Design for Manufacturability (DFM): Tips for Better CNC Part Outcomes
CNC machining is the backbone of precision manufacturing, where ideas are carved into reality with micron-level accuracy. But the difference between a part that machines like a dream and one that causes unnecessary delays (and headaches) often comes down to Design for Manufacturability, or DFM.
At PE Manufacturing, we’ve seen how good design decisions up front can lead to better performance, lower costs, and faster turnaround times. If you’re designing parts that you plan to have CNC machined, here are some pro tips to help ensure your designs are as production-friendly as they are functional.
1. Stick with Standard Tool Sizes
Sure, custom tooling can machine almost anything, but it often comes with added cost and lead time. Designing holes, radii, and depths that align with standard end mill and drill sizes (e.g., 1/8″, 1/4″, 1/2″) allows for quicker setups and less tool wear. If you’re unsure, we’re always happy to recommend optimal dimensions during the quoting phase.
Bonus Tip:
Avoid inside corners with sharp 90° angles. End mills are round, so include internal radii (typically 0.125″ or larger) to reduce stress concentrations and machining time.
2. Watch Your Tolerances
Tighter tolerances = higher cost. It’s that simple. While CNC machines are incredibly precise, asking for ±0.001” on every feature tells the machinist, “Take your time. Be very careful. Change your tooling every three minutes.”
Instead, assign tight tolerances only to critical features. For everything else, a general tolerance of ±0.005″ usually does the trick and keeps your part affordable.
3. Minimize Deep Cavities and Thin Walls
Deep pockets and thin walls may look sleek on CAD, but in the shop, they often translate to chatter, deflection, and multiple passes, driving up time and cost.
If your part needs a deep feature, try to keep the depth less than 4x the tool diameter. And for thin walls, aim for 0.030″ minimum thickness for metals, and 0.060″ for plastics, unless absolutely necessary.
4. Limit Complex Undercuts
Undercuts add complexity to setups and often require special tools or multi-axis machining. While they’re sometimes unavoidable, consider if an undercut can be redesigned as a stepped feature or broken into a multi-part assembly.
We can help you evaluate whether an undercut is worth the tradeoff or if a simpler alternative will do the job just as well.
5. Design with Fixturing in Mind
If your part needs to be clamped in strange orientations, that means extra setups, more handling, and higher costs. Keep flat surfaces and reference features in your design that make it easy to use fixtures on a mill.
This also improves repeatability and lowers the chances of variation in your final parts.
6. Communicate Surface Finish Requirements Clearly
Want a mirror finish on a prototype face, but only care about functionality everywhere else? Be sure to call that out on your drawing.
Different finishes require different machining processes (and sometimes secondary operations).
If you’re working on a new project and have some questions, let’s talk.
About PE Manufacturing
Located in Clearwater, FL, PE Manufacturing is your local CNC machining and PCB assembly partner. We combine cutting-edge technology with hands-on expertise to deliver precision components on time and on budget.