# RF-45 clone motor issues.



## Thoro (May 17, 2014)

I have a ZAY-7045F/G which is as I believe to be an RF-45 clone.  

It has a 2HP single phase twin capacitor motor that is wired for 220V.

Here's the issue.  Intermittently it will get stuck in "start".  Upon starting the motor from stopped, it will make a screeching howling like sound.  If I turn it off, and back on, usually this will solve the issue and it will start as normal.  Now, one time, this happened, and it would not go away.  So I took the motor off the machine and disassembled it to find that the contacts on the centrifugal start switch inside the motor had "welded" together.  They spung apart easily, and I filed them clean and that solved the issue of it being permanently stuck, but it still intermittently sticks on startup.  

So my question is, how can I remedy this?  It seems fixable, i'm just missing the trick.  I'm attributing it to a cheaper chicom motor and even cheaper parts being used inside.  But maybe I'm wrong.  I was wondering about something like dielectric grease on the contact maybe?  But really, what would help here I think is to understand what is causing the issue of "welding" the contacts and then moving forward from there.  This really makes using the mill a bit of a hassle at times, and I don't want it to stick permanently like it did before while I'm in the middle of a project again.

So here I am reaching out to those more knowledgeable with electric components for advice.

Thanks in advance.


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## Ray C (May 17, 2014)

Thoro said:


> I have a ZAY-7045F/G which is as I believe to be an RF-45 clone.
> 
> It has a 2HP single phase twin capacitor motor that is wired for 220V.
> 
> ...



I'd say you're on the right track...  I've never had one of those motors apart but, is there any way you could use a very fine piece of #200 or #400 emery cloth instead of a file to clean the contacts?  The contacts should have almost a polished look and any burrs will cause arcing and eventual sticking.


Ray


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## Thoro (May 17, 2014)

Hmm, OK. That makes more sense. I remember the contacts being a bit pitted, seemingly eroded from arcing. I'm wondering how far is too far on material removal of the contacts


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## John Hasler (May 17, 2014)

Thoro said:


> I have a ZAY-7045F/G which is as I believe to be an RF-45 clone.
> 
> It has a 2HP single phase twin capacitor motor that is wired for 220V.
> 
> ...



Once the contacts have welded it usually takes more than just restarting to break them loose.  I suspect that there is a mechanical problem in the switch such that it binds occasionally.  The welding may have been a side-effect of the switch staying closed too long due to the binding and so getting much hotter than normal.  Did you clean all the grease out of the switch?


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## Thoro (May 17, 2014)

Didn't clean the grease out..... So you think it could be the centrifugal switch mechanism hanging up?


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## John Hasler (May 17, 2014)

Thoro said:


> Hmm, OK. That makes more sense. I remember the contacts being a bit pitted, seemingly eroded from arcing. I'm wondering how far is too far on material removal of the contacts



AC contacts like that are usually a little disc made of two kinds of material (though the boundary between the layers may not be visible).  Once the top layer is gone the contact is done for.  Don't try to sand off all the pits.  Just get a flat surface.

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Thoro said:


> Didn't clean the grease out..... So you think it could be the centrifugal switch mechanism hanging up?



Well, it's something I've run across before.  They stick open more often than closed, though.  I'd get the switch out on the bench and go through it and try to eliminate all possible causes of binding.  Clean up the contacts as well, of course.  Possibly you need to weaken the spring a bit.


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## silence dogood (May 17, 2014)

While you are about it on repairing the motor, check the capacitor.  Short it first to eliminate any residue charge and check with an ohm meter. It should measure infinity.  Also, if you see any bulges or cracks, replace.
Mark (Silence Dogood)


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## Wireaddict (May 18, 2014)

I'd like to add a few things: first, as already mentioned, the contacts have a thin layer on them.  This is silver which is a better conductor & apparently resists welding so you don't want to sand them much.  If they're bad you might try taking the switch contact assembly to a motor shop to see if they have anything that'll fit, if not you need a new motor.  Also, if you check the starting cap, use an ohmmeter & if it's good it'll read infinite as mentioned but beware when you first connect a discharged cap to the ohmmeter that it'll read a short then the resistance will slowly climb toward infinity as it charges.  This is because the ohmmeter uses scale multiplying resistors which limit the current & may cause the charging time to take several minutes.  Motor shops & places like WW Grainger sell motor run & starting capacitors.


