Design For Manufacturing And Assembly
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Published: Mon, 08 May 2017
A design process that focuses on meeting customer requirements meanwhile balancing the important aspects such as cost, quality and performance is Dfma.
DFMA is an abbreviation for “Design for manufacturing and assembly”. It a software comprised of various principles or methods when used properly will improve the ability of design to be easily manufactured and assembled thereby decreasing the costs. This system can be divided into three major sections. The first is the raw material. Choosing the right material is the foundation of a good design. Second is the machines and processes used to work the raw material. The right process is essential for creating finished parts that will meet your design requirements. Third is the assembly of the product. It is during the assembly of the finished product that provides the greatest opportunity to apply DFMA principles. The proper use of DFMA principles will allow one to design a quality product.
- DFMA follows an exacting design review method
- It identifies the following features:
-Optimal part design of the product.
-Assembly and fabrication operations to produce an efficient and cost effective product
- It reveals that initial ideas may not be the most efficient in all the cases.
- It is a structured catalyst methodology used to analyze a design and generate ideas for further improvement.
- DFMA encourages concurrent engineering during product design so that product qualities exist in with both the designers and other members of the production team.
- It is a communication tool for the team.
- It is a bench marking tool.
- It defines the design and manufacturing capabilities of self and competitor
- It provides a non-threatening way to get people talking about a design without feeling like others are encroaching on their territory
- Einstein said “ the best design is the simplest one that works “. DFMA provides the cheapest way to that goal.
Customer requirements and product specifications are useful for guiding the concept phase of product development. But during the later stages product design teams often have difficulty linking needs and specifications to the specific design issues. Due to this, many product design and development teams practice ‘Design for X’ (DFX) methodologies .The most common of these methodologies is Design for Manufacturing and Assembly (DFMA), which is an engineering philosophy used generally by design and manufacturing engineers that promotes simplifying parts and product designs to reduce production costs. Other (DFX) methodologies are
- DFD Design for Disassembly
- DFEMC Design for Electro Magnetic Compatibility
- DFR Design for Recycling
- DFE Design for the Environment
- DFS Design for Safety
- DFT Design for Test
DESIGN FOR MANUFACTURE:
Design for manufacturing software follows a simple rule which states one can improve the efficiency of a product by minimizing the number of parts that have to be assembled so the cost of the product is efficient and easy to manufacture. This manufacturing approach is different from the traditional approach where a huge project is broken down in smaller parts (steps) and then these steps are assigned to various departments. These departments then work independently most of the time. The traditional approach enhances the specialization and functional job focus of the product devolpment. But the main drawback with the traditional approach is the market time plus various difficulties that arise in the manufacturing process.
While designing a product lots of parameters have to be kept in mind ot of which that most important one which manufactures ask is can we build the product now that they have the product designed. A way to design a particular product is to make sure that the product maintenance is less, its reliable, time factor, its simple. Maintenance of a particular product shold be less or else it could cost a huge amount for maintenance. Reliability of a product is also a key factor because if the product fails consistently it makes little sense and thereby it’s a huge money waste to the organization. Speed is the another key factor in designing, if it take too long to make the product then it will have more and more competitors. Competitors control the market by releasing their product faster than fellow counterparts. Using few parts also increase the simplicity and saves money as well, more parts for a product increases the rate of complexity which can lead to malfunctioning of a product. The simpler the product is the fewer are its problems.
Over the wall syndrome process was used before the use of DFMA process. Over the wall syndrome is a process where if an idea was generated in a company it would first have to be approved by the president of the company. It would then go then go to the manger of the process deign to be devolved into a product. If any problems would arise it would then be asked to redesign and then brought into the notice of the manager. The resolved problem would then be sent to the engineers where the work would continue where they left from. This process was a huge time consuming process because everyone is not situated in the same location and it would also take a lots of time to solve the problems. The total process sometimes could take year or more. The concept of design for manufacture was used to break these barriers and thereby reducing the time spent on designing the products.
DESIGN FOR MANUCTURING
has some advantages and disadvantages just like any other software. Firstly dfma tools don’t take into consideration many manufacturing capabilities or tolerance. DFM has many computer based tools which nearly complete the design but when we analyze the design finally there are number of barriers which prevent substantial modification of the design.DFM use’s too many tools which can increase the manufacturing costs of a product, its also gives very little feedback upon which to base the design modifications.
