Mazak QTN250 MS sub spindle cutting oversize?

[CBHanlock]

We have several Mazak QTN250 machines in our shop. One of our older units (2012) has an odd quirk. I need to put a .021" offset on the x axis of any tool cutting on the sub spindle. This is to compensate for an odd miss match between the tool eye and the sub spindle.
I noticed this after an alignment, I get the main spindle cutting with less than .0005" taper in 12", then start working on getting the sub spindle to cut straight and in line with the main spindle. I shoot for .0005" taper in 6" on the sub spindle and less than .001" tir using a coax in the main spindle. Straighten out the turret, set the offsets for the live tooling heads and finally adjust the tool eye offsets to compensate for everything else moving around.

After doing all this, I can touch off a tool on the tool eye and confidently say I am within .001" of my programed diameter on the main spindle, usually better. What is odd and frustrating, I can touch off a tool, and take a cut in the sub spindle, boom .021 oversize? I suspect there is an parameter somewhere for the subsindle x axis offset that needs to be set after the subsindle is moved. I do not know what it is. Has anyone had this issue?

Our newer machines do not have this issue and our Mazak repairman could not figure it out.

 

[Mr. Atoz]

We have several Mazak QTN250 machines in our shop. One of our older units (2012) has an odd quirk. I need to put a .021" offset on the x axis of any tool cutting on the sub spindle. This is to compensate for an odd miss match between the tool eye and the sub spindle.
I noticed this after an alignment, I get the main spindle cutting with less than .0005" taper in 12", then start working on getting the sub spindle to cut straight and in line with the main spindle. I shoot for .0005" taper in 6" on the sub spindle and less than .001" tir using a coax in the main spindle. Straighten out the turret, set the offsets for the live tooling heads and finally adjust the tool eye offsets to compensate for everything else moving around.

After doing all this, I can touch off a tool on the tool eye and confidently say I am within .001" of my programed diameter on the main spindle, usually better. What is odd and frustrating, I can touch off a tool, and take a cut in the sub spindle, boom .021 oversize? I suspect there is an parameter somewhere for the subsindle x axis offset that needs to be set after the subsindle is moved. I do not know what it is. Has anyone had this issue?

Our newer machines do not have this issue and our Mazak repairman could not figure it out.

This leads me to believe that main and sub spindle centerlines are not identical, even though your co-ax says they are. You may have a twist in your bed, so when your sub is next to your main your co-ax says good, when your sub is back home, it is not so good. Check for level and twist. Can you turn a part in your sub with it as close to the main as you can get and then see if it turns the same dimension with your sub at home? For a quick fix, it seems that there is something like "tool eye comp" or "easy comp" ( cant remember exactly) on your tool offset page. Try putting in your .021 offset there and leaving it.

 

[Ox]

Does the WEAR value reset automatically when you hit the touch probe?


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Think Snow Eh!
Ox

 

[Mr. Atoz]

Every Mazak I have ran retained the wear offset after touching off. Prolly can be changed by parameter.

 

[CNC Hacker]

I'm not sure if that vintage lathe had the function, but check PLC parameters RS17 and RS18 to see if they have values in them.