ME3101 / ME3102Mechanical Systems DesignChapter 5Basic Design for Manufacturing

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

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?

Estimating Manufacturing CostsEstimate

manufacturing Costs of Proposed Design

Reduce costs of assembly

Reduce costs of Supporting Production

Reduce costs of components

Consider DFM impact on other

factors

Recompute Manufacturing Costs

Good Enough? Accepted Design

Extracted from: Karl T. Ulrich, Steven D.Eppinger (2008) Product Design and Development McGraw Hill International

N Y

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.)

Whenever possible, opt to use the standard part sizes from vendors, as it is mass made and cheaper to purchase rather than custom dimensions!!!

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

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

Thus..make necessary design modifications to reduce number of custom components!

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

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 attainTake into consideration the ease and costs of manufacturing w.r.t. design!!

Eliminating Process Steps

Complicated Design Simpler Design

Vs.

Eliminating Process StepsWhile 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.

Economies of scaleHypothetical costs vs

number of units

MachiningInjection Molding

Number of units

Cost

s

When considering the number of units to be made, take into consideration:

1. Initial start up costs2. Incremental costs per unit

There will be a point of production volume whereby another production method

willbe more economically viable.

An example to show that at certain production volumes, alternative production methods

becomes increasing viable

Standardization of PartsDuring 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.

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!