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CNC Machining Design Guidelines
CNC machining via the Firstcut machining process produces functional parts from solid blocks of real plastic and aluminium. 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 process uses CNC mills capable of producing parts within an approximate 254mm by 177mm by 95mm deep envelope. The maximum depth that can milled from either side of the part is 50mm.
Parts smaller than 6.0mm by 6.0mm by 6.0mm 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 0.5mm. The spacing between characters on raised text should be 0.5mm 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
Unlike injection moulding, CNC machining can produce very thick walls without sink or warp and there is no requirement that wall thicknesses be uniform.
Walls thinner than 0.5mm typically do not survive the machining process.
Tolerances of +/- 0.1mm are expected and generally achieved. There is no provision within the Firstcut process to tweak any dimensions.
The Firstcut Process | Rapid Prototyping Process | Design Guidelines | Material Selection Guide | Frequently Asked Questions | Case Studies | Firstcut Client Testimonials | Machining Tips e-Newsletter | Journal Magazine | CNC Machined Part Glossary
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