretty confident everything is wired in correctly. I have my doubts.

J Tiers
02-28-2015, 09:22 AM
OK, so you said power checks out good at the electrical panel.

WHICH panel? The service entrance, or the one near the machine?

How is the voltage if you measure across the wires going to the machine where they connect in the nearby electrical panel?

How is the voltage if you open the "inverter box" and measure the voltage on the input to the VFD (inverter)?

Does the machine have a worklight? If so, does it light up correctly?

If you do not have a voltmeter, you should get a decent one. Depending on house wiring electricians for what is more like industrial wiring is a problem sometimes. Far better to get enough knowledge to do basic troubleshooting yourself, even if local codes prevent you (at least theoretically) from doing the work yourself.

Richard King
02-28-2015, 09:30 AM
Call the electrician back up and tell him it doesn't run. He should come out for nothing. It's probably a loose connection and he made the mistake, not you. If he hard wired it, didn't he test run the machine after he did it? If your not electrically inclined let a pro do it or you might get hurt or even worse.

bborr01
02-28-2015, 04:10 PM
That's my guess too. I had a SB lathe several years ago that wouldn't run. Turned out someone had a ground and a hot wire switched in the plug. Changed them around and it ran fine.

Brian


Bet you have the ground and a hot swapped.

flylo
02-28-2015, 04:12 PM
That's why the pros get the big $$.

J Tiers
02-28-2015, 06:27 PM
That's my guess too. I had a SB lathe several years ago that wouldn't run. Turned out someone had a ground and a hot wire switched in the plug. Changed them around and it ran fine.

Brian

Well, I wouldn't change them around just to see......... you might see something, hopefully not St Peter......:D

The meter tells the story, no volts. no run.

flylo
02-28-2015, 06:53 PM
Why doesn't my knee mill run?
Must be an old mill. Hard to run on just knees, should have bought a leg mill, but don't feel bad one of my lathes has a Pacemaker :rolleyes:
Sorry, just couldn't resist, hope you get it going soon.

TGTool
02-28-2015, 10:35 PM
Why doesn't my knee mill run?
Must be an old mill. Hard to run on just knees, should have bought a leg mill, but don't feel bad one of my lathes has a Pacemaker :rolleyes:
Sorry, just couldn't resist, hope you get it going soon.

I've been biting my tongue ever since this was posted and it's so hard to resist. My thought too was that it's probably so old its knees are shot and it can only walk and not that fast.

Lew Hartswick
03-01-2015, 10:10 AM
Have you checked to see that the motor CAN turn. Maybe the gearing or drive is jamed from the move.
...Lew...

Darrp
03-01-2015, 12:03 PM
Look in the panel to see it he accidently put in the 2 pole breaker on the same line.... for 220/240v it should be straddling Line 1 and Line 2

Rosco-P
03-01-2015, 12:25 PM
Look in the panel to see it he accidently put in the 2 pole breaker on the same line.... for 220/240v it should be straddling Line 1 and Line 2

In a breaker panel, how would that be physically possible?

chipmaker4130
03-01-2015, 01:11 PM
In a breaker panel, how would that be physically possible?

It isn't with a 2-pole breaker, but if the panel was full, someone might have tied into two separate single pole breakers serving otherwise light loads, and got two on the same pole. It is ok to do that but they should be pinned together so that if one leg trips the other follows. If you skip a slot you'll end up with two on the same pole. No electrician would have done that, but...

Rosco-P
03-01-2015, 01:32 PM
It isn't with a 2-pole breaker, but if the panel was full, someone might have tied into two separate single pole breakers serving otherwise light loads, and got two on the same pole. It is ok to do that but they should be pinned together so that if one leg trips the other follows. If you skip a slot you'll end up with two on the same pole. No electrician would have done that, but...

No licenced Electrician would do that and if he found a condition like that wouldn't complete the job without correcting it. The OP did say he hired an Electrician, not a handyman.

