ORIENTATION

[[Zo...]]

This has been a thorn in my side from day one: Clearance groups, orientation of origin, references.
I program CNC machines, and had been for decades, XYZ axis are easy to use and understand, but in Calypso, things are a bit different, or more complex rather. Opened a program I had used in the past, with no problem, but today, after I did manual alignment, it recognizes the XYZ gnomes, but the feature measurements seem to 180 degrees off. On the screenshots the yellow path shows the probe's programmed path and the red arrow shows the probe moving upward in an arc move, which is how I intended it, but in reality, on the pictures the actual probe touches the part on the opposite side, and starts moving in a downward direction, following the same arc movement-but in the wrong way. I don't know how and why it had changed it's reference, worse yet, I don't know what exactly is changed because the blue arrow clearly points up, in the "Z+" direction.
Naturally, I get error messages that the "Z+" clearance plane cannot be approached from "Z-" clrnce plane, choose another clearance group, and a few other suggestions.

I just calibrated the master probe to the sphere and even that shows upside down...see picture below

I don't know what is affecting the reference. This is Not the first time it happened, I had deleted programs and wrote new ones before because of the same reason, but it's time to understand it but Calypso doesn't seem to be helpful, or rather I cannot find the right information.
Any help is appreciated.

Capture- 3 JPG.JPGIMG_7503.JPGIMG_7502.JPGCapture2.JPGCapture1.JPG

[[Ün...]]

Can you share screenshots of BA.

[[Cl...]]

The Base Alignment should be something like this: The face (plane) with the 5 holes would be
Spatial X+. The ID of the nut as YZ zero and the hole at 12 o'clock for planar Z+. Plane again
as X+ origin. That probe facing X- should have a CP of X+. Make sure your base alignment is
in the same orientation (direction) as machine coordinates (same XYZ directions).

[[Zo...]]

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BA.JPG

[[Zo...]]

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I have neglected to mention that I am checking the part before the 5 holes get milled in, so there is no planar rotation.
I also have to have the hex feature pointed to the right, so I can use the proper probe (a number 3 stylus) to check the crescent feature on the front face, on the left side of the part

[[Cl...]]

Probe a line on each of the four angled planes on the nut (12:00 & 6:00). intersect each
set of lines for two points. One will be Z+ the other Z-. Construct a 3d line from those
two points and use that line for the planar.

[[Da...]]

The base alignment looks fine. Click 'Execute Run Now', but before that: Resources > Utilities > Set Base Alignment to Zero

[[Cl...]]

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It still needs a planar rotation.

[[Ma...]]

In those cases where you want to be sure in planar orientation i often use start alignment. Just using table, fixture and part to get some point. Then you can omit planar in BA.
Then you can run it without start alignment until BA got screwed up again.

[[Zo...]]

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This part is one of many of the similar part family, I think I have close to 25 or 30 of these round parts, and they all require planar rotation when the 5 or 6 holes get put in, but they run without planar rotation, since they are circular parts, so when I check them before, just for the turning work ,no "clocking" is needed. This one also ran fine without planar rotation in the past, but stg got changed, somewhere, and I do not have a clue what

[[Ma...]]

You can recall machine alignment - then make theoretical 3d line with machine alignment - now you should have bulletproof planar 😃

[[Je...]]

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Hi Zoltan!

First of all, thanks for sharing about your frustrations here. It's understandable to feel this way when the alignment inverts unexpectedly.

This is a problem I ran into often in my early days of learning Calypso. There are more than a few times when I had to get up and walk away from the CMM and stress eat from the vending machines in our factory 😂 .

There are a few common causes of why base alignments invert after manual execution. I'll list a few causes, but first let me offer a workflow that I've adopted that nearly eliminates the inversion problem.

