Changing Base alignment Zero without a manual alignment?

[[To...]]

On the granite of our CMM we have a V-Block that is bolted down and never moves. Our machinists bring in their round parts and station them against the V-block. We have programs for them using PCM to check changing inside or outside diameters. The outside diameters change therefor their zero center changes in the base alignment and they have to manually align their first part every time. Is there a way using formulas in the base alignment or through PCM to have their center zero change based on the outside diameter that they enter in before running their parts, that they could just hit go and it would calculate the new zero and find their part?

[[Je...]]

There are 100s of combinations of ways to achieve this. Can you provide some additional detail, such as range of part sizes and how the base alignment is structured. Specify if cylinder/circle features are ID vs OD
Spatial - __________ - Strategy
Planar - __________ - Strategy
X Origin - __________ - Strategy
Y Origin - __________ - Strategy
Z Origin - __________ - Strategy

My first thought is a parametric start alignment based on "CMM_system" (since the V-Block NEVER moves) or off a saved alignment from V-block itself. Its more robust but adds a layer of complexity.

[[To...]]

Generally the sizes range from 2-10" outside diameter that rests in the v. OD mostly a circle. ID circle or cone mostly

Spatial - Plane/granite table - Strategy
Planar -None - Strategy
X Origin - Circle/cone to be measured - Strategy
Y Origin -Circle/cone to be measured - Strategy
Z Origin - Plane/granite table - Strategy

[[Ke...]]

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Another option that has the same effect without having to utilize a saved alignment would be to make the base alignment on the V block, then simply use a secondary alignment on the part and do all measurement to that secondary alignment, which can easily be modified with formulas or pcm

[[To...]]

Also OD and ID are concentric.

[[To...]]

I know how to do it using the block as base alignment but we do not want to go that route. We would like it to just start measuring the part. We are trying to do this as a time saver.

[[Mi...]]

*Set Program to run from features list*
*I assume you're setting sizes via parameter files or asking questions at the start with PCM*
*assuming the XY offsets don't matter or are small enough the machine with still find the part*

He's a method I use to adjust the X Location of the Start Alignment, you can do this directly with a Base Alignment, but I much prefer to roughly find the part with fast features in a Start Alignment, then Loop with important features for the Base Alignment.

This part goes through a half dozen machining operations and that makes it sit in a different spot in space in X, but I have all programs share 1 start alignment... meaning I need it to move based on where it finds the part taken with a single point that has lots of search distance.... To Force this point to ALWAYS run before the Start/Base Alignments, the first feature of the Start Alignment has

getActual("Pt. X Check - SA").comment

in the Presettings.
Notice I set the variable "startAlignmentOffset_x"

In my start alignment features which are a plane and a circle I use that variable, as it is for the Plane since it's the same surface, and I use it with a "startAlignmentOffset_x-2.5" to make it measure 2.5mm from the surface.
For you, it's similar I would measure something meaningful that DOESN'T move... the granite, or the VBlock, then grab the Z value, set it to a variable like I did, and do the slightly more complicated math to adjust it.

Example:

Using the Granite since that should always be available, knowing the VBlock sits 100mm above the granite, part has a 50mm OD that you use in a Start Alignment - and that OD is set via a Parameter. Start Alignment should be made from a Plane and Circle measured on the part itself.

In the Circle, since this will be setting the Z from 0 you would simply take your Z value from the point, and add 100mm + the radius of the OD.

For the Plane, the Z value would be Whatever the starting Z is of the plane +100+the Radius of the OD. For this plane I would set the strategy to a 3-4 point circle path and have it's diameter also controlled by a variable relative to the OD.

The success of this depends how well versed you are in the alignments and PCM... there may be an easier way but this is likely how I would do it.

[[Mi...]]

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I pictured the wrong orientation, but my method will still work, just not using Z.

Your parts move... you will have to measure SOMETHING that doesn't. A single point on the V Block face opposite the part would be enough to give you something to use as the reference, I can't imagine getting this to work without at least that.

[[Je...]]

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Hey Tony.

Great question. As others have mentioned, what you are attempting is very possible, and there are several ways to achieve it. No, you do not have to have the operators manually measure the fixture during each run, and I agree that this is waste. I think Mike's start alignment pcm strategy looks very promising and perhaps the best option for your particular situation.

On a big-picture process outlook, I prefer to have operators use the Autorun interface and stored alignments. There are several advantages to using autorun and unique measurement plans for each part, one of which is simplicity for operators and avoiding manual probings. You can still utilize PCM to cut down on programming time, but you would need to have a unique base alignment stored for each unique part. The features in the base alignment are populated from actual features on the part, not the fixture.

And yet another method, a cruder method that I do not recommend, is to use the (cnc) alignment to automatically recall a previously measured set of features, such as the fixture, which will allow you to bypass measuring base alignment features. I cringe when I see this method used, because it assumes there is no significant source of variation introduced between the new measurement and the original stored alignment. If your operator places the workpiece in a slightly different orientation than when the fixture was measured, besides the normal risk of collision, there is also increased risk of measurement error.

Bottom line: use features on your workpiece to populate your base alignment when possible and leverage the fact that you use singular static fixturing.

[[Ch...]]

Also if your rotational bolt holes need to be measured, it may be best to come up with a mechanical fixed stop to strive for a fully constrained set-up, etc.

If these are not needed - please disregard - just a TIP.

This situation is precisely what PCM is for.

Good luck.

[[To...]]

How about this?

https://inspectionarsenal.com/inspectio ... oad-chuck/

[[To...]]

This might be something worth looking into.

https://inspectionarsenal.com/inspectio ... oad-chuck/

[[Mi...]]

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Well that's just fancy as hell... wonder if I can convince the bean counters to buy me one...

[[Wo...]]

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In my case, I've looked at the price and already know the answer haha 😉