If you are part of a product development team working on a product that may reach millions of parts, or are a growing start-up about to ramp up production volume, this article is a refresher on basic design for manufacturability, or DFM. At Enplas, we believe that DFM is a collaborative process between our customers to enhance their original part designs. Read on to learn how injection molding engineers can help ensure your components are manufacturable and cost-effective at scale.
Design for manufacturability is the process of designing products to facilitate the manufacturing of components. DFM is especially critical for mass produced components and assemblies. It safeguards quality, it saves time, it saves money—and most importantly, it can prevent potential problems down the road.
Although there are many dimensions to DFM, the most basic goals ensure that:
- It’s physically possible to manufacture your part, and
- The manufacturing process is streamlined to be simple, efficient, and robust.
Basic Design for Manufacturability for Injection Molding
Due to the nature of the injection molding process, there are guidelines to follow when designing components. In injection molding, you have two molds enclosing a cavity that is filled with plastics to form the component. After the heated liquid material is injected into the cavity, cooled, and solidified into the part, the molds separate to eject the product. (This is a different process from 3D printing, a popular prototyping process. A part that can be 3D printed may be impossible to be produce via injection molding.)
Below are a small portion of the many basic DFM considerations required to ensure that the final part design is possible to manufacture. Without proper consideration, the part may have defects or be vulnerable to breaking. These considerations include:
- Undercut: A simple mold like the one shown in Figure 1 cannot open when there is an undercut. Certain undercut features could still be injection molded with special tooling, which would make the tooling more complex and costlier.
- Draft: To ensure the molds open smoothly, products need draft. A product’s draft angle is a slant that is applied to each side of an injection molded part. The angle is positioned to run toward the direction of a mold’s pull and parting line; this helps to release the part from the mold. Draft considerations are important to meet your quality standards. Without it, major problems can arise that increase production time and cost.
- Wall Thickness: Something seemingly as simple as wall thickness can have a remarkable effect on a product’s success. For instance, thinner walls require less material and cool faster. This reduces a mold’s cycle time (increasing the number of units that can be made per period) and input costs. But go too thin, and the product becomes brittle and unreliable. Too thick? Your process is not optimized. Another major consideration is the uniformity of wall thickness; a lack thereof can cause weakness and unsightly “sink marks.” Optimizing wall thickness is a basic—yet critical—consideration for your injection-molded product.
- Rib Ratios: Walls that are thicker or non-uniform by necessity of design can sometimes cause problems. To counteract these issues, ribs are used. Ribs are thin structures that add support and rigidity to injection-molded parts. This solution, however, can cause problems of its own. To prevent these problems, rib design must adhere to certain proportions. For example, if your product’s ribs are too tall, breakage can occur during use or during ejection from the mold. Rib ratio must be carefully planned and evaluated for success.
Design for Manufacturability for Assembly and Overall Product Performance
In addition to ensuring that your part is injection moldable, other DFM considerations contribute to the function or overall assembly process of the product. For example, the addition of measured features could make the assembly process easier and less costly further down the road. Combining two components in one is another way to simplify overall assembly. Read our blog on advanced DFM for more information about DFM that enhances product performance and simplifies assembly at the same time.
Failure Mode and Effects Analysis (FMEA)
Any basic DFM done well should also include a failure mode and effects analysis (FMEA). This is the process of identifying the risk of possible modes of failures while a product is still in the development phase, and the development of measures to mitigate those risks. FMEA is a critical part of the initial phase of process validation for our projects.
At Enplas, we believe design for manufacturability is a way to solve difficult engineering challenges collaboratively with our customers. DFM enhances component designs by improving product manufacturability. Enplas has a long history of successful collaborations with engineers at market-leading, global OEMs and innovative start-ups alike, in the medical, diagnostic, and biotech industries. Have a design ready for production? Contact us.