1. ME3101 / ME3102
Mechanical Systems Design
Chapter 5
Basic Design for Manufacturing

2. DFM - Design for Manufacturing?
While product specifications and customer’s
wants are important, there are other design
issues to consider. DFM decisions are
applied throughout the design process and
it affects all aspects from the design phase
to the production phase
Consider:
•Costs control
•Methods of production
•Time required to production
•Production process impact on performance
•Availability of raw materials

3. DFM - Design for Manufacturing?
Ask the following questions:
•Can the same demands be met with a
cheaper material?
•Is it possible to use lesser material?
•What kind of materials are available? And
in what specifications?
•How many units do I have to make?

4. Estimating Manufacturing Costs
Estimate manufacturing
Costs of Proposed
Design
Reduce costs of Reduce costs of Reduce costs of
components assembly Supporting Production
Consider DFM impact
on other factors
Recompute
Manufacturing Costs
N Y
Good Enough? Accepted Design
Extracted from: Karl T. Ulrich, Steven D.Eppinger (2008) Product Design and Development McGraw Hill International

5. Breakdown of component costs
Components of a product may be:
•Standard parts. Available for purchase
from vendors.
•Custom parts that require modifications
by vendor. (Different
sizes/dimensions/finish etc.)

6. Comparing costs of standard components
Do:
•Compare costs of different suitable
materials to explore alternatives
•Obtain quotations from several
vendors to make comparisons
•Some vendors offers a discount if
multiple purchases are made or
when purchase quantity is high.
Students can find a list of useful vendor contacts on the website. The
link is under the resources tab  Sample Vendors

7. Costs of custom components
On top of the base Material
Costs, custom made components
costs more due to:
1. Additional processing steps
required (Eg. Machining)
2. Additional overhead costs for
processing

8. Reducing Component Costs
Reductions of component costs requires the following:
•Understand process constraints and related costs
•Eliminate processing steps through smart design
•Selection of production methods w.r.t. scale of production
•Standardization of components

9. Process Constraints
•Understanding process constraints
are important as designers might
create features that are difficult to
achieve in manufacturing
•Examples:
•Delicate internal features are
difficult to manufacture using
standard processes. EDM might
achieve a small internal corner
radius, but the process is costly
•Tight tolerances are difficult to
attain

10. Eliminating Process Steps
Complicated Design Simpler Design

11. Eliminating Process Steps
While most real life examples will not be as simple as the comparison made
between the bikes, some general guidelines can be followed to reduce
processing steps:
•Reducing number of components. Make it as one whole piece rather
than many small pieces fixed together.
•Eliminate redundant steps. For example, painting internal components
that are not visible.
•Wherever possible, avoid using complex shapes.

12. Economies of scale
Hypothetical costs vs number
of units When considering the number of
units to be made, take into
consideration:
1. Initial start up costs
Costs
Machining
Injection Molding
2. Incremental costs per unit
There will be a point of
Number of units production volume whereby
another production method will
An example to show that at certain production be more economically viable.
volumes, alternative production methods becomes
increasing viable

13. Standardization of Parts
During the design process, it will be good
for the designer to try to use the same
components as much as possible.
For example:
1. Using the same drill sizes and screws
2. Using the same length of materials
This reduces the types of tools required and
minimizes processing time.

14. In conclusion…
Take into consideration the ease of manufacturing during the design process!
While the design can be spectacular, it means nothing if it cannot be made!