Validating a Product through Tool Control and Tool Inspections

[Marcia L]

Can anyone provide information for developing a process to accept product characteristics based on tool control/tool inspections? I've been asked to take on this initiative in an attempt to reduce in-process inspections.

Here is some information about our operation that may be useful in formulating your reply. We are a small machining facility preforming CNC milling and turning operations. Our products (Aerospace Cases & Rings) are very large and quite complex. They normally consist of anywhere from 100-300 dimensional characteristics. We usually perform about 5-10 operations on each part. Our run time for one operation can be as much as 1-3 days (2 Shifts).

 

[Bev D]

Well, this isn't easy.
First your SQE and the requirements are going to have to be satisfied. The things you make can be very catastrophic (for the passengers, the engine manufacturer, the airplane manufacturer and the airline - I'm assuming you are making aircraft parts) so indirect 'validation' of critical dimensions is difficult to get approved. Especially when the tooling isn't the only cause of nonconforming features and dimensions.
It can be done but we will need to understand a bit more about the part(s), how they are manufactured adn what you mean by tooling control and tooling inspections.

 

[Marcia L]

Thanks for the reply. What I have been asked to do is implement a process where a characteristic can be accepted based on tool size or based on the results of another characteristic within the same tool path. For example, accepting hole diameters produced with a CNC program by inspecting the drill size before and after a series of holes have been drilled rather than inspecting each hole (tool size) or accepting a milled height because another height in the same tool path of a CNC program has been inspected and found acceptable (tool Path).

One thing to keep in mind is that I am only referring to in-process inspection, meaning that all risk falls on my employer, as all finished parts are 100% inspected on all characteristics (either by CMM or Plate) prior to release to our customers.

 

[Mikishots]

Especially when the tooling isn't the only cause of nonconforming features and dimensions.

Exactly right.

 

[Marcia L]

I understand that there are other risks that must be considered, however, I was hoping there may be someone in our group who could offer some guidance on an approach to developing such a process. To me it seems that the likely starting place would be to assure that an adequate tool inspection occurs upon receipt, then a tool life study involving both the hole size and tool size to determine the tool inspection frequency. Then what?