Yea I agree with you, your origin is more proper than what I was imagining, I started confusing planar setups for inclined datums vs a primary as a cylinder which is not in the standard. I do need to share a weird thing with you once I get back to work tomorrow regarding this which may be...
Burunduk,
I'm skimming some chapters just as a yearly refresher and I don't remember this particular issue. I understand the surface method and hard gaging the virtual condition.
If those 35mm cylinders were machined separately and have a decent amount of difference, how are we determining...
Burnunduk,
The inclinded datum would be at a basic to the primary cylindrical axis so it would be simulated not from the datum feature(real surfcace) but from a perfect basic angle simulation. My interpretation is that it isn't one of those cases where you have the unrelated vs related mating...
Appreciate your replies. What 3DDave made sense b/c when I modeled the assembly in Solidworks the inclinded datum removed all the dof, but in GOM inspect it does not. I have an immense respect for the GOM software so I was intrigued when it didn't arrest the rotation. Solidworks is assuming a...
In this mock example I have a yellow fixture with a cylindrical boss as Datum A, then an inclined Datum B at 20 deg Basic. We slip the gray part over Datum A which let's just say expands b/c it is at RFS, so Datum A is locked in solid.
'
I don't think I've seen an example in the standard for an...
We just onboarded a new customer. All their prints have unequally disposed surface profiles. And their CAD models are all made at MMC condition. That causes some issues with surface hits on the CMM with tight tolerances. So I'm in the middle of altering their models to what we make the parts at...
My thoughts are there is no stated tolerance on straightness so rule #1 is basically still in place. They are doing the same thing with form but obviously straightness doesn't care about location
Straigtness also cares about derived median line coming from many midpoints created from opposite...
pmarc,
my brain hurts after a full day of getting beat up. After a recalc on your example, I think your example matches the above image diagram. So if you replaced the composite tolerance callout with yours you get similar results but you cannot get bonus on profile so I'm too late in the day...
Pmarc,
Sorry my last picture has the incorrect engraving on the part....it is 20.05 part diameter not 20.5, but the model is correct(edited pic, now correct). Below is another example. Since the upper segment is analyzing the surface when it is machined at 20.05, some of the tolerance is gone...
Below is the composite example. The basic diameter is 20mm and b/c the lower segment ultimately controls the size, the part is made at 20.05mm. As you can see you lose half your tolerance in the upper segment callout, limiting the deviation in location you are allowed.
Burunduk, I have a good graphic later to post, I just need to improve it for clarity.
pmarc,
Walking thru your example on paper:
Dia. 20.0-20.1
|POS|dia. 0.1 (L)|A|B|C| The hole at LMC is 20.1 and you get no bonus here. At 20.0 you get additional .1 bonus. Hole can be at most .1mm away...
I agree in theory, but you have to extract a measured value from both callouts, otherwise you don't have a value to pass or fail a part.
The measured value of the top callout is based on a diameter of 20.1, so if you make the part correctly at 20.05 that measured value throws up a false flag. It...
I feel similar to you on this as in the end all works out nicely, but the wrinkle here is that I have a machinist making the feature at 20.05 and obviously the hole has some deviation in X and Y location so the top profile callout they don't get the full .100mm of tolerance. They only get .050mm...
