Start Alignment/Base Alignment help

[[Za...]]

Hello all,

I have a part that's a metal casting and I'm having a hell of a time trying to get the base alignment to exit my loop and run the program. There's not really a great place to probe for my start alignment and I'm running out of ideas. Does anybody have any suggestions?

There aren't any finished surfaces on the left or right of the part to touch and the top is pretty rough as well except for the spotfaces, but the stylus keeps falling off after a couple times through the base alignment loop.

EDIT: I've also tried touching off on the fixture for the X and Y points, but when it goes to execute the base alignment, the stylus falls off of the +Z spotface being used for the alignment.

[[Ma...]]

I'm guessing you have datum target points to use for your alignment? If this is the case you could try doing a RPS alignment. And with the start alignment I would try to over complicate it. I have used start alignments that are a simple 3 points for x,y, and z dependent on part and fixture. Also what condition break value are you putting on your alignment loop?

[[Er...]]

When dealing with casting surfaces and checking machined surfaces along with casting surfaces, i have learned to use machined features as a base alignment to find the part location. I would use the 4 points as a plane on one (or both if they are the same height) spot faces, a diameter on both ID's at the top before the threads. (It looks like these might be cones, which is still OK. You are taking a diameter for a center point so it will repeat great.) You can then use this alignment to find the rest features on the part whether casting or not. If some of the casting features are a Datum, you can now setup alignment within the program to check your features to those alignments. This should repeat very accurately.

[[Za...]]

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Matthew, my GD&T knowledge is a work in progress, what would datum target points look like on a print? valueA<0.005 is my break condition.

[[Za...]]

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I'm going to attempt to do this after I go to lunch here in a few minutes and I'll get back to you.

[[Me...]]

Eric is "spot" on with his reply. 🙂

Often it's easier and more reliable to work from the inside out when dealing with castings. Unless I'm verifying a raw casting pre-machining I almost always use machined features for alignments and checking back to the cast surfaces.

[[Za...]]

I tried using the spotface plane (2 points on each SF) as well as circles on the cones and it's still not wanting to go through its base alignment correctly. And now I have more castings to program with less machined features... I'm starting to get frustrated 😠

[[Me...]]

Are the spotface planes coplanar? Have you checked your feature nominals? Do you have a model? If the machine is driving to the wrong position and/or falling off the part then I would suspect the nominals are incorrect for the features and/or the alignment is unstable.

I would make the most basic and stable alignment possible to get started. A single plane on the spotface with plenty of points (probably a circular scan on a plane), a circle on the cone for origin, and a circle on the other cone for rotation.

[[Ow...]]

Give us a screen shot of your base-alignment.

[[Za...]]

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The spot faces have the same height, but I ended up using your suggestion and just using one of the spot faces (the larger one) with the cones and got it to align. Thank you for the help, I'm going to try my luck with this other part and if I can't get it I'll post back on here tomorrow.