Design for Manufacturability
This paper explores design for manufacturability using several scholarly journal articles and books from different sources and industries. It starts by examining the definition of design for manufacturability as it pertains to managers of supply chains. The paper then discusses a fundamental topic that provides a foundation for learning design for manufacturability: the principles of design. The next section of this paper outlines the benefits that design for manufacturability has if a company chooses to implement it into their operations.
Following the benefits of design for manufacturability are several key guidelines that will give a company the best chance for success while using design for manufacturability. The tools used in design for manufacturability are discussed in the next section of the paper. The drawbacks to design for manufacturability follow the discussion of the tools used. Finally, this paper concludes with an in-depth look at the Pro-DFM method of evaluating design for manufacturability in a company.
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Definition of Design for Manufacturability
In today’s fast-paced world, every business is looking to have a competitive sustainable advantage over the competition. If a company wants to achieve this, they need to continually reduce costs, improve quality, enhance customer service, and so forth. To survive in the market, products must satisfy and delight customers. In order to do this, design is the most important aspect. By having a good design, half of the customer’s demand has been satisfied. Having a good design can also help enhance quality of the parts used, increase productivity, and reduce costs in manufacturing and assembly processes.
Design for manufacturing is a process that is concerned with understanding “how product design interacts with the other components of the manufacturing system and in defining product design alternatives that help facilitate global optimization of the manufacturing system as a whole” while still satisfying customers. (Huang, 2003, P. 1) It encompasses areas such as “mechanicals, enclosure and assembly, thermal concerns, fabrication, component selection and procurement, component assembly, test, inspection, rework and repair, and cost. ” (Blankenhorn, 1993, P. 15)
More often than not, employees responsible for product development create designs where the cost cannot be clearly defined or are considered too costly. Studies show that about 70 to 80 percent of the cost of a product results from the design stage. (Venkatachalam, 1992) Design for manufacturability is “a cutting-edge improvement program that can reduce labor, material, and mass requirements without sacrificing the integrity of the product or process. ” (Huang, 2003) Principles of Design Before one can begin to understand the capabilities of design for manufacturability, it is important to understand design as a whole.
There are four main decisions that pertain to design: what to design, who is going to design it, how it is going to be designed, and what technology is needed for the design process. (Youssef, 1994) There are several principles of design, as noted by Gerald Nadler, Ph. D. , P. E. of the University of Southern California. The first is the uniqueness principle, which states that each design should be treated as a different project than the last. It is this principle that creates breakthrough designs. (McClure, 1999) The second principle is purpose.
The moment that a problem occurs, one should question what the purpose of solving the problem is. By doing this, assurance that the correct problem is being solved is created. Thirdly, the solution-after-next principle follows. According to Nadler, “This sets a problem, and even the purpose, aside for the moment and asks, if you had already arrived at an ideal solution, what new challenges would confront you. ” (McClure, 1999) By thinking in this way, the solving the problem becomes a continuous process, as opposed to an end. Next comes the third principle of systems.
A single problem is part of a much larger matrix that contains many different elements. The solution of one problem most likely will not result in total success for the entire project, as it is a part of a system. The fifth principle is the limited-information principle. “The traditional problem solving approach is to bring in a consultant who is an expert in supposedly similar problems or to become an expert in the problem yourself by delving into past problems that seem familiar. ” (McClure, 1999) Information should be limited so that, like traditional problem solving, it is not time consuming and cluttered with useless information.
The people-to-people principle is the sixth principle suggested by Nadler. Anyone that has to do with any area of the problem needs to feel that they are included in implementing a solution. The final principle discussed is the betermant timeline principle. The familiar phrase “If it ain’t broke, don’t fix it” can only be used for the short term. Over time, everything wears out eventually due to change in external and internal factors. Solutions to problems should be monitored to help track change and evaluate improvement. McClure, 1999)
Requirements Before Pursuing Design for Manufacturability After learning about these principles to design, one can now start to understand design for manufacturability and its effects on the design and manufacturing process. While keeping in mind that design for manufacturability creates the reduction of costs, labor, and lead times, there are several considerations that will help a company find operations that make design for manufacturability successful. With any type of design in any company, it is extremely important to discover what the customer is requiring of you.
