CIMtech Mfg. Inc.

CNC machining

Manufacturing consulting.

Manufacturing outsourcing.

Manufacturing Design Tips

If possible, deep milling to a shoulder should be avoided.

Average cutting length of an end mill is 2 ½ times the diameter.

Extra long end mills are available, having a cutting length of 4 times the diameter.

However, cutting performance is much slower and tooling costs are a lot higher.

Due to cost and availability, parts should be designed to accommodate standard inch size tooling wherever possible.

eg. If the pocket containing 7mm radius- 1.2” end mill can be used.

Features can not be machined easily

Features can be machined with one tool/one set up

Tapping Bind Holes

Typically tap drill in a blind hole should be drilled 1 ½ to 2 times drill the diameter deeper, then required full tap depth to clear chips.

Roll Tapping

Number of tools

Designers should be aware of how many different tools will be necessary to make the part.

Try to minimize the number of required tools in part design.

Anodizing

Anodizing adds 8-12 microns per side.Hand anodizing adds 35-40 microns

(unspecified)However up to 75 microns can be added by specifying it.

Solid model is unanodized part.

In early prototyping part can be machined directly from solidmodel without need to create part drawings by adding key specifications annotations on model

TYPICAL HORIZONTAL CNC MILL

80% OF MANUFACTURING COSTS ARE DECIDED IN DESIGN

- Statement from Boeing Aerospace

MAXIMUM COST REDUCTION ACHIEVED ON 3244 MACHINE AFTER DESIGN IS APPROXIMATELY 20%

- provided by: Dave Pires, Project Engineer

Mark Ward, Production Manager

Cost of Tolerances +/- 0.100mm

Finishing cuts = 1 Inspection frequency increased to 20-30%

sampling.

+/- 0.050mmFinishing cuts = 1Inspection frequency increased to 50-75% sampling.

Cost of Tolerances +/- 0.025mm and +/- 0.010mm

Finishing cuts = 2Inspection frequency increased to 100% to maintain this dimension.

Contributing factors:Clamping pressure; fixturing; spring cutting; cutter selection; feeds and speeds; and relation to other tolerances.

Cost of Tolerances +/- 0.002mm

Finishing cuts = 3Inspection frequency increased to 100% to maintain this dimension

Cost goes 2-3 times higher (+/- 010mm)

Contributing factors:Clamping pressure; fixturing; spring cutting; cutter selection; feeds and speeds; and relation to other tolerances.

Cost of Tolerances

5 4 3 2 1 +/- 0.1mm +/- 0.050mm +/- 0.25mm +/- 0.010mm +/- 0.005mm

This design reduces number of tools required to machine part.