[Japazo]

Hey everyone,

We have a number of machines in our shop that use the Renishaw OTS touch setter probe for setting tool length offsets. Up until I started, they were never used for in-cycle broken tool detection (BTD). Our operators have wasted huge amounts of machine time running back and forth between machines which have stopped with an M00 to check the tool and continue. I started playing around with BTD and got it working pretty well, but there is one behavior that doesn't make sense to me. I'm not sure how to change it, or if I even should since I might be missing some bigger picture. Lets say I touch a tool off using the OTS and it is exactly 6.0000" on the offsets page. Then I program a BTD cycle using G65P9858B1.T1.H.005 to make sure it isn't broken (without making chips at all). As long as the combination of the tools geometry height offset and wear height offset are within the .005 tolerance in the BTD cycle, all is well. If I add .0051" to the wear offset, it will alarm out every time. So as the wear offset increases, the functional tolerance of the BTD cycle decreases. I don't understand why the BTD cycle takes the wear offset into consideration at all since I don't want to know if my offset is growing or shrinking, I want to know if my tool is physically getting longer or shorter. The Macro is using parameter #4120 as the current tool's offset, but from there I get lost. Renishaw's Macro's are horribly documented. Has anyone ever dealt with this problem or have any insight as to how to correct the issue (or my way of thinking)?

[CitizenOfDreams]

Here is how I understand it. Your height offset + wear offset determine the expected tool length. You are adding a 0.0051" offset (for test purposes, I presume) without actually grinding 0.0051" off the tool. The BTD cycle measures the tool and sees that the tool is 0.0051" longer than expected. Does that make sense?

[Japazo]

That makes sense when I am actively machining and WANT the tool to be slightly longer or shorter, but the wear offset doesn't reflect the physical length of the tool from gage-line. It represents the length that I perceive it must be in order to make my part. The problem is that every addition to the wear offset decreases the tolerance allowed in the BTD cycle. If, for example, I have a chamfer mill that does some engraving and also some edge deburring and I want to make my engraving slightly deeper, I can't just offset the tool down (and out on the deburring) without also increasing the H value in my BTD cycle. I know the logical solution to that is to edit the program to make the engraving physically deeper, but on a part with 30+ tools and 120+ dimensions on the print, you can spend all day editing programs to make everything run nominal only to have it all be slightly off again the next time you set it up and run it. That also leaves you with a program where the coordinates do not match your print which can create a good deal of confusion.

It seems to me like BTD would work much better (for shops like mine, where geometry is for touchoff and wear is for comp) if it only looked at the geometry offset. That way it is always comparing the physical length of the tool to its previous value without concern for how much I have comp'd it. I also understand that in some cases this may act as a signal to the operator that they have comp'd a tool too much but I think we are able to handle that in other ways. Apparently the way we are currently using BTD is how everyone else is using it...so I may just have to get used to it.