HAAS VR-11 "Z" Drive is floating

[zsinclair]

Good morning everyone,

What a glorious day, one which just starts with problem. I have a VR-11 and have been having a problem for quite sometime now, and I just cant take it anymore I'm hoping someone an here may have a clue what to do. Thanks!

So here it is,

When we set tools on the Reinishaw Tool Setter, we have the set number which it produces for our tool offset. However we also have been checking the tools to the table with a 123 block. we have just been hand jogging down and reading the machine position screen.The number we get there is not a tool offset but it is however a "set" number and should be repeatable.

The problem has been, when we check our tools during the run with the tool check macro (not the tool set), which we do before and after every single tool runs, it is sometimes varying between .005-.010. Originally I thought it was the tool setter coming loose, which is not the case. So after the tool check macro alarms out the machine and tells us we have a broken tool, we reset the tool with the probe and it will come out several thousandths different. I would normally assume the tool pulled but I know tools are not pulling at this rate. after resetting the tool to the probe, we then check it with the 123 block to compare to the number we got before. The "fake offset" we had when originally setting the tool will be off by .005-.010. I know this number should not be changing.

Somehow, the head itself is floating around. The machine has not been recently crashed and HAAS service has come out and told me nothing is wrong. I have no more ideas about what could be causing the problems if anyone out there can help please do. Thanks all.

Zack

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[Delw]

could the tool seeter angle not be sqr?
Try running a indicator from your table along the top of the tool setter too make sure its not cocked.

also have you set your toouch prob on the toolsetter to make sure you get the correct dims, check the touch probe also to make sure its not loose.

Not saying these are the problems just seeing if you checked them.

the only thing else I can think of is your machine is not level. a VF11 is what a 120" table machine?

one way to check to see if its the Z axis is to do 3-5 tool sets and not the number in the offsets each time. if this only changes a few tenths then theres nothing to worry about and its not the z axis, if it changes .005-.010 its the z axis.
reason I say this is the only thing that moves would be the z axis, the x and y wont move. then try moving the table in different spots and see what you get on heigth.

Delw

[zsinclair]

Ive checked the tool setter several times and I am positive it is down flat and is not moving.

Yes the table is 120 inches long but is fairly flat. I tried doing several tool changes and nothing changed at all. I'm not having any problems with the parts as long as i recheck the tools each tool change. The problem is when i run it at night and i can only get twenty or thirty minutes out of an eighteen hour program, before it alarms out, its not worth my time to even try.

[underthetire]

I just have to ask, since I have seen this several times before with other equipment. Is there a skylight above the machine? A heater/AC duct ? Is the spindle chiller (if it has one) set to ambient temp? I once saw a problem on a very large double column, one side would pitch .04" during the day. Ended up a skylight was right above that column, heating the machine up and actually moving it. Another VMC i had a customer think colder must be better, so they set the chiller to it's coldest setting. That made a .015" change throughout the day.

[Delw]

I just have to ask, since I have seen this several times before with other equipment. Is there a skylight above the machine? A heater/AC duct ? Is the spindle chiller (if it has one) set to ambient temp? I once saw a problem on a very large double column, one side would pitch .04" during the day. Ended up a skylight was right above that column, heating the machine up and actually moving it. Another VMC i had a customer think colder must be better, so they set the chiller to it's coldest setting. That made a .015" change throughout the day.

thats a good point, I would think it has something to do with temp sence it was mentioned it happens at night. something somewgere is heating up and changing.
it could even be the friction from the table being used all day heats it up just enough.

A good idea to try would be to sneak in there on a weekend afternoon, dont run duing the day and try it at night and see whats happen. or let it sit for 5-6 hours then try it and see if it lasts more than an hour before erroring out.

[zsinclair]

I'm in an air conditioned shop and there is nothing around which might change the ambient temperature I've thought of that too. Its not only happening during the night its happening all day, only the machinist over there is able to fix it during the day and get it running again. We only run a first shift, because in the past we have been able to run this machine all night before. The other HAAS i have right next to it runs fine all day and all night, so i would have to assume the temperature is fine in the building.

[haastec]

Just to clarify, you said the offset numbers set with the tool setter fluctuates about .005" - .010", but does the reference number that you record with the 123 block repeat?

If the values from the 123 block repeat, this would suggest a problem with the Renishaw system. At that point, I would give Renishaw a call and get ther opinion on the problem. I have always had excellent help from them and they might be able to help you decide for a fact if it is a problem with the machine or the Renishaw system.

Keep us updated, I am interested in what you learn.

[haastec]

Does this machine have Nitrogen c-balance? How old is this machine? If I remember correctly, there are 2 tanks. Make sure they are not over or under charged. Inspect the hose lines also for any defects.

[rjoseph]

First post to forum - looking forward to giving this a try.
I'd eliminate the probe by setting up a gauge pin in a separate tool holder, using it to calibrate the probe. Length of gauge pin/tool being from underside of pin to underside face of spindle, tram work probe and indicate tool setter stylus in X and Y, run all 3 calibration cycles. Use this gauge pin as a tool send it into the carousel so you can pull it down an hour or two later to see the growth.
Gravity with z can easily mask thrust bearing issues in the screw. Eliminating anything mechanically wrong with the screw and much like the other suggestion of sunlight and thermal growth coming from there. There's a parameter adjusting the thermal compensation both for warming and cooling but before this there is a setting were your able to add or subtract +/-30% to the same algorithm. I think it settings 87,88,89 for x,y,z (but don’t hold me to the exact setting numbers) .Aside from growing in the morning it would be good to check when the machine has been cooling down and stationary for awhile, like after lunch or overnight. Hopefully this starts to help. New Machine?