[upnorth]

Hello All:

Since my Novakon was new it has always had an issue with chatter. It works good for cutting aluminum but not on steel. When I try to cut steel it makes a squealing noise. Varying RPM and feed rate changes the pitch of the squeal but it is always there. I don't have the original controller it is run by a Centroid acorn now.

I measured and set up the control to eliminate the backlash which is about .0015" on the X axis. Parts made from aluminum are usually within .001" on both the X and Y axis. Circles are out about .002 on a 45 degree angle to the X or Y axis. This is the amount of the backlash.

Has anyone ever adjusted the backlash of the ball screws to eliminate the backlash?

[metalmayhem]

Adjusting the nut on the bearing blocks might help to reduce your backlash . Conventional milling the finish passes should also help to reduce or eliminate chatter marks when slop is present .
You don't mention the cutter your using , if you using standard end mills then you'd probably have better luck with variable flute / variable helix mills

[upnorth]

Thanks for the response. For Aluminum I use good quality YG1 or Iscar variable flute end mills. Aluminum cuts well and the finish is like a mirror.

For steel I tried many different end mills. They all squealed. Poor life also. Lot's of chipping. I can't remember the exact cut formula I used but it was quite conservative according to a cut calculator. I do run full flood coolant.

[mactec54]

Thanks for the response. For Aluminum I use good quality YG1 or Iscar variable flute end mills. Aluminum cuts well and the finish is like a mirror.

For steel I tried many different end mills. They all squealed. Poor life also. Lot's of chipping. I can't remember the exact cut formula I used but it was quite conservative according to a cut calculator. I do run full flood coolant.

Sounds like the spindle is not rigid enough for the steel cutting, either Bearings support or flex in the spindle tool mounting, steel takes a lot more force to cut and defects show up in spindle design when poor quality of cut happens, backlash is easy to see in a cut, if it is still backlash, try a 6-flute cutter and see if this makes the cut better

[upnorth]

Sounds like the spindle is not rigid enough for the steel cutting, either Bearings support or flex in the spindle tool mounting, steel takes a lot more force to cut and defects show up in spindle design when poor quality of cut happens, backlash is easy to see in a cut, if it is still backlash, try a 6-flute cutter and see if this makes the cut better

Good point maybe it is a rigidity problem. I do know some people here are successfully cutting steel with the same Torus Pro that I have. I'll order in a couple of stub end mills to reduce flex. I'm thinking maybe I should get some solid end mill holders instead of the collet type that I ususally use.

[metalmayhem]

if your using er holders then chances are that the holder is most of your problem . Er collets are designed more for precision than heavy cutting . Tg are much better steel cutting holders but solid holders are the way to go

[upnorth]

if your using er holders then chances are that the holder is most of your problem . Er collets are designed more for precision than heavy cutting . Tg are much better steel cutting holders but solid holders are the way to go

Yeah I have to agree with you. When I first got the mill I bought a few solid end mill holders and a lot of ER-20 collet type tool holders because I thought they would be more versatile. I eventually realized that it was best to standardize on .125", .250" and .375" end mills at least for aluminum. I'm going to order in some solid holders for .250" and .375". I'll see what happens.

[metalmayhem]

I bought a set of solid holders and a lot of er holders when I bought my torus . The er holders are great for being able to toss any tool into but they are limited . I have a job where I gradually ramp a 1/2" ballnose to .25 depth , the width and depth have to be held to within .0007 " . In a solid holder it purrs through the aluminum , in an er it sings .

Also any slop in the bearing blocks (usually the y) would also have an ill effect on things . The stock and replacement bearings from novakon are crap . The x hasn't been a problem but if I recall correctly I went through 3 sets of bearings on the y until I finally replaced them with with better quality . It would be worth checking the tension on those bearings if your chatter continues

[Jmhx2]

As Mactech pointed out the lack of rigidity is the primary cause of chatter. I have cut thousands of lbs of steel on mine. Mine was singing as well. I was concerned I had a bad spindle bearing, but everything was okay after checking them out. I started to notice on a large part that it only screeched while the X axis was moving, it was silent when the direction changed and the y was moving. The part was around 15"X20", bolted to a sacrificial plate mounted in my vice, the part overhung the plate by a few inches all the way around. I assumed this lack of rigidity was causing the resonance. In part it was, I fixtured it in a more supportive way and the chatter reduced, but I was curious as to why it was X and not Y. I then adjusted the gibs and it went away completely. I try and stick with 1/4 & 3/8 " end mills but have used smaller and larger. I typically have a WOC of .075 on a 3/8 4 flute carbide end mill.

[Veloso]

have you tried endmills with serrations along the cutting edge as chip breakers?