NC Costs?

jan,
what were you referring to?

Many people say you can not measure on machines. In principle they may be right. In practice, I have found them to be wrong.

You are right, it is mostly for parts that I do not want to break the setup yet. Intermediate runs are good. But also final runs. You can NEVER replace a CMM, but you may find that if you get good correlation between CMM and machine tool, you may go over to the machine tool and not to the CMM anymore (except for first artical and spot checks). Yes, I buy hardware off of the machine. But my machines are all calibrated and we use artifact to check for drifting.

Our justification is that we run extreme close tolerance parts. They are very valuable and we want them to be right the first time. I can track tool wear, tool wander, offset correction etc. This all while the part is still ON the machine. After the operator is done machining, he cleans the part and runs the program. Takes all of 1 additional hour (it takes them about 20 hours to make manufacture the part in the first place). After that run, I have instant feedback. If the part is good, it immediately moves on to the next operation. No queue time in CMM land. And there you have the justification. Our queue time in CMM land was 2 to 3 days. That has evaporated to nothing on most parts. On top of that, we get better and faster SPC feedback. Also, we were looking at buying more CMM's. Still need one addional machine, but not 3, as originally planned.

Access to datums is an issue. We therefore work with simulated datum structures on the fixture. And you are right, this is a weak point. But we have overcome that issue with experience. If you have a part that has a LOT of springback, from restrained to un-restrained, that's a problem of course. But we have found that if you have a good fixture, that issue just goes away.

There must ALWAYS be independance in measuring, so CMM measurements will never go away. However, how many do you really need to do? In our case we have to do full inspection. By moving it to the machine, we have eliminated lots of queue time plus the need to buy more CMM's is lower now. Sure Hexagon wants to hear that one...


Jan.

jan,
what were you referring to?

Many people say you can not measure on machines. In principle they may be right. In practice, I have found them to be wrong.

You are right, it is mostly for parts that I do not want to break the setup yet. Intermediate runs are good. But also final runs. You can NEVER replace a CMM, but you may find that if you get good correlation between CMM and machine tool, you may go over to the machine tool and not to the CMM anymore (except for first artical and spot checks). Yes, I buy hardware off of the machine. But my machines are all calibrated and we use artifact to check for drifting.

Our justification is that we run extreme close tolerance parts. They are very valuable and we want them to be right the first time. I can track tool wear, tool wander, offset correction etc. This all while the part is still ON the machine. After the operator is done machining, he cleans the part and runs the program. Takes all of 1 additional hour (it takes them about 20 hours to make manufacture the part in the first place). After that run, I have instant feedback. If the part is good, it immediately moves on to the next operation. No queue time in CMM land. And there you have the justification. Our queue time in CMM land was 2 to 3 days. That has evaporated to nothing on most parts. On top of that, we get better and faster SPC feedback. Also, we were looking at buying more CMM's. Still need one addional machine, but not 3, as originally planned.

Access to datums is an issue. We therefore work with simulated datum structures on the fixture. And you are right, this is a weak point. But we have overcome that issue with experience. If you have a part that has a LOT of springback, from restrained to un-restrained, that's a problem of course. But we have found that if you have a good fixture, that issue just goes away.

There must ALWAYS be independance in measuring, so CMM measurements will never go away. However, how many do you really need to do? In our case we have to do full inspection. By moving it to the machine, we have eliminated lots of queue time plus the need to buy more CMM's is lower now. Sure Hexagon wants to hear that one...


Jan.