Bore interpolation circularity

[roddyf]

What is the cirularity that you guys have found when interpolating a bore with your haas mill?

Thanks

[Geof]

Better than I can measure with a telescopic gauge and micrometer. Certainly less than 0.0005" variation in diameter and probably 0.0002" or even less.

[HuFlungDung]

+/-.0002 or better if the feed is slow.....somewhere between 10 to 20 ipm. The closer the endmill diameter is to the finished hole size, the slower the feed needs to be to keep the effective tangential feedrate within that range.

[roddyf]

Wow, I am getting .013-.014 with a telescoping gauge and a caliper. If I tighten my telescoping gauge in the x and move it to 90 degrees to measure on the Y-axis it rattles in the bore.

[roddyf]

I am running 1/2" 4340 plate waterjet cut .200 smaller than finished diameter. I take 2 cuts with a 1" insert endmill rough cut and a .030 finish cut. Posting out with MCAM.

I just checked a hole that I am drilling with a .413 bit then helix boring with a single flute 1/2 EM to .630 and its better than I can measure.

[Geof]

Originally Posted by roddyf Wow, I am getting .013-.014 with a telescoping gauge and a caliper. If I tighten my telescoping gauge in the x and move it to 90 degrees to measure on the Y-axis it rattles in the bore.

I do not trust calipers to closer than +/-0.001" but even with that your measurement shows something seriously wrong.

It sounds a bit like something is badly worn or loose in your ballscrew(s), how old is your machine.

[roddyf]

Yeah my machine is 2 months old. I just tried doing a helix bore with the same tool and 4.375" D circle and it came out .001 to .002 out of round.

[Geof]

Two months, this is a warranty issue, get onto your Haas dealer. One possibility on a new machine is that the backlash parameter has been set incorrectly, but whatever it is you need to get it fixed. Check the specs for Haas machines and you will find they have repeatability of 0.0001" and accuracy of 0.0002" so obviously your machine is not up to spec.

[Delw]

Telescopic guages in my opiion are are not a good form of measurement for anything under .002. Most people don't know how to use them correctly. Don't get me wrong you can get .0005 or less out of them repeatally but unless you used them alot dont depend on them. not to mention if there is taper in the bore your going to get false readings

Use a dial bore to check your bores accuratly, if you dont have one Make one out of a flat pcs of alum or steel with a dowel pin or tooling ball and a indicator.

Also chuck a indicator in the spindle and run the z axis to see if you have taper in the bore.


I doubt its the machine but it could be, my first guess is you have taper in the bore, second guess is you need to take 1 or 2 spring pass's with a fresh tool as your tooling is worn out or not cutting correctly.

one other thing to do is since you have cad. start your hole at 30 to 45 degress and run it, this will help eliminate if its the parameters/ballscrews or progam/tooling.
as the ball screws reverse at 0 - 90 - 180 - 270º starting your program at 30 -56 degress will help you find out if its out only on that angles or if its your program or tool pressure

[roddyf]

I did a test with some round stock aluminum, I contoured down to a .750 post and I get readings to .0015" with a mic.

I also don't get any taper on the post but it is aluminum.

I think I will flip my inserts and try interpolating the 3.992 bore again and see what I get.

[Delw]

your getting .0015 with inserts or an endmill on aluminum?

Inserts at least the ones I used, I never used for finishing a bore always followed it up with a solid carbide endmill for finish work.
I know they make them that do finish work now.

You mentioned a big bore Dia. on 1/2" thick stock. just out of curiosity how are you holding this part? how much webthickness do you have around the bore?
I am leaning more towards your set-up and/or tooling is no good or not rigid enough and the parts moving or tweaking.
of coarse its hard to say with out knowing or seeing exactly what you are doing and how.
but I am doubting its the machine from what I've read.

Not trying to say anything bad about your machining skills so dont take that wrong.

Delw

[roddyf]

No offense taken, I am learning. I have a plate that has been waterjetted out with .100 left all around for cleanup.

I have aluminum jaws cut to hold the outside profile, the bore is out to the edge with about 5/8" of material around half of the circle. I am gripping on this thinner material.

I did some program modification and am going to try it again, gonna try a few more passes.

The one problem I thought is the first pass is not pulling the same amount of material all the way around, could be distorting from pressure.

Thanks for the help guys, after profiling that aluminum I feel a lil better about it not being the machine.