The Importance of DFM, DFMA and SPC to Manufacturing Processes - Essay Example

The Importance of DFM, DFMA and SPC to Manufacturing Processes. By The Importance of DFM, DFMA and SPC to Manufacturing Processes Section one Design for Manufacturing (DFM) is the practical planning of how products are going to be manufactured with the purpose of optimizing all functions attached to the manufacturing process and this include, cost of production, quality and other procurement services. Through this approach, resources like time and cost to be spend in manufacturing process, is greatly minimized. For instance, when designing electronic component, manufactures specify tolerance level of around 0.5 or any value. The aim if this is to avoid investing resource and time with an aim of achieving 100% quality. As a result, these extra resources are channeled to other processes hence saving them (Anderson, 8). There are seven principles of an optimal cost effective design. First is, reducing the number of parts used in manufacturing. This effectively reduces the manufacturing cost. The fewer the number of parts, the lesser the purchases, handling, assembly difficulty, service inspection and testing. A part which is not dependent in terms of relative motion to other parts ought not to be manufactured with a different material. Components that make the assembly or service of other parts extremely difficult or impossible should be removed. Manufacturing process such as modeling of injections and powder metallurgy are meant to cut down cost this is because designs from such process consist on minimal materials. Secondly, development of a modular design: The adoption of a modular based design of a product saves time and again aids manufacturing. It is a flexible design approach where a product is updated by redesigning the manufacturing process. Furthermore, modular design approach help to run tests before the final assembly is created. This allows the utilization of the standard components to minimize product discrepancies. A setback of this factor could be the connection in terms of application. Harnessing standard components has proved to be more cost effective in DFM. The third principle is designing of multifunctional parts. Multi-functional parts refer to parts which are manufactured to offer more than one function. Designing multi-functional parts reduce the total number of parts to be used in a design and manufacturing process. This approach is analogized to killing two birds with a single stone. An example of multi-functional part design approach is an electrical conductor. An electrical conductor acts as a structural member and also as a heat dissipating element. Fourthly, designing parts for ease of fabrication. Designing a product which is easy to manufacture is another principle of design for manufacturing. The object to be designed is critically examined and to identify which materials can be used to make the design. Afterwards a methodology, of selecting the best combination of materials and manufacturing process, is employed in order to reduce the manufacturing cost (Priest, John and nchez, 11). Artistically, tempting procedures such as painting and machining should be avoided as they are deemed as waste resources and only add cost to DFM. The fifth principle is, avoid separate fasteners. Fasteners always increase the cost of manufacturing. In addition to that, operations that involve fasteners are not 100% successful, hence they reduce the efficiency of the manufacturing process. If fasteners have to be used, then some guides should be followed for selecting them. This guides aims at minimizing the number, size and variation used as well as utilizing standard components where possible. Screws that are too long or too short should be avoided. Likewise separate washers, tapped holes, and round heads and flatheads should be used. The sixth principle is, make the most of compliance. During insertion operations, due to differences in part dimensions or accuracy of positioning device, errors can originate leading to damage of a part or to the entire equipment. Therefore, it is essential to include conformity in the part design and in the assembly process. This can be attained through accurate measurement. For instance, when one is manufacturing a shaft and hole tool, accurate measurement will enable the shaft fit into the hole without damaging it, Finally, reducing the number of times of handling. Handling is a common term that is used to describe positioning, orienting and fixing activity of a designed part or component. The process of designing components that required minimum handling is another principle of an effective design for manufacturing strategy. One way to minimize handling is to design symmetrical and flexible designs that are easy to place or orient. Any component, for instance, people, material, environment, that has the ability to produce an output, is called a process. It is good to note that these factors are subject to variations due to various reasons. As a result, they have to be well monitored if a desired quality of products is to be attained hence statistical process control (SPC) tool come in handy. SPC, as an analytical tool, enables one identifies flaws within a process so that correct improvements can be made where necessary. The most commonly used approach in making improvements is measurements. However, in most designs, measurements used are not based on the international standards (Chowdhury, 10). Therefore, there is need for organizations like International Organization for Standardization (ISO) and others to develop measurements that are globally acceptable. Six Sigma is a SPC business initiative management tool first introduced by Motorola in the early 1990s and it assists in identifying the quality deviation a product. The concept of Six Sigma has evolved over the last couple of years. Six Sigma has a literal, conceptual, and practical definitions and it can be viewed from a metric, methodology as well as the management system. In Six Sigma, process disparities and product or service defects are scaled down by extensive use of statistical techniques. These statistical techniques employ the use of tool such as control charts, design of experiments, and response surface methodology among others. While reporting the process improvement, certain numeric values, herein referred as Six Sigma Metrics, such as Defects per