Designing parts for CNC routing - 10 tips that save money and rework
Practical design-for-manufacture rules for acrylic, HDPE and polycarbonate parts run on 3-axis routers.
Most CNC routing quotes come back high because the part is hard to make, not because the factory is greedy. Tweak the design with these ten rules and watch the price drop.
1. Specify the cutter, not the corner
Inside corners can't be sharper than the radius of the smallest practical end mill (typically 3 mm). Adding 3 mm fillets to every inside corner removes a tool change and a slow finishing pass.
2. Keep wall thickness above 2× material thickness
Thin walls vibrate, chatter and need slow feeds. Beef up internal webs and rib structures wherever the design allows.
3. Tab parts that float
Small parts that get cut free mid-program become projectiles. Specify 2–3 small bridge tabs and a manual snap-off - you save the factory the cost of a hold-down fixture.
4–10 - quick rules
Avoid laser-cut edges if the part will be flame-polished - laser leaves stresses that crack. Spec hole sizes that match standard drill bits (M4, M5, M6 clearance). Send a STEP file, not a PDF. Confirm the layer for cut vs engrave. Mark the 'good face' clearly. Provide a chamfer on screw holes if the part is countersunk. And include a written quantity range - pricing changes step-wise.