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## Craig_J (May 18, 2014)

I have a similar machine which came with the same type of motor.  After less than 20 hours of use the starting capacitor blew up spectacularly.  I attributed this to the centrifugal start switch sticking, although I had no notice other than an unusual humming.  The distributor of my machine readily agreed to replace the motor, but I asked them for the same size 3-phase motor (which they offer on other versions of the machine).  They were reluctant ("The wiring is not correct for a 3-phase motor!") but I assured them that I would take responsibility and they sent me a new Chinese 2HP, 3phase motor, I gutted the wiring and added a TECO VFD, and now I have a variable speed drive with NO capacitors or contactor relays.

I originally thought to get a Leeson metric 2HP motor locally (as I had done a similar conversion on my Grizzly 10x22 lathe), and was asking the dealer if they would cover it under warranty, but gave up when I found out the the shaft of the motor on my mill was smaller, the same size as a 1.5HP motor.  It was much easier to get the factory to supply the replacement 3-phase motor, as drop-in fit, than buy the Leeson, turn and key its shaft, etc.

While I was waiting for the new motor to arrive from China, I cleaned up the explosion and tested the remaining run capacitor, which was good, and tried a new starting cap (just for a few seconds!) to determine that the centrifugal switch was indeed welded.  After removing the temporary start cap (150uF), I also found out that the motor would start okay without it, although it was slow to spin up on the highest speed gearing and I am not at all sure it would have been safe to run it this  way for an extended period.

A note about the conversion to VFD:  you have to completely rewire the controls to do this.  The VFD generates 220V 3 phase power from the 220V single-phase line.  Its start, reversing and E-stop functions are all controlled by low voltage signals.  So If you can handle the electrical changes, you get a superior machine:  no start or run capacitors to fail, no centrifugal start switch, programmable start, stop, and E-stop speed ramps.  Most machinists will also tell you that a 3-phase motor is simply more powerful than a single phase of the same nominal rating.  I set the output frequency range to go from 30-90 Hz, which is equivalent to 1/2X to 2X the nameplate rpm in each gear range;  I still use the gears to optimize the power for various operations.    I am very happy with the conversion.

I have attached a photo of my mill.  Note the new box to the left of the controls with the VFD.  I welded this up to fit but of course the VFD could be mounted externally in a stand-alone enclosure.  If you have access to the Yahoo Mill/Drill group there are more pictures under "Craig's RF-45 clone."  If you are interested in going the VFD conversion route I can also supply a wiring diagram of the way I did it.

Craig


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## Craig_J (May 19, 2014)

After posting the message about my exploding cap and subsequent 3Ph +VFD conversion, another thought occurred to me:  Both my original 1single phase 1HP, 120V lathe motor and the 2HP, 240V mill motor used the same capacitors --150uF starting cap and 30uF run cap.  This suggests two things: one, that if the start winding impedance is as low as I think it is, the start current would be 2X as much on 240V as on 120V.  Since the 1HP lathe motor could be hooked up for either 120V or 240V, I would think the centrifugal switch would be much more abused at the higher voltage and current.  In any case, the starting circuit is a weak link.  Secondly, the phase shifted run current would be inversely proportional to the cap value, or 1/5 the starting cap current.  The 3ph motor is superior because all three windings are equivalent and all contribute to establishing the direction of rotation.  And, like I said, no switches, no capacitors....
Craig


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## Thoro (May 19, 2014)

Craig_J said:


