Automation in Manufacturing (Unit-4) by Varun Pratap Singh.pdf

Automation in Manufacturing
(MEPD-4010/4014)
Mechatronics/Mechanical Engineering
Unit 4: Production and assembly systems
By
Varun Pratap Singh

Disclaimer
This document does not claim any originality and cannot be used as a substitute for prescribed textbooks. The
information presented here is merely a collection by the subject faculty members for their respective teaching
assignments, research articles, subject books, and any other sources of information. Various sources, as mentioned on
each slides or at the end of the document as well as freely available material from the internet, were consulted for
preparing this document. The ownership of the information lies with the respective authors or institutions. Further, this
document is not intended to be used for commercial purposes and the subject faculty members are not accountable for
any issues, legal or otherwise, arising out of the use of this document. The subject faculty members make no
representations or warranties concerning the accuracy or completeness of the contents of this document and
specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. The subject faculty
members shall be liable for any loss of profit or any other commercial damages, including but not limited to special,
incidental, consequential, or other damages.

Content
1. Automated production lines -introduction
2. Automated production lines - fundamentals,
3. System configurations,
4. Work part transfer mechanisms,
5. Storage buffers,
6. Control of production line,
7. Automated production lines applications.
8. Automated assembly systems – introduction
9. Automated assembly systems - fundamentals,
10. System configurations,
11. Parts delivery at work stations,
12. Automated assembly systems-applications.

Syllabus
Unit 1: Production systems Lectures
Categories of manufacturing systems, manufacturing support systems, automation in production systems, automated
manufacturing systems, opportunities for automation and computerization, types of automation, computerized manufacturing
support systems, reasons for automating, automation principles and strategies, the USA principle, ten strategies for automation,
automation migration strategy.
8
Unit 2: Automation and control technologies in production system Lectures
Basic elements of an automated system, advanced automation functions, levels of automation, continuous and discrete
control systems, computer process control, common measuring devices used in automation, desirable features for
selection of measuring devices.
8
Unit 3: Material handling system Lectures
Material handling equipment, design considerations for material handling system, material transport equipment, analysis of
material transport systems, storage systems and their performance and location strategies, conventional and automated storage
systems, overview of automatic identification and data capture, bar code technology, RFID, other AIDC technologies.
8
Unit 4: Production and assembly systems Lectures
Automated production lines- fundamentals, system configurations, work part transfer mechanisms, storage buffers, control of
production line, applications.
Automated assembly systems- fundamentals, system configurations, parts delivery at work stations, applications.
8
Unit 5: Cellular manufacturing Lectures
Group technology, part families, parts classification and coding, production flow analysis, Opitz coding system, composite part
concept, machine cell design, applications of GT
7
Unit 6: Flexible manufacturing systems Lectures
Introduction to FMS, types of FMS, FMS components, applications and benefits, planning and implementation issues in FMS,
6

Suggested Text/Reference Books
Text Book:
1. Mikell P. Groover, Automation, Production Systems,
and Computer-integrated Manufacturing, prentice Hall.
Reference Book:
1. Theory of Automation of Production Planning and of Tooling:
Algorithms for Designing
Machine Tools in Automated Industrial Plants, By G. K.
Goranskiĭ"
2. Serope Kalpakjian and Steven R. Schmid, Manufacturing –
Engineering and
Technology, 7th Edition, Pearson.
3. Yoram Koren, Computer control of manufacturing system, 1st
edition.
4. Ibrahim Zeid , CAD/CAM : Theory & Practice, 2nd edition.
MOOC:
Production and assembly system- NPTEL Online Courses:
1. https://elearn.nptel.ac.in/shop/nptel/Production and assembly system/
Video Lectures:
Unit IV- Production and assembly systems
https://www.youtube.com/watch?v=BoUDrZPrt8c
YouTube Channel/videos:
1. https://www.youtube.com/watch?v=1O7d2b05A-E
In Class
For knowledge

Manual Assembly Lines- Introduction
Factors favoring the use of manual assembly tines include the following:
• Demand for the product is high or medium.
• The products made on the line are Identical or similar.
• The total work required to assemble the product can he divided into small work elements.
• It is technologically impossible or economically infeasible to automate the assembly operations.
Products characterized by these factors that are usually made on a manual assembly line are as:
• Specialization of labour,
• Interchangeable parts,
• Work principle in material handling,
• Variable Line pacing.
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by M.P. Groover.
Portion of this section are based on M.P. Groover; Fundamentals of manufacturing: Materials, processes and systems

