Help with Start alignment

[[MI...]]

Hello,

I need some help on creating a start alignment. Also wondering if this is similar to a readpoint alignment in PC-DMIS? I want to be able to set my part up and just drive the probe to a circle or an intersection instead of taking manual points every time I set up a new part. Is this possible?

[[Cl...]]

Similar to read point as I remember. Although, the start alignment uses actual measured features. If I have the luxury of a stable well-constructed Poke Yoke fixture, then three points (XYZ) work fine for my start alignment. This simply tells the software the location of the part/fixture in the CMM's space. It also reports to you the offset between the base and start alignments. After you perform the initial start alignment then you select Base Alignment, the name of the base alignment from the drop-down. (NOT THE ONE WITH (CNC) AFTER IT). As long as the fixture/part are always in the same spot, not start alignment needs to be done again.

Start.PNG

[[Ri...]]

I teach users that the Base Alignment can be your Start Alignment.
I have never used a Start Alignment.
The solution, your Base Alignment should be as simple as it can be.
Plain, Line, Point.
Plain, Circle, Line
Plain, Circle, Circle

In cases where fixturing is well established and your part has simple features for an alignment I would use:
Point (Z), Point (X) and Point (Y).
The Base Alignment doesn't have to be DATUMS!
The features can be anything that is easily accessible.

You can use what I have termed as a "CNC Alignment". Using complex features in a CNC Alignment means there is no user incidental contacts with surfaces that could skew an alignment resulting in errant data and or crashes.

The CNC Alignment is my main Datum Structure per the B/P. This is what most users use in there Base Alignments.

Hope this is helpful.

[[Jo...]]

Start alignment can be any feature that has a relationship to the Base alignment geometry. If you were doing a cylinder /plane as the base alignment(2 rotation, 3 translation), maybe the start alignment is a plane on the end and a circle(2 rotation,3 translation), That would be close enough to execute a looped base alignment to whatever degree of stability required. Start alignment is used to allow the machine 'find' the part in measurement volume. If the part is oriented roughly aligned with machine axis, just skip the rotation in Start alignment. Remember, you can always add start alignment later..

There are options like loading a base or fixture alignment. If you have a family of parts that use a common location, it can save work. Autorun utilizes this concept.

[[Je...]]

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This is 100% backwards and incorrect.

Your Base Alignment should be ROBUST. Flimsy Base Alignments are the cause for non-repeating measurements, machine crashes and failing GR&R. Your Start Alignment is used to physically locate the part so that the Base Alignment can be measured in a robust and repeatable fashion. Using Datums is not necessary but the features should be of reasonably repeating geometry with sufficient surface area to utilize the space axis. I typically recommend the primary datums of a component and/or the fixturing/qualifying surfaces utilized in machining/manufacturing. This application is dynamic and proper application is based on experience in that particular industry (injection/machining/casting/forged etc).

The Start Alignment is used to locate a part that may not be located PERFECTLY in a fixture the same way each time. Usually a 3-2-1 alignment or minimal points probing is best using. The Base Alignment should be a full scan of the features used to locate the part in a robust and repeatable manner. This can be as complex as you need it be provided you have adequately located the part with your Start Alignment. Your Base Alignment determines the navigation of all features and base calculation for location in the program unless they specifically utilize a Secondary Alignment in the feature.

The Start Alignment can be then used during the run of each inspection. 100% of all of my production environment inspections include a Start Alignment as they are easier to replicate and do not alter the coordinates of the inspection program feature nominals.

My Start Alignments typically mimic my Base Alignment but utilize fewer points. If I use a standard Plane/Circle/Circle for the Base Alignment, the Start Alignment may be the same 3 features but with minimum points +1 to define that geometry. (4 Probing points for each) I increase search and retract distances based on the machine/part conditions. The Base Alignment will be a robust scan of those features necessary for proper measurement/reporting.

[[Je...]]

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.

I'm glad this is such a low-key topic with zero conflict 🤣

I do agree with with you on this, Jeff. Start alignments reduce the complexity and risk of locating a part via manual probing. Base alignments dial in the workpiece for robust navigation.

Chronology: 1) Start Alignment > 2) Base Alignment > 3) Secondary Alignments

Purpose:

Start alignment: locating workpiece
Base alignment: primarily serves in establishing navigation, secondarily and sparingly used for evaluation
Secondary alignment: primarily for evaluation and can also aid in establishing finer navigation for localized features

.

[[Ri...]]

The great thing about Calypso is that there are a million ways to skin the kitten.

You can write programs that don't even have a Base Alignment that purely run off of Machine Coordinates, and stair-step through a series of Secondary Alignments. I'm not a fan of this, but I've seen use cases where this works well for the customer's application, and it achieved everything that they were wanting the Measurement Plan to accomplish.

I know a lot of people who do not scan in their Base Alignment. There are pros/cons to this.

I know a lot of people who do scan in their Base Alignment and typically use the full DRF. There are pros/cons to this.

What I will say is that whatever you do, it should be stable and robust. I don't agree with flimsy alignments or anything of that sort.

Whatever you do, it should be backed with data that supports in doing what you're doing. Typically this is done with an MSA and possibly a correlation study.

Start Alignments are great if you have a rather complex Base Alignment, and are typically recommended when you don't have a repeatable fixture/part location. It ends up being a time saver because if you had to do a manual Base Alignment and multiple cylinders/planes are involved, it can be time consuming to take a lot more points over-and-over. The most common Start Alignment is a 3-2-1, but it purely depends on your parts and what features you have available to you. You should still choose features that build a robust alignment.

[[Ri...]]

