PM932 Mill Motor Upgrade

[mksj]

A 19mm shaft is typical of a IEC 80 metric motor frame which would be 1 Hp. The 1.5 and 2.0 Hp metric motors have 90 metric motor frames with 24 mm shafts. Marathon Electric does make a 1.5Hp metric motor with a 19mm shaft, but only for their 3600 RPM motors which has an IEC 80 motor frame. http://www.electricmotorwholesale.com/MARATHON-R395.html

It would be possible to machine/turn an adapter shaft/coupler with a motor riser, but probably more trouble than it is worth unless you cannot find a 3 phase motor. Another alternative would be to use a BLDC or AC servo motor with controller instead of a VFD. I had this one on my last mill and they pack a lot of Hp/kW into a small motor package. The NEMA 42 looks to have a 19mm shaft, but would still need an adapter plate.
https://www.aliexpress.com/item/AC-...M-110ST-AC-Servo-Motor-110ST/32356188922.html

DMM is in the US and also sells AC servo drives at reasonable costs, may be worth checking into. They have a 1kW model with a 19 mm shaft, 11A-DST-A6HK1
http://www.dmm-tech.com/ac_servomotor_main_a1.html

 

[Muskt]

Thanks guys. Bill, the motor sits directly into the top of the mill head via a round keyed shaft. No telling what kind of worms that would release to dig into it.

Mark, thanks for the info. I think I'll just wait to see what Matt comes up with. This whole conversion process is more a matter of something I want, more than something I need.

I'll keep the group updated as events unfold.

Jerry in Delaware
(Currently getting the first snow of the year--After 30 years in Alaska, it's much too soon to suit me.)

 

[Silverbullet]

You could turn the motor shaft to fit not hard to do.

 

[Morgan RedHawk]

I got a 3ph motor from Matt that was a drop in replacement. The price was pretty good, too..only 200 bucks when I ordered it back in May.

 

[Muskt]

"The price was pretty good, too..only 200 bucks"

That's what I'm talking about!
I did email Matt on Friday--I'm patiently awaiting his reply.
Thanks, Morgan.

Jerry in Delaware

 

[pbiYoung]

Sorry to dig up an older post, but wondering if anyone has found any other alternatives for 2HP three phase motors with 19mm shafts? I called QMT last week and they told me they did not have a three phase option for the 932 so they are apparently not offering this anymore. After searching all the post here with 932 and VFD options it appears that many have been successful but all the links to motor options are either dead or the motors are discontinued and the replacement motors offered have 24mm shafts. I realize i could take the motor apart and turn down the shaft, but not my first choice. Thanks

 

[B2]

Edited to remove some redundant postings.

This topic has been visited before at HM and others replaced the motor. Maybe this is where Mark got his posted info? If so ignore this. You may want to follow that string a bit. It is old but folks talk about the motors that they used so maybe you can at least find out the physical dimensions!

Another question. What is the frame size for the originally supplied PM-932 motor? Below is a picture of the motor data plate. Best I can determine it's a frame size 90L.

Second thought:

In general I do not think you want to randomly try to run a single phase motor off of a 3-phase line. However, I think some motors will run fine. After all any two legs of a three phase power systems is single phase! The problem for a VFD is that the legs of the power out of the VFD are unbalance and I suppose this might harm the VFD. One would have to understand the internal VFD workings to know, but a quick search of VFD supplier sites did not reveal an answer to this.

You might also want to read this string: https://www.practicalmachinist.com/forum/threads/single-phase-motors-3-phase-power.156954/ There is probably as similar string on HM.

I believe that some folks have run an induction motor from two legs of 3phase power... and in concept there should be no reason why you cannot do so. However, you commonly see startup capacitors on single phase motors, which is because the startup current in a motor is high and this is an attempt to supply a phase shifted current to a secondary coil during the startup. After the motor is up to speed this circuit is commonly removed via a centrifugal activated switch. Your plate indicates starting capacitor(s) via MFD value. Without a start up capacitor the motor will usually just sit there and get hot until it burns out.... unless is is thermally protected.

