CNC Machining Design Guidelines
CNC machining via the Firstcut machining process produces functional parts from solid blocks of real plastic and aluminum. Read on to learn more.
Unlike additive processes that can create geometries of almost unimaginable (and, unfortunately, un-manufacturable) complexity, subtractive rapid prototyping is limited to shapes that can be cut out of a block of solid material using CNC milling machines.
At this point in time the Firstcut prototype process uses CNC mills capable of producing parts within an approximate 10 in. by 7 in. by 3.75 in. deep envelope. The maximum depth that can milled from either side of the part is 2 in.
Parts smaller than 0.25 in. by 0.25 in. by 0.25 in. are (really) hard to hold on to while machining.
The Firstcut process is currently limited to 3-axis milling from 6 perpendicular sides. We mill from one side and rotate the part 90 degrees or 180 degrees as necessary to mill as many features as possible. Your quote will highlight any features that cannot be machined.
Sharp inside corners on a part will be radiused as a natural result of the CNC milling process. Your quote will highlight areas where these radii will occur.
Very small features, particularly if they are deep, may not be machinable. Recessed text should have a minimum stroke width of 0.020 in. The spacing between characters on raised text should be 0.020 in. or greater. Your quote will identify any issues with small features.
Firstcut now offers threaded holes. Additional information including supported thread diameters and pitches is available here:
Threaded Holes Information
Threaded Holes Maximum Reach
Demo FirstQuote/Threaded Holes
Unlike injection molding, CNC machining can produce very thick walls without sink or warp and there is no requirement that wall thicknesses be uniform.
Walls thinner than 0.020 in. typically do not survive the machining process.
Tolerances of +/- 0.005 in. are expected and generally achieved. There is no provision within the Firstcut process to tweak any dimensions.
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