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Writer's pictureOzark DesignWorks

Design for CNC Machining: Part 6 - Reducing Tooling Count, Free Corner Radii, Sharp Edges/Deburring

Updated: Jul 20, 2022



Part 6 - Reducing Tooling Count, Free Corner Radii, Sharp Edges/Deburring


In Part 1, I talked about how dimensioning with common stock sizes in mind can reduce costs and save time. In Part 2, I talked about how the shape of the finished part can impact costs. In Part 3, I talked about lowering costs by thinking about inside corner radii and depth during the design process. In Part 4, I talked about the importance of designing to minimize distortion and warping. In Part 5, I talked about holes and tapping depths.


Best Practice #10: Reduce tool requirements.


A part with M4, M5, M6, and M8 holes requires the machinist to load 4 taps and 4 drills into the machine. Changing the model to all M6 and M8 threaded holes would reduce setup time, programming time, cycle time, etc.


Best Practice #11: Consider both cost and user experience with corners and edges.


In these days of sophisticated CAM programming, some design rules are outdated. These three versions of this part below will be quoted the exact same. In fact, your machinist may likely add a tiny radius to the first one just to avoid hand deburring sharp edges. An operator in your facility handling these parts all day would much prefer the free radii.



These 3 versions below may have a different cost, but it can depend on the note(s) on the drawing. A large min/max tolerance on the chamfer or radius can allow the machinist to use tooling that he is familiar with and may not increase the cost much, if any. The better shops out there will likely deburr most of the edges on the machine anyway with a chamfer tool (as opposed to hand deburring).


Note: Personally, for parts I machine myself, I like to add a R0.062 radius to the top of all my parts. This cutter has a permanent spot in my tool changer. I would not increase the cost due to this radius. But if it was a R2.0mm radius, toleranced so that my R0.062 tool would not work, then you might see $50 (or more) added to the quote (tool programming and setup cost, possibly a special tool purchase required).







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