One must determine whether the customer wants something completely different or an upgrade of what is currently being offered. The processes used in creating designs should be looked at as well to see if they are reliable enough to handle the new design. If the processes already used cannot handle the capability of design for manufacturability, new ones need to be created. (McClure, 1999) Tolerances are an important aspect of determining whether design for manufacturability is feasible for one’s company. Can the manufacturing plant handle the tolerances that the process calls for?
If not, is there a company that can be subcontracted to handle the tolerances? These are both questions that should be answered in relation to tolerances in design for manufacturability. Another factor is repeatability. This is affected by the tolerances of the processes. An important question is to determine whether the design can be repeated quickly and accurately for every single product. (McClure, 1999) In the process of design for every company, the costs of manufacturing along with the material costs and availability of those materials should be well thought through and planned.
This involves the discussion of how much labor is going to be required, where resources can be found, and the lead-time for those resources. Ergonomics also plays an important role in design for manufacturability, as it is “The applied science of equipment design, as for the workplace, intended to maximize productivity by reducing operator fatigue and discomfort. ” (Ergonomics, 2011) This will allow for a shortened manufacturing process along with better employee morale. Safety is a much-needed consideration for design for manufacturability. All processes created to carry out the design should be as safe as possible for employees.
In order to carry out safety and the process as a whole, technology should be looked at. It is important to figure out whether technology is readily available from other projects or if it needs to be developed especially for this design. The reliability of the technology needed for the design should be assessed as well. (McClure, 1999) The following checklist can be used to help determine operations that will need the most work in implementing design for manufacturability: Figure 1: Checklist to evaluate the company’s operations pertaining to Design for Manufacturability (McClure, 1999) Benefits of Design for Manufacturability
Implementing design for manufacturability has four main benefits. The first is that it can result in a simplification of the product’s design. Secondly, there is an integration of parts, which results in the reduction of total parts overall in the design thus reducing costs and improving reliability of the product. Next, there will be an improved productivity due to the standardization of components and lower inventory. Lastly, there will be a reduced development cycle time, which will allow for products to be produced quicker and more efficiently resulting in more satisfied customers.
Venkatachalam, 1992) Along with the direct benefits to a company that implements a design for manufacturability, there are indirect benefits. Organizations can improve their competitive stance in their respective markets. Design for manufacturability can help to break down the barrier between the design and manufacturing processes, along with increasing employee moral. The process also has an effect on warranty claims for products. It can help to reduce the amount of claims that occur with given products. (Venkatachalam, 1992) Keys Guidelines for Successful Implementation
The success of the implementation of design for manufacturability depends on two main factors. The first is “a commitment and support from top management to bring about cultural changes, establish goals and objectives, and determine the dimensions on which to compete” (Youssef, 1994) and the second is several key guidelines. Management should create improvement programs and evaluate these programs regularly. These programs will allow for the company to continuously improve their processes and can be applied to every area of the company, not just manufacturing.
The focus should also be on teamwork, which plays a huge part in design for manufacturability. In order for design for manufacturability to have a lasting positive effect, emphasis should be on the long-term as opposed to short-term productivity boosts. Another activity that management can do that will help the design for manufacturability process implementation is to have a close relationship with suppliers and customers.
“The successful implementation of these cultural changes will foster full integration of all activities and functions involved in creating a product or providing a service. ” (Youssef, 1994, P. 4) There are several key guidelines to follow while implementing the design for manufacturability process. The first key guideline is to understand the manufacturing problems that have occurred in past products along with the issues of current products. Understanding the problems and issues with these products in the areas of manufacturability, quality, serviceability, and others allow for one to learn from past mistakes to prevent them from occurring in the future. It is especially important to understand past mistakes if the engineering used in previous products is being applied to new designs.
If the mistakes from the past are not caught, the design for manufacturability process will not work as well as it should. (Anderson, 2010) The second key guideline is to design for easy parts fabrication, product assembly, and material processing. Although the cost of labor may be minimal when compared to the selling price of the product, issues with these three activities can create excess costs. They may also cause delays in production along with demanding the time of significant resources. As expressed in the definition of design for manufacturability, its goal is to minimize costs.
