Checking Formed Parts

No guru here... are you working with a cad model and do you have a good alignment to the part? Posting your code and or print would help.
eric

what is the tolerance on the around 35 deg. formed angle? are you taking points on a surface that is out of tolerance? Also bend lines are reference dimensions only. The pressbrake operator can alter bend line dimensions to hold the final formed dimensions that are critical and are tolerance.

Hi,

I check quite a few formed parts. I've ran into an issue a couple times now and I'm interested if the gurus have any answers, the problem goes as follows:

I setup a part on the table and begin inspection. I take a bunch of vector points that are on the surface of a formed angle (around 35 degrees) when I turn those vector points into a scan and assign it a profile of surface FCF the part is out of tolerance.

I wondered if when I convert the points to a scan if it assigns the scan a workplane and the worklplane caused issues but I tried the same experiment without putting the points into a scan to no avail. Additionally when I check the angles and bend lines the part seems to be right there for the basic dimensions.

does anyone have any ideas?

Thanks,

Frusturated inspector.

Think about what happens when you take a Measured Point. The arm shoots from ball center, and compensates the hit by the known value of the probe tip. It decides what direction to comp the hit based on your arm angle, but it'll only comp in X+/X-/Y+/Y-/Z+/Z-. This is why, in class, we instruct people to never use measured points unless you are aligned, and then only on surfaces flat to an axis. Note that this is Measured Points.

Auto Vector Points are a little more flexible. If you know the IJK, you can type it in when creating a point. Alternately, you could click it in from a CAD model (and use Point AutoTrigger to strike it accurately). But the AVP is still going to compensate in the direction of that IJK.

Now let's talk about your part. Do you know the IJK for the surfaces you're striking? You haven't mentioned a CAD model, so it doesn't seem likely. If you don't know that IJK, then what's happening, most likely, is that PCDMIS is probecomping the points incorrectly (as it's been instructed to). So your points float off the surface and don't represent the position you wish them to.

I note you haven't talked about an alignment, hopefully that's already in place.

If somehow you know the XYZ and IJK for the points, shot them with AutoTrigger, Constructed a Feature Set, and Surface Profile'd it, it'd work perfectly. But I think your points are created incorrectly, so it won't work.

Scans don't rely on a workplane, only 2D operations like Measured Circles, Lines and Slots, and 2D Distance and Angle Dimension make use of it. But for the same reason your Points aren't coming out correctly, your Scans are going to fail -- how is the probe compensation being calculated? This is why, in class, we taught you to scan only when you have a CAD model, and we discussed using the Find CAD Nominals option, so that your probe 'searches for' available CAD surfaces and collects them during the scan. When this option is enabled during the Scan, PCDMIS can use the CAD surface to determine the nominal IJK of the surface and use that to probecomp correctly.


Lacking a CAD model, I don't ever bother inspecting freeformed parts. It's way too difficult to hand-calculate the IJK vectors on all the surfaces so that PCDMIS can probecomp correctly. Hope this helps.