I program 90% from CAD, but even when I don't this workflow seems to be effective:

1. I always create my base alignment first and then assign probing strategies to the base alignment features.

2. Then, I create a simple start alignment. This specifies the x-y-z origins of the workpiece without defining spatial rotation (level) or planar rotation (skew). There are only two types of start alignments that I use: (1) three points or (2) a circle and one point.

3. I manually run the start alignment and then allow the CMM to automatically run my base alignment.

This minimizes unintentional inversion of the alignment because the main cause for the problem is probing in a way that defines the reference geometry in a different orientation than its actual orientation. The CMM thinks the workpiece is upside down due to how it was probed.

A few common causes of the alignment getting "flipped":

- manually probing a line in the opposite vector that it was originally described (left to right instead of right to left, etc.)
- Cylinder depth vs. diameter issues and not enough manual probing points to clarify the feature's space axis
- Cones.
-Flipped the drop-down menu for planar rotation (rotation in space) for the base alignment.
-a CAD entity used in the base alignment was extracted opposite its normal vector (rare)
-When all else fails, blame second shift or the new employee or an opposing political affiliation

Also, I wish someone had described the CMM's coordinate system when I started programming, so to pay it forward for future forum guests:

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Good luck, and keep us posted on how things resolve with this.


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[[Zo...]]

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Thank you for that, but quit frankly, after using this machine for nearly 4 years, I still don`t get the concept (or the need) for a start alignment. I get the base alignment, but struggling with the start alignment. Again, I use the 3 axis system in CNC programming, and I am very good at that, but Calypso is a different animal...

[[Cl...]]

Start alignment tells the machine (software) where the part is.

[[Zo...]]

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I thought that was the base alignment that located the part. What is the difference then between start and base? I've been using base alignment all this time to tell the machine where the part is located. Why is there a need for both? I am sure there is a logical reason, at least I hope...

[[Cl...]]

You can use the base for the start, but I like to keep it simple and have a 3 point (XYZ) or a circle and a point type start
alignment. Depending on the complexity of base alignment it can save you some time. Especially if there are probe changes involved. When done initially It gives you the offset between the two in XYZ. It simply locates the part in the volume of the CMM.

[[Ün...]]

I usually use 2D lines in these types of pieces, this controls the rotation. [attachment=0]Capture.PNG[/attachment]

Capture.PNG

[[Da...]]

You should generally set "Set base alignment to zero" under Resources/Utilities AND the same setting in the base alignment window.

That prevents the base alignment from flipping 180°.

[[DW...]]

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Bold emphasis mine.

Wanted to jump in here and really, really advise against this practice of using a single circle to clock rotation. Ideally, a perpendicular plane is best. In a pinch, a 3d line recalled from two aligned circles and projected to a plane would be better than a single circle. As noted, the part has large planes for spatial orientation in either the +X or -X directions. The nut has multiple perpendicular planes to those large faces. I would place a small level on the indicated surface and level it in Y and measure that plane with 4 points, using it as a rotational lock in +Z. From experience, a program using a circle to clock rotation gives bad measurements and will cause the guys on the floor to be chasing good numbers from bad data.

InkedIMG_7503.jpg

[[DW...]]

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Bold emphasis mine.

This needs to be highlighted, and is often the source of so much anger and frustration when beginning to program.

[[Je...]]

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.

Hey Zoltan. Great question.

You're correct that the base alignment is the official definition of where the workpiece is located and how it is oriented in the cmm's work volume.

The purpose of a start alignment is to provide a simple way to manually probe the workpiece that assists the base alignment in finding the workpiece.

Using a start alignment can minimize the chance of incorrect calculation of the base alignment. This is because incorrect locating, such as the kind you are encountering here that inverts the base alignment trihedron, often involves how the features used for spatial rotation (aka level) and planar rotation (aka skew, rotation lock, clocking, etc.) are manually probed.

A start alignment can also be a great way to allow operators/leads to manually probe the first part in an inspection run of multiple parts. It can also save the cmm programmer time over needing to manually probe every feature in the base alignment.

