Total Runout

[[Ma...]]

Good afternoon,

My team and I are having a discrepancy with a customer regarding the evaluation of a total runout of .0005 (imperial). We are not privy to the way our customer is evaluating their piece only that their results vary as much as .001(imperial) from ours. Below is a run down of how the features are being evaluated as well as our evaluation of the runout characteristic. I have attached a small snippet of the drawing containing the related features for this characteristic. If there is anything we are missing, or input that may help us confirm our execution of this measurement it would be greatly appreciated. Thanks in advance for any information you can provide to me and my team.

.3777 Bore : Cylinder measurement with 4 equidistant circle paths

Y: Two circle paths on the plane

X: Cylinder with two circle paths

All features are measured with standard speed, point density and filters/outliers per cookbook recommendations

I am currently using Calypso 2016 with Vast XXT sensor

To evaluate the total runout feature, we are using cumulative radial runout with "thru" as the feature, the primary datum being X and inside that feature we are constraining the Datum X datum to Y.

runout snip.png

[[Ri...]]

Welp this is another great case of your primary datum not being sufficient enough to be a primary datum.

The axis line for Datum X is too short to be measured as a cylinder that is then used as a primary datum - especially when comparing it to the length of your feature's axis.

Have you tried measuring Datum X as a circle instead of a cylinder? This would force the software to use Datum Y as your spatial rotation for the evaluation.

If you are set on measuring Datum X as a cylinder, you should look into constraining it to Datum Y.

You can also do some testing where you flip the feature and the datum around - this will show you how unstable your datum is.

[[Je...]]

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Mark,

I echo what Richard mentioned about Datum X being too short in depth.
This is irrelevant, but which nasty designer designates X & Y letters as datums 😮 ??

If allowable, Y should be the primary datum, and X should be constrained to Y. This way, Datum Y (it just feels wrong to say! 🤣 ) constrains two degrees of rotation, and if necessary, translation along Datum Y's axis. Datum X (I'm gonna bust a gasket before I finish this 😡 ) constrains two degrees of translation and is constrained in its rotation to be perpendicular to Datum Y . There are a few different ways to constrain Datum X to Datum Y in Calypso.

Make sure that you and your customer are using Calypso's total runout characteristic. If they are using a dial-indicator setup, they need to also include a way to sweep the indicator parallel to Datum X's axis. The full indicator movement along the inspected feature's axis is the total runout. Needless to say, total runout is an expensive setup via manual indicators and is much more capably handled on a CMM. And of course the result of total runout will almost always be greater than circular runout.

Also, check the flatness of Datum Y. In a very similar situation I inspected, we discovered that the features represented as Datum Y and X in your drawing were being clamped too tightly in the machinist's vise, which distorted the planar datum.

There's a lot more to evaluate between your setup and your customer's setup (alignment of software programming, fixturing and inspection hardware), but I would start with the Datum setup.
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[[To...]]

Since you can only select one datum feature in a runout, the only way I see of doing this is creating a Perpendicular Construction of Circle X (Feature 1) and Plane Y (Feature 2). This creates a 3D line centered on Circle X and perpendicular to Plane Y. Use this construction as your datum feature in a total runout.

[[Ma...]]

Can it be done like that?

• you make geometric alignment from plane Y
• create theoretical 3d line or cylinder with alignment from previous step
• callout cylinder 10 to theoretical cylinder

[[Ma...]]

Thank you for the input. As you mentioned I can only input one datum on a run-out so the way I went about that is I constrained X to Y with this method in the attached image. I'm truly not sure if this is best practice, but I was under the impression it satisfied the drawing and that my issue may be more in part to the axis of X being so short.


I will try a perpendicular with a circle for X to the Y plane as Tom suggested to see if my results can match those provided by our end customer. I'll also try to test the stability of the datum by flipping them around as Jeff mentioned. With the length of the Axis of X not being as robust as I'd prefer I can see how using a circle measured on X, perpendicular to the Y plane to create the axis may add some stability to the measurement. I also am glad to hear that I'm not the only one who was a little disgusted by the datum's being X and Y. 😡

runout snipp.png

[[Jo...]]

With tolerances like these, I would disclose the Datum feature's form. The Datum using O.T.E could also be an issue if they are checking with indicator.

[[Ma...]]

So I tried Tom's suggestion to compare results and came up with almost identical findings. The difference was .00002 from my original method. I also tried to flip the datum's and the results were slightly better but still violating the tolerance. I ran the same part a total of 10x while loading and unloading the piece from the fixture the results of all 3 methods maintained within .00005 I was able to get in touch with an applications engineer from Zeiss who confirmed that the evaluation of the runout was executed the way they would recommend. It's a weird situation where the customer says the sample parts we sent are good, but stubborn me is hesitant to put my stamp of approval on something that I feel violates the tolerance. At the end of the day they're paying us so I should just move forward and into the next project. Thank you guys again for taking the time to offer suggestions. I've said it a few times but the active folks on this forum have been critical in my growth as a CMM programmer.

[[Ri...]]

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Mark,

I'd love to help you out. Feel free to reach out directly via PM, and maybe we can review the measurement plan, and if needed, be a 3rd party sanity check.

Thanks.