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.
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
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
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