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Is there such a thing as an acceptable step height at tool overlap?

Shawn_Laughlin

Aluminum
Joined
Mar 28, 2019
This could all be bc I don’t have much experience with milling but I do on a lathe, at least manual not cnc. So I understand tool deflection and how important feeds and speeds and other things are but when cutting with a razor sharp emdmill in aluminum,taking a skim of a cut at a depth of .015625 / 1/64”, at 10,000rpm and 40 ipm, with a .375 step over, the finish should be smooth as long as machine is level and spindle is trammel, right?
I understand these aren’t the ideal feeds and speeds but moving at such a slow ipm there should be no material left to cut if I run back over the work without changing the z depth,right?
I can run over it 3 or 4 more times and it keeps making chips. Not like if it was a fresh cut but enough so that each pass takes off more and more and its as smooth as I think you could possible get.

It’s been coining also so kinda makes me feel like it’s a controller problem than can be programmed out maybe?

It’s weird thou bc it doesn’t matter if I’m spinning a 3” face mill or 1/2” endmill, the steps feel the same. Easily catch your finger nails on them. I would think that a 3” face mill with the wider tool path would have a much more pronounced step but it doesn’t look that way. I broke my indicator and have another one that’s suppose to be delivered today so I’ll check when it comes in.
 
This could all be bc I don’t have much experience with milling but I do on a lathe, at least manual not cnc. So I understand tool deflection and how important feeds and speeds and other things are but when cutting with a razor sharp emdmill in aluminum,taking a skim of a cut at a depth of .015625 / 1/64”, at 10,000rpm and 40 ipm, with a .375 step over, the finish should be smooth as long as machine is level and spindle is trammel, right?
I understand these aren’t the ideal feeds and speeds but moving at such a slow ipm there should be no material left to cut if I run back over the work without changing the z depth,right?
I can run over it 3 or 4 more times and it keeps making chips. Not like if it was a fresh cut but enough so that each pass takes off more and more and its as smooth as I think you could possible get.

It’s been coining also so kinda makes me feel like it’s a controller problem than can be programmed out maybe?

It’s weird thou bc it doesn’t matter if I’m spinning a 3” face mill or 1/2” endmill, the steps feel the same. Easily catch your finger nails on them. I would think that a 3” face mill with the wider tool path would have a much more pronounced step but it doesn’t look that way. I broke my indicator and have another one that’s suppose to be delivered today so I’ll check when it comes in.
Alot of things can effect it. how is the material held in place, thickness of material. Endmills length of holder etc etc

on my haas vf2ss I take no more than .008 clean up pass, anything more will result in slight steps, other wise its perfectly flat and smooth ie hit it on a rock with sandpaper and you dont see it. On my Fadals I can go 0.01-.0.012 for same finish.
all with 1/2" endmills up to 100 IPM.
as far as keep hitting material every time you run it, check your thrust bearings
 
With everything dead perfect for tram and true and the spindle parked give a solid push to one side of the 3" cutter about 50 pounds push and see what deflection you can see under an indicator, do the same to the table. Trig out that deflection to reflect at 3" cutter face and you may see the reason for a step.

Even cross-hatch lines can give some idea of deflection and tram.
 
Is this a new machine from the factory?

Brand new 2020 vf4ss. The tech didn’t even level it. The two middle screws were not even touching the pad so I spent 4 hrs after work 3 days in a row leveling it. When the tech came out he proved he leveled by showing it was perfectly level. Actually made me feel good lol. And when He was shown a cut and the step it was leaving he shrugged his shoulders and spit ina cup. I honestly didn’t know what to say after that. Now I’m worried if I call the same positive, give a shit guys is gonna come out for the 4th time.
 
With everything dead perfect for tram and true and the spindle parked give a solid push to one side of the 3" cutter about 50 pounds push and see what deflection you can see under an indicator, do the same to the table. Trig out that deflection to reflect at 3" cutter face and you may see the reason for a step.

Even cross-hatch lines can give some idea of deflection and tram.

I did just that but with an end mill and by grabbing the top of tool holder at the gauge flange and got .008 of movement.
 
I did just that but with an end mill and by grabbing the top of tool holder at the gauge flange and got .008 of movement.

.008 inch? That’s a lot, like way too much for a new mill.
You are saying you got .008” of deflection by putting force on the tool holder by hand?


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Thank you Michiganbuck for taken the time to do that. Like he asked, if guys with like machines coul do that for me and report your findings, would be extremely helpful and appreciated.
 
Ripperj, that is correct. I used a Fowler .0005 test indicator and I got it to deflect about 12 to 16 lines. I will do it again this evening to be certain. I’m waiting on a .0001 mitutoyo to verify my Fowler but probably won’t be in till Friday or next week. But I will test it again with the one I have when I get off at 3:30 and report back. By the way I figured that was a lot and would certainly cause the inconsistent finish in my cuts. The only way to get a nice smooth cut when facing is to cut and then do 2 or 3 more passes without changing the z. That works with aluminum, as long as the cutter is nice and sharp but steel is a no go bc the tool just rubs.
 
If I remember I'll check our vf2ss's in the morning. We have 3 2020, two of them with sequential serial numbers so that should show something...
 
I used a Fowler .0005 test indicator and I got it to deflect about 12 to 16 lines.

A decent indicator so good enough test. I think my ww2 German mill has close to zero with a one and two-hand push.

How to take up to preload maybe now the question.

Take care, everybody, not to cut hands with sharp cutters.
Buck
 
You can get some Z mismatch if rapiding to final Z point. If it is, Change it to a feed move of 200ipm for the last .100". That may help. However, it is concerning you have .008" of movement when pushing on the tool. I just checked our 2014 VF2SS and saw maybe .0002".

Have you tried measuring the play with a new/different holder? If so, and it's the same and there have been no crashes, I'd send a video to Haas and tell them to fix it asap.
 
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Here are the results of the pull test, .0075. I didn’t yank or jerk just a steady pull but I was pulling about as much I could being that I was leaning forward into the machine. That just seems excessive to me, the .0075. I would like to hear from some vf2,3 and 4 guys.
 
Arm pressure likely about 60 70 pounds. A 6" face mill or 2"' end mill likely that and more presser milling steel. Way too much slack at .007 one way. an arm wrestler guy might pull 125 or 150 pounds. could be the spindle was not pre-drawn to set the bearing to full stop in the bearing register. Heat/cool and milling pushed the bearing nearer to set.

Or the holder had a defect in the spindle.. check to see the actual spindle nose is having some sideway Slack.

The machine tec guy should fix it PDQ.

If a new machine, I would negotiate for an extended spindle life ..if any warranty is due.

*I would not like that tec guy to install a new bearing.

Be sure it is the spindle and not just the tool or tool holder moving.
 
I haven’t forgot about this thread. My new indicator should be here today or tomorrow and I’m going to do every single suggestion and get back with an update.
 
Mike1974 I somehow skipped right over your post and didn’t realize until I just noticed it. That would be freaking awesome if you could do that. Being that they are all 2020’s should say a lot.
 
AARONT I have not taken a video but I will as soon as the new indicator is delivered I will if it proves that it indeed is moving that much. I have not tried another holder to be honest but I am going to try everyone’s suggestions and get back with y’all. Thanks
 








 
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