Below is an abridged interview. To see the full story, download the Guide to Additive Manufacturing for Medical.
How do I identify a specific candidate part for additive manufacturing?
Coates: It is important for companies interested in additive manufacturing to put time into strategically selecting the right part. Additive manufacturing offers a competitive alternative to other manufacturing processes for companies with low volume, high cost parts or for parts where customization offers a competitive advantage.
We’ve seen some of the best results when customers employ an auditing process using simulation software, in particular topology optimization, to evaluate part candidates. This helps identify weight reduction opportunity. From there the redesigning process starts. After conducting this a few times, the team involved gains experience to strategically (and easily) select the part using a combination of simulation and growing knowledge.
Is simulation important after the candidate selection?
Coates: Leveraging simulation to evaluate manufacturability and predict part behavior can save a lot of money historically spent on trial and error. On average, the use of simulation can cut the costs of low production volume parts by 50 percent to 75 percent. I recall working with a client on redesigning a part for additive manufacturing where the client estimated the cost to be around $2,000, which seemed to be very high. When we asked why it cost $2,000, the answer was, “well, it only costs $500 to print one part, but I probably have to do it three, four, or five times to get the right build parameters so that I can deliver a quality part.” Simulation give companies the ability to print right the first time.
The availability of the advanced tools allows designers to design for efficiency regardless of the manufacturing constraints. Designers can explore the most optimal designs enabled by topology optimization technology, then decide on the manufacturing process that offers the best cost-weight metric.
Analysis is often thought of as virtual testing, but your example is much more about answering a business question. Can you explain a little more about how simulation influences cost and decision-making?
Coates: A good question to answer early on is, “what is the minimum amount of material needed to meet performance requirements?” Topology optimization is a type of generative design that enables the creation of an optimal design that can then be targeted towards a specific manufacturing process. When an optimal design is generated, it can be constrained and refined for any manufacturing process. Developing parts based on optimization results ensures efficient, cost effective, and smart manufacturing process. This creates an opportunity for a better performing part manufactured in a process that offers the best cost-weight metric.
Simulation is the key to leveraging additive manufacturing’s myriad of benefits. It allows you to explore different configurations and placement of lattice structures, the use of different materials, and even the orientation of the part in the print bed to reduce the number of supports needed during the printing process. Analysis and optimization ensure that you’re getting the most out of your part in terms of cost, weight, and performance.
Through rigorous simulation, the solid-lattice hip implant below was optimized to reduce weight by 39 percent and stress shielding by 57 percent comparing to a generic implant. The optimized design has a fatigue life of more than 10 million cycles. In addition to its performance gains, printing considerations were factored into the design process, ensuring an overhang angle is smaller than 45 degrees for manufacturability.
Are there certain process or manufacturing considerations for medical additive manufacturing that differ from those of other industries?
Coates: Certainly, each industry and even each product you’re designing has its own unique considerations and challenges. FDA regulation comes to mind as one that uniquely shapes medical product design. Other industries have regulatory oversight, from the FAA in aerospace to crash and emissions testing in automotive, but often additive is used in these industries to redesign existing parts which already meet those standards.
The medical community in many cases is developing brand new solutions where no previous guidance exists, so it is extremely importance to using FDA controls as initial design variables so you can thoroughly document and validate performance through analysis. Simulation ensures potential issues are recognized and addressed early in the development cycle so you have confidence that the part will meet performance claims and pass the quality assurance and physical testing stage.
What is the one take-home message you’d want every person to consider when embarking on a medical additive manufacturing project?
Coates: Additive manufacturing by itself not a magic bullet. The manufacturing method is only as good as the design you feed into it. In order to maximize the value delivered to the patient and reduce your overall investment, product design and manufacturing need to work in harmony. I see the use of simulation and optimization as imperative to arriving at an optimal part design for your selected manufacturing method.An intelligent approach to design that includes the proper choice of material layout is critical but is perhaps the most overlooked aspect of additive manufacturing is part design. Topology optimization details the ideal load paths for minimizing stress distribution, giving you confidence that your part will not only be lightweight, but also meet your cost, fatigue, and performance criteria. Enabling the engineer to individually tune a part or system for a particular use case maximizes the value to the patient and gives manufacturers a clear competitive edge in terms of part quality and time-to-market.
Simulation in the design and development process is also very much grounded in practicality. You need to be able to build what you design with quality and consistency. By simulating part build, cooling, cutting, and springback, you can anticipate and address manufacturing issues before they happen and deliver designs using the fewest supports, optimally oriented on the print bed. Trial and error iterations in the prototyping phase are an absolute killer to your bottom line, which is why I firmly believe in a “first-time-right” approach to design, driven by simulation and optimization.
If you want to fully exploit the benefits of additive manufacturing, you need to incorporate simulation and optimization or risk leaving opportunity on the table.
To see the full interview and learn more about leveraging simulation to optimize additive manufacturing processes in medical device development, download the Guide to Additive Manufacturing for Medical.
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