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ClaudiuCraciun1-Visitor
1-Visitor
January 14, 2012
Question

Global Interference Check

  • January 14, 2012
  • 3 replies
  • 5415 views

Recently teh management asked for every proejct to be run a global interference checking.

This report sometimes give up to 700 interferences.

Verification of these 700 is not kind of big deal. Can ve done in 10 minutes but this big number scaried most of the people.

Most of the interferences are from screws with the thread.

Now the management want to change the screw shape on the way not have interference with the thread(in the thread ared inteasd to continue to be cylinrical will have a smaller diameter)

do you think that this is a good ideea. somebody is usig this approach?

it's kind of cheatig for something that is real.

CC


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3 replies

BrianMartin13-Aquamarine
13-Aquamarine
January 14, 2012

Hi Claudiu...

Personally I think it's a bad idea and it displays a fundamental misunderstanding of the CAD tools to even suggest such it. But what do we know about your management and your PDM team? We know they've already demanded you break apart all family tables because they're afraid of them. They've already displayed a tremendous lack of understanding and continue to do so.

You're likely going to be stuck but here are a few ideas:

  • Consider making a simplified rep (you can even use the "By Rule" feature) to make a version of your assembly without the hardware. Leave nuts, washers, etc... but remove the bolts and screws. Run the interference check on the simplified rep. This should remove almost all hardware-related interferences while leaving the master model and the hardware itself intact.
  • Run the interference check as-is... but save the results and open them in Excel for further processing. You can selectively filter out interferences of negligible value (like .00001 inches, etc). You can also selectively remove certain pieces of hardware from the listing to reduce the number of interferences in the report.

I would not advocate taking an accurate parts library and making it INACCURATE to work around a feature that's working properly! There is a small interference between screws, bolts, and the threads they're engaged with. This is also a small, small number. You can sort the interferences by value. You'll probably notice all M6 hardware interferes the same exact amount in it's threads... this can be filtered out!

I'd continue to let Pro/E do it's job correctly and convince management to spend the few minutes investigating the results of the interference check... and having a thinking, intelligent human do the work to determine which interferences are important and which are irrelevant.

Ultimately your software is only as good as your people... and this is a time where you shouldn't cheat the system. Instead, your company should rely on it's people to do the job of interpreting the results.

Thanks and good luck!!

-Brian

ClaudiuCraciun1-VisitorAuthor
1-Visitor
January 14, 2012

Hi Brian,

The biggers problems are between screws and the component that contain the tap geometry. Now if I exclude the screws I cannot catch the error.

Also the same screws sometimes are comming with a bigger ar smaller interference (lets say if there is a washer, or a small step the amount of interference volume will be a little bit changed)

I tried at the begining to complicate the stuff and create a data base where I strored the interference volume for each type of screws.

I created an application that calculate the interferences and compare the volume with the value from the database, but this value not being the same all the time the application didn't wprl properly. More than this this datatbase need to be updated with all posible and imposible combination at the end to have the right result.

Actually my manager want if it's possible to press a button and what is a really a problem to be highlited and not the other interferences that are normal interferences and don't cause any problem.

Pro/E give us a tool that generate a report with and the component that interfere, the amount of intereference and also highlited these components in case that visually I want to see the issue.

I believe it's a waste of time to create complicated application that decide if an interference can be a real problme without deigner interaction with the models and report

KevinBrault10-Marble
10-Marble
January 16, 2012

We addressed this issue by changing the model of the screws. The threaded area of the screw is modeled at tap drill diameter. A revolved surface is used to represent the major thread diameter. Here is how our models work:

  1. All dimensions are at MMC.
  2. The threaded volume is modeled at the nominal tap drill diameter per thread standards.
  3. Insufficient thread length on screw will create an interference during check (screw too long or nut threaded too far condition).
  4. A revolved surface is used to represent the thread OD.
  5. The lead-in on the thread surface represents the minimum full thread length.
  6. Two datum points, PNT1 and PNT2, represent one full thread diameter and two full thread diameters of thread engagement from the minimum full thread length.

Advantages:

  1. Correctly located and sized screws and holes do not interfere.
  2. Interference Check will find if screw engagement exceeds thread length.
  3. Quick thread engagement checks can be made when viewing the model in wireframe mode.

Disadvantages:

  1. Revolved surface is an additional feature (but a lightweight feature).
  2. In cross sections screw threads do not appear. Screw looks odd.
  3. Undersize screws still not detected by interference check.

Kevin

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