rotary

[gage guru]

Just curious if anyone uses a rotary table with a CMM.

We have a B&S Microval 3.7 mr3

What does a new one(rotary table) run $$$$

Are there any used ones out there?????

Is is difficult to use????

We have 20 holes to measure that are 18 degrees apart and because of the angle difference(as well as a true pos callout) from the probe to the part we are running into problems. Thanks for the help in advance....

[BSchwark]

It has been a long time since I used one. Issues would be one more axis, since it moves it would need to be qualified or calibrated and since you are using a microval size would be a big consideration. Cost? If it is for 1 or 2 parts I would look for a work around solution. Just some things to think about.


BS

[gage guru]

Understood, but I was told to check into it and in some respects if we can aquire one it could be a help on some of our parts and save time to calibrate probe angles. I guess I was just curious a sto what anyone else uses. The way the holes are shanking is an issue. I already am looking into a fixture as well to rotate the angle and then I will have the CMM do the rest. There is a cost either way and need to know which is more dollar for dollar effective.....thanks.....Hopefully more feedback will follow....

[Jan d.]

You will be unpleasantly surprised, when they tell you how much this will cost. Even a small accurate rotary will cost them at least $3 to $4k. Let alone the integration etc etc. So your cost will quickly soar well above $10k.

You need a very accurate rotary. Angular accuracy is important, but a much more important error is the wobble. That is the angular motion of table perpendicular to the table surface. Since this is an angular error, it can cause huge errors, if your part is somewhat larger. Most manufacturers comp for angular error. Few comp for wobble! If you get one, make sure they at least test for wobble (done with 2 call spheres). I would insist on wobble comp.

If you feel that a rotary table is the solution, get a real good one (be aware that it may take a lot of your measuring volume away too)! And calibrate it continuously. If you fail to do that, using your PH9 angles (or re-datuming) is quickly going to be much more accurate.

It has been my experience that if you have a machine and a family of parts that can use the table (in other words, you seldomly (re)move it), it makes sense to invest in a rotary. If you have a few part numbers (and therefore take the table off a lot), I would first try every other measuring method in the book. It would be my very last choice.



Jan.

[Hilton Roberts]

We do not have one here. I used to calibrate rotary tables with a device known as an Ultradex precision indexer and auto-collimator. I cannot imagine a CMM tech hauling one of thos around to calibrate a precision rotary table.

If you were checking gears it might justify the expense but you certainly will lose some measuring volume.

H

[cmmguy]

Look to AG Davis for a rotary table. The cmm controller OEM will have to integrate it. I don't know if PCDMIS supports it without buying a "module". They work great but I dont think you will find anything acurrate enough under 50k. The thing Hilton mentioned - the ultradex - was made by AA Gage but they were bought out by AG Davis back in the early nineties.

Hilton is also correct in that the table will have to be calibrated. It doesn't have to be calibrated by the CMM Tech. It can be calibrated standalone. The CMM will qualify the table much like a probehead using a masterball.

Unless you want to requal each table index you will need a table with at lease 1/2 arc second accuracy. Do the math on the error of a 10" diameter part. Error accumulates quickly with a table less accurate than that.

[gage guru]

thanks - got a call into B&S to see what they say/recommend etc. Just thought I would see what the group has done. I found some of them out on the web, accuracy pretty good for what we need, just need to see how to make it work with controller of CMM. I am sure that is where we will get ripped.......the other path I am pursuing is using a zero spindle(already have) and implementing a holding fixture.....only issue is have to manually move it 20 times to get measurements. thanks again for all the feedback - this group deserves rewards daily for all of the knowledge that is out here!!!! thanks!!!

[gage guru]

Ok back to the holes.....we have gotten away from rotary table and also fixture to rotate and then measure because as usual $$$$$.

So now the concept is to place part that has -A- as ID and -B- as back of flange on a 'fixture'. We then want to align the part - measure the 20 holes(of which we only get half of). Then flip the part over - realign and measure the 20 holes the other half) and then get make them cylinders then callout true pos.

OK now in order to have any of this work we need to do the following and I am looking for your expertise to confirm the proper way to do it.

1. When we initially align we need to establish the plane on the back of the flange in a manner to make sure when we flip it we hit the same(theoretical) points so we do not induce error into the alignment - hence also the tp.

2. Make sure the alignment of when we flip part becomes the same to avoid issues when the cylinders are created etc....

See attached and then I will await the feedback....thanks!!!

[Don Ruggieri]

Equate Alignment

Are you familiar with Equate Alignment? If you expect to relate anything between the two measurement "halves" you will need it. It does work, but there are some rules you'll need to follow. . .

[gage guru]

Sorry never did that - at the outset I understand the concept...what are the rules.....

1. no running with scissors
2. no chewing gum in the classroom
3. no stealing others avitars.....
4. no highjacking threads.......

sorry had to do it.....LOL

seriously let me know....we are waiting for the actual parts - have one that we used for basics, but the real thing is on its way today/tomorrow. Thanks

[Mr.Natural]

Mr. Guru, We have one that has a 36" dia table DC servo drive, full DCC operation, running 3.7 mr2. set-up & calibration is very easy, i think so anyway. I am the only one who has ever used it in our shop, doors, decklids, etc. don't ask me why the rest don't want to learn how to use it, chicken maybe, o well their loss i guess, anyway once you set up your part & run your alignment your all set to go. i think it is just amazing how PC Dmis translates the alignment with the rotation of the table & knows where everything is. A small problem is that when you have to jump into a feature in the pgm you need to be very careful as to table/tip angles, you need to make sure PC Dmis knows where it is in the pgm. I have found it very easy to "confuse" PcDmis & after that it DOES NOT know where the part/table is & sometimes it is just easier to start from the begining. as for cost, go sit down, i was told it was about $ 120,000. if you have any questions PM me.