Member postings for alan w

Hopper / Clogs - thanks for the useful feedback. SO many possible ways to go.

Thanks gents. I have an unknown number to drill - I'm making plastic injection moulding machines to order.

I've heard 2 schools on big drills - one saying go u pin stages, the other saying to it in one slow stage. My personal experience with Blacksmiths drills has been that one stage is better, though still not without misery.

Yes, the hole is blind. Well there's a 6mm exit for the molten plastic at the "other end". I'd never heard of Rotabroach before, but I just checked out a video. If it works by pushing a central slug out the far side, then it's no good for this.

I did wonder about a zonking great end mill, but I suppose that's no good in a lathe.

However, I never - oddly - considered using a morse tapered drill. So I'll but one or more - good quality large drills - and see how they do.

I'm machining 35mm bars of 303 stainless in a Chinese CV8VS lathe. I need 20mm wide holes, 50 - 60mm deep. Currently I'm using a 17.5mm "Blacksmith's drill" first, then finishing with a boring bar. It takes a couple of hours, and the Blacksmiths drill wear out fast, and have a tendency to bind inside the hole high up the shank as the hole gets deeper.

Does anyone know of a better way to do this? If so, I'd really appreciate your advice.

Thanks John. I think we'll do that.

Final update(?):

Neil, the old, blown, motor, also turned slowly on a 12V charger which really convinced us it HAD to be OK. But if you pinched the shaft whilst it was turning though, you'd feel it kick once a revolutions. One of the windings was shorted out. The new motor doesn't do this.

POST MORTEM:

Almost certainly, I caused the problem whilst spending a morning taking 2mm cuts on a large piece of stainless 303. I had a lot of material to remove, and everything seemed happy - no bad noises, vibrations or poor finishes, so I pressed on until, apparently, the motor got so hot the windings' lacquer presumably melted, then shorted, That blew the controller. My understanding is that this problem is exactly why you all prefer AC motors.

Chester advised we return the controller to base. More than two weeks later, they told us is was blown and sold us a new one which we fitted. However, because the motor was blown, fitting the new board also blew that, though we didn't know it at the time.

So we bought a new motor from Chester. Actually, it was an old motor - grubby, rusty in parts, chafed labels and obviously-used wire connectors. Also it squeaked when on the battery charger. It didn't work on the machine because the controller was now blown.

I complained to Chester about faulty advice and the squeaky second-hand motor, being £200 down, nearly a month older and no working lathe. I have to say Tony in sales, did a fantastic job. THE NEXT DAY we received another motor and another new controller board. I fitted them and they work. Chester will pick up the faulty board and the squeaky second hand motor free of charge. So - all ended well, but we're about a month down, and no work on client projects. Now my car's failed it's MOT so I'll be bussing to the workshop when I can.

LESSONS LEARNED:

1. The 12V charger test does not guarantee a good motor.

2. Fittng our bad motor blew its controller in an uneventful instant.

3. Do John Rudd's bulb test to verify a controller board

4. Working this lathe hard will burn out the motor with no warning

LOOKING FORWARD, I think I might fit a fan in the motor compartment to help keep it cool and a temperature sensor with a display up on the lathe where I can see it. Has anyone done this or is there a better way?

Chris

John,

I took the 133 Ohms reading to be a sign that all was well with the thyristors, not that they were faulty. I was wrong on that.

I reasoned that the worse the controller can do to a motor is dump full WPM into it. For the short time I had it connected I didn't think it would do any harm. I was wrong on that too - not realising it might dump AC.

Clearly I should have stuck to the experienced advice you offered us. I'm afraid urgent desperation got the better of us.

Luckily, it doesn't seem to have done the motor in. At least it turns evenly on a 12v battery charger.

Meanwhile, the motor Chester sent us - though working - is clearly second-hand and it squeaks. I've taken that up with Chester.

I will email you about the controller board repair John.

Thanks,

Chris

Hello again. I'll post here in case it's helpful to others.

John - we followed your procedure. The resistance on the A+ to A- (armature) leads on both the old and new boards is about 132 ohms. We connected an incandescent mains bulb as suggested to the new controller board where the motor would be. With the controller speed set to the slowest, the bulb was at full illumination.

That's not what we'd expect, but - what to do now? We bit the bullet and connected the new motor. With the controller still set to the slowest speed, the motor ran very fast for a very short time then the fuse blew.

Hopefully, the motor didn't have enough time to overhead and break down the lacquer on a winding as before.

So it looks like both boards are faulty. Wonderful.

