WM18 – Broken it again :(

[SillyOldDufferModerator @sillyoldduffer]

Posted by not done it yet on 20/02/2020 08:24:40:

Posted by JasonB on 20/02/2020 07:49:38:

'cause it's easier for them to set their compass to the radius

No, not really. They only use a mm measuring stick in schools? Setting a compass doesn’t rally come in into use for determining the value of Pi – one of the first things for students to investigate and determine that Pi is a constant.

In real life we measure diameters, not radii. When did you last measure a radius? What are your drills marked in? Radii, or diameters? When did you last turn a bar to a radius? So it goes on – diameters are far more useful/important than radii.

Same as teaching subtraction in schools – a cluttered top line when so easily the number changing could be spread over both top and bottom lines of the sum. Different approach but the same outcome (with fewer mistakes, I would suggest).

They would need to find a centre first, so if drawing it they might as well draw a diameter.

It comes down to just using r^2 instead of (r^/2) ^2, which, of course, simplifies to D^2/4.

Got to say NDIY has a strange notion of what's taught in schools. Perhaps he remembers what he was taught and assumes that today's equivalent has been dumbed down. My granny thought anyone who couldn't name all the bays, capes and rivers around the british coastline was a hopeless thicko.

I happen to have a GCSE Maths Textbook and it doesn't support NDIY's simplistic view. It's about triangles based on chords leading into trigonometry in the widest sense. It describes 3 different ways of calculating pi, none of which are how it's computed today, but hey it's historically correct. Radius and diameter are described in a way making it fairly obvious they're both useful.

In respect of geometry, trigonometry, graphs, probability and algebra it seems GCSE covers much the same ground as my O-Level maths syllabus did. But a couple of differences leap out. First, GCSE puts more emphasis on practical applications, I remembering feeling O-Level maths was too theoretical and none of it was useful. Second, a fair amount of new ground has been added to GCSE – transformations, symmetry, and data, while others like Matrices, algorithms, critical path, and statistics have been extended.

Although there's a fair amount of common ground, I wouldn't be confident of passing GCSE Maths today without doing a fair bit of study. And at my age I'd rather sit on my fundament & tell youngsters how much harder I had it when I was their age. They nod politely, but know I'm hopelessly ignorant of their challenges and can't be trusted to remember a short shopping list, or who's birthday is next!

Dave

[Anonymous]

Posted by SillyOldDuffer on 20/02/2020 12:27:06:

It's about triangles based on chords leading into trigonometry in the widest sense. It describes 3 different ways of calculating pi, none of which are how it's computed today, but hey it's historically correct.

Hang on while I go and get my wind up handle. Does the syllabus cover non-Euclidian geometry then? You can't calculate pi, only approximate it, as it's an irrational number.

Wouldn't want to sit my school exams today, although I didn't exactly cover myself in glory at the time either. My secondary school assessed me in the stupid category.

Andrew

[Anonymous]

Posted by Howard Lewis on 20/02/2020 11:26:20:

………it seems to me that the lesson is that if you overload a machine of any sort, you damage it. How badly will depend on the safety factor, if any, designed into it.

I'd disagree with that. Sure if one runs a tool into a rotating chuck for instance then something is mostly likely going to break. But if I overload a machine tool simply by being over-ambitious with the cut then I expect the machine to survive without damage. By experiment I've proved that most of my machine tools will happily survive an overload without damage. The only exception is the horizontal mill; as I've never got close to overloading it.

Andrew

[Howard LewisParticipant @howardlewis46836]

Andrew

It has to be doubtful if any designer allows for a toolpost being run into a chuck. Few of us avoid that failure of care!

What do you expect to happen if you hang a 500 Kg load from a length of 2mm diameter mild steel wire?

Hooke's law will provide you with a beautiful example of a cup and cone fracture, because of an overload. in tension.

The fact remains, as I said earlier, if you overload something it is likely to suffer damage. The extent of the damage will depend upon the safety factor designed and built in.

An overloaded machine tool, will with luck, have the belts slip, if not, the overloaded motor will overheat and suffer damage to the insulation. How long before the motor fails depends upon how long it is allowed to overheat.

