Night Shift Blues !!

[jon_dav_uk]

Can any of you guru's out there help me out, not sure if I am just having a typical nightshift meltdown or I have a problem with PC Dmis

I have a simple part which I have aligned to both manually and in DCC mode using itterative alignments and everything works fine. I then perform a patch scan on the flat face that is my level plane using the following criteria

Direction 1 Tech - Nullfilter
Nominals - Findnoms
Execute - Relearn

I am using a CAD model and a 4mm dia probe so have set the find noms tol at 3mm.

When I run this offline everything is OK. When I run it online it stops and I get a message which says PC Dmis cannot find nominals for the hits it has taken and do I want to change the find noms tol, if i just accept the 3mm value I already had the program runs and the scan is within 0.025mm all over which I would expect as this is the datum.

I cannot understand why

a) It cannot find nominals for the hits but will if I accept the same value it is questioning
b) It asks this every time I run the program

PC Dmis V3.7MR3
Global Performance 7-10-7 using SP25M

4.30am in the morning and my head is done in, help

Cheers
Jon

[FAT FREDDY]

When you mark the surface to scan on the model,are'nt you already finding the NOMS for each hit? I myself just got off nights. I worked them for ten years.

[Matthew D. Hoedeman]

Well, if you have CAD data, do NOT use FINDNOM or RELEARN.

FIND NOMS is for use when you CHANGE the cad data to a new revision
RELEARN is not really for checking, but for reverse engineering.

Set to NOMINALS = MASTER and EXECUTE = NORMAL

Then, once you have defined your boundaries, click on GENERATE and Pcdmis will pull all the XYZIJK values from the cad data and you are set to run.

[Boomer]

Scanning blues

I have the same issue with the patch scans and using a constant touch probe finding the nominals...I dont know the answer. Matts post was telling you to use a regular touch probe..Using Matts idea will work and you wont have the issues that you are currently having. As for the patch scan and an SP25 I think that it is a software issue. When I have this issue, I end up making a sieries of linear open scans and creating a feature set.

[jon_dav_uk]

Thanks for the replies all

Matt - Maybe I am wrong but when scanning with a constant touch probe such as the SP25M my understanding was the CMM collected the data and then went back and pierced the CAD to collect the nominals for each point it took, this is what I was taught anyhow. If I was scanning using touch trigger probing I would agree as the nominals would be generated from the CAD and the CMM would just drive to these nominals

Boomer - I have noticed that Linear Open Scans always work so maybe I will just use this and hope Hexagon will get back to me with an answer, wont hold my breath though

Cheers
Jon

[JamesMannes]

One thing that I noticed. When a patch scan is created, if you select the CAD surfaces that it is to use for finding nominals and you replace the CAD data aftethe fact, PC-DMIS cannot find the nominals because the number value associated with that particular surface has changed. Now you know and I know that this is an issue, I believe WILCOX does/did becaue I believe (don't know for certain) that this was corrected in 4.0/4.1. Anyways recreate your scan without choosing surfaces and that may take care of your problem.

Also, what about increasing your find nominals tolerance?


Here is another one for you in, 4.0/4.1 you can go into the clip planes dialog box, and unchoose "two sided shading", at that point you will see all CAD features that are not properly vectored. After doing this a new option is provided to the programmer called EDIT>>CAD VECTOR. Box select the entire model and hit ok. This will "fix" any vectors that are improperly represented. This representation doen't really effect the normal type of operations, like a auto-vector point or auto-circle, but does have an affect on continous scan operations. See? I am good for something and so is 4.1.

Now all you people can ask me how this all works and I'll tell you "I don't know, I just know it works". Read the help files in 4.1 (you have down loaded 4.1 right?).

[jon_dav_uk]

I always select the surfaces so will try without selecting them on Monday and let you know how I get on.

Jon