The one caveat is that the workpiece does need decent fixturing and needs to be oriented fairly close to its intended clocking/skew, because the start alignment is only establishing location (in best practice).


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[[Je...]]

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Devin, thank you for mentioning this idea and providing a cool graphic that explains your concern.

I respectfully disagree with the overall concern, but in the example you showed in the picture I can see where the circle feature would cause a problem due to its relationship to the level feature. In that particular instance, I agree that a 3D line would be a better choice for establishing planar rotation.

I have often found a single circle section to be a great way to establish rotational constraint of the workpiece. This especially true when the axis [edited: I should have used "centerpoint" instead of axis per Devin's correct point about circle geometry] of the circle feature is parallel to the axis of the feature establishing spatial rotation. This is assuming that the base alignment is run in cnc mode and not probed manually. Also, make sure that the circle strategy has at least four points, ideally more, and that the probe is not shanking out on the workpiece.

The reason for errant measurements may relate to the fact that base alignments are meant to establish navigation of the workpiece and only secondarily assist in evaluation of characteristics. I agree with your concern that errant measurements that be produced when the cartesian coordinate system from the base alignment is not set up properly,

[[DW...]]

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Greetings sir.

Here's the problem. A circle has no axis. Visually eye balling one of these circles and saying, "Yup, she's all lined up in Z" is not the correct way of performing a measurement. Can it get you close? Yup, I've seen it. Is it correct - nope. Does it cause problems for the guys on the floor who are trying to make sure one face is perpendicular to another face and are chasing their tails because someone used a single circle in a threaded hole pattern to clock rotation in +Z? Yup, I've seen that too.

If I open a program and see someone used a circle to clock rotation, when there are perpendicular planes available I immediately know the person who created the program does not grasp the basics of constraining degrees of freedom.

This is meant respectfully, can we get the forum heavy weights to chime in?

[[Je...]]

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THIS!

I also second the notion of recalling a 3d-Line from cmm_System. I have also advised on constructing a 3d-line from recalling individual probing point features from a fixture (or granite) when the part is not constrained about the X or Y axis (human nature - usually Y). Applying this ensures the part alignment never "flips". The "flip" is usually associated with probing of features in an improper order.

Additionally, some may experience navigation issues when probing OD cylindrical surfaces with 180° scans where the stylus attempts to navigate UNDER the part to go -X > +X or vice versa. To circumvent this, set your strategy to start at 5° and scan length of 170°. On the next scan path, make an inverse scan with start angle at 175° and a length of -170°. Continue this pattern along the feature as needed. This ensures the stylus navigates along the cylinder axis path from one scan to the next rather than go over (or under) the part to the next scan within the strategy.

Mr Frodermans advisement of a Start Alignment is SPOT ON. A Start Alignment can be CNC or Manual and can be as simple as a single probing point used to establish a single axis location. This is a highly under utilized utility in CALYPSO and its use should be explored by more programmers as it improves Base Alignment measurement (reduces looping iterations) and reduces time required of operators to "touch off" on parts that aren't fixtured 100% repeatably. The simple addition of a Start Alignment to inspection plans would go a long way in preventing improper BA measurements and machine crashes.

I strongly encourage everyone to explore the use of Start Alignments in your production runs. Your operators (and purchasing departments) will thank you.

[[Je...]]

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Devin, you are 100% correct. A circle has no axis. I should have used the word "centerpoint." My understanding is that when Calypso uses a circle section for for constraining rotation in space it calculates a line from the origin constrained normal to the spatial rotation feature and then rotates the base alignment to this line. In a way, it's like using a 3D line as a planar rotation feature without actually creating one.

I can definitely see where manually probing a bore or shaft for a circle feature used to constrain rotation could be problematic. I'm sure the type of workpiece (machined surface, die casting, plastic) would also be a consideration. The method you described is probably more error-proof for manual probing, especially when done by operators and others with less experience on a cmm.