When it comes to the cost of CNC Machined Parts, the largest variable is machining time. The cost of the machine time can often out weigh the cost of the material and set-up cost. Reducing the machine time is often possible by optimizing the part design through the process of D.F.M. (Design For Manufacturing), resulting in more economical parts with a significant reduction in required lead times.
Below are our top 5 Design Considerations that will help keep the part cost low.
1) Limit the Use of Tight Tolerances
Typically there are only a few features that are critical to the fitment or function of a part, and they should be denoted with an asterisk (*) to signify a feature critical to the function of the part. Our standard tolerance of +/-.005″ will suit 99% of typical consumer parts but we are capable of +/-.001″ on critical features.
2) Utilize Standard Drill Sizes
Using standard drill sizes will help to keep the cost down, non-standard hole sizes typically require being reamed to size or the hole bored to size which in turn adds to the machine time and to the total cost. See Drill Chart on our reference material page
3) Divide Up Complex Parts
In many cases complex parts are significantly cheaper to manufacture if they are designed and machined as separate components and assembled afterward. This is true for parts containing deep pockets or channels that would require additional time to remove the material and at a significantly higher material cost.
4) Radius Internal Corners
A milling machine produces an inside corner radius that is equal to the radius of the tool that is cutting, for example: a 1/2″ Endmill produces a 1/4″ inside corner radius. Smaller corner radius’ typically require several passes with smaller, more fragile Endmills and significantly increase the machine time required. We recommend optimizing the inside corner raduis’ 3:1 (depth : diameter of the Endmill) for example: using a 1/2″ endmill, a 1.5″ depth is possible and will produce a 1/4″ corner radius.
5) Material Selection
Typically softer materials are cheaper to machine than harder materials for several reasons
- Softer materials cut more easily, which results in less machine time
- Harder materials require slower feed rates and require much more expensive tool that are more likely to break or wear out
If materials like Delrin or Aluminum are too soft for your project try a 1018 Mild Steel, or if corrosion resistance is a concern try using 303 Stainless Steel