Increasing belt tension, to prevent slip, may damage bearings eventually.

If you lock a Myford by engaging back gear without freeing the bull wheel, when you hit the chuck key with a heavy hammer, you are very likely to break the chuck key, or teeth off the gear. You have overloaded things, and they break, because you have exceeded the load, shear, torsional, or tensile that the part was designed to withstand.

I ran my saddle into the headstock. The pinion engaging the rack, and the rack, were damaged. Simply because I overloaded things, Accidental or deliberate, damage ensued.

Many years ago a tower crane collapsed on the London North Circular Road. Like all tower cranes, it had been designed with a small safety factor . The loads imposed by high winds, and having been locked so that it could not "weather cock" to minimise side loading, resulted in loads in excess of the maximum allowed for by the safety factor.

Possibly if the safety factor had been greater, it might have sagged or bent, but not completely collapsed, killing people.

The C47 Dakota was designed with a large safety factor. During WW2 in the far east one was loaded with, supposedly Aluminium perforated runway strips. When it had struggled into the air and delivered the load, it was found to be Steel! A smaller safety factor would probably have meant the aircraft collapsing on the runway, and never even managing to get airborne, But that event must have surprised the designers!

You are experienced enough to know that beyond the yield point, the elongation is permanent. U T S is the abbreviation for Ultimate Tensile Strength. If you exceed it, it breaks!

So we should work within the limits of our material of machine, or suffer the consequences.

Howard

[Dave HalfordParticipant @davehalford22513]

Posted by Neil Wyatt on 20/02/2020 09:51:37:

I don't have a WM18 manual but one for a similar machine states very clearly:

"Never force the tool or attachment to do the work of a larger industrial tool. It is designed to do the job better and more safely at the rate for which it was intended."

Neil

Does it then go on to document those rates? It would be really useful if every machine was supplied with at least the max boundaries. Just saying capable of drilling16mm is no help if half the available speed range might burnout the motor. My old lathe has the dangerous threading speeds marked up on the gearbox as for backgear only.

The old iron is better argument is kind of pointless as there's not enough to go round so the newcomers have to buy Asian.

I do wonder how many Asian machines are out there, out of guarantee with overloaded electrics waiting for the shed roof felt to blow off just for the lack of guidance on speeds and feeds that could have been supplied with the machine when new.

[JasonBModerator @jasonb]

Worth bearing in mind that many of these machines don't have the traditional V belt so may not slip as easily. Many have Poly flex or Poly vee belts which will grip for longer or like my previous Emco lathe and current X3 mill have a toothed timing type belt from the motor.

I seem to recall that this mill has already stripped a gear and we don't know if it has been regularly expected to drill holes larger than 16mm so this may simply have been the straw that broke the donkey rather than going bang the first time it was overloaded. Just have to hope the newly fitted Z-axis power feed was not being used to force the drill into the work which would remove all "feel" for the forces needed!

Edited By JasonB on 20/02/2020 16:04:33

[SillyOldDufferModerator @sillyoldduffer]

Told to "Let the tool do the work" when I was at school. And we were beaten if caught misusing tools. Didn't make any difference, most men in a hurry will thrash the machine. And some folk are naturally heavy handed, insensitive to the sound of distressed mechanics, and unable to smell smoke. Damn the torpedoes, full speed ahead! Testosterone rules, KO.

Dave

[oldveloParticipant @oldvelo]

So many explanations of what went wrong and why it happened at what needs to be done to fix it.

Prevention is better than cure. Fit a an AMP meter to the DC motor leads in a position where you can see it easily..

Fit auxiliary cooling fan to the motor

Mark the Meter With Maximum Rated Amps of the motor.

Adjust the speed and feed to below the marked amps.

A KB Electronics AC to DC controller set up correctly with the "Locked Rotor Test" to Less than the rated motor AMPS will trip on excessive loading.

Either one will will help I prefer both "Belt and Braces" man myself

Edited By oldvelo on 21/02/2020 18:05:12

[petro1headParticipant @petro1head]

Bugger, for some reason I have never recd email notification of replies to this. Poss because I forgot to check the box.

So appologies for not replying.

