Chapter 15 Flashcards Preview

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Flashcards in Chapter 15 Deck (16)
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1
Q

Name the three material removal processes

A

Machining - sharp cutting tool

Abrasive process - Hard abrasive particles like grinding

Nontraditional process - Energy forms

2
Q

Benefits of Machining (3)

A

Screw threads

Accurate round holes

Very straight edges and surfaces

3
Q

Disadvantages of machining (2)

A

Wasteful of material

Time consuming relative to another shaping process

4
Q

Explain turning. What moves what does it form

A

Single point cutting tool

rotate workpiece to form a cylindrical shape. Move tool.

5
Q

Explain drilling. What moves what does it form

A

Rotate toolpiece. Move tool.

Creates round holes with two cutting edges

6
Q

Explain milling. What moves what does it form

A

Rotate multiple-cutting-edge tool. Move piece.

Cut a plane or straight face.

7
Q

Explain single-point tools vs multiple cutting edge tools.

A

One dominant edge. Point rounded to form a nose.

More than one cutting edge.

8
Q

Describe the three dimensions of machining.

State the Material removal rate formula Rmr

A

Cutting speed v - Primary motion

Feed f - secondary motion

Depth of cut d - penetration of tool below work surface

Rmr = v f d

9
Q

Roughing vs finishing

A

Roughing - High feeds and depths; low speed

Finishing - Low feeds and depths; high cutting speed

10
Q

State the three functions in machining

A

Holds workpart
Positions tool relative to work
Provides power at determined speed, feed, and depth

11
Q

State the Chip thickness ration r

A

r = to / tc

to - depth of cut
tc - chip thickness
Ratio always less than 1

12
Q

State the four basic types of chips (3)

A

Discontinuous - Brittle work. Low cutting speed. Large feed and depth of cut. High tool-chip friction

Continuous - Ductile. High cutting speed. Small f and d. Low tool-chip friction

Continuous with Built-up edge - Ductile. Low to med v. Tool-chip friction causes portions of chip to adhere to rake face. Built-up edge forms and breaks off cyclically

Serrated - Difficult-to-machine metals. High cutting speed. Cyclical chip forms with alternating high shear strain then low shear strain.

13
Q

State the merchant equation for minimizing the energy thru shear plane angle phi. What does it say? (3)

A

phi = 45 + alpha/2 - beta/2

Phi is angle from surface to chip shear plane.
Alpha is orthogonal angle to tool face.
Beta is orthogonal angle b/w resultant force of tool to face of chip.

In order to increase shear plane angle increase rake angle and/or reduce the friction angle (reduce coefficient of friction).

Larger shear angle, smaller shear plane which lowers shear force, cutting forces, power, and temp

14
Q

State the Power to perform machining formula

A
Pc = Fc v
HPc = Fc v / 33,000

Pc - cutting power
Fc - cutting force
v - cutting speed

15
Q

Problems with high cutting temp (3)

A

Reduce tool life

Produce hot chips = safety hazard

Cause inaccuracies from thermal expansion of work material

16
Q

Cutting temp formula

A

T = (0.4 U)/ (p C) (v to/K)^0.333

T = temp rise
U = spec energy
v = cutting speed
to = depth of cut
pC = volumetric specific heat of work material
K = thermal diffusivity of work material