hexagon logo
Register Sign in
  • Replies 6 replies
  • Subscribers 221 subscribers
  • Views 81 views
  • Users 0 members are here
Options
Related

Hexalobe bone screw iterative rotation tolerance

lovethepirk
We run profile of a surface on a hexalobe for several bone screws. Our quantity of checks per order just doubled. When we do an iterative alignment to cycle thru how well the screw hexalobe is oriented we commonly get an iterative error on the rotation. I do not program the part, but have discretion to make changes within reason. All the rotational tolerances are set to .006mm for the iterative tolerance, which is crazy too low in my opinion.

Even if the error pops up at .02mm on the rotation, every operator enters thru the error and the program works fine. Would it seem reasonable to set this at a max of around .0254mm or 1 thou? I don't see how a 1 thou error couldn't be allowed for the program to proceed without an error msg popping up taking a 3min program and turning it into a potential 10 min program if the operator is doing other things.

The vectors on the rotation of the hexalobe rotation are not clean either, they are far from a pure X plane direction, they have plenty of Y in them as well.
Parents
  • No worries, we use a readpoint on everything. The RP can only take you so far with a bunch of lobes that are almost hard to see with the naked eye while you are fixturing it. You can only visually get the lobes clocked I'd say at a +-5 deg repeatability. So the iterative is diving into the hex trying to find two points to establish a rotation line to clock to. I guess if you fixture it outside the vector hit directions it somehow calculates an iterative error on the line. If someone understands how it gets a value of say .0174 I be interested in how it is identifying this number. So if you fixture it say 8 deg wrong and the value is .037 and you just enter thru the error, it will still find the two lobes to clock to on the next alignment you will just be very tight to one side of the hex cylinder, but once you establish that you can dive in for a final blow with more precision.
Reply
  • No worries, we use a readpoint on everything. The RP can only take you so far with a bunch of lobes that are almost hard to see with the naked eye while you are fixturing it. You can only visually get the lobes clocked I'd say at a +-5 deg repeatability. So the iterative is diving into the hex trying to find two points to establish a rotation line to clock to. I guess if you fixture it outside the vector hit directions it somehow calculates an iterative error on the line. If someone understands how it gets a value of say .0174 I be interested in how it is identifying this number. So if you fixture it say 8 deg wrong and the value is .037 and you just enter thru the error, it will still find the two lobes to clock to on the next alignment you will just be very tight to one side of the hex cylinder, but once you establish that you can dive in for a final blow with more precision.
Children
No Data
© 2024 Hexagon AB and/or its subsidiaries. Privacy Policy | Cloud Services Agreement