Rules for Nesting

Nesting for CNC router
When nesting parts for a CNC router, there are numerous considerations; surface area for successful vacuum of parts, size of end mill and the force it applies to the sheet when cutting, the density of the parts, is the material flat?

Surface area:
For a CNC router to be successful, the vacuum must hold the pieces in place, ensuring they do not move during the cutting process. Your vacuum pump is a high determining factor for the amount of surface area required to successful cut your pieces. The more you cut through te material, the more you diminish your vacuum performance.

End Mill size:
A rule of thump; a 1/8” endmill will cut 1/8” depth per pass. The same can be said for a ½” end mill will cut ½” depth per pass. The ½” endmill has a 16x greater cutting area then a 1/8 endmill, this the force applied to the material is much greater. Considering the force factor on the material with cutting on a vacuum CNC router, one must make a judgement call to find the balance between speed and reliability. High density parts (small surface area) tent to be cut with smaller end mills while a large part can be cut with a large end mill as the surface area is greater, thus a greater force from an endmill can be applied to the part.

How flat is your material:
Once of the greatest battles when operating a CNC router is, how flat is the material. If your material had a natural curve, you have now introduced a new force that is fighting against the vacuum pressure of the CNC bed. If a material is curvy but 1/8 thick, the vacuum pressure is typically strong enough to fight the delaminating pressure of the material. If you have a piece of 1” plywood with a curve it in, it is highly unlikely you will successful vacuum the sheet and a mechanical fastening system is required.