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Fixture Design Basics 210

Workholding Training

Class Information

Tooling U classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and typically requires at least two hours of instruction time.

Class Name:	Fixture Design Basics 210
Description:	This class identifies the major factors to consider when beginning the design of a customized fixture. Includes an Interactive Lab.
Prerequisites:	100200 100106
Difficulty:	Intermediate
Number of Lessons:	15

Class Outline
Objectives Design Criteria for Fixtures The Base Plate Supporting Principles Support Components Locating Principles Locating Components Clamping Principles Clamping Components Power Clamping Standard Workholding Components Tolerance Considerations Lot Size Nonproductive Time Summary

Class Objectives

Describe the design criteria for a workholding device.
Describe the base plate.
Identify the principles of support.
Describe support on a plate fixture.
Describe locating on a plate fixture.
Describe locating components.
Describe clamping on a plate fixture.
Describe clamping components.
Describe power clamping.
Identify the benefits of standard workholding components.
Identify the required tolerance in a workholding device.
Describe the impact of lot size on fixture design.
Describe nonproductive time.

Class Vocabulary
3-2-1 method	An effective method for locating a rectangular workpiece. Three datum points support the workpiece, two datum points locate a flat workpiece surface, and a single datum point locates a second surface perpedicular to the previous surface.
base plate	A precisely ground plate that acts as the foundation of a fixture. Various components, such as locators and clamps, are fastened to the base plate.
clamping	The appropriate forces used to hold a workpiece against the locators during the machining operation.
external locating	The use of external surfaces to locate a workpiece. The 3-2-1 method is an external locating method.
fixture	A customized workholding device used on machine tools to position and hold a part during various machining operations. A fixture is built to hold a specific part design.
ground	Machined with an abrasive to achieve highly accurate measurements.
hydraulic power	Power created by water or fluid pressure.
inspection fixture	A fixture used to hold a workpiece while it is being examined. Inspections usually involve comparing workpieces with desired measurements for accuracy.
internal locating	The use of internal surfaces to locate a workpiece. The most common internal locating method is the use of a round and relieved pin to locate two machined holes.
locating	The accurate positioning of the workpiece in a horizontal plane to establish a relationship between the workpiece and cutting tool.
locating pin	An assembled locating device that can be used to locate either an outside workpiece surface or an interior hole. Locating pins are available in numerous shapes and sizes.
lot size	The number of parts created during the use of a particular tooling setup.
nonproductive time	Time that is spent without the machine in operation producing chips. Nonproductive time includes setup time, changing of parts, equipment failure, etc.
plate fixture	A fixture consisting of assembled components such as a base plate, locating pins, rest buttons, clamps, etc.
pneumatic power	Power created by air pressure.
power clamping	A clamping system that converts hydraulic or pneumatic power into mechanical clamping forces.
relieved pin	A locating pin with a diamond-shaped head that is used to position a workpiece in only two opposite directions. Relieved locators are most often used with an internal locating pin.
rest button	A short locating pin that is used to both support and locate a workpiece.
setup time	Time that is spent setting up the fixture, calculating tool offsets, and performing all the necessary tasks to produce the first accurate part.
strap clamp	A type of clamp that reaches over the workpiece to hold it in place. Strap clamps are often used when extra toughness is required.
supporting	The process of locating from underneath the workpiece. Supports generally restrict motion down along the Z-axis.
toe clamp	A type of low-profile clamp with a serrated surface that reaches forward and down to grip the workpiece on its edge.
toggle clamp	A type of clamp that operates on a pivot and lever system. Toggle clamps have a limited clamping range.
tolerance	An unwanted but acceptable deviation from the specified dimension.
tool steel	A specialized type of alloy steel that has excellent strength, toughness, and wear resistance. Tool steels are used in cutting tools, punches, and other industrial tooling.
workholding device	A device used to support, locate, and hold a workpiece during machining. The workholding device accurately references the tool performing the operation on the part being held.