Surfaces

[quality2214]

Thanks for all your help on the other posts. You all have been such a great help. Last question I hope. I am instructed to digitize a clamp shell so that we can add some length to the part. I am going to scan the areas that I can and measure the remaining areas. Is there a way to construct surface from all the different scans and export that surface with the measured dimensions so that the engineering group can bring in to the CAD software and write a program to machine the part. I have always exported one scan at a time and it has always worked but this time there will be multiple scans and also measured features on top of it. Thanks for any help that you can give me.

See attached drawings.
FLANGEBOTpdf.pdf

FLANGEFIXpdf.pdf

[Matthew D. Hoedeman]

Yes, you CAN make surfaces from scans in Pcdmis, BUT ONLY from patch scans and it does not work for crap. You can export ALL the scans at once, you don't have to do it one at a time.

HOWEVER, unless you are generating your nominal scan data from CAD data, you will NOT get correct probe comp in your scan data. It will only comp correctly in 2 directions. It will not put in any kind of correct vector for the 'cross-axis' direction of your scan. Meaning, if you do a linear scan, the axis that crosses the scan line will not be correctly comped. Think of it as a slice, lay the slice down flat and the comp in the 'up-and-down' direction will not be correct.

HOWEVER, there is 2 ways to get the correct probe comp:
1) Use surface points with 3 sample hits, this will force Pcdmis to find and calculate the surfaec vector for each and every point in the scan, giving you 4 hits for each data point
-OR-
2) Turn off the probe comp. All data will then be to the center of the ball. When you export the data, tell the cad department they will have to offset the surfaces they create by the radius of the probe (my method).

[c4821]

Thank you Matthew , it is a really helpfull info! So I also would like to ask about the constructed surfaces from skans - is there some way to make and export / for example to NX/ a real CAD model? I am with Pcdmis 3.7 and DEA Global.

[Matthew D. Hoedeman]

You can make surfaces from patch scans, but it is neither very good nor is it quick. It takes FOREVER to do even a little patch into a surface. Also, unless you are dealing with very little surface detail, you will need a HUGE amount of points, small increments, small step-over just to cover the part. Unless you have a scanning head (laser or continuous contact) I would not even TRY to make surfaces with Pcdmis. In fact, we quit scanning with Pcdmis completly (except for strictly 2-D scans) and have gone with an independant laser scanning camera. The couple times I tried making surface with Pcdmis, from scans of about 500 points, I had to do a 3-finger re-boot to get out of it, after about 15 or 20 minutes. it is a SERIOUS drag. Pcdmis is already a huge resource hog, then adding making a surface on top of that, YUCK. BUT, if you DO create a surface (and you can ONLY do it from a patch scan) you can export it as an IGES file or any other format your version of Pcdmis will export to (depends on what you have paid for).

[c4821]

Hi everyone again. I have a control over the scaning with a continuous contact head already ( Renishaw PH10M with SP25M ) and I can make a surfaces with Pcdmis. All above is right. I would like to add just a note - the patch scan can be from minimum TWO ROWS and from minimum FOUR POINTS per row to close the surface. It possible to export points in some cad modeling software, NX for example and make a surfaces. But as you know that kind of soft is not just for that. So I would like to ask whish software is good for that purposes? Can you say some?

[Matthew D. Hoedeman]

To make surfaces from point clouds, Geomagic works real well, but, it is a major software and is not cheap.

[jon_dav_uk]

Imageware is a good package for creating surfaces from either raw point data or IGES curves.

Is the shape you are trying to create rational, i.e. round / square etc or freeform ? This generally forces me to choose a particular piece of software. I use Imageware for freeform surfaces or ProEngineer for the rational stuff.

Imageware although time consuming creates Class A surfaces upto G2 curvature matched. As Matt said dedicated sufacing packages are not cheap tho so if this is a one off it may pay to send the data to a dedicated surfacing company who will create the model from your own data.

[AJHVW93]

I Agree with the above comments on patch scans!! Not had much success myself!! Anyone use any of the other software packages to actually scan,not just create surfaces from dmis info? I heard good things about Geo Measure as well!