Your repair description looks like special knowledge is a real benefit, so - if the offer is still available - we'd like to ask you to fix one of them for us. We'll happily pay for your time and of course the postage. If the offer IS still on, please message me your postal address and payment details. If not, I'll do my best with the instructions you've already kindly provided.

Many thanks,
Chris

John, many thanks for all of that. You're a kind a patient man.

I'll give it a go. I may come back to haunt you - no good deed, after all, should go un-punished.

Thanks again,

Chris

OK well, surprisingly, Chester got back to me this morning to say they have a direct replacement DC motor for shipping today and arrival tomorrow. I have heard what people have said about superior AC motors, but because we have clients waiting on projects, this is our fastest easiest route back to production, so it's what we'll do. Contrast this to yesterday when they didn't know anything.

We may take the upgrade route when things are less hectic and funds allow.

John, as we may have blown even the new controller board, any guidance on how to fix it would be welcome. I have an electronics background, and oscilloscope, multi-meter and soldering iron, but I have no knowledge of or experience with these boards. I assume they're PWM controllers? Even if the new one is OK it would be nice to fix the old one and maybe sell it on to recover some of our £120 outlay. I could also clobber Chester for not offering to repair it at a far lower price.

BTW, I am Chris, Alan, the lathe owner and my older brother is Alan, the subscriber to model engineering. As his underling (I'm only 57) he's delegated the clerical drudgery to me.

Also tea making.

Bang. Just like that - instant help. Heh. Chester - if you're watching - see that? These people are more helpful for free than you people are at £1,200 a pop.

Gents, thank you all greatly for your interest, ideas and advice. John Rudd - thank you especially for your kind email. I will meet with my brother today and discuss what you have all said, and decide on our way forward and John - I'll get back to your email after that.

Best Wishes,

Chris

We have a DB8VS Chinese lathe from chester. It's been working OK for 7 yaers, but recently it blew a fuse, then another then wouldn't come on. We sent the controller board off for inspection. Chester told us it was blown and sent us another for £120. We fitted it, and the fuse blew again - and perhaps the board - don't know yet.

A local engineering firm tested our motor and tell us a winding is shorted and want £300+ to rewind it.

Chester cannot yet tell us how much a new motor will be nor when we might receive one. Since they took three weeks to get around to looking at the controller board, we're not holding our breath on a rapid response on this.

The motor is 220V DC, 750 Watts. The rating plate says it's type is ZYT95-02T1. I cannot find it anywhere online.

If anyone has any useful comments, I would be very grateful to hear them. Do you have a spare you can sell us for a pittance? Can you rewind ours for a Kit-Kat? Do you know where we can get a replacement or of other names this motor goes by, or which company ZYT is? Or maybe alternative motors which will do the job?

What other options do we have?

Thanks for your time.

Thanks all for the advice on milling in general, which are much appreciated. Last weekend, we prepared to implement the quill movement fixes proposed here, and rapidly worked out a depressing fact. Our mill is not the X2 I told you it was. It's a Super Mill XN2. I don't know if the N makes a difference - pictures on the web look identical - but I think it must because the description of what we'll find inside the quill housing is entirely wrong. What you find is just a motor mounting plate - with slotted bolt holes to allow belt tension adjustment, and another mounting plate around the quill assembly. That plate does not "hold the quill - you can remove all the bolts ad wiggle the plate but you don't get any access to the quill. And we can't remove the toothed pulley which the drive belt from the motor engages with.

Looking at the exploded diagram in the manual, it seems the quill assembly bearings (top and bottom) are a press fit into the casting. I don't know how to get it out, but moderate force is entirely unhelpful. So - we'll implement the milling methodologies you've outlined for us, but I can't see how a mill with 0.1mm play can ever machine engine parts accurately, so I think we're still stuffed until the play issue is gone.

Edited By alan w on 26/09/2014 14:31:02

Thanks again people. You've given us a lot to think about and to try. So we need to adjust the pre-load thingy, verify we can plunge our cutters, cut smaller slots first and finish to size on a second pass, and cut shallower passes.

I think we'll print this all out and set to again at the weekend.

Thanks again, Alan

We have a Sieg X2 super mill and we're milling dreadful crooked lines in aluminium and wondering why. We can mill straight edges but not plunged slots. There is deviation of more than a millimeter from a straight line using a 6mm mill.

We noticed that - with a DTI on the quill sleeve, we can pull and push the quill to reveal a 0.1mm play. Is this normal? If not, do we need to replace the bearings?

If this is not the problem, any thoughts would be very welcome.

Alan