One advantage with DFM it suggests the optimal assembly and the degree of automation. DFM can produce higher products yields through manufacturing. It also increases the performance and the predictability of the product yields.DFM analysis helps us to compare various materials and manufacturing process for the parts of the components. There is an increase in the performance and the cycle time is reduced enormously.
DESIGN FOR ASSEMBLY SOFTWARE
Design for assembly can be defined as a analysis for improving the product design for a simplified and low cast assembly. Design for assembly main aim is to simplify the product so that the cost of assembly is reduced. By applying dfa we can also improve quality, reliability in the production equipment and the part inventory.
G. boothroyd was the person who promoted the usage of DFA in the industry. The practice of dfma is a relatively recent development, but many companies have been following this process form a long time. For example, a company called general electric published its own internal manufacturing handbook as a set of guidelines for its engineers to follow. These guidelines had the same set of principle of DFA without actually distinguishing it from the rest of the product development process.
Assembly methods can be divided into three different groups
In manual assembly the work is mainly done manually parts are transferred from one work bench to another. Worker use different types of hand tools. This is one of the most flexible and the adaptable of the assembly methods methods.
Automatic assembly follows a process where it consists of a custom built machine that assembles one and only a specific kind of a product. In this assembly large amount of investment is needed and as the production increases the total manufacturing costs decreases. These types of assembly can be only beneficial when a product is produced in bulk.
Robotic assembly in this the assembly we use robotic systems. The robotic systems can take the form of a single robot or a multi station robot. Robotic assembly also involves huge capital costs. In robotic assembly the robots are normally controlled by computers, one company can have huge flexibility on different types of products in robot assembly
Assembly methods are chosen by a company keeping two important parameters in mind ie time and costs.
Relative costs of different assembly methods by type and production volume.
Design for Assembly
Vincent Chan and Filippo A. Salustri
Design for assembly is an experimental way to identify the unnecessary parts in a product and to determine its assembly time and costs. DFA is a software which gives the design engineers more tools to analyse various design concepts and therby creating innovative products with few and simpler parts.
Using DFA software helps engineers to assess the costs of each part and then modify the product through part reduction concepts. The outcome of a DFA based design is a much well designed product with fewer parts which is both efficient and also easy to assemble. The benefits of a DFA based design are reduced part costs, improved quality and reliability, and shorter development cycles.
DESIGN FOR ENVIORMENT:
Design for environment is an idea of implementing various environmental friendly aspects to create a product. Design for environment helps a company to minimize the waste and also decrease the pollution thereby saving some money which can be used for other processes.
Design for environment helps engineers at various stages of the manufacturing process. While selecting a manufacturing process for a product an engineer should also keep in mind various aspects such as amount of energy used, amount of energy released, process should be non toxic. These are all the various aspects an engineer also has to keep in mind other than manufacturing and assembly of the product. Dfma 2009 gives the design engineers an extra option in which they could conduct a environmental assessment during the concept stage.
The analysis helps the designers to select a suitable material from the DFMA library that they prefer to use. Then the software reveals the various proportions of those materials in a particular product. It also estimates various other proportions like reuse, recycle, end of life destinations and landfill. All these measure help the company meet the requirements set up by ROHS.
DESIGN FOR RECYCLING:
Design for recycling en-cooperates methods such as recycling and recyclability of products to obtain recyclable products. Recycling is a process where a product or a raw material is recovered from waste stream and is reused as a raw material in the manufacturing process of a new product. When a part is recycled it does not affect or change the properties or the price of a particular product. Design for recyclability helps a manufacturing process to reduce the environmental impact of a material and by following design for recyclability large number of parts can be reused this thereby decrease the cost for raw material and thus decreasing the overall costs for manufacturing a product.
DESIGN FOR SAFETY:
Many companies use safety standards purely as guidelines. Although some safety equipments are costly the future savings make up for the cost invested. Safety production also helps the company in producing more. Safety also improves the morale of the worker which helps in the increase of production.