By not designing for easy parts fabrication, product assembly, and material processing, the design for manufacturability process is not being achieved. (Anderson, 2010) The third key guideline to design for manufacturability is to follow specific process design guidelines that have been pre-determined by research. The significance of using specific design guidelines for parts to be created by specific processes is greatly expressed.
All processes have their own set of guidelines that show how to make the specific parts. In order to receive the guidelines, one can research each process and find a plethora of information. Anderson, 2010) The fourth key guideline is that the product should be designed in such a fashion so that the same part can be used in both left and right hand modes. Mirror image parts should be avoided wherever possible. If the parts are not performing as both left- and right-handed functions, features should be added so that the parts can act as such. In order to avoid this altogether, one should design paired parts instead. The purchasing of paired parts is for twice the quantity and half the number of types of parts. This has the possibility of having a significant impact with many paired parts at a high volume.
An example of paired parts is a briefcase. Most people who own a briefcase have opened it upside down at one point. This is due to the fact that a briefcase is made using paired parts. (Anderson, 2010) The fifth key guideline is that parts used in the process should also be designed using symmetry. This is so that the part does not have to be rotated to fit during the assembly process. During an automatic assembly, these parts do not require the machine to have sensors or special mechanisms that scan the part and rotate it correctly.
The money saved from not having to create machines like this will outweigh the costs of making the parts completely symmetrical. Felt-tipped pens utilize symmetrical parts in the way of the felt tip. It is pointed at both ends so that the machine used to manufacture it does not need to rotate the parts to fit correctly. (Anderson, 2010) If completely symmetrical parts cannot be achieved, it is recommended that parts be made as asymmetrical as possible. The worst part for the process of design for manufacturability is a part that is slightly asymmetrical.
This may cause the machine to install the part incorrectly because the sensors could not recognize that the part was not symmetrical. More harmful than this is the fact that the machine could potentially force the part into place. By creating parts that are very asymmetrical, machines may be able to orient the part with less expensive sensors so that minimal cost is achieved. (Anderson, 2010) On a similar note, the manufacturing process should be understood well enough so that parts can be designed and dimensioned for fixturing. Parts that are designed for automation need registration features for fixturing.
The parts of the manufacturing machine need to be able to grab the piece and hold it in a known position accurately for all sequences that the part is used. This requires the registration of locations in the machine’s memory. (Anderson, 2010) Concurrent engineering should be used in parts and tooling to help minimize complexity, cost, and leadtime. (Anderson, 2010) It “involves separating product realization activities so that design activities can be executed independently while simultaneously incorporating relevant information from downstream domains such as manufacturing, assembly, or recycling. (Xiao, 2007, P. 429) This will also maximize throughput, quality, and flexibility.
“Concurrent engineering is based on cooperation, synergy, frequent communication, and the anticipation of potential business and technology problems. ” (Nuese, 1995, P. 109) It is a natural by-product of self-directed work teams. Each team has its own development team that has a broad range of skills and who carry out a program from beginning to end. Concurrent engineering puts the power to do things in the hands of the people who know the most about whatever the project is.
By having teams that are multifunctional, there is more of a chance that problems in all stages of development will be caught and fixed. Concurrent engineering has the potential to reduce developed cycle time by about 40-60%, reduce manufacturing cost by 30-40%, reduce scrap and rework by 75%, and reduce engineering change orders during production by about 50%. (Nuese, 1995, P. 110) The last key guideline is that quality parts should be specified by reliable sources. There is a rule called the “rule of ten” that states that it costs ten times more to find an repair a defect at the next stage of assembly.
At the sub-assembly level, it costs ten times more than at the part itself level. At the final assembly level, it is one hundred times the part itself level. At the distributer, it is one thousand times more than the part itself level. Finally, at the customer level, it is ten thousand times more than the part itself level of completion. In order to prevent this from happening, steps in cutting parts should be minimized in order to improve accuracy. The minimum number of tools used to cut the part should be minimized as well. Lastly, the tolerance step functions should be understood and specified.