Million Opportunities (DPMO), are used. Thus, Six Sigma was initially started as a defect reduction effort in manufacturing and was then applied to other business processes for the same purpose. The application of Six Sigma as a management system highly improves the performance of a given system. CP and CPK are proficiency statistics which enable one evaluated the process of a given specification. They are very effective tools as far as quality management in involved. Before designing a particular product or design, it is always good to set the standard or the quality of the product one want to acquire. This is made possible by these two statistical tool. Every product produced has boundaries defined as upper limits and lower limits. In DFM, these limits are referred to as uppers and lower specifications respectively and this limits are effectively determined using CP (Whitehouse, 13). In addition to that, quality of a product can also be measured by calculating its sample mean and standard deviation. Standard deviation enables one know the degree of variation the designed product is from the sample mean and CPK assists in measuring them. The process of manufacturing heavily relies on probability. The outcome of the product cannot be accurately predicted. In order to address such problems, computer simulations can be used to model the process of manufacturing and enable the manufactures come up with optimized ways of achieving a process effectively and efficiently. The purpose of simulation is to enable abstract combination of materials without physically performing the actual process. This helps minimize risks involved in manufacturing uncertainties. Section two Geometry is the art of representing information using diagrams and symbols. In engineering, variations, between features, has to be allowed so that accuracy can be achieved (Kenneth, 14). The table below shows some common geometric tolerance symbols and their functions. Section three ISO standards are standards unit of measurement which are used in any engineering work. These standards were first implemented in the year 1994 as a common units for all engineering framework. This was a measure taken to ensure that engineer do not come up with their own measurement methods but adhere to one common unit of measurement that was to be used globally (Bralla, 16). In order to understand the concept if ISO measurements consider this example. The measurement in the table below are taken from a micrometer screw gauge. How do various standards improve the measurement and hence increase confidence in measurement let consider a series of measurements of a fine turned shafts using a micrometer and corresponding uncertainty associated in measurements as given in table 1.1 below. Contribution Source Uncertainty (μm) uc Uncertainty (μm²) uc² Uncertainty (%) of uc² Uncertainty (%) of uc² Error indication Micrometer 1.8 3.24 23% 33% Anvil 1 Flatness 0.5 0.25 1.5 Anvil 2 Flatness 0.5 0.25 1.5 Parallelism 1 1 7% Repeatability Operator 1.2 1.44 10% 17% Accuracy of 0 point 1 1 7% Temperature Environment 1.96 3.48 27% 27% Temperature difference 0.28 0.08 0% Work error Work piece 1.8 3.24 23% 23% uc= 3.79 μm uc² =14.34 μm ² uc² =100% 100% U=7.6μm Table 1.1 Vagueness values in a micrometer test In the above table the value U=7.6 μm is the diameter tolerance of work piece calculated thorough meteorological standards (ISO-14253-1). This value means that the diameter tolerance of work. The piece must be reduced by to take account the uncertainties associated with a series of measurements and how they can be removed through slandered meteorological measurements that enhance confidence in measurements. Shaft-based ISO standards are standards in which the dimensions of the shaft are included as a limit of the measurements, that is, the hole is usually bigger than the shaft. On the other hand, in hole-based standards, the limits of measurement are not an inclusion of the basic size, that is, the size of the hole is smaller than the shaft (Hoffman, McCauley and Hussain, 6). When assembling two parts together there must be a range of tightness that is allowed between the two parts, this range is what is called a fit. Discussed in the subsequent paragraphs, are the three main types of fit and how they can be used. They are, clearance, interference sliding and fit respectively. A clearance fit is a fit in which one part, the shaft, fits into another part, the hole, and leaves a clearance gap. In this case, the hole is usually bigger than the shaft. This kind of fit can be best used to make pulley systems (Tennant, 4). The second fit is the interference fit which is defined as a fit in which one part, especially the shaft, is larger than the hole and therefore force must be used to fit them together. Finally the sliding fit, this is a fit in which when it is loose it provides clearance fit and when it is tight it gives way to an interference fit. It is mostly used to identify shafts that are compatible with one another. As to conclusion, minimizing cost of production while maintaining quality of product is very beneficial to a business or a company. DFM is a tool that enable monitoring components of production while adjusting them to get the best output. Coupled with useful statistical control tools like SPC, CP and CPK, more efficiency for better output, is attained. Finally, with DFM, high rate of production is achieved this is because the main focus is manufacturing products easily. References Anderson, D. M. (2010). Design for Manufacturability and Concurrent Design Cambria: CIM Press. Chowdhury, S. (2003). Design for Six Sigma. London: Prentice Hall. Hoffman, E. G., McCauley, C. J., and Hussain. M. I. (2000). Shop Reference for Students and Apprentices from Machinery Handbook (2nd Ed.). New York: Industrial Press. Kenneth, D. P. (2011). Manufacturing and Assembly Manufacturing and Assembly DFMA New York: Prentice Hall. Tennant, G. (2001). Six Sigma: SPC and TQM in Manufacturing and Services Aldershot: Gower Publishing Limited. Whitehouse, D. (2003). Handbook of Surface and Nanometrology Bristol: Institute of Physics Publishing. Bralla J. G. (2006). Handbook for product design for manufacturing: a practical guide to low-cost production. McGraw-Hill Priest, John W., and J. M. nchez. (2001). Product development and design for manufacturing: A collaborative approach to producibility and reliability. Marcel Dekker. Read More