WM14 from WARCO

[HS93]

I have a WM14 mill I use it for small brass work and some aluminum, I only use small cutter so I have to run it at it's top speed that is 2300 rpm, the problem is it then gets very very hot, I have been on to them since I bought it and after 8 months still no joy, I feel they are trying to run the warrantee out, has anybody else had problems or have they changed it (WM14) to Belt drive. or sorted the over heating I have tried fans and removing the motor cover and also have fitted a new motor.


Peter

[EdK]

Peter,

What is getting hot? The motor or the spindle bearings?

Ed

[Hopefuldave]

Hi Peter,

In my experience, *all* Chinese machines' DC motors run hot - whether in the small mills, lathes or the accessory power-feeds - it's just a fact of life, economics being what they are. Many (if not all) of the motors have been "optimised" to reduce the amount of (expensive) copper by using thinner-gauge windings and (relatively cheap) higher-temperature winding insulation and varnishes to allow higher than expected running temperatures :(

The real killer is actually running them at low speed delivering high torque (actually or close to stalling is the worst), where:
a) The fan isn't rotating fast enough for sufficient ventilation, causing the temperature to rise *significantly*
b) The speed of rotation doesn't generate enough back-EMF in the armature windings and the current rises significantly too...

Once a DC motor gets close to stalling, the current can be several times that at full-load *at the rated speed*, which is why even the cheap DC motor drives have current-limiting built in - and some importers are specifying additional fuses between motor and controller (a *very* good idea!).

I've used a WM14-alike as power source for a flexible drive for extended periods (well over an hour at close to its maximum speed, porting a cylinder head when my German-made drill press had died) and the motor was uncomfortably hot to touch by the time I'd finished, but it doesn't seem to have suffered any harm, even with heavy grinding loads - so far, anyway!

I've also used it for some very odd things, like spinning a 6" ally disc with pieces of hard-disk magnets glued on to simulate the CDI pickup on my son's motorbike, while reverse-engineering an unobtainable Japanese ignition system... 6 magnets at 2150RPM gives a good approximation of its 13,000RPM redline

Dave H. (the other one)

[HS93]

So It looks Like what I thought the mill may be able to run at these speeds but will get very hot My Problem may be a mis aligned bearing as it stops dead the second power is removed, and yes gear heads dont usuly run on but the also dont stop instantly , the problem I have is I am a wheel chair user and so major repairs on the higher parts of the mill call for me getting someone in to sort it I have had to do that already when I replaced the motor, unfortunatley when fitted it ran backwards, not the electricans fault as he just wired it up as it was the wires on the new motor was wrong the teck at Warco ( http://www.warco.co.uk/milling-machines/...chine.html ) thought it was hileriouse, I didnt see the funny side and all he could say was a lot of the motors are badly wired. now after 8 months I am still no further on I was told that just becaause they will run at 2300 we dont expect people to run at that speed. I have asked them for a head swop or this one repairing,but am again waiting to find out what they are prepaird to do,, the other thing about Warco is never expect a retur phone call they never do , and you never get an appoligy gust a we are very busy, so if you are in the uk and thinking of buying of warco think again as they have no customer service, by the way this is the 3rd machine I have bought of them, ok it was 0nly £670 about $1000 but it still should be supported.

peter

[f350ca]

Peter,
Is it possible that they have electronic braking on the motor. Many new tools do. If a bearing is slowing it down that fast I would expect the bearing to be getting hot.
Greg

[HS93]

(04-18-2012, 12:14 PM)f350ca Wrote: Peter,
Is it possible that they have electronic braking on the motor. Many new tools do. If a bearing is slowing it down that fast I would expect the bearing to be getting hot.
Greg

I thought that at first so I turned it off via the plug not the switch just to see if it stoped the same, and it does also the main casing gets hot this has been a problem on the Grizzly G0703 that shares all the same head componants except it has a 600w motor insted of a 5oo w on mine.

Peter

[Hopefuldave]

HS93 Wrote:I thought that at first so I turned it off via the plug not the switch just to see if it stopped the same, and it does also the main casing gets hot this has been a problem on the Grizzly G0703 that shares all the same head components except it has a 600w motor instead of a 500 w on mine.

Peter

Hi Peter,
mine stops on a sixpence too, particularly if I have a small tool in the spindle (e.g. a Clarkson-alike quicklock chuck and 1/2" endmill), less so with a big heavy fly-cutter (I've made mine quite hefty, a 6" disc of 1" cast iron from and old chuck backplate and a 2 Morse blank... it seems to calm the chatter down!) or something similar with quite a bit of rotary momentum.

I'm not sure, but there may well be an anti-parallel diode on the motor side of the speed-control which would do two things: it'd absorb spikes generated by the motor when the speed control shuts off (winding inductance tries to keep the armature current going, there's no path for it, so it behaves like an ignition coil - not nice for the semiconductors that tried to stop the current!); and it would also shunt the motor-generated EMF and brake the motor, whether you switched off at the stop button (which on mine just cuts the mains to the electronics, yours may differ) or at the wall.
It'd be interesting to compare the behaviour with one of the DC-motor mills with a forward/off/reverse switch, as that would I think disconnect the motor from the controller?

Bigger machines would probably have a dynamic braking resistor to absorb the stored energy (I have one attached to my lathe VFD - gets quite warm after a few stops with the big chuck), but it's possible the board just dumps it into a hefty diode? Thinking about this has got me worried that my big fly-cutter may push the diode too far...

That's the absolute minimum I'd do (anti-parallel diode) if I were designing it, based on some time working on *big* DC servo systems in a past life!
Does yours have the American KB speed control board or a Chinese "tribute to", as there may be some big differences?

