A major cost factor in the production of and component or assembly is its assembly. This section looks at some commonly used techniques which a designer can employ to ensure that assembly is cost effective and efficient. This is then linked to the use of jigs and fixtures for this purpose.

1. HNC year 1
Design for Manufacture
Author: Leicester College
Date created:
Date revised: 2009
Abstract: A major cost factor in the production of and component or assembly is its assembly. This section
looks at some commonly used techniques which a designer can employ to ensure that assembly is cost
effective and efficient. This is then linked to the use of jigs and fixtures for this purpose.
© Leicester College 2009. This work is licensed under
a Creative Commons Attribution 2.0 License.
Design for Assembly

2.  Introduction
 Assembly Methods
 Design Guidelines for Manual Assembly
 Using Jigs & Fixtures
 Design Guidelines for Automated Assembly
 Basic DFA Guidelines
 Credits
These files support the Edexcel HN unit – Design for Manufacture (NQF L4)
File name Unit outcome Key words
Design for assembly 1.1, 1.2,1.4 Overview, Cost, quality, reliability, assembly, guidelines
FMS 2.2 Models, work cycles, volume, machine utilisation, automation, flexible, systems
Geometric Tolerancing 3.1,3.2 Geometric, tolerance, system, symbols, orientation, BS, ISO, location, runout, datum
Industrial Robots 2.2,2.3 Robot, industrial, robot arm, Cartesian, polar, cylindrical, jointed arm
Jigs and Fixtures 2.1,2.3 Efficiency, production, jigs, fixtures, tooling, production,
Kinematics 2.1,2.3 Machines, kinematics, Degrees of freedom, configuration, space, work space, robot,
joints, forward, inverse
DFM introduction 1.1, 1.2, 1.4 design
For further information regarding unit outcomes go to Edexcel.org.uk/ HN/ Engineering /
Specifications
Design for Assembly

3.  "a process for improving product design for easy
and low-cost assembly, focusing on functionality
and on assemblability concurrently."
--Vincent Chan & Filippo A. Salustri
Design for Assembly

4.  Reduce cost of assembly
 Improve quality and reliability
 Reduce part inventory
 Reduce production equipment
Design for Assembly

5.  Manual assembly
 Fixed automatic assembly
 Flexible automatic assembly
Design for Assembly

6.  eliminate the need for workers to make
decisions or adjustments.
 ensure accessibility and visibility.
 eliminate the need for assembly tools and
gauges (i.e. prefer self-locating parts).
Design for Assembly

7. Hull Forming Jigs at Offshore Steel Boats Ltd.
Image source: www.geograph.org.uk/photo/1230702
© Copyright David Wright and licensed for reuse under this Creative Commons Licence.

8.  Minimise the number of standard different
parts – use ‘standard parts.’
 minimise the number of parts.
 avoid or minimise part orientation during
assembly (i.e. prefer symmetrical parts).
 prefer easily handled parts that do not tangle
or nest within one another.
Design for Assembly

9.  reduce the number of different components by
considering
 does the part move relative to other parts?
 must the part be isolated from other parts (electrical,
vibration, etc.)?
 must the part be separate to allow assembly (cover
plates, etc.)?
 use self-aligning and self-locating features
 avoid screws/bolts
Design for Assembly

10.  use the largest and most rigid part as the
assembly base and fixture.
 Assembly should be performed in a layered,
bottom-up manner.
 use standard components and materials.
Design for Assembly

11.  avoid tangling or nesting parts.
 avoid flexible and fragile parts.
 avoid parts that require orientation.
 use parts that can be fed automatically.
 design parts with a low centre of gravity.
Design for Assembly

12.  Minimise part count by incorporating multiple
functions into single parts
 Modularise multiple parts into single sub-
assemblies
 Assemble in open space, not in confined
spaces; never bury important components
 Make parts such that it is easy to identify how
they should be oriented for insertion
 Prefer self-locating parts
Design for Assembly

13.  Standardise to reduce part variety
 Maximise part symmetry
 Eliminate tangling parts
 Colour code parts that are different but shaped
similarly
 Prevent nesting of parts; prefer stacked
assemblies
 Provide alignment features
Design for Assembly

14.  Design the mating features for easy insertion
 Insert new parts into an assembly from above
 Eliminate re-orientation of both parts and
assemblies
 Eliminate fasteners
Design for Assembly

15.  Place fasteners away from obstructions; design
in fastener access
 Deep channels should be sufficiently wide to
provide access to fastening tools; eliminate
channels if possible
 Provide flats for uniform fastening and
fastening ease
 Ensure sufficient space between fasteners and
other features for a fastening tool
 Prefer easily handled parts
Design for Assembly

16. HNC year 1

17. This resource was created Leicester College and released as an open educational resource through the Open
Engineering Resources project of the Higher Education Academy Engineering Subject Centre. The Open
Engineering Resources project was funded by HEFCE and part of the JISC/HE Academy UKOER programme.
© 2009 Leicester College
This work is licensed under a Creative Commons Attribution 2.0 License.
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England & Wales Licence. All reproductions must comply with the terms of that licence.
The HEA logo is owned by the Higher Education Academy Limited may be freely distributed and copied for educational purposes
only, provided that appropriate acknowledgement is given to the Higher Education Academy as the copyright holder and original
publisher.
The Leicester College name and logo is owned by the College and should not be produced without the express permission of the
College.
Design for Assembly