ME3101 / ME3102Mechanical Systems DesignChapter 5Basic Design for Manufacturing
DFM - Design for Manufacturing?While product specifications and customer’swants are important, there are other designissues to consider. DFM decisions areapplied throughout the design process andit affects all aspects from the design phaseto the production phaseConsider:•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 Costs Estimate manufacturing Costs of Proposed DesignReduce 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
Breakdown of component costsComponents of a product may be:•Standard parts. Available for purchasefrom vendors.•Custom parts that require modificationsby vendor. (Differentsizes/dimensions/finish etc.)
Comparing costs of standard componentsDo:•Compare costs of different suitablematerials to explore alternatives•Obtain quotations from severalvendors to make comparisons•Some vendors offers a discount ifmultiple purchases are made orwhen 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 componentsOn top of the base MaterialCosts, custom made componentscosts more due to:1. Additional processing steps required (Eg. Machining)2. Additional overhead costs for processing
Reducing Component CostsReductions 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 constraintsare important as designers mightcreate features that are difficult toachieve 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
Eliminating Process StepsComplicated Design Simpler Design
Eliminating Process StepsWhile most real life examples will not be as simple as the comparison madebetween the bikes, some general guidelines can be followed to reduceprocessing 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 scale Hypothetical costs vs number of units When considering the number of units to be made, take into consideration: 1. Initial start up costsCosts 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
Standardization of PartsDuring the design process, it will be goodfor the designer to try to use the samecomponents as much as possible.For example:1. Using the same drill sizes and screws2. Using the same length of materialsThis reduces the types of tools required andminimizes 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!