26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process The `best' design solution can only be determined if the selection decisions for material, shape and process are all considered simultaneously. The degree of difficulty involved in performing this co-selection is normally prohibitive. As a result, some iteration between the areas of selection decisions will be necessary. In practice, the relative importance of the links will vary from problem to problem, guiding the way a selection should be performed. Given the iterative nature of design, this route towards an optimal selection is to be expected — it is important to consider several solutions (combinations of shape, material and process) rather than attempting to finalise the choice of one element before considering the effect on the whole inglés In a practical design situation, it is usual for the rough shape of the components to be fixed first. If the design is performance-driven it is often Choosing a process obvious whether the material or the process should be selected next. More usually, however, the design is cost-driven and it is not so apparent ESPAÑOL whether the material or process should be selected next. The most common approach in the literature is to select the material first [5], Elegiris un proceso a subset of suitable materials and then to generate subsets of although this is not always the case [6]. Another approach to determine suitable processes for each of these groups [7]. AsOPCIONES a designDEproceeds, increasingly important to incorporate some element of coEXTENSIÓN it becomes MÁS » selection between material and process into the selection in order to make a robust decision It is widely recognised that the most appropriate approach to selection during engineering design depends on the design context. This is just as true when selecting processes as it is when selecting materials or components. For convenience, we can follow Pahl and Beitz [1] and split the context of design loosely into conceptual (preliminary), embodiment (intermediate) and detail (final) stages During the preliminary design stages, when little design or material detail has been fixed and all processes are open for consideration, a broad-brush approach to selection is required. To allow a rapid assessment of the options, with minimal user input, all processes may be described in a common format. The Cambridge Engineering Selector software [2] takes this approach: by using a database that describes process capabilities with records which are universal to all processes, it allows processes which meet certain design needs to be quickly identified. https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 1/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process During the final stages of design, when almost all the details of process, material and shape will have been determined, it is only necessary to optimise the fine details. Knowledge-based software plays an increasing role at this stage — for example, by providing checklists of “Frequently Asked Questions” (FAQs) to help identify and avoid common mistakes (e.g. TWI's Web-based software “JoinIT” [3]), or by applying “design for manufacture and assembly” (DFMA) techniques to rationalise number of parts in an assembly process [4], [5], [6]. Similarly, there are many software packages for problems such as mould design in casting or injection moulding, which help designers to ensure good mould filling In the intermediate design stages, however, when some design details have been fixed but there are still competing possibilities, these approaches have various shortcomings, such as: • the selection tools may not be sufficiently discriminating; • the optimisation tools may take a prohibitive length of time to assess all the possibilities; • data may be too sparse or unreliable to give any realistic alternative to physical prototyping (in spite of the associated cost). It is apparent, therefore, that different approaches are required to successfully choose processes in this ‘middle-ground’ of design, when selection is confined to a subset of processes which are truly competing. We call these selection problems manufacturing tasks. It should be recognised that “selection for manufacturing tasks” implies a much wider scope than “process selection”, because it is often not simply a matter of choosing “which process”, but simultaneously refining the choice of material to be used and/or refining features of the design. intermediate stage - no stakes inthe ground -this is the tricky area https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 2/22 26/5/24, 15:50 https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 EG5601_SEM3_2023/24: Choosing a process 3/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process https://www.sciencedirect.com/science/article/pii/S007964250000013X There are therefore three main aspects to address: Performance: After processing, the component must be left with a satisfactory set of engineering and material performance characteristics. Processability: The process must be able to modify, form or join the material in the required manner repeatably and reliably. Cost: Processing the material in the given way must be reasonably economic. https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 4/22 26/5/24, 15:50 https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 EG5601_SEM3_2023/24: Choosing a process 5/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process During phase 1, the task is defined in such a way as to enable the creation of the procedure. The first stage is to outline the task in detail, specifying the requirements that will form the inputs to the selection, and the results that will be needed. The second stage is to specify the relevant process attributes that will be used to describe the process in sufficient detail for selection to take place. It’s imperative that the manufacturing technique is selected before spending large amounts of time creating a 3D model. This is because each manufacturing technique will require different design details. There are hundreds of manufacturing processes. You are likely to already be familiar with the most common, e.g. casting, forming, moulding and machining. For any given product, there will be multiple manufacturing processes that you’ll need to select from. The process you choose will depend on many factors called the process selection drivers. These process selection drivers include the following: An experienced manufacturer will have a good idea of all the process selection drivers mentioned above. Depending on the product design and manufacturing considerations, a good manufacturer will be able to guide you through the selection process Factors that need to be considerd in selecting a process https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 6/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process Manufacturing Costs Left CNC milling, no tooling cost, high part cost. Right Die Casting, high tooling cost, low part cost https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 7/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process There are two main costs associated with any manufacturing process: Tooling Costs, and Part cost Tooling cost is the cost of creating the mold, jig or other one time setup cost associated with starting production. The part cost is the cost incurred each time a part is manufactured. Generally speaking the higher the tooling cost the lower the part cost and visa versa. For example, die casting molds are expensive, but once made, the cost of producing each part is low. By contrast a CNC machined part requires very minimal setup, and no molds, but milling each part takes time and is thus more expensive. The same part can be made with either method. However, depending on the number of parts being made, either or might