The main aspects or the principles on which DFMA focus are:
- Raw materials
- Minimize the number of parts
- Minimize the number of fasteners
- Avoid difficult components
- Use modular subassemblies
- Use multifunctional parts
- Minimize reorientation
- Use self-locating features
- Avoid special tooling/test equipment
- Eliminate Interfaces
- Minimize operations & process steps
- Part Interchangeability
- Design Tolerances to Meet Process Capability
- Determine Capabilities of each Process Step
- Design for Ease of Part Orientation for Assembly
- Eliminate Multiple Solder and Cleaning Steps
- Eliminate Adjustments
DFMA Raw materials:
Choosing the best raw material for the design is the first step in designing a world class product. There are many factors that need to be considered when choosing the best material for a design. At first the material must have the correct mechanical and chemical properties to meet the design criteria. Secondly when possible one should choose a standard material that is readily available. Using special materials may increase purchase price and lengthen deliveries. Third use near net parts whenever possible. The raw material’s profile should be as close to finished parts as possible to reduce processing.
DFMA Minimize the number of parts:
Minimizing the number of parts directly affects the final cost of the product. By minimizing the number of parts Product quality, flexibility and reliability of the product is increased. The fewer parts a product has the fewer chances of misalignment.
DFMA Minimize the number of fasteners:
Fasteners increase the complexity of a particular product, thereby increasing its weight and cost. Dfma main aim is to eliminate the fasteners and include self aligning features into a part. If fasteners are needed in a part then its better off using self tapping screws
Standardization is a phenomenon which requires increase in communication between different design teams working on a complex product. The more standard products an engineer uses for manufacturing of a product the less number of tools are required and it gradually decreases the cost for production. The best method is to create a list of various standard parts available for each project. In order to smooth the progress of the standard parts, the design and manufacturing team should make the most of the different resources such as trade magazines, various vender catalogs and various part manuals.
DFMA modular sub-assemblies:
With the help of modular designs, the identification of problems becomes easier by reducing the number of parts. Maintenance and serviceability of a product also increases by using modular assemblies. By designing parts as independent modules times for disassembly are reduced thereby decreasing the overall repair time.
DFMA Using stack assemblies:
Stack assembly is stacking up the components of an assembly from bottom to top. The main purpose of using stack assemblies is it requires less reorientation of parts which leads to speeding up the assembly process, which thereby decreases the cost for assembly.
DFMA self locating features:
The use of Self aligning parts speeds up the assembly process. Self aligning parts don’t need any kind of adjustment or re-orientation. The more the self aligning parts present in a product assembly the much easier it is for an assembly worker to assemble the product. Different types of self aligning parts are washers, ball bearings, roller bearings.
DFMA simplifies and optimizes the manufacturing process :
Minimization of manufacturing process reduces the direct and overhead costs. While designing a production process a designer’s main aim should be on various factors like
Smooth flowing of materials.
Using various processes than can easily be controlled.
Separating different operation (like manual and automated )
DFMA Eliminate Interfaces:
Eliminating of interfaces is an important phenomenon while assembling of a product. The amount of interfaces increases the cost of an assembly. Each interface present on the part increases the time for assembly as it requires double the amount of information.
DFMA Part Interchangeability:
Interchangeability is a phenomenon where similar parts are used for manufacturing of a product that can be interchanged. This phenomenon reduces the number of parts used for an assembly which leads to a decrease in assembly time and costs. While using interchangeability left and right handed parts should be avoided because they create confusion which directly leads to increase in time.
DFMA Design Tolerances to Meet Process Capability:
Tolerances are such parameters of a part which tend to complicate the design. If a tight tolerance has been specified for a particular part, other process such as inspection or fixturing has to be done. Which gradually increase the overall cost of a product and also time is wasted. They fore a designer during the design process should understand the manufacturing and suppler capacity while specifying different tolerance to make sure that tight tolerances are necessary
DFMA Minimizes parts for interconnections:
Interconnected parts are flexible parts which are used to connect two parts in an assembly. Interconnected parts are prone to get damaged when compared to other parts. When harnesses are used in an assembly of a product always ensures that we are using distinctive connectors for a simple reason to avoid the connectors being misaligned
DFMA Determines Capabilities of each Process Step:
Process capability can be defined as an ability of an process to produce within a suitable specification. When the correct process capabilities of a particular deign are determined, it also helps the design team by giving them some valuable information from which they could choose a simple technology and a simple sequence. Which directly decreases the costs for assembly and gradually the time for production is also decreased.
