Unit iii. automated assemby systems

Rajarambapu Institute of Technology, Rajaramnagar

Department of Mechanical Engineering

Industrial Automation & Robotics

UNIT IV


Automated Assembly Systems

The term automated assembly refers to the use of mechanized and automated

devices to perform the various assembly tasks in an assembly line or cell.

As with transfer lines discussed earlier, automated assembly systems are also the

examples of fixed automation. Most assembly systems are designed to perform a

fixed sequence of assembly steps on a specific product. Automated assembly

technology should be considered when the following conditions exist:

• High product demand

• Stable product design

• Assembly consists of no more than a limited number of components:

• The product is designed for automated assembly


Automated Assembly Systems

Automated assembly systems involve a significant capital expense,

although the investments are generally less than for automated transfer

lines. The reasons for this are:

1. Work units produced on automated assembly systems are usually

smaller than those made on transfer line.

2. Assembly operations do not have the large mechanical force and

power requirements of processing operations such as machining.

Accordingly, in comparing automated assembly system and transfer

line both having the same number of stations, the assembly system

tend to be smaller in physical size. This usually reduces the cost of the

system.


Fundamentals of Automated Assembly Systems

A typical automated system consists of following subsystems:

1. One or more workstations where assembly steps are

accomplished.

2. Parts feeding devices that delivers individual components

to the workstations, and

3. A work handling system for assembled entity.


Fundamentals of Automated Assembly Systems

Control functions required in automated assembly machines are the same

as in the automated processing lines discussed earlier:

1. sequence control

2. safety monitoring

3. quality control.

The issue of instantaneous control and memory control is relevant in multi-

station automated assembly systems.


System Configurations

Automated assembly systems can be classified according to

physical configuration. The principal configurations, illustrated

here are:

1. In-line assembly machines

2. Dial type assembly machines

3. Carousal assembly system, and

4. Single station assembly machine.



Automated assembly systems can be classified according to physical

configuration. The principal configurations, illustrated here are:

1. In-line assembly machines



2. Dial type assembly machines



3. Carousal type assembly machines



4. Single Station assembly machines




Parts Delivery at Workstations

In each of the configurations described above, a workstation accomplishes one or

both of the tasks

1. A part is delivered to the assembly workhead and added to the existing base

part in front of the workhead (in the case of the first workstation in the system,

the base part is often deposited into the work carrier), and

2. A fastening or joining operation is performed at the station in which parts

added at the workstation or at previous workstations are permanently attached

to the existing base part. In the case of single station assembly system, these

tasks are carried out multiple times at single station. For task (1), a means of

delivering the parts to the assembly workhead must be designed.

The parts delivery system typically consists of the following hardware:

Hopper Parts feeder Selector and/or orientor

Feed track Escapement and placement device


Vibratory Bowl feeder



Selector and Orientor Devices


Applications

Automated systems are used to produce wide variety of products and

subassemblies. List of typical products made by automated assembly is given

below:

Alarm clocks Light bulbs

Audio tape cassettes Locks

Ball bearings Mechanical pens and pencils

Ball point pen Printed circuit board assemblies

Cigarette lighter Pumps for household appliances

Small electric motors Electric plugs and sockets

Spark plugs Fuel injectors

Gear boxes Wrist watches.


Operations in Automated Assembly

The kinds of operations performed on automated assembly covers wide range.

Representative list of these operations is provided below:

1. Adhesive bonding (automatic disposing of adhesive)

2. Insertion of components (pin in hole printed circuit board assembly)

3. Placement of components (surface mount printed circuit board)

4. Riveting

5. Screw fastening (automatic screw driver)

6. Snap fitting

7. Soldering

8. Spot welding

9. Stapling

10.Stitching


Design for Automated Assembly

The following are some recommendations and principles that can be applied

in product design to facilitate automated assembly:

1. Reduce the amount of assembly required

2. Use of modular design

3. Reduce the number of fasteners required

4. Reduce the need for multiple components to be handled at once

5. Limit the required directions of access

6. High quality required in components

7. Hopperability
