DRAGON INNOVATION, INC. !

DESIGN  FOR  MANUFACTURING  !

COURSE 8: PART 1 - MACHINING (CNC) !!!!!!

SCOTT N. MILLER | CEO | @DRAGONINNOVATE | WWW.DRAGONINNOVATION.COM

•Overview •Process •Part Design •Materials

AGENDA

Machining (CNC) Overview

Typical Machined Parts

• Precision Gears

• Fittings

• Drive Components

Machining Advantages

• Wide range of materials available. • Does not require uniform wall thickness. Can create

geometry not possible with injection molding. • Does not require tooling. • Ability to make changes quickly. • Repeatable and precise.

Machining Disadvantages

• Depending on geometry, can result in long cycle times. • Limitations on possible geometry (i.e. no hollow vessels). • Subtractive process can be wasteful • Requires clamping area which can restrict the design.

Machining Process

Overview

• Subtractive process (i.e. wasteful) • Tools: Lathe (H/V), Mill (H/V), Drill, Grind • Process: Material or cutting tool moves • Machines hold both tool and workpiece, and provide

relative motion between the two. • Rough and Finish Cuts • Cost driven by material, time, tools, overhead,

maintenance. • Tolerances

– Easy: > 0.01” – Medium: >0.002” – Expensive: >0.0005”

Lathe

• Used to create features around an axis of revolution.

• Material Rotates

• Processes

– Turning

– Facing

– Boring

– External Threading

– Cut-Off

Lathe

https://www.youtube.com/watch?v=MwgobIVj4fU

Mill

• Process

– Horizontal Surfacing

– Vertical Surfacing

– Form Cutting / Pocketing

– Slotting

– Straddle

– Angular

– Drilling

Mill

Drill

• Process

– Center Drill

– Drill (typ L <= 5D)

– Ream

– Spot Face

– Tap

Grinding

• Surface Grinding

• Plunge Grinding

https://www.youtube.com/watch?v=sesxx-­‐U_0FU

Machining Part Design

Design Guidelines• Pre-shape (near net shape) to reduce time and waste. • Use COTS components manufactured in high volume. • Select materials that are easy to machine. • Use only one machine / tool if possible. • Avoid re-chucking to create concentric features. • Design component so machining is only required on

exposed surfaces when gripped. • External diameters should increase. • Internal diameters should decrease. • Avoid drilling holes in long slender components. • Avoid tool interference with component • Avoid thin, flat components that are difficult to grip. • Avoid blind, curved holes.

Reference: Product Design for Manufacture and Assembly. Geoffrey Boothroyd,, Peter Dewhurst and Winston Knight.

Materials

• Steel • Stainless • Aluminum • Titanium • Copper

Common Materials

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