hexagon logo
Register Sign in
  • Replies 10 replies
  • Subscribers 222 subscribers
  • Views 227 views
  • Users 0 members are here
Options
Related

True Position v Legacy - Explaining to People.

MK1966

The above callout is on my drawing and it seems to be how our designers tolerance everything.
I need help explaining to designers about GDT in terms they can understand.
My datums have been generated using 3 generic planes with the correct vectors ie 1,0,0 / 0,1,0/ & 0,0,1 from 0,0,0, origin.
Sample below,
F1 =GENERIC/PLANE,DEPENDENT,CARTESIAN,$
NOM/XYZ,<0,0,0>,$
MEAS/XYZ,<0,0,0>,$
NOM/IJK,<1,0,0>,$
MEAS/IJK,<1,0,0>​
I can now calculate my true position for each individual hole.
​
If I use legacy dimensions without datum ref I have to use ±0.125
​Is this the correct way to do this​.​
Parents

  • The above callout is on my drawing and it seems to be how our designers tolerance everything.
    I need help explaining to designers about GDT in terms they can understand.
    My datums have been generated using 3 generic planes with the correct vectors ie 1,0,0 / 0,1,0/ & 0,0,1 from 0,0,0, origin.
    Sample below,
    F1 =GENERIC/PLANE,DEPENDENT,CARTESIAN,$
    NOM/XYZ,<0,0,0>,$
    MEAS/XYZ,<0,0,0>,$
    NOM/IJK,<1,0,0>,$
    MEAS/IJK,<1,0,0>​
    I can now calculate my true position for each individual hole.
    {"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":537342}​
    If I use legacy dimensions without datum ref I have to use ±0.125
    ​Is this the correct way to do this​.​

    This is just lazy design practice in my opinion but what you've currently done should give them what they want. If it were me, I'd perform a 3D bestfit of all features / pointcloud data and then construct three ALIGNMENT Planes, one for each workplane (+X, +Y & +Z). I'd then use those three alignment planes as my datums (Generic planes constructed at the alignment origin in each of the thee workplanes would be equivalent). If I wanted to really play them at their own game, I'd name my primary datum TO, my secondary datum _C and my tertiary datum AD. That way, the datum reference frame would spell out TO_CAD Wink

Reply

  • The above callout is on my drawing and it seems to be how our designers tolerance everything.
    I need help explaining to designers about GDT in terms they can understand.
    My datums have been generated using 3 generic planes with the correct vectors ie 1,0,0 / 0,1,0/ & 0,0,1 from 0,0,0, origin.
    Sample below,
    F1 =GENERIC/PLANE,DEPENDENT,CARTESIAN,$
    NOM/XYZ,<0,0,0>,$
    MEAS/XYZ,<0,0,0>,$
    NOM/IJK,<1,0,0>,$
    MEAS/IJK,<1,0,0>​
    I can now calculate my true position for each individual hole.
    {"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":537342}​
    If I use legacy dimensions without datum ref I have to use ±0.125
    ​Is this the correct way to do this​.​

    This is just lazy design practice in my opinion but what you've currently done should give them what they want. If it were me, I'd perform a 3D bestfit of all features / pointcloud data and then construct three ALIGNMENT Planes, one for each workplane (+X, +Y & +Z). I'd then use those three alignment planes as my datums (Generic planes constructed at the alignment origin in each of the thee workplanes would be equivalent). If I wanted to really play them at their own game, I'd name my primary datum TO, my secondary datum _C and my tertiary datum AD. That way, the datum reference frame would spell out TO_CAD Wink

Children
© 2024 Hexagon AB and/or its subsidiaries. Privacy Policy | Cloud Services Agreement