The CNC machining process is widely used to produce custom machined parts with muscular strength and tight tolerance. It is a fast and cost-efficiently way to manufacture prototypes and production parts. An optimized designed CNC machined part will serve to accelerate production time while saving cost.
To fully optimize your design and save cost for CNC machining parts, you should look at the below design tips:
1. Round the Internal Corners
CNC machining tools – such as an end mill or milling cutter – will leave rounded inside corners. The corner radius can be reduced by using a smaller diameter machining tool, but it requires both a smaller tool to machine away material and more passes – often at a slower speed to reduce the risk of deflection or tool breakage – Resulting in more machining time.
So we would suggest adding an inside corner radius of at least 1/3 of the depth of the cavity and use the same radius in all internal edges. This helps eliminate tool changes, which add complexity and can increase run time significantly.
2. Avoid Deep Cavities
End mill cutting tools have limited cutting length, they typically work best when cutting cavities with a depth of up to 2-3 times their diameter. To minimize cost. We suggest limiting the depth of the cavity to the 4X diameter of the tool to ensure good results. Anything greater than that will improve the cost, as special tooling or multi-axis CNC systems are required.
If larger cavity depth is required, consider designing parts with a variable cavity depth.
3. Increasing the thickness of Thin Walls
CNC parts with thin walls have a tendency to chatter, which slows down machining speed. They can also cause distortion, which is difficult to machine them accurately. The result can be additional machine time and cost.
If you do not sure about your dimension, contact us freely. Our engineer will give you a professional answer and suggestion.
4. Optimize the depth of Tapped Holes
Regarding the tapped holes, increasing the length of thread in a hole does little to hold the belt tighter. It’s really just the first two or three turns that do everything that the work. Going deeper just increases the likelihood of tap breakage and adds time to the tapping operation.
So we don’t suggest threading a hold to more than 3 times the hole’s diameters. Normally, the thread length would be from 1.5X to 3X of the hole’s diameter.
5. Limit Use of Tight Tolerances
Typically, only a few surfaces of a part are essential to its function. More features with tight tolerance, the more expensive a part to be
Manufactured. Because it increases the machining time and cost.
So we would suggest only assign tight tolerance on some critical features and surfaces. Other less significant features should be controlled by standard tolerance of ±0.10mm, which is sufficient for those features.
6. Reduce Small Features
Small features such as micro-deep-holes (less than 2.5mm in diameter) will increase the machining difficulty and machining time, thus should be prevented unless absolutely necessary.
7. Split up Complex Parts
Machining multiple simple parts are less costly than machining one complex divide. Especially for parts with deep pockets, which would require hours of machining time to remove material, plus additional material costs. And most shops will charge a premium for more complicated parts. This is because if a mistake occurs it is costlier to redo a composite part than it is to redo a simple one.
So we would suggest splitting up the intricate parts into some simple parts and assemble them together if possible.
8. Design holes with Standard Size
Holes can be CNC machined fast and with great accuracy using standard drill tooling. It won’t need end mills or reamers to finish the hole size to a non-standard dimension. This will help reduce machine time and lower the cost. Also, limit the depth of all holes to 4 times their diameter.
Contact us if you aren’t familiar with customary drill tooling sizes. And do not hesitate to let us know if any machined parts project needed to be quoted from our CNC machining service.