It would be nice if you already had a 3-phase VFD. I think you could then just hook up two of the VFD output lines to the inputs of the single phase motor and see if your current motor would run ok for you. (I have never tried this so do not know what the possible failure modes are that might affect the VFD, however one of these days I might as I have several devices that have single phase motors that I would like to slow down.) However, the motor will be fine for a few seconds even if it does not start up. It takes a bit for it to get so hot that the wires fry. Anyway, then you might not have to switch out motors. Not the best of all worlds, but might get you what you want without buying a new motor and working through all of the mechanics. A VFD has three leads out. Any two of them generate a single phase (220V). Wires A, B, and C. So A-B, B-C, C-A each provide a single phase. You motor might not start at a low frequency, but if it starts at 60Hz and you then slowed it down it should continue to run. Power maybe off at non-60Hz, but do you often work a full power, 1.1 KW. Not all 3 phase induction motors like to run at low frequency either.

Surely someone makes special VFDs for "some types" single phase induction motors? I got this idea somewhere, but I no longer recall where nor why.???

Yet another .. useless but inspired thought!!! Scrap the DC magnet motor and batteries from a Tesla-3 and then you can control the speed via the foot pedal with plenty of power! (-:

Good luck.
Dave L.

 

[pbiYoung]

Thanks for the response (I think ?). Maybe your info was meant for someone in some of the earlier posts to this thread ? I was simply asking if anyone has found a suitable 2HP (1.5kW) 3ph replacement for the 932 since PM no longer offers a three phase replacement motor. It's an IEC80 flange frame because it has a 19mm shaft. All the readily available 80 frames with 19mm shafts only go to 1 or 1.5 HP (1.1kW). I've already read though all those old posts that mostly result with "get a motor from QMT", but that's no longer an option. Don't need any VFD's or any of that other stuff you are talking about, but thanks anyhow.

 

[B2]

Hi @pbiYoung

Sorry, I may have wasted yours and everyone's time. It was a pretty poor posting on my part and was a mistake! I was sitting at my PC waiting for something else and just started writing without fully reading the entire string. I am glad you have the info you need.

By the way, I have one of the few PM940M-VS-CNC machines that PM sold (~2017). It is a bigger machine than your PM932 in that it weights in at ~1400 pounds. It has a 1.5KW 3 phase motor on it and a Delta VFD driving it. Most of my jobs are pretty small (small cuts and soft material) and never need this kind of power. However, I did make a long run where I was using a 2"dia, 3 carbide index fly cutter cutting a ~1.25" swath in steel. Over multiple passes I removed a volume of 2" wide x 8" long by 1" deep using flood oil cooling. I do not recall all of the operating parameters, but I know it went slow, taking a depth and a forward motion cuts of less than 0.010" each per cutter pass. At the end of this long run the motor was hot to the touch, but it was running fine. I don't think I have ever simply turned the motor on and let it run for the equivalent amount of time with no load so don't know, but it might have been the normal operating temperature. Unless you are going to do bigger jobs and try to take big bites ... are you sure you need a motor bigger than 1.5KW? I will attach a photo of it. It too has an unknown model number, but it has on it the operating frequency of 2-200Hz which is an interesting and useful observation for VFD operation (some induction motors do not like to run slow). If you want I can get you more info on the VFD.

There was another time where I tried to make a similar cut in steel using the same tool. Something went wrong with the mill and the z-axis dropped down to make a 0.10" deep cut while the x-motion was a little faster than the one above. (This height drop was due to a bad gib slipping and the stepper motor not holding position.) As the tool advanced into the material, the motor did not seem to initially care, but the spindle did not like it. It all jammed crooked and then the motor stalled. The spindle sheer pin was severly damaged/sheered but did not quite yield to allow the spindle to turn freely. It was jammed. Later it finished coming loose so that the spindle freely turned and I had a pretty difficult time getting the tooling out so that I could replace the pin. So the 1.5KW of power is enough to destroy the machine if not operated correctly! Anyway, maybe there are good reasons not to have too big a motor!

Good luck

Dave L.

 

[pbiYoung]

The original current motor is 1.5 and works fine ... I just want to replace it with same size ... Thanks