CNC Machining, QA/QC, And the World of Good Enough
Quote:
Originally Posted by
26 Inf
I would agree that Eugene Stoner and everyone else that had a hand in developing the AR and the final TDP for our battle rifle strove to eliminate tolerance stacking. The weapon was designed to be mass produced with no final hand fitting of parts required.
Your statement - companies that produce their own parts shouldn't experience it, and companies that use "bin parts" from another vendor most certainly will - flies against the basic concept of mass production and the TDP. In an ideal system the parts flow into the assembly line just in time to be installed.
Generally those parts are manufactured by vendors with machines set up to manufacture those parts in high volume. Efficiency in production and cost is achieved by this small number of vendors specializing in the production of a greater number of the part than one individual manufacturer needs. Those shops should be more set up to ensure that tooling remains within spec as well as ensuring the raw material is as specified.
As an example of this I would invite you to run around Wichita, Kansas, and check out all the machine and instrumentation shops that exist along the periphery of the aircraft manufacturer's facilities.
In closing, do any of the AR producers make ALL their own parts?
I'm well aware of manufacturing processes and JIT. If a part is designed with tolerances that will work with other parts, and those parts are in spec, then tolerance stacking should not occur. It's when you get companies using parts--the manufacture of which they have no control over--from vendors, that you start seeing that.
The company I work for, we make everything but the coil steel the products are made from. Whether that steel is used for a product that is rolled, formed, stamped, welded, or machined...we are in control of its design and manufacture. That includes the engineering and design where the tolerances are spec'd. Therefore, if parts are in spec, they won't stack.
My Division, which I am the manager of, has over 32,000 active part numbers. If we have issues with any of them, they are NCR'd back upstream.
On the occasion we use vendor stuff, it is still designed and spec'd by us.
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