Yes an expensive lesson thats now fix. It was the motor and I suspect I had cooked it when I had a jam a couple of months ago and beoke the sacraficial cog between the motor and spindle and then the drilling opperation was the final straw. Warco had stock and got it next day. Cost £270!!!

Now I see that Ian was offering his grrrrrrrrrrrrrrr My loss

My pal also suggested I 3 phase it but that was after I had bought the motor

So Ian, in case there is a next time what motor did you use for the 3 phase conversion and was it a straight saw or did it need some fettling?

Email noitification box ticked

[petro1headParticipant @petro1head]

I just saw the first page when I posted my reply but oh boy 3 pages

Skimming thro I would agree that it was my fault, impatient git that I am and the learn the hard/expensive way.

[petro1headParticipant @petro1head]

Posted by oldvelo on 21/02/2020 18:04:11:

So many explanations of what went wrong and why it happened at what needs to be done to fix it.

Prevention is better than cure. Fit a an AMP meter to the DC motor leads in a position where you can see it easily..

Fit auxiliary cooling fan to the motor

Mark the Meter With Maximum Rated Amps of the motor.

Adjust the speed and feed to below the marked amps.

A KB Electronics AC to DC controller set up correctly with the "Locked Rotor Test" to Less than the rated motor AMPS will trip on excessive loading.

Either one will will help I prefer both "Belt and Braces" man myself

Edited By oldvelo on 21/02/2020 18:05:12

One of the problems with the WM18 is the motor is emclosed in a fibre glass case with little ventilation. When I stipped the old motor down it was obvious it had overheated several times so some sot of aux fan would help. Have a few large computer fans lying around that I could use. Note sure where I would fit it ie above the motor and would it suck out heat or blow in cold air?

However I also understand that because I have fans does not mean I can, again, try to make the mill do what it was never inteneded to do.

[oldveloParticipant @oldvelo]

"Note sure where I would fit it ie above the motor and would it suck out heat or blow in cold air?"

If the fan on the motor air flow comes out of the top Then mount the fan on the top of the fibreglass housing to suck out the hot air. Push old air in if the outlet is at the spindle end of the motor.

Fit a duct to fit over the diameter of the motor to the fibreglass cover to get maximum air flow through the motor.

I fitted an auxiliary fan on the mill years ago the motor never gets hot even at slow speed and a heavy cut with 4 AMPS showing on the meter

[petro1headParticipant @petro1head]

Had a look at the current setup.

Using a jos stick to see the flow of air, the fan is at the top of the motor and draws air from the bottom of the motor and exhausts out the top of the motor. However what is very telling is until the motor is spinning at about 900 there is little to no air being drawn in.

So basicall the motor is starved of air at low speed, just as you said. So I am going to route out a 120/140 dia 12v computer fan and mount that iside the cover with a suitable hole cut and suck air out. I am also going at add some holes at the bottom of the cover so more air can get in.

All I need to buy is a 12v supply for the fan

Edited By petro1head on 22/02/2020 19:11:12

[Martin WParticipant @martinw]

If you use a 12V fan similar to those found in computers then a relatively small wall wart psu will be adequate and they are only a few quid each from the likes of CPC or Ebay etc.

Fitting one directly to the motor could be problematical if there is a motor reverse function as then it would be opposing the air flow from the motor. However being aware of this and not running it for extended periods in this mode would mitigate this problem.

Have fun

Martin

[Howard LewisParticipant @howardlewis46836]

Possibly a few holes at each end of the glassfibre motor cover (So that swarf cannot get in) may help extend motor life.

My lathe used to eat Q H worklight bulbs. Took it apart, and filed, a couple of 8mm dia slots om the rim of the "reflector". Bingo! Lamps last MUCH longer; can't remember when the last one failed

ASKING for trouble!

So a little extra cooling air might work wonders in lowering temperatures below some critical value that divides LIVE from DIE.

Howard

[oldveloParticipant @oldvelo]

Sounds like good plan with a 120 mm computer fan on the inside of the cover, As Martin points out that running in reverse may be a problem running in reverse,

The computer fan will cope at low speeds. How many times will you be running in reverse at highest speeds if a problem switch off the auxiliary fan.