Eliminate multiple solder and cleaning steps:
The more processes one uses in manufacturing of a product the more are its risks, costs and potential for delays. Production engineers use DFMA to minimize the processing technologies used in the manufacturing process. The more the number of technologies the greater are the chances for various errors and part malfunction.
Minor adjustments only affects the look of the product, but it does not affect the functionally of the product whereas the major adjustments have a major affect on the functioning process of the product. Adjustments are normally complicated process which involves huge costs. Elimination adjustments could also include replacement of parts in the assembly.
- Dfma can be used as the basis for engineering studies and thereby provide a guidance for the design team to simplify the existing product, reduce its manufacturing and assembly costs.
- It can also be used as a benchmarking tool to study competitors and to quantify manufacturing and the difficulties that arise during assemblies
- One can also use Dfma as it “should-cost” tool to help validate design concepts, provide cost predictions, and to negotiate suppliers bids and contracts.
The main purpose to use dfma is
Dfma also helps us to keep various aspects in mind during the manufacturing and assembling a product.
- Is material that we are going to use available in standard stock configuration.
- Is material well-suited with the most desirable manufacturing process.
- Is the material available from reliable sources.
- Do material prices fluctuate widely over time.
- Are special alloys and exotic materials used only for environmental or functional demands.
- Are tolerance dimensions realistic.
- Is marking and stenciling defined and visible.
- Are assembly notes complete and definitive.
- Is internal wiring layout critical? If so, is the location and routing specified?
- Is harness development required? If so, can the harness be fabricated outside the unit and installed as a subassembly.
- Does the design lend itself to automated assembly.
- Are component parts accessible for assembly.
- Can testing be performed without disassembling the unit.
- Are standard connectors and assembly hardware used.
- Are circuit cards, if used, designed to plug in.
- Has the assembly been analyzed to meet electrical, thermal, vibration, and shock Specifications.
- Can printed circuit flex cable or moulded ribbon be used in place of hard wiring.
- Can plastic tie-wraps be used in place of lacing or spot ties.
Designers do not enter a new design situation as newcomers or novices. Through education and practice they have acquired a vast repertoire of design solutions, which they will carry over the design task at hand (PASMAN, 2003).All these experiences are due to the result of several situation mistakes, improvement opportunities or just real good new ideas acquired due to development and research on design area.
A good engineer must know what happens in his factory in a detail level that can permit an assembly to be done and an injected part to be extracted and also must know were the assembled parts are and the injected material should be in the correct geometry. These means two different conflicting conditions. The designer cannot stay in his area ignoring what is happening around and the designer must know his tasks perfectly to justify his work position.
The question remains, is it possible to be in simultaneously in the factory and in the design office? FERREIRA and TOLEDO (2002) say so and suggested how using the technique of Design for Manufacture and Assembly is possible to “hear the voice of the production line” and been virtually near to the information. BUSS et al. (2001) agreed with this point of view, saying that the DFMA allows bring to the project area the considerations related to the assembly and manufacturability of the product. Finally FAGADE and KAZMER (1998) defended that the most significant advantage of DFMA is the encouragement of the teamwork between project and production, improving the reliability of the final product and generating the possibility of cost/time to deliver reductions due decreasing in the parts number and/or more productive parts that can accelerate processes.
WHAT TO HAVE DFMA:
First of all we need to understand the project with DFMA techniques. For this is important to define the product conception as a task of multiple responsibility, from the conceptual sketch to the packed assembly delivered there are many operations and actions that need to be considered. Thus in accordance with the key points the total chain of the process is to be defined in an clear form from one (process) to another to provide or receive services/pre-processes
Also is essential to let all teams warned that the project is designed for manufacture and assembly – and this means that all attention is focused in a development for that condition and this means that the manufacture must be heard all time.
To achieve all this, there should be efficient communication, efficient information, translation of data is the basic requirements on a DFMA driven development.
What’s the correct time to carry on a Dfma driven project?
CAPUCHO et al. (1997) adopted after observe the behaviour of multidisciplinary teams that the local rework caused by an activity with adverse results is much smaller then a global restructuring of a project – also, a global reproject may be impossible due costs (according to HARTLEY and OKAMOTO (1992)) the inclusion of a change in a running project is more expansive as more is close to the project end or due other factors as time and market expectations.
So, once the projects main activities are defined the doing them is a good option irrespective of their order of development. Mistakes, adverse results and budget can less compromise the project running timetable.
