Inventor Best Practice – Manufacturability

It doesn’t matter if you are creating a design in 2D on paper or in 3D as a virtual prototype, the entire purpose of the design is manufacturing. In this best practice, I’ve highlighted a few ways that you, as a designer, are in nearly complete control of the cost to build the design.
So, how can you, the designer, affect the cost? Here’s some examples or ways to lower the build cost of a design:

  • Design parts out of the least amount of material needed.
  • Always think about the manufacturing process as you design.
    • Reduce the number of manufacturing steps.
    • Remove unnecessary features such as fillets, radii, and chamfers.
    • Reduce the tolerances where every possible.
    • Reduce or remove surface finishes when not needed.
  • Start with standard raw material shapes.
  • Use the least expensive material specification you can.

Those of you with lean manufacturing experience will recognize the items above as waste removal. Waste on many fronts…Waste of Engineering, and Waste of Manufacturing time are the first two that spring to mind. When starting a machine design, ask yourself a few questions:

  • Do you need a high-end, feature riddled design or will a basic, functional design suffice?
  • What are the problems that you are trying to solve?
  • What features add real hard and true value to your product?
  • As a customer, what requirements would you be willing to pay for? Which features wouldn’t affect your user experience, and by extension are not adding value?

Take the problem back to the root cause…sometimes this leads to a very different set of specifications than initially thought of.

My last thought for this best practice…consider the cost of tolerances. Have you every actually tried to hold +/-0.001″ when making something? It’s not really all that difficult given reasonable manufacturing parameters, it just takes care and caution. Two very expensive commodities in the world of manufacturing. Now, I’m not saying that you shouldn’t do high precision, tight tolerance work. I am simply saying think about the tolerances you apply.

Lets consider the manufacturing process for cutting bar stock to length.

  • Tolerance: +/- 1/16″ – Simple process; Measure with a tape measure and start the saw.
  • Tolerance: +/- 0.005″ – First step is to cut the length to +1/16″ same as before, plus then a machining operation. Probably milling, with a setup and care precision to get it to tolerance.
  • Tolerance: +/-0.001″ – The first two steps are the same, as before, except that you must leave the part at the plus side of the tolerance, and this time, set-up a secondary machining operation – possibly grinding, with its own set-up and care and caution to produce the part.

I know we can argue the details of this process over that, but in general terms, the more precision that you, as designer need, the higher the cost to manufacture that part. There are cases where any of these different tolerances are be necessary, but the trick to controlling cost is understand when to apply each.

Give me some feedback, what types of things do you do when working in CAD to cut the manufacturing cost of a design? Are there other best practices you’d like to discuss? Leave your comments below.

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