# PM1127 motor seizes up when parting



## Pcmaker (Nov 8, 2020)

It slips a lot when I'm parting. Very annoying. Didn't have this issue before

What belt do I need to replace it with? Is it something I can get from AutoZone?


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## Pcmaker (Nov 8, 2020)

I thought it was the belt, but it's the motor. It seizes up when I'm parting. It didn't used to do this before. Anyone have any idea? It's less than 2 years old with very light use.

Using a freshly sharpened parting blade, 1/8" thick. Parting 1" 1045 round bar. Locked carriage, blade parallel to the workpiece

Even  with very careful feeds it seizes up.

I used to use the power feed with no issues when parting.


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## mattthemuppet2 (Nov 8, 2020)

what do you mean seize up? Does the motor slow (bog) down and then stop? Or does it stop suddenly? What type of motor is it - AC (1ph or 3ph?) or DC? Does it do it under other high load conditions?


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## markba633csi (Nov 8, 2020)

Is this the PM1127VF?  If so there may be an adjustment needed to the inverter drive parameters- I would contact PM
-Mark


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## darkzero (Nov 8, 2020)

mattthemuppet2 said:


> what do you mean seize up?



Sounds like stalling to me, not seized, which is not uncommon.


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## Pcmaker (Nov 8, 2020)

it would stop completely like it doesn't have enough power to cut through.


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## sycle1 (Nov 8, 2020)

Just a thought.
Is the Belt nice and tight?
Asking because it happened on mine the other night for the first time, it stalled the chuck on a parting off operation, I could tell it was the belt slipping.
My lathe isn't a PM


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## tweinke (Nov 8, 2020)

You should still be under warranty I would think.


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## Pcmaker (Nov 8, 2020)

I thought it was the belt slipping, but I took off the cover and it was the shaft of the motor that  quit working and I could hear the motor humming like it's trying to turn, but doesn't have enough juice.


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## mattthemuppet2 (Nov 8, 2020)

darkzero said:


> Sounds like stalling to me, not seized, which is not uncommon.



hence the request for clarification 

I looked up the model. It has a 3ph motor and VFD, which I don't know much about, but that behaviour sounds like an overload (overcurrent really) protection is kicking in. Either the VFD is programmed incorrectly or you're doing something that is placing more load on the motor than it is allowed to provide. Parting is a high load operation, so is drilling large holes in hard material, taking really deep cuts etc. Could be that the end of your parting tool is no longer square to the work, say if it's been ground recently, as the blade is wandering and binding in the cut. Happens to me a bunch - if I pay attention I hear the motor starting to labour a bit so I can back the tool out. When you feed it back in you'll see it cut on the flanks of the cut.

Try some other high load operations and see what happens. If it reoccurs, it's an issue with the VFD/ motor. If it only occurs during parting, then it's something specific to that operation.


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## Pcmaker (Nov 8, 2020)

Not sure if it's the overload. The motor is still humming like it wants to spin, but the steel is preventing it.


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## mattthemuppet2 (Nov 8, 2020)

uh huh, that's what an overload sounds like


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## higgite (Nov 9, 2020)

What RPM are you parting at? (Prior to seizing, of course.)   

Tom


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## Cooter Brown (Nov 9, 2020)

..


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## Pcmaker (Nov 9, 2020)

higgite said:


> What RPM are you parting at? (Prior to seizing, of course.)
> 
> Tom




I'm on the low gear, tried from 50 to 350 with similar results.


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## ttabbal (Nov 9, 2020)

I've only seen that on mine when feeding way too fast or the tool catches on the metal and binds rather than cutting. Can you show us a pic of the setup? I've almost totally eliminated parting problems by using a rear mounted solid block to hold the parting tool. I know you said you sharpened it, but running too fast could dull it. It doesn't sound like that should be the case with 1" 1045 though. Could it have work hardened? 

Note that you get lower torque from the motor with the dial turned down really low. I find for 1" that 200ish works well. I don't have any 1045, but I've done 304 stainless without much hassle.


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## Pcmaker (Nov 9, 2020)

Yea it catches on the metal and stops. The thing is, I didn't have this issue before. If I do autofeed on the slowest feed rate, it still does it.


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## Pcmaker (Nov 10, 2020)

I emailed Precision Matthews a few days ago, still waiting on a response


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## ttabbal (Nov 10, 2020)

I guess if there is a problem with the motor or VFD it could be something they would be able to help with. I honestly think that you're getting a little movement somewhere that's binding the tool. If you are using the normal setup with the QCTP on the compound, then there is slight movement you can't get rid of. The parting blade holder it comes with holds it at an angle, I think that contributes to the problem by increasing the possibility of binding when things move. I got less chatter and binding when I used a setup with the blade held flat.


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## RJSakowski (Nov 10, 2020)

Check your tool height.  If the tool is above center, when the tool grabs, it drives it deeper into the work guaranteeing a stall.  Tool holder geometry is complex because there are a number of places where flex can occur.  The tool can flex from play in the carriage, the compound, the tool holder and the tool itself.  It varies from lathe to lathe.


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## Pcmaker (Nov 10, 2020)

I made a video. I sharpened the parting blade, re-zeroed the height, locked the carriage, paralleled the blade holder to the chuck, then tried parting a piece of 1018 round bar. I was hand feeding it slowly. I used to just use the auto feed on the slowest setting, but that makes it bind up more often.


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## RJSakowski (Nov 10, 2020)

To help to identify the cause, try making a heavy cut while turning.  If you are able to stall the motor that way, then I would look at the motor for some possible damage.  If it only occurs when parting, then I would look at at the tool setup.  You can roughly judge the loading by motor slowing down.  A more accurate way is to monitor motor current.   A clamp on ammeter around one of the motor leads will work.  You could also use the ammeter to compare each of the three legs of the motor.  They should be essentially equal.


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## Pcmaker (Nov 10, 2020)

I'm going to try doing heavy cuts when turning. Maybe over 100 DOC

see if it'll seize up.


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## Pcmaker (Nov 10, 2020)

Interesting... I just did a .200 cut and the the motor never froze up, the clutch just kept on slipping.

The maximum cut I usually do is .050.


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## Pcmaker (Nov 10, 2020)

Just for the heck of it, I changed out the parting blade from a 3/32 to a new 1/8 Cobalt one and no seizing!

I tried parting using the slowest "C" feed rate, and it did it.

I tried parting on the "A" feed rate, the 2nd fastest and it managed to do it. 

Crisis averted. I still can't figure out why the old 3/32 blade has anything to do with the motor seizing, considering it's in good condition and has been resharpened/leveled height.


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## 5tmorris (Nov 11, 2020)

I parted off a piece of 1/2" round hot rolled last night with a 1/8" carbide parting tool with no problems on my 1127(It's three months old).  Really nice finish too.


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## MikeWi (Nov 11, 2020)

Pcmaker said:


> I emailed Precision Matthews a few days ago, still waiting on a response


I realize you've fixed the issue, but I can't find any email from you. Did you email tech@precisionmatthews.com or a different address?


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## Pcmaker (Nov 11, 2020)

I filled out the form on the site itself. Might've been bugged as I didn't even get a confirmation email like I usually do when I ask a question.


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