Each process used to produce parts has a certain tolerance limit. If the tolerance is close to the limit, a different process should be used that has a higher tolerance limit. (Anderson, 2010) Tools of Design for Manufacturability The implementation of the design for manufacturability approach requires coordination between many different tools. Some examples of tools include, but are not limited to: the axiomatic approach, design for manufacturability guidelines, design for assembly, the Taguchi method, process-driven design, facility-specific design for manufacturability, computer-aided design for anufacturability, and traditional approaches.
The axiomatic approach’s main goal is to optimize manufacturing systems through the use of axioms, also known as good design principles. There are two steps involved in this process. The first is the specification of the functional requirements of the end product. The second step is specifying the constraints. (Venkatachalam, 1992) Design for manufacturability guidelines are frequently used and have been created from years of design and manufacturing experience.
Design for assembly aims to create quantitative evaluations of the ease of assembly in designs. The Taguchi method is focused on the development of robust designs. The main steps in the process are to identify product and process concepts that are insensitive to changes and to determine the optimal values of parameters in designs that allow for the maximum robustness. Process-driven design is “based on the application of process specific expertise in the form of heuristics while designing a product to be manufactured using a specific process. (Venkatachalam, 1992) Facility-specific design for manufacturability allows for the design of products to be created using facilities that are specialized for manufacturing.
Computer-aided design for manufacturability is different types of software that improve the quality of products and process design decisions in the beginning of the design stage. Traditional approaches include items like group technology, failure mode and effects analysis, and value analysis. Each of these try to help the company avoid failure when it comes to designing a new product along with cutting the cost of the operation. Venkatachalam, 1992)
A fundamental element of design for manufacturability is a process for product development that “involves the use of multi-function teams, working to design marketplace winners, not simply products that are easier to assemble. ” (Youssef, 1994) It is this distinction that will put one’s company at a competitive sustainable advantage in the respective market. It has been proven by Hewlett Packard that choosing not to use design for manufacturability can have severe consequences.
Hewlett Packard’s competitors in its market, which includes Toshiba, American Inc. IBM, and Epson, all turned to higher, more advanced levels of design for manufacturability and Hewlett Packard did not. The result for HP was a product that was not competitive with others in the market along with shrinking business. (Youssef, 1994) Drawbacks to Design for Manufacturability Just like anything in business, design for manufacturability also has drawbacks, even though there are numerous benefits from using the process. Current tools in the design for manufacturability process do not take into account all of the manufacturing capabilities that are included in the manufacturing process.
They also do not take tolerances into consideration. Most of the tools also do not take the cost of fabricating an assembly part into account. Another drawback is that it is not completely clear as to whether the design for manufacturability tools are accurate enough to help make correct design decisions when the profit margin of a product is low. The biggest drawback of them all is that if design for manufacturability is not implemented correctly and with 100 percent commitment, it could potentially hurt a company rather than help it.
This is the biggest risk that a company takes when it chooses to implement design for manufacturability. Youssef, 1994) Evaluating Design for Manufacturability using Pro-DFM There are numerous ways to evaluate design for manufacturability in a product’s manufacturing process. One common way is the use of Pro-DFM. Pro-DFM is “a multi-criteria model for manufacturability analysis that identifies product realization opportunities for cost reduction. ” (Das & Kanchanapiboon, 2011, P. 1199) This creates a template for the evaluation of design for manufacturability while simultaneously allowing the actual evaluation to be derived from the judgments of users for a specific process and design.
Having a setup like this allows for the model to be used in a wide range of industries. New product development teams take their design for manufacturability knowledge and convert it to a measure known as the manufacturability penalty. (Das & Kanchanapiboon, 2011) There are four features that create the Pro-DFM evaluation. The first is that it is based on user evaluations. Design for manufacturability evaluations have a tendency of being extremely company specific due to the fact that plants, workers, and profit margins are different for each company.
Pro-DFM creates a common format and scale for the evaluation, but it is the responsibility of the new product development team to select relevant responses. The second feature is that it is a multi-factor model, which “analyzes a new design with three different factors: part fabrication processes, product assembly processes, and inventory costs. ” (Das & Kanchanapiboon, 2011, P. 1201) Each factor is evaluated independently using multiple criteria. The third feature is a scaled query evaluation. The evaluation criteria used in Pro-DFM is represented as simple queries.