New machine not doing what it is ment to.

[Quattromaster]

Mods...Sorry, no idea where to put this so please move if needed.

Amongst other things I own a company that refurbishes alloy wheels, and have just spent rather a lot of money on a CNC wheel lathe, kind of like the one below.



2 of my lads went on a training course, one passing with merit, the other with distinction, we also took 10+ alloys with us on training and they were done on an identical machine,musing the same cutting tip. They looked stunning.

On returning to our own machine things were looking good, we loaded in our first alloy and probed,plotted and optimised it no problem at all, then we cut it, ie machined the front face, removing the damage. And here lies the problem.

We just cannot get a good finish, we are getting marks on the face of the alloy wheel, see below.



We are now 3 weeks in, having done approx 50-60 wheels, trying different speeds, cut depths, turret speed, yet still get this finish every time.

The company who supplied the machine and training are supposed to provide a yr back up service, yet are not interested, they say it's the tip, we have tried 3 in total, it's the tip they recommend, a tungsten diamond carbide insert tip. They say it's the type of alloy we are cutting, yes, some makes, BMW in particular are hard to get a good finish, but we have cut a mixture of BMW, Audi, Range Rover, Mercedes to name a few. All with the same result.

We have noticed the turret , which you turn by hand, when locked in place is not quite straight, we have told them this but they won't have it, say it's normal. We kind of think the tip, which is a 1.3 radius is not cutting central, so not clearing the swarf, could this be "catching" and causing the finish.

So, I ask the PH massive, anybody have experience of using a CNC and in particular on alloy wheels. We really are running out of ideas, and indeed wheels to practice on, I've a nice new machine yet for the moment are still sending this type of alloy away.

Welcome any thoughts, thank you.

[98elise]

Do you have an identical wheel to one you used in the training? If so test that and see if its the same.

[dudleybloke]

Have you clocked up the toolpost to see how far out of square it is?
And I'm not keen on your chucking arrangement, if I were turning something of a large diameter I would like a bigger chuck with jaws that don't stick out that far. But that's me being fussy.
Is the tip you're using a wiper tip? Another issue could be coolant.

Edited by dudleybloke on Monday 30th May 16:31

[Quattromaster]

98elise said:

Do you have an identical wheel to one you used in the training? If so test that and see if its the same.

Yes, have tried identical wheels, in fact have also "remachined " the good wheels from training and still get bad finish.

[spikeyhead]

I'll take a guess that it's wobble on the tool post, though that chuck looks a very dumb way to hold a wheel.

I'd prefer a backing plate and some short headed bolts rather than a chuck.

It may just need a gibb or two tightening.

[Quattromaster]

dudleybloke said:

Have you clocked up the toolpost to see how far out of square it is?
And I'm not keen on your chucking arrangement, if I were turning something of a large diameter I would like a bigger chuck with jaws that don't stick out that far. But that's me being fussy.
Is the tip you're using a wiper tip? Another issue could be coolant.

Edited by dudleybloke on Monday 30th May 16:31

Tool post is approx 6" sq, and is out by approx 4 mm on one end
Chuck/jaws are what came with the machine, and the same as the machine we were trained on.
Sorry, no idea if the tip is a "wiper tip", this is the tip in question, with a 1.2 radius

http://www.cutwel.co.uk/lathe-tools/iso-turning-in...

Ref coolant, don't use any, never been shown or told to, cut the wheel dry.

Thanks for the pointers so far folks.

[dudleybloke]

First thing I would try is to square up the toolpost if you can. Also check everything is nice and tight.
How does the swarf look?

Edited by dudleybloke on Monday 30th May 17:16

[mr.man]

Describe in greater detail the imperfections on the machined finish. I can't really see the marks only that it's clearly not a diamond turned finish. Without seeing your set up myself it's difficult to help.
Basic facts. This machine using the same purpose made jaws, the same toolpost, the same grade and style of tool is capable of producing the required finish.
Basic things to check. Is there a tiny nick on the nose of the tool?.Are you clamping the tool with minimum overhang? Are you spinning it fast enough?. These tips are good for 3000m/min. What feed rate and depth of cut was recommended?

