Unwanted surface won't go away.

[treddie]

Howdie.
I'm building a vb6 program to write relations for a generic screw and threads. The relations will drive the screw specs to their correct values. This way, I won't have to redo every screw I run into, just alter the relations.

The problem I'm having, is that I am building the threads as a Cut, into a cylinder of metal, rather than a protrusion afixed to the outer surface of the cylinder. I'm doing it this way because I need very realistic threads for cosmetic reasons, so I want to be able to back the Cut away from the cylinder when it's time to terminate the thread cutting operation, near the screw head. This will give a realistic stop to the threads as they get quickly shallower and shallower until they transition into the smooth cylinder. But when I complete the Legacy Cut, I get my threads alright, but in addition, an unwanted surface between the windings, almost as if the pitch was set too high for the height of the crossection, thus leaving uncut material between each thread. But the pitch is correct, and attempting to decrease the pitch ever so slightly, or increase the crossection height ever so slightly, simply causes a regen failure. I wish I could post the images along with this post, but it doesn't look like that's possible.

Any help would be dandy.
Thanks all,
treddie

 

[treddie]

Did it again. After working on this for 2 days, I post a question on the forum, and solve it within 12 hours (see graphic, below).

Anyway, the solution was to INVERT the crossection (put the deepest part of the cut in the middle of the crossection instead of having half of it at top and bottom, and break the cut into two parts; one cut that STRADDLED the deepest portion of the thread crossection, and the second handled the deepest portion of the thread crossection (see crude graphic, below). That way, I avoided the infintismally thin surface that would result at the deepest portion of the threads when the UNinverted crossection came around to build the next level of threads, when trying to do it all as one cut.

Both cuts butted up against each other. I did a Helical Sweep for both cuts. The thread crossection had curved surfaces at both the Major Dia. and Minor Dia.

------------------------
| |
| | ---> Towards
| Top Portion - Screw CL
| of -
| 1st Cut -
| -
|--------------------------------------
| -
| 2nd Cut -
| -
|--------------------------------------
| -
| Bot Portion -
| of -
| 1st Cut -
| |
| |
------------------------

treddie

 

[treddie]

I GOT THE LAST POST WRONG!!! Here is the correct procedure.

The solution was to break the cut into two parts; one cut that did the thread cut, and the second to trim away the excess, unwanted, ProE-bug, surface(see crude graphic, below). The thread cut was, ofcourse a Helical Sweep Cut. The second cut was just a revolved, hollow cylinder the same height as the screw threads, with an inner diameter equal to the major diameter of the threads (same as the screw shaft diameter). The thread crossection had curved surfaces at both the Major Dia. and Minor Dia.

------------------------
| |
| | ---> Towards
| - Screw CL
| -
| -
| -
| -
| -
| -
| -
| -
| -
| -
| -
| -
| |
| |
------------------------

Would be nice if PTC would fix this issue; would speed things up a lot.

treddie