Incoming Inspection Details on Drawings 1

[Michael_Michael_Motorcycle]

Currently our engineering detail drawings that we send to vendors to manufacture components, we have the following included under "Inspection".

(1) Visual and dimensional inspection requirements for the vendor making the part
(2) In-house incoming inspection requirements (checking certificate of conformance, measuring certain dimensions, etc)

I am of the opinion that we should not have (2) on our drawings and that information should go on a separate document because only information relevant to the vendor should be on the drawing that goes to the vendor.

There are others in the company that believe (2) should be on the drawing because it is necessary to fully define the part and that as much information relevant to the part as possible should be coalesced into the drawing.

Is there a standard or principle that dictates what the standard operating procedure should be here?

Thank you

 

[udraft]

Statement 1 begs the question, Inspected by who?
Statement 2 attempts to address that.

 

[CWB1]

Is there a standard or principle that dictates what the standard operating procedure should be here?

Yes. Per tradition that became Y14, the design print describes the part, not the manufacturing or inspection process. The inspection plan drives the inspection, not the print. Inspection isnt a fixed activity that can be easily covered by a few notes, it requires formal planning bc the number and type of operations vary inspection-inspection based on the quality of the last batches received and whether the part is new PPAP or existing production.

I recommend removing all inspection notes from all prints bc you're waving a red flag at suppliers.

 

[Michael_Michael_Motorcycle]

CWB1, thanks for the reply. It makes perfect sense, but just for my own understanding, where in Y14 does it indicate "the design print describes the part, not the manufacturing or inspection process"?

 

[CWB1]

The usual quote is Y14.5(1.4)(e) which states "The drawing should define a part without specifying manufacturing methods," but there are other similar references in other sections. There is allowance for manufacturing and inspection details if they're needed to define the part, but not solely for the sake of driving the manufacturing or inspection processes. ie. Calling out parting lines, size/shape of deburring or cleanup grinding, safe areas where hardness testing dimpling or other destructive testing is allowed, etc is fine. Specifying that a hole be reamed or CMM'ed OTOH is not.

 

[3DDave]

In the manufacture of aircraft, specifying reaming is done. It ensures that there are no axial scratches that can become fatigue sites. It is then specified that the hole is drawn to the final size using a specific expansion tool to provide a compressive field to offset tensile loads that can start fatigue cracks.

 

[Michael_Michael_Motorcycle]

How are inspection plans that are separate from drawings usually constructed?

Does each drawing get its own inspection plan document? Or do multiple drawings refer to the same inspection plan document? Some combination of the two?

How does this work with sending inspection plans to vendors? Are there usually separate inspection plans for vendors and for internal use? Or is there one all encompassing inspection plan that gets sent to vendors?

I realize there probably isn't one correct answer. Looking for maybe a resource that lays out general best practices.

 

[3DDave]

The best practice I have come across was from a guy working for a jet engine manufacturer. He said that before a new product was considered for design they got the reps from engineering, manufacturing, procurement, QA, QC, contracts, and everyone else who represented the design around the big table to hash out how they would proceed, with no steps to starting until everyone understood what everyone else needed.

It came up because he had sniped on a CAD board about someone wanting to covert a weldment into a casting and thought that was the most stupid thing ever. I explained that in my company we had part designed as a casting, but the lead time became too long, so management demanded a change to a weldment, until the estimates for the cost of critical x-rays was added in; then they demanded we get a large block of steel and carve it out; until they found out how much a large block of steel would cost and how long it would take to carve all of them. But wait - yes - management then demanded we go with a casting because it was cheaper.

I still recall his sudden astonishment that this could possibly happen. I said I wished I could feel exactly the same as he did, that people would go through all the planning and agree to that plan before starting anything else.

Anyway, that engine company had the best practice I've heard of.

There are a ton of also ran practices.

Have you no inspection department?

 

[Garland23]

How are inspection plans that are separate from drawings usually constructed?

A variation of an inspection plan is a "control plan." That spells out what to be checked, how many times, and any statistical parameters to be monitored. Perhaps do a web search for inspection control plan or similar keywords -- that might give you more info or even a template to follow.