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Renishaw accuracy


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We have a few fairly new Mazak Integrex I series 5x machines with RMP600 probes. I was wondering if anybody here has had any luck measuring a 3mm wide slot with +/-.0002" tolerance with a probe and adjusting tool diameter to machine the slot in tolerance?

I've made a test program to try before we try it in the actual part, but I'm just curious what success others have had in trying to do this.

Thanks.

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41 minutes ago, #Rekd™ said:

Is the machine capable of holding that tolerance? 

Yes. We've machined these parts before. The problem before was operators were only using gage pins and one operator apparently had a better feel and was able to hold that tolerance. We're researching better methods to inspect the width, but so far our options aren't much better in my book.

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Need to do a gauge R&R and determine what is the true accuracy of the machine. That means running hundreds of checks not one or two. Most CMM's have trouble measuring that tolerance and you trying to take a probe on a machine and do this? What are the underlying most important factors for the machining environment? Temp, Tool, Work holding, Tool Holding, Coolant, and many other factors for this process? I know of customers holding this tolerance with manually process on Mazak's, but with a probe I would need to do as I stated a lot of testing and proving out before I could trust a process holding something that tight with an endmill. Now if you are using a High Speed Head and trying to grind it in then that is a completely different conversation.

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Deltronic Pins are the way. We regularly hold these type of tolerances and hard checking with calibrated Deltronics is typically the final word.

The process I would go thru is you get a set of Deltronic pins. Cut a slot and gage it with the pins and verify exactly what number it is. Then I would check it with the probe and see if it agrees or not.  If the probe does not agree you can try re-calibrating it until it does. The issue I see with it is if the probe starts to lose calibration and eventually starts disagreeing with the pins.

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RMP 600 is a Strain Gauge Probe, not kinematic arrangement, and is far more sensitive than your machine is capable of holding. Accuracy/Repeatability should be on the order of 0.25 Microns to 2 Sigma. That is 10 Millionths.

Make sure you calibrate with the new Stylus (I'd use a 1.5mm or 2mm max. diameter ruby or silicon nitride ball, depending on material being machined).

When you use the "tool wear adjustment" Macro, there is typically an "experience" value. This is poorly-described, but is essentially "the adjustment percentage of the measured deviation between actual and nominal".

You use the Experience value to adjust the amount of "change being made" to the wear adjustment. For example, say you programmed a 2mm cutter to make a Semi-finish pass, on both sides of the slot, leaving 0.1mm per side. This should give you a 2.8mm wide slot. But when you measure the slot width, it is 2.784mm. The difference between nominal (2.8) and actual is 0.016mm. We could then correct the Wear Offset (assuming radius, in this example), by 0.008mm, so it cuts that much additional metal off each side of the slot.

Except in practice, other factors such as tool deflection come into play. Through "experience" you come to find that using between 60-70% of the 'delta measurement', gives you more predictable results in production, to avoid overcutting when making the final finish pass. You could use an "E" value (may be a different Alpha-Address Character), of E0.65, which would tell the Macro to only use "65%" of the delta value.

I will typically use an Experience value of 40%, if I'm doing a multi-step process with the probe to qualify a tool. I find I get the best results by "sneaking up on the adjustment", and then re-cutting the Semi-Finish Pass (again, using 40% as a starting test value).

If you are taking the approach of automating the process, it will be very important to calibrate often, and to be sure the probe tip and the slot is very clean, and that the machine is warmed-up, using the same cutting program that will be run in production. (Don't put "too much heat" into the machine, it needs to be as close to actual "operating temperature" as possible.)

 

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25 minutes ago, crazy^millman said:

Need to do a gauge R&R and determine what is the true accuracy of the machine. That means running hundreds of checks not one or two. Most CMM's have trouble measuring that tolerance and you trying to take a probe on a machine and do this? What are the underlying most important factors for the machining environment? Temp, Tool, Work holding, Tool Holding, Coolant, and many other factors for this process? I know of customers holding this tolerance with manually process on Mazak's, but with a probe I would need to do as I stated a lot of testing and proving out before I could trust a process holding something that tight with an endmill. Now if you are using a High Speed Head and trying to grind it in then that is a completely different conversation.

I have a test program to machine the slot the exact same way we do the part which is to rough it w/in .005 per side with the roughing e.m. Then the finish e.m. mills it to -.0015/side before it stops to allow operator to measure the width. Then the program opens the slot to finish size in 3 more passes with an M0 between each .0005 pass for the operator to measure. I added probing before each M0 and left the M0's for the operator to verify size. I expect to have to run the program several times before I'm comfortable enough to say it will work every time. If it will even work.

The problem we had with the pins is the day operator did just fine, but the night shift operator said he couldn't get the low pin in at finish size so he opened it up and blew several parts oversize. We're still looking for a more fool proof way to measure these slots but nothing I would trust better then pins yet.

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8 minutes ago, Colin Gilchrist said:

RMP 600 is a Strain Gauge Probe, not kinematic arrangement, and is far more sensitive than your machine is capable of holding. Accuracy/Repeatability should be on the order of 0.25 Microns to 2 Sigma. That is 10 Millionths.

Make sure you calibrate with the new Stylus (I'd use a 1.5mm or 2mm max. diameter ruby or silicon nitride ball, depending on material being machined).

When you use the "tool wear adjustment" Macro, there is typically an "experience" value. This is poorly-described, but is essentially "the adjustment percentage of the measured deviation between actual and nominal".

You use the Experience value to adjust the amount of "change being made" to the wear adjustment. For example, say you programmed a 2mm cutter to make a Semi-finish pass, on both sides of the slot, leaving 0.1mm per side. This should give you a 2.8mm wide slot. But when you measure the slot width, it is 2.784mm. The difference between nominal (2.8) and actual is 0.016mm. We could then correct the Wear Offset (assuming radius, in this example), by 0.008mm, so it cuts that much additional metal off each side of the slot.

Except in practice, other factors such as tool deflection come into play. Through "experience" you come to find that using between 60-70% of the 'delta measurement', gives you more predictable results in production, to avoid overcutting when making the final finish pass. You could use an "E" value (may be a different Alpha-Address Character), of E0.65, which would tell the Macro to only use "65%" of the delta value.

I will typically use an Experience value of 40%, if I'm doing a multi-step process with the probe to qualify a tool. I find I get the best results by "sneaking up on the adjustment", and then re-cutting the Semi-Finish Pass (again, using 40% as a starting test value).

If you are taking the approach of automating the process, it will be very important to calibrate often, and to be sure the probe tip and the slot is very clean, and that the machine is warmed-up, using the same cutting program that will be run in production. (Don't put "too much heat" into the machine, it needs to be as close to actual "operating temperature" as possible.)

 

I believe we have a 2mm ruby probe for this slot. Originally they were only using the probe to set the orientation of this slot on a future operation.

I measure the width of the slots in 5 spots because I was trying to catch any deviation in the width of the slot so right now so I'm adjusting the tool diameter with a macro. I've never used the experience value so I'd have to look in to that some more if I'm able to use the built in slot width measuring routine.

As they say, the only way to know for sure is to try it.

 

Thanks.

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3 hours ago, BBprecise said:

The problem we had with the pins is the day operator did just fine, but the night shift operator said he couldn't get the low pin in at finish size so he opened it up and blew several parts oversize. We're still looking for a more fool proof way to measure these slots but nothing I would trust better then pins yet.

Sounds like the short path is training the night shift operator, until they can pass a gauge R&R test.

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