.001 positional tolerance

[ujmujm]

I've got a part I'm making on a Matsuura MX-520 5-axis I have 8 diameter's with a .001 positional tolerance between three datum's I spot, drill, interpolate, and ream to size, I'm having a hard time holding the tolerance, any suggestions ?

Thanks

[Guest]

Hopefully the 3 datums are being machined in the same OP....if not, your fixturing is going to be extremely critical

 

Sight unseen, that general process is what I would use.....

[GoetzInd]

.001 TP is no joke. Like JP said, If your datum reference frame is not all done in one op, you're going to have a hard time. Especially if you have any capability requirements. See if you can get MMC/LMC on the hole and even the datums. Usually there's no functional reason not to and every little bit will help.  Pic of the part and fixturing will probably also help you get some good responses as well.

 

Mike

[ujmujm]

Every feature is machined in the first op except two of the holes, but all of the diameters are not repeating, on one part they will be intolerance  and the next part they will out almost a .001

[ujmujm]

I do have MMC applied to all three datum's how ever our Zeiss programmer does not know how to incorporate it into his program, I was hoping the replies I got would say that tolerance is impossible. 

[mkd]

2 minutes ago, ujmujm said:

I do have MMC applied to all three datum's how ever our Zeiss programmer does not know how to incorporate it into his program, I was hoping the replies I got would say that tolerance is impossible. 

with three feet between features on an aluminum part it may be near impossible. Certainly would be without temperature controls.

 5 inch invar part, would be much better for temperature.

 you need to get more specific if you want more specific suggestions.

[Guest]

6 minutes ago, ujmujm said:

I do have MMC applied to all three datum's how ever our Zeiss programmer does not know how to incorporate it into his program, I was hoping the replies I got would say that tolerance is impossible. 

It's not an impossible tolerance...I have brought in holes with .000/MMC......again though, as we can't see your part, judging your process or whether the part lends itself to it is difficult...

 

[mkd]

also, you need to watch out for Y axis thermal growth on the Mx 520, from what i've Read on other Forums.

[jlw™]

Run a warmup cycle and keep the coolant running thru the frame the whole time.  When it's not running a part put it back in warm up.  I dont know that machine specifically but I've seen Grobs hold 10micron true position for years.  It's all about consistency.  No matter what you do, do it the same everytime and when you get it dialed in keep it running - stop for nothing!!! (except bad parts!)  Also, dont go cheap on tooling.  Cheap tooling costs so much more in the long run especially in this scenario.

 

A few pics or screenshots will get better advice.

[civiceg]

Make sure your reamer is not running out and add a dwell. I would also add spring passes to your pre ream interpolation.

 

 JLW hit the nail on the head with the warm up. It should simulate what conditions you are running parts at, spindle rpm, axis movements and ranges, etc.

And make sure the CMM is calibrated...

 

[taperlength]

10 hours ago, ujmujm said:

I do have MMC applied to all three datum's how ever our Zeiss programmer does not know how to incorporate it into his program, I was hoping the replies I got would say that tolerance is impossible. 

If your Zeiss programmer cannot do something as simple as add MMC to a Characteristic,  it is possible that all of the problems are on his end and the parts are actually good.    

It could also be small burrs or chips in the holes being measured.  

[Guest]

Same tools and no tool changes between the holes? I hate to but am I correct in assuming that the Datums are Perpendicular to each other? Are you using Tilted Workplane (G68.2XYZIJK)?

 

If some are in and some are out, I would look at what's different. Machine sitting or not? Warmed up  = good, cold, not so much, etc...

That tolerance is definitely no joke. It'll be challenging to hold that in a non-climate controlled environment, or without coolant temperature management.

Like has been said, more info is needed to give you good advise.

JM2CFWIW YMMV

[cncchipmaker]

I would try boring the holes. Unless you are helical milling for position prior to reaming you are going to have problems.

[RaiderX]

yes boring is prob best practice in this with positive approach. all errors add up and all machines have some to on extent of another. tough order and any possibility of error eliminated and or mitigated will help you accomplish the task.

 

inspector needs a flogging or education at the very least.????

 

[Leon82]

Had this issue with a .02 mm true pos. All sides machined. All holes were being bored

Matsurra guy came down said machine is fine. Thermal growth is the problem. Thru spindle collant will heat the enclosure 10 degrees or more.

Run the coolant low, fill it up with cold water and watch it shift on you, lol

Ended up putting an moo and indicating the part for each piece using the g54.4 active workpiece function. They usually come in at 10 to 15 micron true pos

[Newbeeee™]

^^^chiller needed in the coolant tank then to keep constant temp?

[Leon82]

35 minutes ago, newbeeee said:

^^^chiller needed in the coolant tank then to keep constant temp?

I agree,but convincing the boss is another story.

We minimize thru spindle coolant and I added an m16 in camplete to override the chassis rinse.