Hole locations - Tru Pos locators

[swisk212]

I know there have been many discussions regarding hole locations (no cylinder tip) and the debate about hole locators vs measuring hole with pitch. Our customer wants us to use tru pos locators, which is fine. Do those of you doing it this way make a cad model of locator and add it to part cad (so you can use auto features ? or is there a way to just change the auto-feature to measure where the locator will be ? 'innie vs outie' & above the part surface? just looking for 'best practice'. Thank you

[Matthew D. Hoedeman]

Use AUTO FEATURE from the part cad model, then change what needs to be changed, DEPTH and IN/OUT to check the type of unit you are using.

[DAN_M]

Using locators WITH CAD:

-If at all possible, go into the native software of your CAD model, add the locators to it, then import the entire thing into PC DMIS as one model. Then program as usual.

-If above is not possible, but you have all of the models you need....see below.

1) Import your part model
2) Import your locator model(s). When you import, PC DMIS will ask you if you want to treat this as an assembly, say YES. Now you'll have multiple models on your screen and they probably look all mashed together/not how you want them.
3) Go to "Edit/Graphic Display Window/CAD Assembly". The Assembly Tree (lower left pane of the dialogue box) once you expand it will have your imported models listed. Click the "+" to expand & see all of them.
4) RIGHT CLICK on the part model in Assembly Tree, click "Transform" out of the list, transform the model as needed. Click APPLY and OK.
5) Go back into "Edit/Graphic Display Window/CAD Assembly". Repeat step 4 for your locator models in the Assembly Tree. "place" the locator model(s) on your part model as needed.
6) Program as usual

^^Regarding above, DO NOT USE Operation/Graphic Display Window/Transform when you're working with assemblies in PC DMIS. YOU MUST TRANSFORM as I have stated above by right clicking from within the CAD Assembly dialogue box.



Using locators WITH NO CAD:

Option 1--> If you don't have the part OR locators already...Use info from your customer, math, or a software to calculate the XYZIJK information for your locators & then use autofeatures containing that calculated info.

Option 2--> Measure the part with your pre-existing program, assemble the locators onto the part, measure their position relative to your datums, then create autofeatures using that calculated data.

On both of these options, make sure the BASIC locations of the locator features you're using are correct per the print so the software calculates your alignment it will come up with properly.

[swisk212]

Thank you both. Thanks for that importing advice Dan, I didn't realize this was possible, appreciate it

[DAN_M]

Happy to help. Feel free to reach out if you have any questions.

[ogcharliebrown]

Using locators WITH CAD:


1) Import your part model
2) Import your locator model(s). When you import, PC DMIS will ask you if you want to treat this as an assembly, say YES. Now you'll have multiple models on your screen and they probably look all mashed together/not how you want them.
3) Go to "Edit/Graphic Display Window/CAD Assembly". The Assembly Tree (lower left pane of the dialogue box) once you expand it will have your imported models listed. Click the "+" to expand & see all of them.
4) RIGHT CLICK on the part model in Assembly Tree, click "Transform" out of the list, transform the model as needed. Click APPLY and OK.
5) Go back into "Edit/Graphic Display Window/CAD Assembly". Repeat step 4 for your locator models in the Assembly Tree. "place" the locator model(s) on your part model as needed.
6) Program as usual

^^Regarding above, DO NOT USE Operation/Graphic Display Window/Transform when you're working with assemblies in PC DMIS. YOU MUST TRANSFORM as I have stated above by right clicking from within the CAD Assembly dialogue box.

I do this when I run the whole part with a stop to flip the part. It really made it nice not having to run two separate programs ( still two programs put into one). Love It!

[DAN_M]

Me too! Just got done with a program that has 4 positions. Assembly importing and using viewsets have worked well for me

[jjewell]

Best practice, do not use them....the accuracy of a threaded hole should never be in question. The tools within pc-dmis, when used correctly, are more than enough. I had an argument with one of my clients over this years ago. He wanted me to spend the money on them to measure his parts....I did a study of using them and not using them....end of story and he backed off....if you have a part with tons of holes, what a total waste of time.....and money

[swisk212]

I guess your customers are different than ours.

[DAN_M]

Should also note...I use pitch all of the time and it works great. We use the CMM for position and accept the thread itself fit/form/function with gages

[joshmxz]

We only tend to use them when the callout has a projected zone that is greater than the depth/length of the thread (or directed to do so by a customer). I built a tool in excel to keep the levels at distances divisible by the pitch so it always rides on the same part of the thread for each level, instead of having one level in the root, one level on the crest, and one somewhere else.

Sandia National Labs did a study on them and can be found at the link below.

https://www.iigdt.com/1/2/Thread%20Hole%20Location%20Study%20-%20Sandia%20Natl%20Lab.pdf