WM18 – Broken it again :(

[Michael GilliganParticipant @michaelgilligan61133]

Posted by mgnbuk on 23/02/2020 10:54:21:

[…]

On your machine the airflow needs to be through the motor, not over the casing – the heat is generated in the armature windings & they are what fails. I would look to removing the internal armature "fan" altogether to reduce resistance to airflow though the motor & duct the external fan airflow into the non-drive end near the brushgear. to maximise air through flow.

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That seems very sound advice, Nigel

You might be the saviour of a good few hobby-machine motors.

MichaelG.

[petro1headParticipant @petro1head]

Posted by mgnbuk on 23/02/2020 10:54:21:

On your machine the airflow needs to be through the motor, not over the casing – the heat is generated in the armature windings & they are what fails. I would look to removing the internal armature "fan" altogether to reduce resistance to airflow though the motor & duct the external fan airflow into the non-drive end near the brushgear. to maximise air through flow.

Nigel B.

So are you suggesting blowing down as opposed to sucking up

Re the fan I may invest in a better fan, the one I have runds at 1200rpm and 70cfm.  Noctua do one thats for industrial use ie servers, that runs at 3000rpm and 110cfm

Re ducting the gap between the top of the motor and the fan is 4mm so think ducting would prob not held and be a bugger to design

Edited By petro1head on 23/02/2020 11:35:07

[Ex contributorParticipant @mgnbuk]

All the force cooled industrial motors I have worked with take ambient temperature air & blow it through or around the motor (depending on motor type). I cannot recall a motor failing through being "over cooled" – more airflow is definately better than less.

Could you introduce an internal baffle part way down your cover that would reduce the air blowing around the outside of the motor casing & force more of the airflow through it instead ?

Nigel B.

Edited By mgnbuk on 23/02/2020 15:12:29

[petro1headParticipant @petro1head]

Posted by mgnbuk on 23/02/2020 15:12:01:

Could you introduce an internal baffle part way down your cover that would reduce the air blowing around the outside of the motor casing & force more of the airflow through it instead ?

Nigel B.

Well I suppose I could use a piece are cardboard

[not done it yetParticipant @notdoneityet]

Posted by petro1head on 23/02/2020 15:24:00

Well I suppose I could use a piece are cardboard

Well, that would be a good permanent/long lasting modification🙂.

[oldveloParticipant @oldvelo]

Re ducting the gap between the top of the motor and the fan is 4mm so think ducting would prob not held and be a bugger to design.

Just an Idea Plywood 10 mm thick say 120 mm x 120 mm bore a hole in the centre to fit over the motor bolt to the underside of the fan.

[petro1headParticipant @petro1head]

Posted by oldvelo on 23/02/2020 17:49:51:

Just an Idea Plywood 10 mm thick say 120 mm x 120 mm bore a hole in the centre to fit over the motor bolt to the underside of the fan.

That sound like a cunning plan to me

[Nick Webb 1Participant @nickwebb1]

Posted by Ian Parkin on 19/02/2020 07:10:37:

Petro1head

I do have a motor and speed control board that I took off my wm18 that you can have for a good price

all working

i fitted a 3 phase and vfd to mine

Ian, having just fried my motor, I was thinking of doing a VFD conversion. Can you tell us what you used – and how you mounted the motor – as far as I can tell it's got a non-standard set of mounting holes. Unless I've missed something. Thanks.

[Roger BestParticipant @rogerbest89007]

Good thread.

It seems that sanity has occured.

Anything that lets heat out will be a great help, a big fan like that should be fine cooling so small a box, its designed to get 600W out of a big empty box of sensitive electronics after all.

[larry phelan 1Participant @larryphelan1]

When drilling holes of that size, would it not make more sense to drill a pilot hole and move up in stages?

When you stop to think about it, it is a fair size for any hobby machine. I have a Craftsman lathe, 1,5 HP but there is no way I would drill 22mm straight off.