[Quattromaster]

mr.man said:

Describe in greater detail the imperfections on the machined finish. I can't really see the marks only that it's clearly not a diamond turned finish. Without seeing your set up myself it's difficult to help.
Basic facts. This machine using the same purpose made jaws, the same toolpost, the same grade and style of tool is capable of producing the required finish.
Basic things to check. Is there a tiny nick on the nose of the tool?.Are you clamping the tool with minimum overhang? Are you spinning it fast enough?. These tips are good for 3000m/min. What feed rate and depth of cut was recommended?

Looks like fine spray water marks.

They say the tips are good for 250 wheels approx, we have tried 3 tips now with no visible damage on any.

Tool was clamped same distance as the one they were trained, though I think the lads have since moved it in up to 20mm to see if any change, there is a limit on how much it can be moved.

Training says RPM of 500, 0.1-0.2 cut depth and 0.1-0.2 feed speed across the wheel. we have tried 500,550,600,700 and 750 RPM with no luck, they say no more than 800 RPM. And tried just about every increment from 0.50-0.2 with still the same poor result.

I'm still leaning towards it being something to do with the tool post not locking straight, maybe the picture below may help in showing how far it's out.

[thebraketester]

Its it making a harmonic noise when its cutting? It could be chatter.

[LDN]

Surely; if they're not proving support and they said they would / it's included then you issue them a final demand for support or else you will take them to court...

The fact you've had to come onto a forum to ask the question means they've really left you up the creek with no paddle. It's not fair and I'm sure you'd win your case if it ever got that far.

[Quattromaster]

anonymous said:

[redacted]

Yes, very happy with the "rings", it's the mottling/water marks that are not right.

I know the one the lads were trained on isn't bolted down, neither is ours.

[thebraketester]

Bearing in mind this is off the lather manufacturers website....




Doesnt look a great finish.

[Quattromaster]

LDN said:

Surely; if they're not proving support and they said they would / it's included then you issue them a final demand for support or else you will take them to court...

The fact you've had to come onto a forum to ask the question means they've really left you up the creek with no paddle. It's not fair and I'm sure you'd win your case if it ever got that far.

It's heading down this route very very quickly, so far I've had 2 lads not machine a "paid" wheel in over 3 weeks, didn't expect to be doing 20 wheels a day from day one but it's becoming very frustrating.

I know the machine can do a good job, I saw one in action last Nov when I went to take a look, plus of course my lads took wheels up to training.

[Simpo Two]

Quattromaster said:

The company who supplied the machine and training are supposed to provide a yr back up service, yet are not interested, they say it's the tip, we have tried 3 in total, it's the tip they recommend, a tungsten diamond carbide insert tip. They say it's the type of alloy we are cutting, yes, some makes, BMW in particular are hard to get a good finish, but we have cut a mixture of BMW, Audi, Range Rover, Mercedes to name a few. All with the same result.

How about challenging them to come over, with a wheel of their choice, and show you how it works? Either you'll find the problem, or they'll be forced to admit it's dud. If they don't take up the challenge, wonder why. It will look good later...

[red_slr]

hard water vs soft?

[dudleybloke]

Is the tool height OK?

[tumble dryer]

Interesting stuff.

I copied OP’s original pic and enlarged in PS. What’s happening is not (immediately) happening at the cutting point. If you follow the cutting marks and look below them, you’ll see the ‘water marks’ spreading across many cut lines.

What could cause that?

[Quattromaster]

Simpo Two said:

How about challenging them to come over, with a wheel of their choice, and show you how it works? Either you'll find the problem, or they'll be forced to admit it's dud. If they don't take up the challenge, wonder why. It will look good later...

Simpo, they are doing just this today, due at 11am, it's only taken them 3 weeks of asking, I posted on here to hopefully get a few more pointers, to throw at them, which I have, thanks for help so far folks.

[dave_s13]

Interesting