> After posting the message about my exploding cap and subsequent 3Ph +VFD conversion, another thought occurred to me:  Both my original 1single phase 1HP, 120V lathe motor and the 2HP, 240V mill motor used the same capacitors --150uF starting cap and 30uF run cap.  This suggests two things: one, that if the start winding impedance is as low as I think it is, the start current would be 2X as much on 240V as on 120V.  Since the 1HP lathe motor could be hooked up for either 120V or 240V, I would think the centrifugal switch would be much more abused at the higher voltage and current.  In any case, the starting circuit is a weak link.  Secondly, the phase shifted run current would be inversely proportional to the cap value, or 1/5 the starting cap current.  The 3ph motor is superior because all three windings are equivalent and all contribute to establishing the direction of rotation.  And, like I said, no switches, no capacitors....
> Craig



So, bare with me here.  Electricity and related are not my strong point.  But I gather you are suggesting that if I rewire the motor for 110V, it may be easier on the start winding?  I'm not sure that that is easily done on my mill as the whole control box, including the power feed and Z axis motor are 220V......

Also, It would have been my assumption that 220V would be less stress on the motor as it requires lees amps to achieve the same power output.

And another also.  That is an extremely slick conversion you did.  Do you happen to remember what the shaft size on your motor was?  I think mine is metric, I want to say it's 25 mm, or something very close to that.
Could you relay the information about that 3ph motor you have on you mill that is pertinent? I would be very interested in switching it over to 3ph with a VFD.


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## Craig_J (May 19, 2014)

Thoro:
My mill had a motor with a metric D90 frame (flange mounted), but the shaft was 19mm diameter, not the normal 24mm of a D90 frame.  Look at a Leeson 192206 (try http://www.electricmotorwholesale.com).  19mm is the diameter of the shaft on a D80 frame. I could not find any off-the-shelf metric motor to drop in without needing to machine down the shaft to fit into the top gear.  I think that the mill's manufacturer (Sabre is the label) originally used a 1.5HP D80 frame motor, then upped it to 2hp and for them it was easier to order a D90 motor with the smaller shaft than to change their gearbox.  Incidentally, the flange mounting is the same for both sizes.  If your motor fits the D90 outline, including the shaft size, the 2HP Leeson should drop right in.  The link above has an outline drawing under the "files" tab.

I did suggest that the stress on the starter switch would be less at the lower voltage, but general wisdom says to operate the motor at the highest voltage available for other reasons, such as lower IR drop in the wiring.  If you look at the nameplate on your motor, it will list available voltages.  On mine, it listed 230/460, so it was already operating at the lowest voltage.  I just think the contact design on my motor was inadequate.
If the Leeson fits and you are up to the rewiring job, it would result in a better mill.  In addition to the advantages of variable speed, I think the Leeson is a better motor than what comes on most of these RF-45 clone mills.  I can't emphasize enough how getting the two contactors, capacitors and centrifugal switch out of the electrics improves the durability.

I have attached the wiring diagram I created for my mill.  (I am an electrical engineer and while motors and such were not my specialty I consider myself competent to do this design.)  Notice, no contactors are needed. Additional information:
1.  Fuses are required by the VFD.  They are of a specific type, listed in the VFD manual.
2.  I added a fan for optimal cooling of the VFD.
3.  My front panel switches are a POWER switch, FWD-STOP-REV, and E-STOP.
4.  Only the POWER switch needs to handle 240V @20A, the others are switching 24VDC from the TECO that it uses for logic inputs.  How they control the unit is part of the software setup.
5.  Do NOT put any switch or relay between the VFD and the motor.  The VFD can actually stop the motor quicker than disconnecting it which might damage the electronics.  I think my ramp-down speed is set to 0.8 seconds for E-STOP.

I have no doubt the cheapest solution for you is to manicure the motor's centrifugal switch contacts and replace the starting cap if it is shorted.  A new motor and VFD will cost you about $400, depending on how much you have to spend for the electrical bits and pieces. If your mill is under warranty maybe you can get the mfr. to replace the motor?  But if you do the 3 phase upgrade, it will be a lot more durable plus have variable speed at the twist of a knob.  Let me know if you need any additional info.
Craig


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## Thoro (May 21, 2014)

This is awesome information. Thanks a lot. I think once I finish my sb heavy 10 rebuild, this vfd conversion for my mill might make it to the top of my roundtuit list.


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