According to BOOTHROYD (2001) the rising sophistication in the use of moulded injection plastics. Injection moulding is an important tool to win the battle of reduces parts to save costs and creates an elegant design.
Based on the literature present and other articles researched by the groups of teams on plastic injection acquired by work and development in other lines (refrigerators and washing machines), where plastics are used in a very large scale,It was decided to try a solution using injection of thermoplastics.
This was a risky decision. First of all the temperature limitations on a plastic material are more severe than in a metal – limits also include the possibility of deformations, flowing and resistance downgrade. After that, a running and deployed solution give some comfort to the project designers and all of other teams: the new idea was offering a possibility of assembly improvement and a bundled possibility of fail, this means that for some parts of the workgroup the manufacturability advantages were not good enough to release the change – in short words that was to develop a substitute part to improve a good working assembly to give some help to line and to reduce costs, with a low, but existent, possibility of further problem.
Case studies of companies that used DFMA software
Company: Harley Davidson
Identify the total costs (make design, material, process) and by making some substitutions to have an impact on cost.
Improve the overall cost predictability of the product to meet the desired revenue and costs targets
Engineers of Harley and the suppliers team up and the cad models of each part are loaded into the dfma software. Dfma software generates cost information that gives rise to various discusiions on cost, labour rate , process materials etc.
A motorcycle frame was designed which was to cut down the costs by 70 dollars . before the manufacturing of the new frame Harley Davidson analysed various departments in DFMA like material cost , operating efficiency, plant cost. The software predicted that the current frame costs within 0.5%.
Frame of Harley Davidson motorcycle
Then the new frame was analysed in DFMA software, the company found out that the new frame would cost 7 dollars more than the old frame (not dollars 70 less as they had anticipated). Harley Davidson was glad to discover this before they went into production and they researched various other areas for cost savings, before the bike was launched.
General goals :
To reduce the costs inside the plant
Generate a good slim design.
Simplify or eliminate assembly processes.
Teams were developed which consisted of all types of engineers (mechanical, electrical, technicians, air ventilation designers. The teams closely observed all the video tapes of the assembly line of the current microwave to spot the different weak or awkward operations. Teams structured a bill of materials and saw how the product was assembled or in what order it would assemble before crating a prototype of the model.
Engineers used DFMA and prepared a performance matrix in which they could evaluate the easiest and the awkward assembly operations.
In the original design, the worker had to turn the chassis over to install the door spring, and then turn it back over to do the rest of the operation. With the help of dfma the engineers can to a conclusion to have the spring in the front of the oven, so that there was no need to turn the chassis to install the spring.
With the help of DFMA analysis whirlpool had the following results.
- 29% part reduction was achieved .
- 106 parts for the new oven, versus 150, this was more than expected.
- Many of the reduced parts were fasteners, cutting assembly time 26%
- Standardized cabling across product lines, creating immediate assembly and part savings
- Payback time was 6 months
Product: Gourmet coffeemaker
High standards of coffe tate
Uniform coffe saturation
Weight of the design is less’
Efficient design for best retail price.
Access group is one of the leading distributor and manufactures of a comprehensive range of durable products, which include water treatment and air filtration systems and most importantly an award winning coffee maker. Which we are going to discuss in this case study.
Two years ago access business group wanted to design an high end coffee maker to support their own line of water filters and gourmet coffees. According to access business group their main was to build a coffee maker which is stream lined and an efficient machine and they achieved their objectives with the help of design for manufacture and assembly software.
Using DFMA analysis:
The major aim of DFMA analysis was to determine the minimum number of parts for this design.
With the help of DFMA the design engineers could reposition the motor much closer to the power and a bit higher on the machine. This phenomenon was achieved due to the reduction in the number of parts. Most companies now a days gives higher priority to the look of a product, designers of gourmet decided to replace the existing motor with a new sleek and a less power motor thereby saving the costs.
Manufacturing of the coffe maker using DFMA involves three stage
- Bill of materials
- Middle product development
- Fine tuning of the design
Design for assembly consists of an index Colum which shows the results or the rating of the design. As the time taken for assembly, costs for the assembly and when the parts are consolidated or omitted the index number rises. The table present below indicates how DFMA software helped kahve coffee maker to reduce the part count, cost and assembly time.
Kahve coffee maker
DFMA Round 1
DFMA Round 2
DFMA Round 3