be more cost effective. At low volumes CNC milling is more cost effective. At high volumes die casting is more cost effective Manufacturing Technique Capabilities https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 8/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process Left Injection Molding, Hollow parts not possible Right Blow molding, Only makes hollow parts Each manufacturing technique is capable of creating a certain type of geometry. Injection molds can create incredibly complex geometries, but they cannot create hollow shapes. This is why water bottles are blow molded, not injection molded. That being said, it’s important to be aware of the various capabilities of different manufacturing processes before deciding on one. https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 9/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process Desired Look and Feel of Product Left Stamped Right CNC Milled The look and feel of a product is incredibly important and the manufacturing process plays a large role in how a product will be perceived. For example, CNC machined parts have a look and feel that cannot be matched by stamped metal parts. https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 10/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process Materials Needed for Production https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 11/22 26/5/24, 15:50 https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 EG5601_SEM3_2023/24: Choosing a process 12/22 26/5/24, 15:50 https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 EG5601_SEM3_2023/24: Choosing a process 13/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process Picture Cast iron being poured into a sand cast mold Some materials can only be formed with certain manufacturing processes. For example, if you need the part to be made out of iron, or any other ferrous metals, die-casting will not be an option due to the high temperatures needed to liquefy those metals. Sand casting or lost wax methods will be needed. https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 14/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process Desired Surface Finishing of Product https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 15/22 26/5/24, 15:50 https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 EG5601_SEM3_2023/24: Choosing a process 16/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process Some manufacturing processes allow for certain surface finishes. Injection molding allows for in-mold decorating, where as extrusion does not. Thus, before choosing a manufacturing process, decide which surface finishing is necessary for the look, performance and longevity of your product. You should now have a better understanding of how an optimal manufacturing process is selected for a product. Need help choosing the the right manufacturing technique for your new product? Give us a call and let our product development experts guide you along the way. https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 17/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process Decide Whether You Require Automation https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 18/22 26/5/24, 15:50 https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 EG5601_SEM3_2023/24: Choosing a process 19/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process Automation has officially entered in the manufacturing process, and manufacturers are using cobots (collaborative robots) to boost the productivity and increase efficiencies. So, you must decide whether you want to take this route or stick to human employees only Don’t Forget the Finishing Needs The manufacturing process cannot be complete without the finishing touches. Finishing a product properly not only makes it look good, but it also enhances the longevity and performance of a product. Hence, while deciding the manufacturing process, you should choose the right process to finish off every product with perfection. Injection moulding is a good option as it allows in-mould decorating. Quantity of the product Cost for tooling, manufacturing machines and equipment Availability of material and cost of material Capabilities required to processes material Product dimensions and size Time required for processing Level of skilled labor required Surface finish required Design tolerances Process supervision Energy consumption Waste produced by the process Maintenance costs Other costs Follow the simple procedure below to select the appropriate manufacturing process for a product: https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 20/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process STEP 1: Selection criteria The first step in manufacturing process selection is to establish selection criteria based on key process selection drivers: manufacturing volumes, value of the product, part geometry, required tolerances, and required material. The material choice will be very effective in narrowing your options down. This is because many processes work exclusively with certain materials. For example, injection moulding can only be used with polymers, whilst die casting can only be used with metals. Your material choice will instantly rule out a vast number of unsuitable processes. The expected manufacturing volume will further narrow down your process options. For a large quantity, a manual production process like manual machining would be completely impractical. Instead, you would need to consider an automated process such as moulding. The geometry and tolerances required for a product will also filter out many processes that would be unable to achieve the desired accuracy. STEP 2: Identify processes After applying STEP 1, a smaller range of processes will be available. At this point, you should ideally work with an experienced manufacturer to identify those processes that can satisfy the required quantity, material requirements, and part geometry. STEP 3: Evaluate processes After identifying the potential processes for manufacturing a product, it is time to evaluate them based on less broad parameters, such as process capability, processing time, tooling and equipment cost, degree of automation available, skill required for operation, waste produced after processing, and postprocessing required. It is a good idea to create a decision matrix with a score or value for each of these important elements. STEP 4: Selection You should now be able to use the weighted decision matrix you created in STEP 3 to identify the best process for your application. If you carefully evaluate each element, giving extra weight to those elements that are most important, the result will be a single process that will produce the part required to the standard required for an acceptable cost of production. As mentioned earlier, it is important that you work with experienced manufacturers or a manufacturing engineer to help you identify potential processes, evaluate each process effectively, and select the best process so that you and your customers will be happy with the final product. https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 21/22 26/5/24, 15:50 EG5601_SEM3_2023/24: Choosing a process References https://surfaceid.com/blog/choosing-a-manufacturing-process/ https://matmatch.com/learn/engineering/manufacturing-process-selection https://industri.fatek.unpatti.ac.id/wp-content/uploads/2019/03/062-Manufacturing-Process-Selection-Handbook-K.G.Swift-J.D.-Booker-Edisi-1-2013.pdf https://coek.info/pdf-manufacturing-process-selection-in-engineering-design-part-1-the-role-of-process.html https://www.sciencedirect.com/science/article/pii/S0261306998000399 https://www.sciencedirect.com/science/article/pii/S0261306998000387 Last modified: Wednesday, 30 March 2022, 3:46 PM https://moodle.glos.ac.uk/mod/page/view.php?id=1783032 22/22
