MEC222 Machining Chip

What is Machining

A material removal process where a cutting tool removes material from a workpiece using a machine tool.

What is the purpose of machining in manufacturing?

TO give parts their final shape, dimensions, surface finish, and special geometric features.

What are the main machining operations?

• Turning

• Drilling

• Milling

What are some other machining operations?

• Shaping

• Planing

• Broaching

• Sawing

What machine tool is used for turning?

Lathe

What machine tool is used for drilling

Drill Press

What machine tool is used for milling

Milling Machine

What does a drill press do?

Creates round holes in a workpiece using a drill bit

What is boring

enlarging an existing large hole

What is a single-point cutting tool?

A cutting tool with one main cutting edge (used in turning).

What is a multiple-cutting-edge-tool?

A tool with multiple cutting edges that rotates (used in drilling and milling).

What are the three main cutting parameters in machining?

• cutting speed (v)

• Feed (f)

• Depth of cut (d)

What is formula for material removal rate (MRR)

MRR = v x f x d

What is roughing

Removing large amounts of material quickly.

• high feed

• large depth of cut

• low speed

What is finishing?

A machining step to achieve precise dimensions and smooth surfaces.

• low feed

• small depth of cut

• high speed

What is Chip formation

the cutting tool shears material from the workpiece, forming chips

What is the shear plane?

The plane where the material shears to form a chip.

What is the formula for chip thickness ratio?

Is chip thickness ratio greater or less than 1?

Less than 1 because the chip thickens during cutting.

What is this formula and what can this be used for

Shear strain formula, can be solved from the geometry

What conditions produce discontinuous chips?

• Brittle Materials

• Low cutting speed

• High friction

What conditions produce continuous chips?

• Ductile Materials

• High cutting speed

• Sharp tool

• Low friction

What is Built-Up-Edge (BUE)

When chip material sticks to the tool rake face and periodically breaks off.

What are serrated chips?

Semi-continuous chips with a saw-tooth patten formed at high cutting speeds.

What two forces can be directly measured during machining

• Cutting force Fc

• Thrust force Ft

What forces cannot be directly measured during machining?

• Friction Force F

• Normal force N

• Shear force Fs

• Normal shear force Fn

What is the formula for Friction coefficient?

What is Merchant’s shear angle equation?

alpha = rake angle

What is the cutting power formula?

Pc = Fcv

What is the cutting horse power formula?

What percentage of machining energy becomes heat?

About 98%

Why are cutting temperatures important?

• Reduce tool life

• Create safety hazards

• Cause dimensional inaccuracies