Urgent Help - PM 940M down. Motor issue

[Rich Berg]

Hi, I did that dance with the centrifugal switch, what I did was remove the shaft mounted part by hitting it with a chisel in the center. that expanded it and it slid off. I purchased a new one (press on) and installed the new one I then pinned it in place. it was impossible for me to get the shaft mounted part to move without destroying it.
the plastic fan was removed with a crowbar on each side.
I guarantee that you will be back in the motor working on that stuff, what I believe is when the motor starts it actually spins the fly weights and that causes it to move.
I realized the problem that I had with the capacitor dying was because of overheating. I was doing small parts and frequently edge finding, that overheated the start capacitor.
I have mine running again, but for how long. I am in the process of replacing the motor with a 3 phase one and a drive. I need the mill to make an adaptor plate for the new one.
I noticed that PM is selling a 940V that has a 3-phase motor and a drive, if they had that when I purchased mine, I would have chosen that one.
good luck Rich

 

[Larry$]

It's really common on a mill to frequently start & stop the motor. To design a mill that can't do that is really cheaping out.
Start motor, Edge find, stop motor, change to spot drill, start motor, stop motor, change to 1/4" drill, start motor, stop motor, change to 1" Silver & Deming drill, start motor, stop motor, change to boring head, start motor, stop motor, check dimeter, start motor ...... 6 Starts in a very short time! What are they missing about milling machine use?

 

[Rich Berg]

Hi I know it's a problem, maybe is ask for a replacement of a 940v. mine ran out of warranty and 1200lbs wasn't something I wanted to deal with, so I change caps repair oil leaks and now VFD

 

[dabear3428]

It's really common on a mill to frequently start & stop the motor. To design a mill that can't do that is really cheaping out.
Start motor, Edge find, stop motor, change to spot drill, start motor, stop motor, change to 1/4" drill, start motor, stop motor, change to 1" Silver & Deming drill, start motor, stop motor, change to boring head, start motor, stop motor, check dimeter, start motor ...... 6 Starts in a very short time! What are they missing about milling machine use?

let the motor coast for a few min to cool or add a blower motor to augment cooling.

 

[mksj]

The problem with single phase motors that uses start capacitors is not motor cooling, the electrolytic capacitors are only able to handle very short periods of on time (less than 1 second), and a few start/stop cycles per hour otherwise they overheat internally and spill their guts. Since it is an internal process and electrolytic capacitors are usually in a plastic body, motor cooling would have minimal effect. Machines that have frequent stop/start cycles with single phase motors often lead to failure of the motor capacitors. The other concern with using single phase motors is that if you suddenly reverse the motor direction, the motor may not reverse direction if not allowed to come to a stop first. Alternative solutions for small motors with single phase power such as going DC motor, 3 phase or BLDC motors, you have the additional expense of generating the 3 phase/controller. Everything is to a price point.

 

[dabear3428]

The problem with single phase motors that uses start capacitors is not motor cooling, the electrolytic capacitors are only able to handle very short periods of on time (less than 1 second), and a few start/stop cycles per hour otherwise they overheat internally and spill their guts. Since it is an internal process and electrolytic capacitors are usually in a plastic body, motor cooling would have minimal effect. Machines that have frequent stop/start cycles with single phase motors often lead to failure of the motor capacitors. The other concern with using single phase motors is that if you suddenly reverse the motor direction, the motor may not reverse direction if not allowed to come to a stop first. Alternative solutions for small motors with single phase power such as going DC motor, 3 phase or BLDC motors, you have the additional expense of generating the 3 phase/controller. Everything is to a price point.

yes they overheat and sit on a hot motor with no cooling air and unless they are divorced mounted they pick up motor heat while it is soaking so yes a blower will help. if they are divorce mounted not so much.

 

[verbotenwhisky]

His is a Mechanical head Manual mill which means it is a single phase, I think B2's is a 3 Phase as is mine which have a separate fan that runs full time.

 

[Sticks]

Correct, Single phase 220, geared head, not variable belt drive.

PM had no data on motor types (at least the one I was dealing with) for a VFD conversion, even though at one point they had a VFD CNC model for sale.

I have switched to reverse when power tapping before the motor has come to a complete stop, keeps going forward and there goes a tap.

At this time, purchasing a 3phase motor, VFD, and single to 3 phase converter is not feasible, regardless of how much I would prefer that. At the time that I ordered this unit I wanted the PM940V, but I missed the last one available by like 3 days, and the next shipment was a long way off, so I went with the 940M.

 

[dabear3428]

Correct, Single phase 220, geared head, not variable belt drive.

PM had no data on motor types (at least the one I was dealing with) for a VFD conversion, even though at one point they had a VFD CNC model for sale.

I have switched to reverse when power tapping before the motor has come to a complete stop, keeps going forward and there goes a tap.

At this time, purchasing a 3phase motor, VFD, and single to 3 phase converter is not feasible, regardless of how much I would prefer that. At the time that I ordered this unit I wanted the PM940V, but I missed the last one available by like 3 days, and the next shipment was a long way off, so I went with the 940M.

the more i learn about the PM940M the less likely it is that i would buy one over the PM940V.

 

[Larry$]

At this time, purchasing a 3phase motor, VFD, and single to 3 phase converter is not feasible, regardless of how much I would prefer that.

Even though all that would be nice to have, what you have works if a bit slower to use. As hobbyists being able to get things done is more important than speed. Many guys would give their left one to have your mill. Have fun, learn, some day you may become rich and famous and have more toys.