Understanding base alignment

[[Jo...]]

I've attended Calypso Basic and even made a few programs at our shop, but for some reason my brain struggles to understand base alignment. Using CAD models I was able to "accidentally" make an alignment for my programs, but I don't understand them.

I had to make a manual program with no CAD model today and my base alignment did not work.

I was working with a hollow gear blank with an internal keyway, so I only have a few flat surfaces to work with, its a big cylinder. I don't really know what spatial or planar rotation means, or which axis to choose afterwards.

If someone could dumb this down for me or point me to a good explanation, I'd really appreciate it.

[[Er...]]

https://www.qualitymag.com/articles/851 ... -alignment

This is a good link about the basics of a CMM alignment. The Spatial defines how the part is on the machine spatially. The Planar is rotation, or how the part is clocked. After that, you set your X,Y, and Z origins. If I had more time I would go further in detail. I'm sure one of these CMM guru's will spell it out better than I do. I hope this helps.

[[Ja...]]

Unless your part is symmetrical (like a pin or something), you're going to want to contrain all 6 degrees of freedom - that would be (3) translations and (3) rotations. In regards to Base Alignment, think "Level, Rotate, Originate." Your spatial (leveling) feature should be big, like a large plane or axis. This tells Calypso how you're orienting the part on the granite. Your planar (rotational/clocking) feature can be another plane, point or axis - I prefer to clock to a point. Then, you want to set your X/Y/Z origin. Again, I prefer a bore's center point, or a point derived from intersections. What matters most is that your Base Alignment uses high-quality, well-defined feature so that it's repeatable. Oh, and the alignment can be made from whatever you choose. Sometimes your datums make an excellent Base, sometimes they don't - datums are for satisfying print callouts, and most people get hung up on that.

[[Je...]]

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Josh,

Thanks for sharing about this. Don't feel bad if understanding alignments seems frustrating. It is both the most important and one of the more difficult concepts to grasp in Calypso. The "ah-hah" moment usually comes when you realize that alignments are meant to constrain degrees of freedom.

Sooner or later the "I got the alignment to work, but I don't understand how it works" will develop into "I understand which degrees of freedom my alignment is constraining and which (if any) it is not constraining." Then, you can work towards becoming the Calypso guru that can even utilize the "special" button in the alignment window to create offsets and other fancy stuff 👩‍🏫


One often overlooked aspect to alignments in Calypso:

1. Base alignments are meant PRIMARILY for NAVIGATION and only SECONDARILY for EVALUATION.

2. Secondary alignments (sometimes referred to as part alignments) are meant PRIMARILY for EVALUATION but can also be used to further refine navigation.

I can provide specific examples of this if necessary. In any case, be encouraged because you want to understand this stuff and not simply "make it work." That's the difference between a competent programmer and a button-pusher.


Jeff Frodermann
Meier Tool & Engineering
Anoka, Minnesota
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[[Ia...]]

If you're working with no CAD, the easiest way to learn (IMO) is to set up the part on the CMM they way you want to inspect it, then open up the base alignment tab. Don't click anything, but probe the primary datum (or whatever feature you feel is most important for alignment). After probing, click ok on the feature tab for the feature you just created. It will automatically input that feature into the necessary section in the base alignment. If it is a plane facing upwards, it will automatically put that plane in the "Z" and in the spatial of the BA. Then do your secondary and tertiary datum the same way, and they will auto update as well, as long as you have the BA window open.

You still need to clean up the nominals after the fact, but it is a good way of learning the Calypso's alignment system.

[[Ow...]]

Josh,
Everybody above has provided great examples and instructions.
I'll add a video link that the guy does a decent job of putting it into layman's terms. I think he uses a basic model when creating the alignment but, you get the concept needed either way.

As you get started, don't ever feel inferior or afraid to ask questions. I've been using Calypso off and on for around 15 years and just when I think I know all there is to know, I find myself coming here to ask questions to this day 🙄.

https://www.youtube.com/watch?v=DR_nzuWWxok

[[Ri...]]

When I create Base Alignments I use features that ease the creation of the Base Alignment.
I don't care if they aren't the datums, or if they aren't related to any datums.
I use Base Alignments only for two reasons.
1. To establish the part and clearance planes within the volumetric area of the CMM.
2. To ease the creation of Base Alignments.

After the Base Alignment I create Datum Features.
Then I create a "CNC Alignment X_X_X (IE: A_B_C etc..)
From this point on no feature is measured against any feature from the Base Alignment.

Attached is a sample program with a sample sat model (Zeiss Cube model) in ZIP format.

Base and CNC Alignment example.zip

[[Jo...]]

Thank you everyone, this was all really helpful. I'll bookmark this for future reference.

As a follow up question, what is the purpose of creating secondary alignments within a measurement plan? Many programs that I run have multiple alignments within the characteristics.

[[SH...]]

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Calypso working with can may must rule. If you understand this rule half of your problems are solved. A feature can constrain a degrees of freedom then it must. This is happens in automatic selection for BA.
Secondary alignment are very buseful in advanced programming. Usually big part can have more than one DRF, in this scenario you have to use secondary alignment. It can be used for creating section in the cad model.

[[No...]]

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Imagine a part like in the video Owen linked above (plate with bores), but with the bore pattern rotated by an angle and you need to measure the distances under that angle. Then the easiest way is to create a secondary alignment just for these measurements..

[[Da...]]

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There are things that a base alignment is for and there are thing a base alignment cannot do:

• A base alignment is the calculational basis for every other element of your measurement plan. The base alignment must be as stable as possible in order for your measurement plan to give you reproducible results
• The base alignment should only be used to locate your part, so that your results are not too dependent on it. Maybe you want or need to change your base alignment without having to change all of your features
• If you decide to use ISO 5459 as your way of calculating your coordinate systems, be aware that the ISO 5459 setting will NEVER be used for your base alignment. The most accurate way of calculating your datum systems according to both ISO or ASME can never be achieved when you keep using the base alignment for all your features.

I personally have never used the base alignment for any characteristics except in very simple plans, where the accuracy of the datum systems are not of importance.

[[Ri...]]

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Ease of programming.
I attach Alignments to features all the time, doing so can make creating other related features simple. I program strictly to absolute Nominal and vectors in all of my programs. By using alignments necessary for Characteristic reporting in your features your nominals and vectors are more likely to be 100% precise.
The more precise your program is the more precise your results will be.

[[Er...]]

Lots of good responses.

When I started Calypso I was hung up on making Datum ABC my alignment. On some parts this is fine. On others it is a headache.

An example is three tooling balls in a vehicle alignment that will need to be mirrored. I find it easier to set the tooling balls in a standard alignment with one ball as X0,Y0,Z0.
Then use a secondary alignment of 3D Best Fit to enter the coordinates of each tooling ball.

Another is I had to measure a split tube. My Base Alignment was a cylinder and a point so I could accurately measure the diameter and roundness.

As always, there are usually a dozen different ways, just find ones that make sense to you.

Looping the Base Alignment is a must for me.

[[Te...]]

Here is my 6°'s of freedom handout I use for training might help you understand what is going on.

Calypso and the 6 degrees of Freedom Rev 02.pdf