[Ian ParkinParticipant @ianparkin39383]

Nick

[wendy jacksonParticipant @wendyjackson]

My warco milling motor went bang a few weeks back. I have replaced it with a three phase motor purchased from , The electric motor man, ilchester. As I only live around the corner. The motor just dropped in, no drilling needed which was good news. I have no connection with the dealer, I just find him helpful, and with the electrical knowledge I don’t have.

[Nick Webb 1Participant @nickwebb1]

Thank you Ian.

Terry, Could you post a photo of the motor's plate, or let me know the make and model?

Cheers.

[Howard LewisParticipant @howardlewis46836]

I have drilled 1" (25 mm ) holes on my 1.5 hp Craftsman lookalike, with VFD drive. But not in one hit, Opened up the hole by about 1 mm each time until it got to size.

How would you cope with swarf 11mm wide curling off at speed?

Having done that with a 21" Dean Smith and Grace lathe, it is not easy!

22mm requires removing 89% more metal than the manufacturer's maximum. recommendation.

Do you think that gross overloading may have any bearing the failure?

Experience allows you to recognise the mistake, the next time that you make it.

Howard

[Martin ConnellyParticipant @martinconnelly55370]

This is what broaching cutters are for, big holes, low horsepower.

Martin C

[Terry KirkupParticipant @terrykirkup37827]

I'm only here because I'm researching everything about the WM18 mill for myself, but on reading all this I can't resist asking –
NDIY, just curiosity but is the VFD on your Raglan lathe a "chinese offerings. Poor design – cheapness?" type or Vorsprung Durch Technik? (or even a 50 year old Western thing?).

[not done it yetParticipant @notdoneityet]

Posted by Terry Kirkup on 02/03/2021 20:57:29:

I'm only here because I'm researching everything about the WM18 mill for myself, but on reading all this I can't resist asking –
NDIY, just curiosity but is the VFD on your Raglan lathe a "chinese offerings. Poor design – cheapness?" type or Vorsprung Durch Technik? (or even a 50 year old Western thing?).

Terry,

I’ve no idea. It is tucked away in a box and was already fitted when I bought the lathe. I have seen it but can’t remember the make/model. Likely was rather more expensive than the present models – prices have reduced greatly for cheaper chinese offerings. I think it is rated for one horse power but cannot be sure about that.

Why do you say “ Poor design – cheapness?" The material I drilled was Aluminium (the OP could have been cutting anything, as he didn’t treat us to any great detail), the drill was sharp, the lathe was slowed, but not by so much electronically as the mechanical variable speed control will reduce to under 300rpm (at full motor power, of course) and the material was, as I stated, Aluminium.

At the time, my initial post was of surprise (well, not really) and compared a well constructed hobby lathe, built at least 50 years ago in the UK. Martin W attempted to argue that the modern chinese kit was (perfectly?) OK and my further posts were put up to defend my ‘old British iron’ – it being far more capable than the cheap chinese supplied modern kit, without recourse to giving the chinese kit ‘an easy time’.

My one horsepower induction motor may possibly not have coped with going from 6mm to 22mm in steel without over-loading, but I am confident it would not have destroyed the motor/drive electronics, making it a very costly operator error. Half the trouble is that the modern machine manufacturers over-hype their machines by making claims which might only be achieved in ideal conditions.

I wonder if there is any directive within the operator manual to provide the user with guidelines re run times at reduced speed? Somehow I doubt it but am open to being informed otherwise.

I am sufficiently savvy to know that these DC motors need to be (severely?) de-rated at slow speed (and not to exceed the maximum capacity, as the operator likely did!). I maintain that my lower-rated induction motor is a far better proposition than the ‘pseudo claimed’ (for the less-savvy) 1 1/2 HP arrangement in that particular chinese machine.

I am confident that both my Centec mill and my Raglan lathe would cope with more arduous tasks – at those slower spindle speeds – because both are rated more ‘honestly’ and have drives which are more suitably adjusted with regard to power output at those lower rpm’s. 270 rpm and 85rpm were the minimum speeds quoted, for full power operation, when both my lathe and mill, respectively, were built.

[petro1headParticipant @petro1head]

Not done it yet, it was aluminium

[not done it yetParticipant @notdoneityet]

Thanks, Petro1head – that at least that makes it clear it was neither steel nor cottage cheese you were drilling through!

