【转帖】parallelism question verification

yang686526

parallelism question verification
so please view the section drawing of a round disk with a raised portion in the center. hopefully it is semi clear?
                 
                      [ // | .01]
                       |  
                       v
____________+++++++++++_______________
|                                      |
|______________________________________|
      .   
     /|\  
      |   
     [a]      
so if the + signs have to be parallel to .01 of datum a then  
if using a cmm then the reference length should be the length of the + signs. is this a correct assumption? the reference length should not be the length of the bottom of the part
usually this area is indicated as a diameter on the print. what the cmm should be doing is establishing the a datum as the granite surface plate then taking multiple points within the diameter that is required to be parallel and establishing an average plane using those points then calculating the parallelism error with respect to the a datum.
powerhound
production supervisor
inventor 11
mastercam x
smartcam 11.1
ssg, u.s. army
taji, iraq oif ii
the area on the surface should be shown with a chain line (fat centre line).
set up on datum a using a 3 point set up. if datum targets are shown - great but if they aren't not, just note where you picked up your points. you have created a plane.
now contact the surface that has a parallelism tolerance of .010. take multiple points and the range of the points must not exceed .010.
parellelism includes angle and flatness combined.
dave d.
the reference length is the length of the + signs. the datum runs to infinity.
it seems as though you are using paralellism line-to-line. i'd think plane-to-plane is more appropriate.