Trimming the Inspection Report - Deciding which are the CTF dimensions


Starting to get Involved
Hello Guys,

In our Organisation, Designer gives the Inprocess Inspection report along with Part drawing. In that, all the dimensions will be mentioned (Both critical & Non-Critical to Function dimensions). But during Manufacturing it is difficult to Inspect all those dimension for about 50 parts. So, I'm planning to trim the Inpection Report by mentioning only CTF parts.

But how can a process engineer decide which are the CTF dimensions. Are there any Guidelines ??

MAchine used is CNC.

Thanks .


Looking for Reality
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But how can a process engineer decide which are the CTF dimensions. Are there any Guidelines ??

Formal, standard guidelines...probably not.

Logical approaches, sure.

Whether part of your sales function, Quality function, separate contract review function, or some other need to consider:

1. What have you contractually agreed to do?
2. What is the risk of NOT measuring a particular dimension or dimension type? (To both your company, and risk to the customer)
3. How does the customer use the do you know whether the dimension is or is not related to Form, Fit, Function?

If you understand the larger picture around what the part is for, and not just "it should be this shape/size", you can make some educated conclusions regarding the importance and potential risk involved with reducing testing burden and cost.

After that...what is the likelihood that a given dimension will be out of acceptable range?
If you run a 50pc batch in line...can checking first and last part give nearly full confidence on 50% of the dimensions?


Starting to get Involved
Thanks Ninja for Reply.

We are not selling the parts. We use the parts to assemble our Machine.

Since we use different settings to conduct CNC operation, we are not able to rely on First sample inspection. But i guess, we can control some dimensions in CNC programming. How to detect which are those dimensions that are controlled in CNC ?? If we can control the dimension in Programming then there is no need of Inspecting right ??
If the parts are used in your assembly, some of the inspection and verification will be determined by the function. "Hey Joe, this doesn't fit...". If the fit and function is good, that is an inspection process. As for the CNC , we do a first pc inspection of each part as validation that the programming is correct. This is done every time the part is run, whether we make 20 or 200, just to verify we are using the correct program and revision level.
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