Saturday, February 25, 2012

Motion-Economy Device Design - Important Devices

These devices improve the efficiency of manual operations.

Important Motion-Economy Devices

Watson and Wise, industrial engineers of Mine Safety Appliances Company mentioned the following as worthy of mention in a list of important motion-economy devices.

1. Holding, positioning, and assembly fixtures

Quick-acting clamps
Ball-joint or swivel fixtures
Hinged joints
Air-cylinder devices
Rotary fixture

2. Hoppers and motion-economy bins

3. Chutes and other drop-delivery methods

4. Removable table tops for planned workplaces

5. Foot pedals for


6. Special devices for indirect–labor operations.


A stop is a device for locating material at some predetermined position so that work can be performed while it is so located.

Quick-acting Clamps

These clams provide an efficient method of holding parts in positions for a wide variety of operations.

Ball-joint or Swivel Fixtures

This has a work table attached to a ball joint. In many assembly operations, work needs to be performed on the sub assemblies and main assembly at various angles and positions. A swivel or ball-joint may be used by the fitter or assembler to mount the assembly on it and enable the operator turn the fixture at will at any position at any time and use his both hands for working.

Hinged Fixtures

This fixture allows the operator to work one side of the part for some time and then turn over the part using the hinge and then work on the other side.

Air-Cylinder Devices

Air cylinders are used in machining, forming, and assembly operations. They are available in a wide range of sizes and types, and engineers can use them ingeniously for many applications.

Air cylinders are also used instead of arbor presses, foot presses, or bench-type punch presses for performing a wide variety of operations such holding, swaging, upsetting, riveting, and forming.

Rotary-Assembly Fixtures

In these fixtures there is a rotating table on which number of work pieces are mounted and each turn of the table brings a work piece to the operator. The operator completes his job and turns the table so that the next work piece comes to him. Another helper can now remove the finished work piece and load a new job.

Hopper and Motion-Economy Bins

A hopper is a storage device for either raw material or a component of an assembly, so designed that it delivers the material t be used at a selected point within the normal grasp area of the operator.

Chutes and Other Drop Delivery Methods

Chutes and drop delivery methods facilitate deliver of the finished work piece to the next conveyor belt or a storage bin.

Removable Table Tops

They provide specially fitted assembly table tops for two or three different assemblies that an operator may be working in a day. They can be removed and kept in a rack and the different top can be put on the work bench.

Foot Pedals

The use of foot-operated mechanisms provides an economical method of holding, releasing, or assembling in various types of operations.


J.P. Watson and D.N. Wise, “Motion-Economy-Device Design”, in Industrial Engineering Handbook, Second Edition, H.B. Maynard (Editor-in-Chief), McGraw-Hill, pp. 2-87  to 2-103.

Originally posted in motion-economy-device-design-important-devices Knol No. 68

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