Ballbar Testing???

[zrwhat]

We just started to conduct Ballbar tests in-house as part of our Equipment Qualifications. We will be running these on a quarterly basis or after any major crash. We will be conducting the tests on all equipment, but I decided to start with our HAAS Mills. We have seven VF-3SS's that are pretty much our work horses for 5-Axis machining. I have the basics of the ballbar test and software down. I am trying to set some machine tolerances, basically an acceptable range that we can run in and anything greater we would need to get maintenance/service involved to troubleshoot the machine.

I did start with my HFO Service Coordinator, but haven't come up with any data yet. I would think HAAS and any OEM would have an acceptable range for say circularity?

For reference one of our brand new VF-3SS's that was tested had a circularity of 0.000457in and another VF-3SS that is almost a year old tested at 0.001087in. That’s quite a difference in my mind, but may still be acceptable?

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[underthetire]

1st, remember a ballbar will show stuff that you may not see in a cut. Now it depends on what is actually out. If it's squareness, than can be easy or hard to adjust. Backlash, usually pretty easy; scale missmatch, servo tunning; cyclic error, mechanical adjustment. .001 on what size diameter? You left a lot open. Maybe post your charts ? Normally, at .001 in our shop on the generic machines, I will try simple adjustments to get it better. If the simple stuff won't get it, we let them run the way they are. If they become worse the next time, then we dive in to it.

[zrwhat]

Here are the charts for the two machines I listed.

1 Year Old VF-3SS



Brand new VF-3SS

[underthetire]

You need to get the tram checked. Adjust X comp by .0001, then I think you will be good, IMO. Guess the Haas's aren't that square, that one would be tough to fix.

[Bryan33]

Haas machines should hold .0005 tir on your circularity

[Bryan33]

haas machines hold a .0005 TIR on circularity

[Bryan33]

The spec on a haas VF machine is .0005 circularity

[underthetire]

On what size circle? Full travel?

[Caprirs]

The ballbar test will reveal a lot. However, the test is performed without the load of a cutter pushing/pulling the head, table, and saddle. Thus, the ballbar test is great, but the machine must ultimately be tweaked to the parts that are being run. For most users, the goal is to get the machine to cut perfectly round using circular interpolation. My experience with the Renishaw ballbar tester is it suggests backlash and reversal spike compensation values that are too high and have to be backed off when actual cuts are performed. These values will vary depending on cutter load, diameter, and feedrate. Cutting a 1" diameter bore in steel with a 1/4" end mill at 20ipm needs different values than cutting a 4" bore in aluminum at 100ipm.

When I worked for a machine tool builder, we would guarantee .001" TIR for circular interpolation. Doing better can be done but takes more meticulous everything; tooling, programming, fixturing, machine calibration, leveling, tramming, climate control, etc.

[Bryan33]

Its a 6in cir

[underthetire]

I know his test was a 6" circle, but if your saying all Haas machines should be .0005, what do you base this on? A 30" Y axis machine is pretty useless if it's .0005 on 6" circle.

[hank123]

I am new to this so if I am posting in the wrong place I apoligize.
I just ran a ballbar test on my VF-3 and can't figure this one out. i will put in pics of the test to see if someone has an idea of where to go from here. i just leveled the machine and it actually got worse. the pics are after i levelled the machine. before it was out .0018

[underthetire]

Personally, I don't see anything that shows squareness out much. Your biggest issue is X axis. looking at the chart, with the backlash and reversal spikes, i'd set backlash comp on X to zero and run it again. You may end up needing thrust bearings.

[hank123]

Thanks. I appreciate the input. after leveling the machine I did reset the comp to 0 and then played with it from there. this was the best i could get it. i was thinking thrust or front mount bearings but wasn't sure. Thanks again

[haastec]

Make sure the lock nuts are tight for the x-axis ballscrew also.

Also, if you are still having problems you may want to start a new thread just so you are not pulling in everyone from this post on a different issue.

Good luck!

[haas tech #3.]

I looked at the ball bar results. I can see that there is an issue with the accuracy of the x-axis. This can be caused by a bad bearing assembly (bearing pack) on the motor mount side or a bad ball screw. It also appears to have loss of motion when changing direction (back lash) you need to replace these items one at a time. You can also contact Haas automation Inc at 805-278-1800 prompt #3 for service a technician will help you trouble shoot this issue.

[Vern Smith]

I'm probably blissfully ignorant but I've had the Renishaw package on my Haas mill for about 5 years and have never found the ballbar test. Is this something one gets from Renishaw? How does it get it's data from the Haas machine? How did I miss the boat

Vern

[underthetire]

I'm probably blissfully ignorant but I've had the Renishaw package on my Haas mill for about 5 years and have never found the ballbar test. Is this something one gets from Renishaw? How does it get it's data from the Haas machine? How did I miss the boat

Vern

Ballbar will not come from haas. It's a separate tool used with a laptop to get a snapshot of machine condition. Runs about 15k now plus a computer.

[KenFoulks]

In most cases a ball bar test is performed by your local HFO tech or a third-party company. Every Haas machine has a ball bar test performed at the factory, although some of the older machines' results are not available. Contact your local HFO if you want to see the original result or want to discuss getting a tech to re-do the test.

[Matt@RFR]

Vern:

http://www.youtube.com/watch?v=fmE7x3R2Wpc]QC10 Ballbar.wmv - YouTube