For some mechanical design engineers, manufacturing process selection is the last thing they think about during the design process. This is a very bad way to work. The best approach is to keep manufacturing concerns in mind throughout the entire design process. This will result in a design that is easier and less costly to produce.
There are hundreds of manufacturing processes. You are likely to already be familiar with the most common, e.g. casting, forming, molding 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.
Follow the simple procedure below to select the appropriate manufacturing process for a product:
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 molding. 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 post processing 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.