
Design for Machining Toolkit
Get in-depth design advice to optimise your plastic parts for CNC machining. Designing with machining in mind can accelerate production time and reduce production costs
Optimising Part Design for Machining
There are many design elements involved when creating plastic and metal parts for CNC machining — design for cost, design for quality, design for assembly, design for manufacturability. And navigating that landscape can be challenging at times. At Protolabs, we provide automated design analysis on CAD models that highlights features in your part design that can be adjusted for manufacturability. It’s a great design resource to have at your fingertips. To keep those manufacturability advisories at a minimum and optimise your part design, we created this helpful kit of different CNC machining resources.
Designing for Machined Parts
→ Tolerances
→ Holes
→ Deep Features
→ Threads and Inserts
→ Text
→ Radii
Navigating Critical Machining Advisories
→ Material Left Behind
→ Thin Walls
→ Holes That Can Be Threaded
→ Part Too Large

Designing for Machinability
CNC machining has been around for decades, and for good reason. It’s one the fastest manufacturing technologies for prototypes and end-use parts. Want to learn how you can optimise your product development cycles with CNC machining? This white paper shares how to design for the subtractive manufacturing process, select the best material for your application, and streamline new product development.
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Notes:
* Try adding steps to buttresses to stiffen your design.
Watch out for deep, narrow pockets, or part features situated alongside tall walls. Cutter or workpiece vibration could cause deflection, and a loss of accuracy or surface finish.
** Generally, radius is a good thing – fillets spread loads well, sharp corners can act as stress raisers and can initiate fatigue cracks.
We deburr every part, but if you are considering adding external radii to improve cosmetic and handling, for CNC a 45° chamfer is quicker to cut and so much more cost effective.
Remember for CNC:
- Internal corners – Fillet/Radii
- External corners – Chamfer
Any part that requires square corners will cost you heavily, as the only way to produce them is to burn them out with Electro-discharge machining (EDM) or cut slowly with extremely small tools.
Navigating Critical Machining Advisories

Part Too Large
Maximum extents refers to the raw material and machining envelope. Depending on part geometry and fixturing/clamping requirements the maximum part size may be slightly smaller. For every upload we will analyse and provide feedback.
Find out the max extents for each, individual, material we stock at Protolabs.
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Enhanced Machining Capabilities with Our Digital Network
Get anodising, tighter tolerances, and volume pricing options through our network of manufacturing partners powered by Hubs. You'll find plating (black oxide, nickel), anodising (Type II, Type III), and chromate coating at scale; tolerances down to ±0.020mm; and cost-efficient machined parts at higher volume.
Try Digital Network at Hubs