Design for Manufacturing Overview
Design for manufacturing (DFM) requires coordination between design engineering and manufacturing engineering to ensure product designs can be efficiently manufactured. The designs need to have achievable parameters and features that aren’t too intricate or detailed to make. This creates several constraints when designing products as designers cannot simply create whichever shape they choose based on functionality and aesthetics. For instance, if a design is too complex, the cutting tool on a CNC machine cannot reach certain areas to create the part. Care must be taken to ensure each component can be fabricated and assembled in a cost-effective manner.
Design for Additive Manufacturing (DfAM) utilizes the same tenets of DFM but centers it specifically around optimizing product designs for additive manufacturing (AM), otherwise known as 3D printing. There are many differences in the layer-by-layer additive manufacturing build process in comparison to other conventional manufacturing methods. As a result, many of the constraints of conventional methods are not applicable to AM. Geometric complexity, material flexibility, and production of customized products are some of the design capabilities unique to AM. To fully utilize these capabilities, CAD designs made to be manufactured with conventional methods should not just simply be loaded onto a 3D printer. Sometimes, the parts are still able to print successfully, but many times the process is either very inefficient or impossible and will lead to a failed print. To obtain maximum efficiency and fully utilize AM’s unique capabilities, product designs for additive manufacturing should start with a “blank piece of paper” and be designed from the ground up to be built using additive manufacturing.
Capabilities of Additive Manufacturing Design
In contrast to mass production that makes high volumes of identical units, mass customization is the method by which to produce high volumes of unique products. Conventional methods such as injection molding require a specially designed mold which adds high fixed costs to each production run, shifting the break-even point to much higher volumes. Manufacturers must produce high volumes to amortize the fixed cost over many thousands of units. As a result, all the units are completely identical. Additive manufacturing requires no tooling and can print directly from a digital file, which enables AM to produce highly customized products. What is uneconomical for other methods, AM can complete with ease and without the risks of investing in large volumes of inventory that may never sell.
Applications of mass customization include major markets such as medical and consumer products. Medical products can be made for a specific patient, improving the effectiveness of treatments and procedures. Consumer products can have customized names, logos, and features built into the products which can help align products closer to users’ wants and needs. Design for additive manufacturing allows for the combination of low unit costs with high customization to enable mass customization.
Conventional fabrication methods have a direct relationship between complexity and costs; the more complex, the higher the cost. With additive manufacturing there is no additional costs associated with increases in complexity. As a result, there are many opportunities for unique shapes and designs that create the “ideal” geometry of the part based on its projected loads and functions.
Generative Design and topology optimization are design for additive manufacturing software tools used to find the ideal shape of the part based on a set of input parameters, loads and constraints. The result is highly complex designs that mimic the look of organic structures in nature. The software adds materials in areas that will undergo high force and less material in areas with no load bearing requirements. Through these software tools and the unique capabilities of additive manufacturing, highly complex structures can be created that weigh less, but provide the same amount of strength.
Part counts on products increase costs, as more parts require more engineers to design the parts and more supplier contracts to supply the parts. Nevertheless, large numbers of parts are required for relatively simple assemblies due to the inherent limitations of conventional methods. Rather than using a high number of parts and increasing design, manufacturing, and sourcing costs, design for additive manufacturing can incorporate multiple parts into a single unique shape. Apart from cost savings, a single continuous part with no joints or connecting components is less likely to have leaks of air or liquids.
Designing and Manufacturing with Multiple Materials
Many designs require different areas of a part to withstand different stressors. Some areas could experience higher temperatures, whereas some areas can experience higher tensile stress. Design for additive manufacturing allows for the creation of single components that utilize multiple materials. Different areas of the part can have different materials, depending on the thermal and strength requirements of the part.
Challenges of Additive Manufacturing Design
One of the main challenges of design for additive manufacturing is building parts with overhanging features. Additively manufactured parts with overhanging features require support structures to prevent warping or collapse. The support structures add to material costs, reduce aesthetic quality, and require manual post-processing operations to remove. In some cases, support removal can contribute up to 70% of the cost of a part. Because of this, parts should be designed with a build direction in mind and oriented in the build chamber in such a way that reduces the amount of support material required.
Additionally, secondary post-processing operations may be required such as sanding, coating or painting. Care should be taken in the design stage to make features and surfaces that would be easy to sand, coat, or paint.
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