Hi everyone,
New user and brand new to the machining world.
I have a new CNC lathe that is a wheel specific machine – it is made to refinish alloy rims. We are in the rim refinishing business and we only machine alloy wheels. The machine is new, and we and the manufacturer have been trying to resolve this persistent issue for weeks to no avail, so I was hoping someone has perhaps seen this or has a way of dealing with it.
The issue: when cutting the face of the wheel, I am getting a “mottling” effect with white spots all over the face of the wheel at random and a cloudy/hazy finish. I’ve been told this has to do with the aluminum cast used in alloy wheels, and specifically that it has to do with silicon content in wheels and that different manufacturers of wheels may have worse material that causes this – but I’ve now tried countless rims from multiple manufacturers and I get the EXACT same finish. Please see some photos attached. It almost looks like the a camouflage pattern that is stained on the wheel. It cannot be removed by washing, wiping, including with cleaning with any cleaning product, acetone, wax & grease remover, etc. Sanding it down removes its, but then I also remove my machined lines and machined finish that I need to have on the wheel. Polishing looks like has some effect, although hard to tell if it is just hiding it or removing it. I have been able to scuff it with high grit scuff pads to a reasonable degree to remove the marks.
Note: the white spots are definitely more pronounced in the centre of the wheel compared to towards the outside lip of the wheel.
At this point, I have tried experimenting and testing with every variable I can think of under the sun based on many people’s advice, including:
- Changing federate from 2 to 15 and everything in between
- Changing RPM from 350 to 900 and everything in between
- Changing cutting tool heads
- Changing turning inserts (carbide, 331, 332, 333), and PCD (332)
- Changing wheels – I’ve now tried wheels from Audi, Mercedes-Benz, Lexus, Honda, Jaguar. All give me the EXACT same issue.
- Changing approach angle
- Using A9 oil, WD 40 to prevent chips from hitting the cut areas
- Not cleaning the wheels and also cleaning wheels before machining, using each of soap and water, acetone, varsol, wax & grease remover
- Chemically stripping the wheels and not
- Sandblasting and not
- “Seasoning” the turning inserts by cutting 20+ wheels and using brand new inserts
None of the above have made any difference in the finish/effect I get. The wheels feel smooth to the touch and there is no texture to the white spots.
Does anyone have any ideas or has anyone experienced this? Any clues or thoughts would be very much appreciated as I am at my wits end with this issue.
Thank you
EDIT - March 10.
It looks like my long response post is not going to get "moderator approval" anytime soon, so will try writing responses again.
Thank you everyone for trying to help!
Dualkit:
- Sorry, I don't know what surface feet is? Feed rate is constant and controlled by the machine, but as above, I've tried feed rates from 2 - 15.
- Tool nose sizes I've used are 331, 332, 333 (aka 160404, 160408, and 160412)
- The machine does not increase the feedrate as the RPMs turn down. The RPMs do go down as the cutting tool moves from centre of wheel out towards the lip.
Delw:
- What are high sheer inserts please? Looking into it. The inserts I use are for Nonferrous, and I've tried a number of them. Please see some photos of some of the inserts I use attached.
- the manufacturer says no one that has this machine uses coolant and it is not required for wheels - I have tried A9 oil and WD40 though.
D Nelson:
- the fastest the machine is able to turn the wheels is about 900RPM for say a 19" rim
- I have tried diamond inserts as well (PCD)
Macds:
- Have tried oxidized/damaged wheels and also perfectly fine wheels, no difference.
- the pattern does not disappear when there is an uninterrupted cut - it doesn't disappear in any case, no matter what I've tried.
- It is a Lehigh MR2540 machine
EmmanuelGoldstein
- have tried diamond, have tried cutting as fast as machine would allow, and have tried cutting dry, and have tried big nose radius and smaller ones, the chucks that are on the machine are purpose built to hold wheels and are the same ones used by all other rim repair shops using this machine
- re aging - have tried old wheels and new ones (i.e. from a 2017/18 model year car), no difference.
- all the wheels I've done I've bought for practice, so none of these wheels will ever hit the road. Have tried wheels that have been extensively cut, and ones that have not been cut at all - no difference.
- How do I get in touch with big nose Tony?
Thanks!