Cool Running

[petro1headParticipant @petro1head]

Can't say I have ever run in reverse but a valid point.

So this is what I have done, 120mm Corsair 12v Fan (140 was just a tad too big) exhausting out at the top of the encloure and several 10mm holes at the bottom

I remembered I already have a 12v supply going to the Angle Eye LED around the quill so can tap into that. Jobs done

Edited By petro1head on 22/02/2020 20:31:11

[oldveloParticipant @oldvelo]

Looks good make sure that the fan has a duct to the top of the motor to get the full airflow over the motor and not bypass it by just ventilating the cover.

[petro1headParticipant @petro1head]

Tbh I suspect the fan is probably only a few mm from the top of the motor but will check

[Enough!Participant @enough]

When BusyBee in Canada first imported the WM16-type mill, it had no agency approvals. The usual approach in that circumstance is to have it directly approved by the local electrical authority – Ontario Hydro in this case.

Ontario Hydro approved it, subject to a reduced rating-fuse being fitted. I bought one of these and it was something of a nightmare. The fuse would blow during any operation the tiniest bit severe.

After many fuse replacements (and stop-works for lack of a fuse). I decided to switch back to the original fuse but supplied power to the mill via an external, local circuit-breaker – rated as the smaller fuse but with a delayed response. This cleaned up the act quite nicely. I haven't replaced a fuse in years, though I have reset the circuit breaker occasionally.

Since then, I also converted the mill to a belt-drive. This removes the box around the motor and leaves the motor standing up in free air which has also improved it considerably (not to mention being an order of magnitude quieter). The only time the CB trips now is when it's not entirely unexpected (tut tut).

Edited By Bandersnatch on 22/02/2020 23:30:02

[duncan webster 1Participant @duncanwebster1]

Posted by Martin W on 22/02/2020 19:27:59:

If you use a 12V fan similar to those found in computers then a relatively small wall wart psu will be adequate and they are only a few quid each from the likes of CPC or Ebay etc.

Fitting one directly to the motor could be problematical if there is a motor reverse function as then it would be opposing the air flow from the motor. However being aware of this and not running it for extended periods in this mode would mitigate this problem.

Have fun

Martin

If it's a centrifugal fan then I think it blows the same direction whichever way it's running. It might blow a whole lot better one way than the other

[clogsParticipant @clogs]

I nearly bought a WM mill……

after reading this and other problems with the brand…….RATHER glad I didn't…..

with all the world sales I would have thought that the factory should have got it right by now…….

Overpriced and over comes to mind…….

[petro1headParticipant @petro1head]

Posted by clogs on 23/02/2020 06:09:51:

I nearly bought a WM mill……

after reading this and other problems with the brand…….RATHER glad I didn't…..

with all the world sales I would have thought that the factory should have got it right by now…….

Overpriced and over comes to mind…….

I would not be so quick to dismiss the wm18. It’s a fab mill and any problems I have had have been down to my own fault not the product

[Martin WParticipant @martinw]

Duncan

The fans on these motor are standard bladed fans that are pressed onto the motor shaft and are internally mounted. Change motor direction and this changes air flow direction unlike some of the fans that can be seen on power hand tools etc. which are centrifugal and can shift a lot of air through the motor when running at a reasonable speed

Martin

Edited By Martin W on 23/02/2020 10:04:30

[Ex contributorParticipant @mgnbuk]

Usual practice on industrial DC motors is to have a separate blower mounted at the non-drive end forcing filtered air through the motor to exit through louvres at the drive end (should be a picture below)

**LINK**

The airflow is usually substantial & is frequently monitored using a flow switch downside of the filter to check for filter blockage. The centrifugal fans are directional – they will move air when running in reverse, but at nothing like the output when running correctly – think summer breeze versus winter gale !. A Gildemeister lathe at work had to have the 22Kw main spindle drive motor rewound due to the previous owner having changed the blower motor bearings & wired it running reversed when replaced – both the armature & field windings cooked at the drive end due to inadequate airflow & the rewind cost £5K 10 years ago + £1k for the Baumueller drive repair, as the failed field windings took out the field controller.

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.

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