MProcesses Notes 3

7/29/2019 MProcesses Notes 3

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Tools

Manufacturing

Processes


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Outline

Types of ToolsTool Geometry

Cutting FluidsEffectsTypes

Tool WearForms

CausesFailure ModesCritical Parameters

Horsepower UsedOperating Temperature

Feed and Speed

Tool Life


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Types of Tools


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Tool Geometry

Single Point Tools

Multiple Point Tools

Chip Breakers

Effects of Material on Design


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Single Point Tools


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Multiple Point Tools


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Chip Breakers


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Important Tool

Properties- High hardness- Resistance to abrasion, wear and

chipping of the cutting edge

- High toughness/impact strength- High hardness at high

temperatures- Resistance to bulk deformation

- Chemical stability (does not reactor bond strongly with the workmaterial

- High modulus of elasticity(stiffness)

- Consistent tool life

- Proper geometry and surface finish


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Tool Materials

- Carbon and medium-alloysteels

- High-speed steels- Cast-cobalt alloys

- Carbides

- Coated tools- Alumina-based ceramics

- Cubic boron nitride

- Silicon-nitride-base ceramics

- Diamond

- Whisker-reinforced materials


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Cutting Speeds of

Tool Materials


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Cutting Fluids

Effects

- coolant

- lubricant

- flushes chips

- reduces oxidation of heated

surfacesTypes

- cutting oils

- emulsified oils

- chemical fluids


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Cutting Fluid

ApplicationFlooding

- 3 gallons per minute per tool

Misting

- atomized fluids

- a health hazard (OSHA limit =.2 mg/m3)

High Pressure Systems

- often applied through the tool


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Tool Wear

Forms

- crater wear

- flank wear

- chipping

Causes

- abrasion- adhesion

- diffusion

- plastic deformation


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Crater Wear and

Flank Wear

Crater wear

Flank wear


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Failure Modes

Fracture

Temperature Failure

Gradual Wear


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Critical Parameters

Horsepower Used

Operating Temperature


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Horsepower Used

MaterialBrinell

Hardness

Unit Horsepower

hpu hp/(in3/min)

Carbon

Steels

150-200 0.6

201-250 0.8

251-300 1.0

Cast

Irons

125-175 0.4

175-250 0.6

Aluminum 50-100 0.25

Values of Unit Horsepower for

Various Work Materials


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Operating Temperature


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Feed and Speed

Speed the rate at which thetool point moves as it rotates

(in a lathe, the rate at whichthe cutting point on theworkpiece rotates)

Feed the rate at which the toolis fed into/along the workpiece


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Feed and Speed

V = DN/12V = surface cutting speed (ft/min)

D = diameter of rotating object (in.)

N = rotation rate (RPM)


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Feed and speed

Example: Assume a high-speed steel saw with 100teeth and a diameter of 6 inches is used to cutaluminum. Determine the proper RPM and feedrate.

V (HSS, aluminum) = 550-1000 ft/min [in table]N = 12V/(D) = 12(550-1000)/(6)= 350-637 RPM

Feed (aluminum, saw) = .006-.01 in/tooth [in table]

(.006-.01)100 teeth = .6-1in(.6-1)350 RPM = 210-350 in/min

Start with the lowest values. They can be increasedso long as the finish is acceptable.


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Tool Life

F. W. Taylor, 1907Taylor Tool Life Equation

vTn= CvTn= C(Tn)

ref


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Cutting Performance

How do we know if cuttingparameters are optimal?

1. Surface finish

2. Tool wear

3. Chip shape

4. Sound

5. Cutting time

6. Heat


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Summary

Tools fail slowly with gradual wear or suddenly withfracture

Cutting fluids help reduce the effects of wear and

temperature failure

The materials of the tool and the workpiece affect thetool shape and life

Higher cutting speeds increase the operating

temperature and decrease tool life

It is necessary to calculate proper feed and speed toprevent excessive tool wear

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u/2650/
http://www.mime.eng.utoledo.edu/people/faculty/imarinescu/2650/http://www.mime.eng.utoledo.edu/people/faculty/imarinescu/2650/http://www.mime.eng.utoledo.edu/people/faculty/imarinescu/2650/http://www.mime.eng.utoledo.edu/people/faculty/imarinescu/2650/


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The End

Documents

MProcesses Notes 3