While I think the CNC would automatically round to the four places in a CNC command (or at least not generate any kind of alarm), here is a technique that will truncate to a four place decimal format. You can do this more concisely, but I break it up for clarity: • #100=#5022 * 10000 (1.2345678 becomes 12345.678) • #101=FIX[#100] (12345.678 becomes 12345.) • #501=#101/10000 (12345. becomes 1.2345) Hope this helps.

I am not sure where to start. Is this a job that has been running properly in the past and only now the problem has come up? If so, obviously something has changed, but I cannot comment on what it might be. Sounds like you have checked all the likely potential causes. Maybe the boring bar manufacturer could help?

Not sure I can help much here. As with some of your other issues, this is more of a tooling issue than a CNC issue. My comment is that if this is happening with a newly sharpened cutter and it eventually works its way out on its own (chatter dissipating after a few components), it is possible that the cutter is "too sharp" at the beginning. There may also be tiny (almost microscopic) burrs on the cutting edges left by the cutter sharpening grinding operation. I know it sounds odd, but one remedy would be to lightly hone the cutting edges of the new cutter with a polishing stone (very fine grain) to take away some of the sharpness - and also remove any "burrs". Again, I'm no tooling expert - but I have seen this work.

Sorry, but I cannot think of a potential cause for the rings.

I'm sorry, but I don't have any experience with honing - if they happen to be CNC honing machines, maybe I could help, but my experience is more with metal-cutting machines.

As for the local variables, you're right, the CNC starts by showing the common variable (#100 series). If you press the page up or cursor up key, you'll scroll into the local variables. Not sure about the "soft control screen". Sound like a feature you need to ask your machine builder about - same for the ability to turn off the foot pedal for chuck open/close. There may be an easier way than going into the ladder logic, but I'd recommend that you ask someone from the machine tool builder.

With FANUC CNC's, local variable registers can be displayed from the OFS/SET page then "MACRO" (with older controls it is from the SET page). Since they are only active when set in a program (cleared at M99 or M30), they will only show you values during the execution of a program that uses them. For example, the command G65 P1000 A1.5 B3.0 C0.4 will set local variables #1, #2, and #3. Then program O1000 will be activated. #1, #2, and #3 will be active while O1000 runs, reset to vacant (blanked out) when the program ends with M99. While O1000 is running, you can monitor them from the MACRO page shown below.

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I'm pretty good helping with application issues but not so much with service and maintenance issues. You've pretty much eliminated the issues I've come up with from a usage perspective. Based upon the machine's age and seemingly poor preventive maintenance practices over the years, I think the issue could be more of a machine problem, in which case I'd suggest that you get a service technician from the machine builder to help. The problem could, for instance, be a malfunctioning encoder for the drilling/depth-controlling axis (the Z axis, I assume). In this case, I believe that the machine would display that everything is moving properly on the display screen (like distance to go and final absolute positions), but the axis would not physically move to the correct location. You would need a service technician to determine if this is the case, and to correct the issue if it is.

It sounds like you've covered pretty much everything I'd suggest. Again, is this a new process or one that has been working in the past but now is not? Assuming it has been working previously, again, something has obviously changed. If the machine has not been crashed, I'd suspect cutting tool or workholding devices. Also, you say the depth of the bore varies, but what machines the surface into which the bore is machined? Could it be varying? 1.0-mm is a big variance. Are parts coming off the process varying with this from part to part - or do several parts come out okay and then a bad one shows up? I know you said the cutting tool has been clamped properly, but if it is a straight shank tool held in a collet, I'd check the cutting tool after a variance to see if its length has changed (though you'd think depths would come out shallower - not deeper).

Glad to hear!

Then something obviously changed - maybe a crash that changed the centerline position of the spindle (boring bar tip isn't on or slightly above center) - or loosened up the way/turret system? A crash could also through the turret out of position - bending/shearing taper alignment pins, for example. Maybe mechanical components in the clamping system are wearing and not gripping as they used to? Maybe degraded hydraulic fluid in the clamping system in need of change - or air in the lines?

Is this a new process - or one that has worked properly in the past, but not now? It sounds like even the part machined in fixture A is "iffy". If not, I'd suspect the issue to be in the work-holding. If it is, I'd also suspect the cutting tool. I'm wondering what kind of boring bar is being used (rake angle, cutting material, and carbide shank or steel shank) and how much material is being left in the hole for finishing. Also, what is the length-to-diameter ration for "hang-out" of the boring bar? Ideally it should not exceed 3-1 for a steel shank bar (three inch hangout for a 1 inch diameter bar). As for work-holding, these can be tough issues to diagnose. If you have a way to measure clamping force within the fixture (not just input pressure for the hydraulic system), you could determine if there are any variations among the fixtures. It's possible that the hydraulic lines are being blocked in some way or the mechanics of the clamping system are not moving freely.