RE: [CAD_CAM_EDM_DRO] Home built machine setup, perpendicularity

Hi Scott,

I was thinking about this last night and if you can do the final
adjustment for perpendicularity after you've mounted a spindle I
think I have a way for you to zero in your machine.

The idea is to use the machine to mill two adjacent sides of say
a 1/4" thick 2' square aluminum plate. Then flip the plate over,
front for back, about X axis and indicate the milled edge parallel
with the X axis. If you then use the Y axis to run an indicator
along the other milled edge, the total reading you get will be
twice the error in perpendicularity. Adjust the Y axis until you
get a total indicator reading of half the original reading and
the Y should be at 90 degrees to the X. I would then mill the
edges again and repeat the test to check the results. If there's
still a bit of error you can repeat the adjustment until you're
satisfied with the results.

Hope this is clear enough.

Drew


-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com]On Behalf Of Scott Riddle
Sent: Thursday, July 07, 2005 9:59 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Home built machine setup, perpendicularity


I am looking to put together my own home built CNC machine with
linear rails and ball screws onto a heavy tube frame. I am trying to
figure out how to drive the main X axis which will move a gantry
over the table. I am contemplating using 2 ball screws(smaller ones)
to drive each set of trucks. This way I can assure no racking
problems and have increased machine stiffness. My main questions is
if I go to the 2 screw system and I am using stepper motors how do I
initially when build this machine get my X and Y axis perpendicular?
Assuming that each X and Y rail setup is straight to start with.

Basically can I measure perpendicularity on a 3' x 3' linear rail
setup with something like indicators. I do not have access to any
large right angle plates or things like that. I would think that
there would be some clever way to measure this.

I used to design machine tools for several years so I know all the
basics but when we did this setup part it was all done with a laser.

Thanks
Scott