Alternative Assembly Systems
The well-defined pace of a manual assembly line has merit from the viewpoint of maximizing production rate.
However, assembly line workers often complain about the monotony of the repetitive tasks they must perform and the
unrelenting pace they must maintain when a moving conveyor is used. Poor quality workmanship. sabotage of the
line equipment's and other problems have occurred on high production assembly lines.
To address these issues, alternative assembly systems are available in which either the work is made less monotonous and
repetitious by enlarging the scope of the tasks performed, or the work is automated.
In this section, we can identify the following alternative assembly systems:
(1) Single-station manual assembly cells,
(2) Assembly cells based on worker teams, and
(3) Automated assembly systems
A single-station manual assembly cell consists of a single workplace in which the assembly work is accomplished on the
product or some major subassembly of the product. This method is generally used on products that are complex and
produced in small quantities, sometimes one-of-a-kind.
Assembly by worker teams involves the use of multiple workers assigned to a common assembly task. The pace of the
work is controlled largely by the workers themselves rather than by a pacing mechanism such as a powered conveyor
moving at a constant speed. Team assembly can be implemented in several ways.
Automated assembly systems use automated methods at workstations rather than humans. In our classification scheme,
these can be type I A or type III A manufacturing systems, depending on whether there are one or more workstations in the
system.

DESIGN FOR ASSEMBLY
Design for assembly (DFA) has received much attention in recent years because assembly operations constitute a high
labor cost for many manufacturing companies. The key to successful design for assembly can be simply stated:
(1) design the product with as few parts as possible, and
(2) design the remaining parts so they are easy to assemble.
• Use the fewest number of parts possible to reduce the amount of assembly required.
• Reduce the number of threaded fasteners required.
• Standardize fasteners.
• Reduce parts orientation difficulties.
• Avoid parts that tangle.

Automated production lines - Introduction
Automated production lines require a significant capital investment. They arc examples of fixed automation, and it is
generally difficult to alter the sequence and content of the processing operations once the line is built. Their application is
therefore appropriate only under the following conditions:
• High product demand, requiring high production quantities.
• Stable product design, Frequent design changes are difficult to cope with on an automated production line.
• Long product life, at least several years in most cases.
• Multiple operations are performed on the product during its manufacture.
When the application satisfies these conditions, automated production lines provide the following benefits:
• Low direct labor content
• Low product cost because cost of fixed equipment is spread over many units.
• High production rates.
• Production lead time (the time between beginning of production and completion of a finished unit) and work-in-process
are minimized.
• Factory floor space is minimized.

Automated production lines - fundamentals,
An automated production line consists of multiple workstations that are linked together by a work handling system that
transfers parts from one station to the next.as depicted in Figure 18.1. A raw work part enters one end of the line, and the
processing steps are performed sequentially a, the part progresses forward (from left to right in our drawing).
An automated production line operates in cycles, similar to a manual assembly line. Each cycle consists of processing time
plus the time to transfer parts to their respective next workstations. The slowest workstation on the line sets the pace of the
line, just as in an assembly line.

Automated production lines - System configurations
Although Figure 18.1 shows the flow of work to be in a straight line, the work flow can actually take several different
forms, We classify them as follows:
(1) In-line,
(2) Segmented in-line, and
(3) Rotary.
The in-line configuration consists of a sequence of stations in 1 straight line arrangement, as in Figure 18.1. This
configuration is common for machining big workplaces, such as automotive engine blocks, engine heads, and transmission
cases. Because these parts require a large number of operations, a production line with many stations is needed. The in-
line configuration can accommodate a large number of stations. Inline systems can also be designed with integrated
storage buffers along the flow path.

The segmented in-line configuration consists of two or more straight-line transfer sections, where the segments are
usually perpendicular to each other. Figure 18.2 shows several possible layouts of the segmented in-line category. There
are a number of reasons for designing a production line in these configurations rather than in a pure straight line,
including:
(1) available floor space may limit the length of the line,
(2) it allows reorientation of the work piece to present different surfaces for machining, and
(3) the rectangular layout provides for return of work holding fixtures to the front of the tine for reuse.

Figure 18.3 shows two transfer lines that
perform metal machining operations on a
truck rear axle housing. The first line, on the
bottom right-hand side, is a segmented
inline configuration in the shape of a
rectangle. Pallet fixtures are used in this line
to position the starting castings at the
workstations for machining. The second
line, in the upper left corner. is a
conventional in-line configuration
consisting of seven stations.