To be clear it is not okay to take two single pole breakers and tie the handles together to make a 2 pole...ever. Multi-pole breakers are tied together mechanically and electrically so all poles trip together.

chipmaker4130
03-01-2015, 01:42 PM
Whatever. I'm not an electrician and am not familiar with all the subtleties of today's code but long ago it WAS common to tie two single pole breakers together and pin them through the holes in the lever. I've seen 'real' electricians do it and they even had pre-fab pin kits to accomplish just that. The OP said 'electrician' but for some people that might be cousin Fred who has wired a few houses. And, I should have said that it 'used to be considered ok' and that it might have been done. Clear?

Rosco-P
03-01-2015, 01:49 PM
Crystal.

My vote is for cousin Fred or some guy who said, "Yeah, I can do 'lectircal woik."

Darrp
03-01-2015, 02:39 PM
In a breaker panel, how would that be physically possible?



It isn't with a 2-pole breaker, but if the panel was full, someone might have tied into two separate single pole breakers serving otherwise light loads, and got two on the same pole. It is ok to do that but they should be pinned together so that if one leg trips the other follows. If you skip a slot you'll end up with two on the same pole. No electrician would have done that, but...


In single phase panels the circuits are fed L1, L2 L2, L1 L1, L2 L2 etc. If it was a double pole breaker and he clipped it on L1 and L1 or L2 and L2 it would give you 110/120v

Black_Moons
03-01-2015, 02:52 PM
I hooked my mill/lathe to a heater 240v circuit...
Boy was I ever surprised when one day, the 60 year old 'load regulator' thingy that involves huge 60A contacts and a small 120v AC motor with worm drive to move them decided to switch all the heaters over to 120v

From what I could tell, it had been rewired and bits of cardboard stuffed into the motors contacts to prevent it from ever moving again.. Yet somehow it managed to come back to life.

Rosco-P
03-01-2015, 02:53 PM
In single phase panels the circuits are fed L1, L2 L2, L1 L1, L2 L2 etc. If it was a double pole breaker and he clipped it on L1 and L1 or L2 and L2 it would give you 110/120v

In a word, no. Open up any panel-board, single or three phase and you'll see what you are saying is physically impossible with a two pole breaker. The panel bus is designed so that does not and can not happen.

flylo
03-01-2015, 03:15 PM
Whatever. I'm not an electrician and am not familiar with all the subtleties of today's code but long ago it WAS common to tie two single pole breakers together and pin them through the holes in the lever. I've seen 'real' electricians do it and they even had pre-fab pin kits to accomplish just that. The OP said 'electrician' but for some people that might be cousin Fred who has wired a few houses. And, I should have said that it 'used to be considered ok' and that it might have been done. Clear?

I've seen electrticans do that in fact the 1/2 size breakers have a hole in the lever to hook them together but he used 4 stacked & pinned the center 2 together & used a stiff wire to tie the outer 2, so it worked but may have not been code.

PStechPaul
03-01-2015, 04:33 PM
Tying two breakers together in most cases will just allow manual switching of the two poles together. Breakers have a "trip free" mechanism that internally disconnects the circuit even if the handle is held closed. Thus the handle might not have enough force to open the other pole. It will be interesting to learn what the problem actually is.

lakeside53
03-01-2015, 08:29 PM
Time to diagnose the power - less then 1 minute.. and most of that is taking the screws out of the receptacle plate.

lakeside53
03-01-2015, 08:32 PM
Tying two breakers together in most cases will just allow manual switching of the two poles together. Breakers have a "trip free" mechanism that internally disconnects the circuit even if the handle is held closed. Thus the handle might not have enough force to open the other pole. It will be interesting to learn what the problem actually is.

"Today" (for some time) you cannot do this unless the breakers are mechanically connected together, and listed for such operation. i.e. taking two single pole breakers and tying them together is not code.

ulav8r
03-01-2015, 10:34 PM
Why doesn't my knee mill run?

Because there an no legs below the knee.

Black_Moons
03-03-2015, 04:00 AM
My mill used to not run like yours. Then it took an arrow to the knee.

krems
03-14-2015, 10:58 AM
Knee mill is running again. As suspected by many of you the wiring wasn't correct. Took a real electrician 10 minutes to figure this out. Thanks for your help. The red and white wires were reversed. The motor was only getting 60v instead of 120v.