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I'm going to disagree with you and have about 22 years to back it up.
During my first Basic class, we were taught this method.
I have not had a CMM program fail a GR&R or Correlation or any other tests using that method.
This has been used in Aerospace, Medical, Automotive and general use across the US.
🙄

[[Jo...]]

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Also FYI, start alignment can be restricted to MANUAL execution only, and unlike PcDmis, you only need to take minimum required points for feature. Ex. 3 point plane, 3 or 4 point circle etc.. You also have the choice to skip it. I may use a startup alignment the first time I measure the part, and not need it again. It is simply a tool of convenience for me. My goal is to never have an operator drive the machine.

[[Mi...]]

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Going to keep this tangent going because I've had to spend so many hours fighting this mentality.

I am constantly having to fight the methods described above. If a simple alignment is required because you don't trust the loading or whatever, it should be a Start Alignment. The tools for verifying alignments all apply to the Base Alignment... to not use them is crazy. The person I fight with has been programming since before Calypso was Calypso, and learned in a DMIS.... still programs like it DMIS with cascading alignments. No Looping.

Until we were arguing results with our German customer who uses Calypso programmed properly...and uh oh - we were wrong and I had to write a new program from scratch because trying to diagnose what was going wrong in a program with 15 secondary alignments and different features being measured in different coordinate systems was impossible.

Program Calypso the way Zeiss intended - I guarantee you're making your life harder by cascading alignments. Base Alignments should be large, stable, and control all 6 DoF unless you have a very good reason not to. If part loading is a concern Start Alignments can be used possibly in conjunction with PCM controlled points to verify loading.

For production CMMs I have done similar to Jeffery but even more. I adopted a single shared Start Alignment for all programs for a given part number. Generally the Start Alignments are checking similar or even the same features as the Base Alignment, but with points and farther retract/Clearance/Search distances, possibly some PCM to react to different situations like somebody running the wrong part or operation. But then each program has it own complete, looped Base Alignment using whichever features make sense for that operation. I generally, but not always, use the main datums for that operation in the Base Alignment for program efficiency. We often make parts in a family that will be similar to eachother and share fixtures, all of these will also share that same Start Alignment.

I just recently started a new part family that ended up with 44 programs controlled by a single Start Alignment. Meaning after proving out the programs via Simulation and a real machine, I can move all of them to any of our other 33 machines and only have to do 1 manual run to have everything working.

PS Yes I know I could use PCM to make a parametric program that does all the various machining operations in 1.... but QC-CALC sucks and we won't by PiWeb.

Rick, you are doing people a disservice by teaching people that way. I'm a younger programmer who had to attempt to learn from somebody who does that. It's caused nothing but problems. Basically all I learned is what not to do, and Start over, don't attempt to diagnose and fix. Most recently I replaced a program that had over 400 Secondary alignments to a new CAD based one, with less than 10, and most of them aren't actually used other than for programming.

[[Je...]]

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Spot on. That is the entire design intent from the first version of CALYPSO.
The irony of this is topic being debated so often is that there isn't room for debate. There is actually a "right way" and a "wrong way". Any ZEISS training course will reinforce this as it is written right into the Training manuals for our CALYPSO-BASIC course.

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You've misunderstood. This isn't a debate. I'm telling you the right way. Images below directly from CALYPSO-BASIC Training manuals compliments of Ryan Stauffer

[[Ri...]]

Maybe you should read the areas not highlighted.
Not one statement I made is out of line with "basic training".
A simple 3-2-1 base Alignment is ROBUST.

🙄

BaseAlign_Manual1.png

[[MI...]]

Wow thanks for all the useful information! 😮

[[Cl...]]

I haven't read through all the replies, so maybe someone has mentioned
this already? If not, I recommend always looping your base alignment.

baseSystem().valueA<0.0010

[[Je...]]

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This is just a calypso problem. Rick has the perfect way to write measuring programs. I did that since 2003 on PC-DMIS and Quindos. Some other software- solutions have problems with that, too. But they are much cheaper and it´s ok for that.

[[Ri...]]

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I'm glad that I don't have to remember that anymore. 2022+ has it for you.

[[Je...]]

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Have you tried it with Point Sets in RPS or 3D-Best-Fit yet? Proper application of Point Sets in an iterative alignment negates the need to remeasure the feature. The iterative alignment is simply computed from existing data rather than remeasured. Essentially, if you use a set of Point Sets for all features in an RPS or 3D-Best-Fit alignment that has a break-condition, you only need to measure each feature 1 time and the iterations are calculated rather than requiring subsequent measurements.

[[Ri...]]

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Hmm. I haven't tried this yet. I don't typically deal with 3d Best Fits, but I deal with RPS a lot (dang aerospace lol).

I'll give it a shot. Thanks, Jeff.

[[Cl...]]

Thanks Jeffrey. I have not yet used the RPS or 3D-Best-Fit alignments.
Are one or both generally use for non prismatic parts like airfoils, turbine
blades etc?

[[Cl...]]

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What do you mean? Is it done automatically now?

[[Ri...]]

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A standard RPS is just a 3-2-1 alignment, so can be on virtually anything really, but 3d Best Fit is typically used for the cases you stated.

[[Ri...]]

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You just don't have to input the formula now. You have select Delta Value and input the break value you want
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Capture1.PNGCapture.PNG

[[Cl...]]

Awesome, thanks!

[[Ch...]]

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[[Ch...]]

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I mostly agree with Jeff and I don't think any of us would question the great Ryan Stauffer. But since we have a lot of new people listening and watching there is something they need to know.

Teaching new people that Zeiss and the cookbook is always 100% right is just as dangerous as teaching them to use unstable features in the base alignment.

Knowing how to prove your measurements with proper statistics is what we need to be teaching.