In the rotary configuration, the work parts are attached
to fixtures around the periphery of a circular worktable,
and the table is indexed (rotated in fixed angular
amounts) to present the parts to workstations for
processing. A typical arrangement is illustrated in Figure
18.4.The worktable is often referred to as a dial, and the
equipment is called a dial inducing machine, or simply,
indexing machine. Although the rotary configuration
does not seem to belong to the class of production
systems called "lines," their operation is nevertheless
very similar. Compared with the in-line and segmented
in-line configurations, rotary indexing systems are
commonly limited to smaller work parts and fewer
workstations; and they cancer readily accommodate
buffer storage capacity. On the positive side, the rotary
system usually involves a less expensive piece of
equipment and typically requires less floor space

Work part transfer mechanisms
The work part transfer system moves parts between stations on the production line. Transfer mechanisms used on
automated production lines are usually either synchronous or asynchronous. Synchronous transfer has been the traditional
means of moving parts in a transfer line. However. applications of asynchronous transfer systems arc increasing because
they provide certain advantages over synchronous parts movement :
(1) Greater flexibility.
(2) Fewer pallet fixtures required,
(3) Easier to rearrange or expand the production system.
These advantages come at higher first cost. Continuous work transport systems are uncommon on automated lines due to
the difficulty in providing accurate registration between the station work heads and the continuously moving parts.
In this Section, we divide work part transfer mechanisms into two categories:
(1) Linear transport systems for in-line systems and
(2) Rotary indexing mechanisms for dial indexing machines.
Some of the linear transport systems provide synchronous movement, whereas others provide asynchronous motion. The
rotary indexing mechanisms all provide synchronous motion.

(1) Linear transport systems
Most of the material transport systems described in previous unit provide a linear motion, and some of these are used for
work part transfer in automated production systems. These include powered roller conveyors. belt conveyors, chain-driven
conveyors, and cart-on-track conveyors. Figure 18.5 illustrates the possible application of a chain or belt driven conveyor to
provide continuous or intermittent movement of parts between stations, Either a chain or flexible steel belt is used to
transport parts using work carriers attached to the conveyor. The chain IS driven by pulleys in either an "over-and-under"
configuration, in which the pulleys turn about a horizontal axis, or an "around-the-corner" configuration, in which the
pulleys rotate about a vertical axis.

(1) Linear transport systems
Many machining type transfer lines utilize various walking
beam transfer systems, in which the parts are
synchronously lifted up from their respective stations by a
transfer beam and moved one position ahead to the next
station. The transfer beam then lowers the parts into nests
that position them for processing at their stations. The beam
then retracts to make ready for the next transfer cycle. The
action sequence is depicted in Figure 18.6.

(2) Rotary indexing mechanisms
Several mechanisms are available to provide the rotational indexing motion required in a dial indexing machine. Two
representative types arc explained here: Geneva mechanism and cam drive.
The Geneva mechanism uses a continuously rotating driver to index the table through a partial rotation, as illustrated in
Figure 18.7.If the driven member has six slots for a six station dial indexing table. each turn of the driver results in 1/6
rotation of the work table or 60°.The driver only causes motion of the table through a portion of its own rotation. For a six-
slotted Geneva. 120 degree of driver rotation is used to index the table. The remaining 240 degree of driver rotation is dwell
time for the table, during which the processing operation must be completed on the work unit.

Automated production lines -Storage buffers
Automated production lines can be designed with storage buffers. A storage buffer in a production line is a location where
parts can be collected and temporarily stored before proceeding to subsequent (downstream) workstations. The storage
buffers can be manually operated or automated When automated. A storage buffer consists of a mechanism to accept parts
from the upstream workstation, a place to store the parts. and a mechanism to supply parts to the downstream station. A key
parameter of a storage buffer is its storage capacity, that is, the number of work pans it is capable of holding, Storage buffers
may be located between every pair of adjacent stations or between line stages containing multiple stations. We illustrate the
case of one storage buffer between two stages in Figure 18.9.
There are a number of reasons why storage buffers are used on automated production lines. The reasons include:
• To reduce the effect of station breakdowns.
• To provide a bank of parts to supply the line.
• To provide a place to put the output of the line.
• To allow for curing time or other required delay.
• To smooth cycle time variations.

Automated production lines- Control
Controlling all automated production tine is complex because of the sheer number of sequential and simultaneous
activities that must be accomplished during operation of the line. In this Section, we discuss:
(1) the basic control functions that are accomplished to run the line and
(2) the characteristics of controllers used on automated line,
Control Functions: Three basic control functions can be distinguished in the operation of an automatic transfer machine.
One is an operational requirement, the second is a safety requirement, and the third j, fur quality control. The three basic
control functions are:
1. Sequence control. The purpose of this function is to coordinate the sequence of actions of the transfer system and
associated workstations. The various activities of the production line must be carried out with split-second timing and
accuracy.
2. Safety monitoring. This function ensures that the production line does not operate in an unsafe condition. Safety
applies to both the human workers in the area as well as the equipment itse1f.Additional sensors must he incorporated
into the line beyond those required for sequence control to complete the safety feedback loop and avoid hazardous
operation.
3. Quality control. In this control function certain quality attributes of the work parts are monitored. The purpose is to
detect and possibly reject defective work units produced on the line. The inspection devices required to accomplish
quality control are sometimes incorporated into existing processing stations. In other cases, separate inspection
stations are included in the line for the sale purpose of checking the desired quality characteristic.

