Molding is a well-established, mature component fabrication method, and yet, plenty of designers are still unsure of the best practices involved to achieve an ideal design at the right price. As such, it’s critical to collaborate with the molding service provider to achieve the optimal part with the right material, dimensions, and functionality.
Early inclusion of the molding manufacturer will not only save on costs but can ensure time is not wasted on poor designs or specifying unnecessary dimensional requirements, which can impact the project in later phases. The molding partner maintains expertise on the decisions that need to be addressed to achieve the greatest final result.
Fortunately, to help clarify the aspects of a molding project medical device developers should keep in mind when designing their next innovation, Patrick Haney, R&D engineer at MTD Micro Molding, responded to several questions around this topic. He shares insights on optimizing the price, design considerations, and the impact of micromolding.
Sean Fenske: When working with a molding partner, how can the partner aid in optimizing the design?
Patrick Haney: A molding partner can assist with specifics like designing for the injection molding process and how to demold the part. From a design standpoint, this can encompass anything from plastic fluid flow, gating location, and cavity pressure considerations to factors like undercut features, draft, nominal wall thicknesses, and other part geometry-related aspects. This can make or break whether a part can be manufacturable and perform the specific function for which it is designed. Product development teams design for application first and sometimes, there are directly competing demands from the “want” and “need” lists for a design. This can make tool designs extremely complex, driving up cost and program lead time. Molders can help hash out nuances of injection molding by making a part design manufacturable and achieving more specific goals like optimizing cycle time, part cost, and throughput.
Fenske: When does optimization of the price take place? Is this part of the DFM process?
Haney: Typically when Design for Manufacturing (DFM) is talked about in the industry, we are referring to part design as it relates to manufacturing—considerations like draft, preventing undercuts, and optimal wall thickness. What we like to highlight at MTD Micro Molding is DFM refers to Design for “all of the Ms”, such as materials, mold design, molding, and metrology, as all of these impact the product development cycle. The reality is that price optimization happens during the entire lifecycle of development; it starts with material selection and sourcing and moves to optimization of the part design. For materials, the consideration is not just the raw material cost; processability is also a cost factor. The selected material dictates the “personality” of a mold. Higher-temperature materials can affect cycle time and mold functionality. For example, if a tool is highly complex, a higher level of preventative maintenance is required, which incurs costs every time.
To facilitate the DFM process, understand the “needs” versus “wants” for a given part or device design and determine what is flexible in the “wants” list. Having this understanding early can drive non-recurring engineering (NRE) and unit costs down significantly when working alongside your molder during the DFM process.
Fenske: Where are the most common opportunities to optimize price? Is it with material, tooling, the molding process, something else, or a combination of factors?
Haney: Front-end decisions like material choice and part design as it relates to mold complexity are the biggest factors. In general, engineering projects never get simpler as they go on for medical devices; they only get more complex. Spending time on the front-end decisions with your molder helps simplify the later decisions about augmenting a process for higher volumes or automation, which can result in optimized unit costs now and later. Part design relates to tool design which relates to automation design, and the same goes for materials. Material selection relates to how extensive the process engineering phase will be which impacts cost and, more significantly, lead time.
Fenske: How does micromolding affect this? Are there additional opportunities or considerations that must be addressed with micromolding?
Haney: When you put everything we’ve discussed into the world of micromolding, it becomes even more magnified and important. The impacts of all decisions are exacerbated, emphasizing the importance of selecting the right micromolding partner. There are so many nuances to consider from material cooling rates to shear exposure to micromolding materials fundamentally changing the microstructures of the polymer matrix, yielding a difference in mechanical properties or chemical resistance.
Fenske: Do you have real-world scenarios in which price optimization occurs?
Haney: Regarding materials in the medical device industry, there is understandably a tendency to select materials because there is regulatory pre-approval or because there is familiarity with a certain material. Micromolders can help look at the demands of a device application and balance that with finding the most processable material at the lowest cost. In most cases, we can provide samples of multiple molded materials for functionality assessment and testing. There are numerous considerations for material selection and OEMs can take the guesswork out of this process by involving their micromolder early in the conversation.
From a part design perspective, let’s consider an example of a medical device designed to perform a puncturing function (see illustration below). The assumption is often that the puncturing features need to be as sharp as a knife’s edge (0 radii). The reason this doesn’t work in application is plastic materials at that 0 thickness often show very low integrity, limiting functionality. What we have found through experience is if you can spec in a smaller radii tolerance (as small as 0.0005”), you can improve the puncturing capability of a material by slightly dulling the feature. The crux of this design choice is it significantly reduces the amount of tooling inserts that need to be created for the mold stack-up, resulting in a simplified tool construction and significantly lower cost to manufacture, with better part functionality.
Fenske: What factors with molding price are often overlooked or ignored? Where is the “hidden” savings opportunity?
Haney: A good example is over-dimensioned part designs. If the dimensioning and tolerancing step is not optimized, part inspection might cost more than it actually costs to manufacture the part.
In micromolding, minute changes in part design can mean significant updates to the mold. For example, adding undercut features on a non-primary axis can create the need to add side actions and staged opening features in a mold. In addition to feature complexity, feature orientation can drive the complexity and cost of a mold.
To process monitor and meet specific demands on very small part features, inspection, testing, and extra engineering activities take place throughout the entire development and molding protocols.
Everything is more delicate on the micro-scale from tooling components to measurement techniques. Small changes or additions to a design can make a huge impact on mold cost, processing cost, and project timing. Working with a molder upfront to uncover cost and time savings opportunities for a given project will help in the long run.
Fenske: Do you have any additional comments you’d like to share based on any of the topics we discussed or something you’d like to tell medical device designers?
Haney: The question is “What is the net result of true proactive decision-making in a partnership and how does that manifest to actual savings?”
If design considerations for all the “M” categories can be achieved effectively in a partnership, significant cost savings can be realized—up to 25% savings in NRE costs, 20% to 30% savings in unit cost, and 35% to 45% improvement in lead times.
Click here to discover more about MTD Micro Molding >>>>>