Parallellellellellelism question...

[Farmer]

(Please see attached)

Ok, I want to measure the parallelism of a plane (area a) in relation to datum A. My question is - how do I define that this particular plane only exists within a given area (i.e. between the 2 dark green lines). Doesnt dmis project planes into infinity? Or does it construct the plane within the confines of the 3 points taken. How does it measure parallelism?



Thanks all,



F.

*Geopak convert*

[phil george]

I believe it is confined to the area the hits are taken rather than to infinity but once you create the dimension there is an "EXTENDEDLENGTH" parameter you can change.

[Mike N.]

how do I define that this particular plane only exists within a given area (i.e. between the 2 dark green lines).

If I understand correctly that would be PROFILE using form and location

[dccfreak]

It could be that this a special attention area or a secondary mounting area and this is the need for the zone. I see customers do this all of the time in stampings where there might be a particular area that is coined on a surface to insure it is good and flat in that area. The still want it to be parallel so that when the datum is mounted the coined area will be able to support a mating part at 90 deg. Although, a profile could also be used for that need as well.

To answer the question, the plane will be confined within the boundary points you used to establish the plane. You then just need to make sure to pick the datum feature second in the parallelism dialog as PC-DMIS treats the last feature as the datum by default. You should be able to get what you are looking for with that.

Just a note: It is probably a good idea to stay away from using 3 point planes when measuring surface features (if that is what you are doing) because PC-DMIS typically treats 3 point planes as perfect flat, and that could wind up providing some wacky results on certain features, especially when measuring flatness! I usually use a 3 point plane only to establish level when doing a manual alignment. Hope I could help a little bit!