Automated production lines- Applications
Automated production lines arc applied in processing operations as well as assembly. Machining is one of the most common
processing applications and is the focus of most of our discussion in this section. Other processes performed on automated
production lines and similar systems include sheet metal forming, cutting and rolling mill operations, spot welding of
automobile car bodies and painting and plating operation.

Automated assembly systems – introduction
The term automated assemblv refers to the use of mechanized and automated devices to perform the various assembly tasks
in an assembly line or cell. Much progress has been made in the technology of assembly automation in recent years. Some
of this progress has been motivated by advances in the field of robotics. Industrial robots are sometimes used as components
in automated assembly systems.
Automated assembly technology should be considered when the following conditions exist:
• High product demand. Automated assembly systems should be considered for products made in millions of units (or dose
to this range).
• Stable product design. In general. any change in the product design means a change in workstation tooling and possibly
the sequence of assembly operations. Such changes can he very costly,
• The assembly consist of no more than a limited number of components. maximum of around a dozen parts.
• The product is designed/or automated assembly. we examine the design factors that allow the assembly of a product to
be automated.
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 lines, and
(2) Assembly operations do not have the large mechanical force and power requirements of processing operations such as
machining. Accordingly, in comparing an automated assembly system and a transfer line both having the same number
of stations, the assembly system would tend to be smaller in physical size. This usually reduces the cost of the system.

Automated assembly systems - fundamentals
An automated assembly system performs a sequence of automated assembly operations to combine multiple components
into a single entity. The single entity can be a final product or a subassembly in a larger product. In many cases, the
assembled entity consists of a base part to which other components are attached. The components are joined one at a time
(usually), so the assembly is completed progressively.
A typical automated assembly system consists of the following subsystems:
(1) one or more workstations at which the assembly steps are accomplished,
(2) parts feeding devices that deliver the individual components to the workstations, and
(3) a work handling system for the assembled entity.
In assembly systems with one workstation, the work handling system moves the base part into and out of the station. In
systems with multiple stations, the handling system transfers the partially assembled base part between stations.
Control functions required in automated assembly machines are the same as in the automated processing lines:
(1) sequence control,
(2) safety monitoring, and
(3) quality control.
The issue of memory control versus instantaneous control is especially relevant in multi-station automated assembly
systems.

Automated assembly systems - Configurations
Automated assembly systems can be classified according to physical configuration. The principal configurations, illustrated
in Figure 19.1, are: (a) in-line assembly machine, (b) dial type assembly machine, (c) carousel assembly system, and (d)
single station assembly machine. Table 19.1 summarizes the possible combinations of work transfer systems that are
utilized with these assembly system configurations.

Automated assembly systems
Parts delivery at work stations
In each of the configurations described above, a workstation accomplishes one or both of the following tasks:
(1) a part is delivered to the assembly work head and added to the existing base part in front of the work head (in the case of
the first station in the system, the base part is often deposited into the work carrier), and/or (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 10 the existing base part. In the case of a single station assembly system, these tasks are carried out multiple times
at the single station. For task, a means of delivering the parts to the assembly work head must be designed. The parts
delivery system typically consists of the following hardware:
1. Hopper: This is the container into which the components are loaded at the workstation. A separate hopper is used for
each component type. The components are usually loaded into the hopper in bulk. This means that the parts are initially
randomly oriented in the hopper.
2. Parts feeder: This is a mechanism that removes the components from the hopper one at a time for delivery to the
assembly work head.
3. Feed track: The preceding elements of the delivery system are usually separated from the assembly work head by a
certain distance. A feed track is used to move the components from the hopper and parts feeder to the location of the
assembly work head, maintaining proper orientation of the parts during the transfer.
4. Escapement and placement device: The purpose of the escapement device is to remove components from the feed track
at time intervals that are consistent with the cycle time of the assembly work head. The placement device physically
places the component in the correct location at the workstation for the assembly operation.

Automated assembly systems-applications
Automated assembly systems are used to produce a wide variety of products and subassemblies. Table 19.2 presents a list
of typical products made by automated assembly. The kinds of operations performed on automated assembly machines
cover a wide range. We provide a representative list of processes in Table 19.3. It should be noted that certain assembly
processes are more suitable for automation than are others. For example, threaded fasteners (e.g., screws, bolts, and nuts),
although common in manual assembly, are a challenging assembly method to automate. This issue, along with some
guidelines for designing products for automated assembly, is discussed in the following section.

Automated assembly systems-applications

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