To achieve a high precise 3 axes alignment

[raulkam]

I want to develop and mount an L-shape profile (highly precised finished) on a 3 axis milling machine (XY-Bed, and vertical axis Z).

Mounting:
Mounting will be done with 8 screws. 4 screws will be used to mount base of the L-Shape profile with XY-Bed of the machine. Rest of 4 screws will be used to mount the back of L-Shape profile with Z-Axis of the machine.

It is required to achieve a perfectly aligned mounting of L-Shape profile with all three machine axes within 1µm accuracy.

Questions:
Could it be achievable? If yes, how to achieve it?
Is 8 screw mounting is OK? If not, which other mounting design could be more suitable?

Extra Info: The L-Shape profile has linear slides and bearing between its base and back. Thus machine can be operated in all three axes even after mounting the profile.

Thnaks

 

[BobM3]

I don't think you'll be able to locate anything mechanical to that precise a position. Lasers are often used for precise alignment. See

http://www.renishaw.com/en/laser-interferometer-systems--6800.

 

[hydtools]

Mount an intermediate piece on the table. Machine surfaces in the intermediate piece to create mounting surfaces to match the L-shape. That would align the mounting as accurately as the mill can machine.

Ted

 

[IRstuff]

What do you mean by 1 um accuracy? Alignment to axes is an angular problem. 1 um accuracy is a positioning problem not an alignment.

If you are actually trying to do an alignment, then you can achieve arcsec accuracy with an autocollimation approach against your reference surfaces.

Positioning accuracy could be do with micrometers or interferometers against your reference surfaces.

TTFN

FAQ731-376

 

[dicer]

You can only hold the tolerance that the milling machine is capable of. And it also depends on how well that machine is designed and how well it is alined. Does this milling machine sit on a very thick concrete pad? Is it in a temperature controlled atmosphere? It does no good to come up with some kind of DREAM tolerance that is, number one not really needed, and would cost millions to try to achieve. You can install the part on the machine and cut it with the machine. If you can't figure out how to do that job, find a compentant machinist that can. Precision work is a machinist job not an engineer job. If you can find someone that can hand scrape and lap and use laser alinement equipment, he could get it close enough for what ever it is you need to accomplish. Why do you think you need something so close, when most likely the machine will not be able to hold that kind of tolerance?

 

[zekeman]

What are you trying to do after this alignment has been achieved?
State of the art interferometers for this purpose are not cheap.

 

[raulkam]

Thanks a lot!
I would be using then using laser interferometer.
Could there be a better mounting mechanism? Current design is based on 8 normal screws passing through L-Shape-profile and attaching it with machine bed and Z-axis.

Information about the final task:
I am planning to design an equipment to monitor the 3D- machine path at TCP. The equipment will contain positions sensors which could give the 3D path measurement directly at TCP.
The body/assembly of the equipment will be the L-Shape profile. the base and back of the profile can move relative to each other. The concept will only work if the profile would be aligned very precisely with all three machine axis. Any misalignment in profile with directly influence the measurement of the 3D path.

Thanks

 

[IRstuff]

The concept will also only work if you have a workable approach to moving the bracket during alignment? Did you plan to nudge it with your fingers?

TCP????

Doesn't your mill already have position sensing? How does it even know where it is when it's milling?

TTFN

FAQ731-376

 

[raulkam]

TCP = Tool center point, Tipp of the mill
The Mill do has its position sensing. But I plan to develop an additional for performance monitoring purposes (fine calibration of machine). Thus will monitor the position right on TCP.

 

[dicer]

Some very accurate CNC machines combine encoder and linear scale encoding.
Just do a search for machine tool alinement, lots of laser type alinement systems come up. Save some headaches.