At £270 just for spare parts alone, it was a salutary experience – you have, at least, taken further (not insubstantial) precautions to prevent reoccurrence of that type of failure with your machine. IMO, that should not be necessary.

We read/hear of serial failings of this type of motor and also of problems with single phase motors (mainly capacitors, centrifugal switches and poor starting torque), yet I can not recall any such expensive 3 phase motor failures. Undoubtedly the manufacturers prefer fitting these DC motors, these days, but they still don’t seem to make them safe from serious mishap (see Andrew’s post on that).

I note the recent (old?) thread with one of Warco’s direct drive machines being apparently fitted with a 3 phase motor and VFD. Perhaps the suppliers are eventually seeing the light (which is as clear as day, to me)? Perhaps a small increase in production cost (if this is actually the case, now that VFDs are so inexpensive) might be a better sales point than outright cheapness, with no mitigation against premature failure – leading to cheaper (and more satisfying) overall ownership by the purchasers of such machines.

A comparison might be the automotive industry, which will undoubtedly lose very lucrative service/repair income as BEVs become more universal? ICE vehicles require far more service items than electric equivalents.

I seem to be in the minority – these DC type of motors are strongly defended by some – possibly by some with vested interests (not wishing to ‘diss’ advertisers’ products?). Or am I just being too honest, as usual?

[Howard LewisParticipant @howardlewis46836]

Some retailers are more honest than others.

The less scrupulous try to blind the less knowledgeable with science, or what they claim to be science.

MANY years ago Hoover introduced a washing machine that was programmed by inserting a "key". The key was a block of composite with a different sequence of slots moulded into each of the eight edges.

A salesman was explaining how "The key programmed the electronic brain" to provide the required wash program.

"You mean it operates a number of microswitches"?

Crestfallen,salesman "Yes"

Beware the man saying "This machine will last a lifetime" without specify the lifetime.

No one expects a F1 engine to have a lifetime of 100,000 miles do they? Some don't even last the race

Mean time to failure is the important number.

Howard

[Tom SheppardParticipant @tomsheppard60052]

In what way is a number of microswitches not an electronic brain? The principles were carried over into the 4004, " micro processor" which was created to run washing machines.

Edited By Tom Sheppard on 03/03/2021 15:27:16

[noel shelleyParticipant @noelshelley55608]

Howard ! It was the KEYMATIC I think ! B–l S–t baffles brains ! Remind me to tell the tale of differencial springing ! Noel

[Nick Webb 1Participant @nickwebb1]

I decided to go down the route suggested by Ian, using a VFD drive and a 1.5kw motor (80 frame (reduced) B34)

The controls are taken from the original box, and I used the contactor to supply the place of an NVR, and do some of the interlocking. There is a 12v fan on top, controlled by the VFD, which runs while the motor is at low revs to provide extra cooling.

The drive is via 36 and 72 tooth timing pulleys and a 500mm long belt. The larger pulley is mounted on the spindle via a collar, drive being transmitted by 4 dog point grub screws which locate in holes which were already in the spindle.

I used to use those holes for my spindle lock, so have made more in the lower section of the collar, and moved the lock there.

The motor mounting plate is currently 3D printed, so the first job will be to make a replacement in aluminium. Let's hope the plastic holds up long enough to finish that.

The VFD shows the spindle speed (scaled from the motor speed) when the thing is running.

For those who are interested, the motor and VFD came from Inverter Drive Supermarket, the belt and pulleys from Bearing Boys. The fan is a Noctua 140 mm 1200 rpm Quiet Case Fan. I have no link with those companies except as a customer.

Edited By Nick Webb 1 on 05/03/2021 16:28:33

Edited By Nick Webb 1 on 05/03/2021 16:30:00

Edited By Nick Webb 1 on 05/03/2021 16:42:26

[Nick Webb 1Participant @nickwebb1]

This is what the inside of the control box looks like.

[Ian ParkinParticipant @ianparkin39383]

Nick looks a fine job you have done there

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