MET33800ManufacturingProcesses
Chapter27
WorkholdingDevicesfor
MachineTools
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Chapter 27 - 1
Workholding Devices
Introduction
Workholding device locates work in machine tool with
respect to the cutting tool.
Critical for repeatability.
Trend toward flexibility: family
of parts and manufacturing cells.
Primary functions:
Locating
Clamping
Chapter 27 - 2
INTRODUCTION
Fixture Specialized workholding device that holds
workpiece during machining or assembly operations and
establishes size dimensions.
Jig A special type of fixture that, through built-in
features, determines both location and size dimensions
that are produced by machining or fastening operations.
Chapter 27 - 3
1
INTRODUCTION
Fixture size Jig location and size
Chapter 27 - 4
FIXTURE DESIGN
Chapter 27 - 5
FIXTURE DESIGN
Chapter 27 - 6
2
FIXTURE DESIGN
1. Locating function is to orient and position workpiece in
the machine tool:
Provides positive location for the 12 degrees of
location freedom:
o Linear: X, Y, Z
o Rotational: A, B, C
Location by 321 principle
Chapter 27 - 7
3-2-1 FIXTURE DESIGN
3Points
2 Points
1Points
Chapter 27 - 8
FIXTURE DESIGN
1. Locating (continued):
Repeatability: fool proofing.
Low profile: clear cutting path.
Chapter 27 - 9
3
FIXTURE DESIGN
1. Locating (continued):
Cutting forces: press part
into locators.
Accommodation: allowing
workpiece variance.
Chapter 27 - 10
FIXTURE DESIGN
Chapter 27 - 11
FIXTURE DESIGN
2. Clamping Function to hold and/or maintain location:
Adequate: balance strength & deflection.
Reliability: repeatable clamping forces.
Clamping forces: toward locators.
Loading/Unloading time: dependent on clamp type.
Chapter 27 - 12
4
FIXTURE DESIGN
3. Other Design Factors:
Chip disposal and removal: heat
and interference concerns.
Ruggedness
Construction ease
Ergonomics and safety
Flexibility
Chapter 27 - 13
JIG DESIGN
4. Additional Jig Functions:
Location - position geometric shapes with respect to
each other.
Size - size of geometric shapes.
Dimension control.
Examples:
Drill jig
Welding jig.
Chapter 27 - 14
JIG DESIGN
Drill Bushings:
Press Fit
Slip Fit
Chapter 27 - 15
5
TYPES of JIGS
Plate jig - plate w/drill bushings and locating pins,
clamped to part.
Channel jig - part in open side, locate on outside of part.
Ring jig - for end/surface of round parts.
Diameter jig - for cylindrical surfaces.
Leaf jig - hinged leaf or cover.
Box jig - boxlike construction, tumble.
Assembly jig - welding or riveting, open frame typically.
Chapter 27 - 16
TYPES of JIGS
Chapter 27 - 17
TYPES of JIGS
Chapter 27 - 18
6
TYPES of FIXTURES
Fixtures categories include:
Vises
Lathe chucks and collets
Faceplate fixtures
Milling and grinding fixtures
Modular fixtures
Chapter 27 - 19
TYPES of FIXTURES
Chapter 27 - 20
TYPES of FIXTURES
Chapter 27 - 21
7
TYPES of FIXTURES
Chapter 27 - 22
TYPES of FIXTURES
Example of a Lathe
Faceplate Fixture
Chapter 27 - 23
TYPES of FIXTURES
Example of
Multiple Parts on
Single Fixture
Chapter 27 - 24
8
MODULAR FIXTURES
Modular fixtures
provide versatility
and adaptable to
different workpieces.
Chapter 27 - 25
MODULAR FIXTURES
Chapter 27 - 26
MODULAR FIXTURES
Chapter 27 - 27
9
MODULAR FIXTURES
Chapter 27 - 28
MODULAR FIXTURES
Chapter 27 - 29
ASSEMBLY FIXTURES
Chapter 27 - 30
10
MASTER (GROUP) FIXTURES
Used for part families:
Group Technology (GT) concept.
Chapter 27 - 31
MASTER (GROUP) FIXTURES
Chapter 27 - 32
CLAMPING
Chapter 27 - 33
11
CLAMPING
Chapter 27 - 34
CLAMPING
Fixture types which used other clamping methods:
Magnetic chucks - ferromagnetic materials only.
Electrostatic chucks - conductive materials only.
Vacuum chucks.
Chapter 27 - 35
CLAMPING
Chapter 27 - 36
12
CLAMPING
Permanent-
Magnetic Chucks
Chapter 27 - 37
CLAMPING
Electro-Magnetic
Chucks
Chapter 27 - 38
CLAMPING
Chapter 27 - 39
13
ECONOMICS of FIXTURES
Chapter 27 - 40
ECONOMICS of FIXTURES
Chapter 27 - 41
FIXTURING EXAMPLE
Chapter 27 - 42
14
FIXTURING EXAMPLE
Chapter 27 - 43
TheEnd SeeOncourseforVideos
Chapter 27 - 44
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