Anyway, there's not a lot of momentum in the motor/gears/spindle so I wouldn't expect it to carry on spinning for long, particularly with the expected friction from the gears added in? Most gear trains are between 70 and 90% efficient, so for a 3/4 HP motor anything up to about 1/5th HP could be dissipating in the gears? That'd stop it pretty quick, and warm up the headstock a bit!
The Chinese DC-motor variable speed lathes I've seen in action seem to stop pretty quickly too (despite having perhaps a 6" chuck spinning at 1000 RPM!), and I guess they probably use the same / similar speed controls...?

Dave H. (the other one)

[HS93]

(04-19-2012, 05:23 PM)Hopefuldave Wrote:

HS93 Wrote:I thought that at first so I turned it off via the plug not the switch just to see if it stopped the same, and it does also the main casing gets hot this has been a problem on the Grizzly G0703 that shares all the same head components except it has a 600w motor instead of a 500 w on mine.

Peter

Hi Peter,
mine stops on a sixpence too, particularly if I have a small tool in the spindle (e.g. a Clarkson-alike quicklock chuck and 1/2" endmill), less so with a big heavy fly-cutter (I've made mine quite hefty, a 6" disc of 1" cast iron from and old chuck backplate and a 2 Morse blank... it seems to calm the chatter down!) or something similar with quite a bit of rotary momentum.

I'm not sure, but there may well be an anti-parallel diode on the motor side of the speed-control which would do two things: it'd absorb spikes generated by the motor when the speed control shuts off (winding inductance tries to keep the armature current going, there's no path for it, so it behaves like an ignition coil - not nice for the semiconductors that tried to stop the current!); and it would also shunt the motor-generated EMF and brake the motor, whether you switched off at the stop button (which on mine just cuts the mains to the electronics, yours may differ) or at the wall.
It'd be interesting to compare the behaviour with one of the DC-motor mills with a forward/off/reverse switch, as that would I think disconnect the motor from the controller?

Bigger machines would probably have a dynamic braking resistor to absorb the stored energy (I have one attached to my lathe VFD - gets quite warm after a few stops with the big chuck), but it's possible the board just dumps it into a hefty diode? Thinking about this has got me worried that my big fly-cutter may push the diode too far...

That's the absolute minimum I'd do (anti-parallel diode) if I were designing it, based on some time working on *big* DC servo systems in a past life!
Does yours have the American KB speed control board or a Chinese "tribute to", as there may be some big differences?

Anyway, there's not a lot of momentum in the motor/gears/spindle so I wouldn't expect it to carry on spinning for long, particularly with the expected friction from the gears added in? Most gear trains are between 70 and 90% efficient, so for a 3/4 HP motor anything up to about 1/5th HP could be dissipating in the gears? That'd stop it pretty quick, and warm up the headstock a bit!
The Chinese DC-motor variable speed lathes I've seen in action seem to stop pretty quickly too (despite having perhaps a 6" chuck spinning at 1000 RPM!), and I guess they probably use the same / similar speed controls...?

Dave H. (the other one)

in your first post you put that you had used a "I've used a WM14-alike as power source " which mill was it and you have said in your last post you have a VFD is that on a WM14 ?
I have a vfd on my lath but it is set to stop slowley so the chuck does not become a bowling ball.

Peter

[Hopefuldave]

HS93 Wrote:in your first post you put that you had used a "I've used a WM14-alike as power source " which mill was it and you have said in your last post you have a VFD is that on a WM14 ?
I have a vfd on my lath but it is set to stop slowley so the chuck does not become a bowling ball.

Peter

Hi Peter,
The Mill's not *exactly* mine, to be honest... One of my biking mates (who lives in Deepest Darkest France) picked it up in a flea-market a few years ago, can't remember the exact make / model but it's a "Fraiseuse something-or-other" - painted white, but otherwise apart from the red LED speed readout it looks pretty much identical to the WM14 and the other Weiss-sourced WMD16's... He brought it over on a visit to his folks last summer and spent a couple of evenings learning how to use it (he's managed to learn his way around an old Colchester Student on his own!) then had to dash back and left it with me
He happened along just as my drill-press had packed up (popped run cap) and during some work on an old Suzuki I used to play at racing, so while he was out visiting I made use of it with a flexi-shaft to muck up the gas-flow - since then I've made a lot more use of it! Unfortunately he's back over in his van in June, so... Mill required, probably a bit bigger!

The VFD's on my lathe, an ABB ACS-301 hacked to fool it into driving a BTH 3HP 415v motor - the lathe's brake is a bit pathetic, and as I do a lot of metric threading on an imperial machine I have to do the "leadscrew nuts engaged, forward and reverse" trick, so I'm forever starting, stopping, reversing - the VFD was giving over-voltage faults with a quick stop and reading the manual suggested using a brake resistor would cure this - true! The resistor's home-brewed, a bunch of 750W halogen heater elements in series/parallel to give 80 Ohms and about 3KW-continuous power handling (with a 10A fuse in series - I think this allows the equivalent of about a 4HP maximum braking effort?) - and yes, on a rapid stop it *does* glow a bit! I'm lucky enough to have a D1 camlock spindle nose, so no chance of the chuck unscrewing (and I use all 6 camlock pins with the big 4-jaw / faceplate, which helps take the stress when slamming it into (electrical) reverse!)

Dave H. (the other one)

EDIT: I took a look, the brand-name on the WM-alike is "Multirex", a quick google finds that to be a French hobbyists' retail outlet for various tools and small machinery - they only seem to stock the smaller mills now though, perhaps there aren't many French model engineers! Also edited the brake resistor spec', memory fade!