How Does Additive Manufacturing Complement Injection Molding?

The Additive Manufacturing Workshop for Plastics, a half-day event held during the recent Amerimold 2019 in Chicago, brought together mold builders, technology providers and companies providing industrial 3D printing services. These mold builders, technology and service providers gave insights into digital modeling, design considerations, how AM is used in mold shops, how it complements injection molding and how AM can succeed in production.

Opening the AM Workshop for Plastics, Additive Manufacturing Media Editor-in-Chief Peter Zelinski introduced Marc Mitchell, design center manager, Byrne Tool + Design and Lester Jones, vice president, Custom Mold & Design and TeamVantage. Jones and Mitchell provided an inside look at how moldmakers and molders are adapting to AM to reduce cost and lead times, eliminate rework and detect errors early to keep projects on track.

Byrne Tool + Design: Reducing Expensive Tooling Changes

Rockford, Michigan-based Byrne Tool + Design produces prototype parts for its customers on a Stratasys Fortus 250 MC FDM machine and uses a Stratasys Polyjet J750 to produce fixtures and 3D printed molds for low-volume production using the actual part material. Reducing the time to market for their customers is key, Mitchell explained, and using printed molds for customer approval to reduce or even eliminate expensive tooling changes can reduce product launches by weeks or even months.

One of many examples of what the company prints on its Stratasys machines is a mold for a switch button for UL. Byrne Tool decided to kick off production and prototype tooling at the same time, so parts from the printed mold could be taken to UL for approval to reduce expensive rework. To create the mold, 3D printed handloads were used to create undercuts in molded parts, steel dowels ensure mold half alignment and a printed ejector is used to push on all pins at the same time. According to Mitchell, creating prototype tooling made from PolyJet photopolymer Digital ABS on the J750 parallel to the production process sped up the customer’s product launch by seven weeks.

Another project involved Byrne Tool + Design building a new production mold for a deep, cone-shaped part utilizing conformal cooling in the core via a two-piece construction. According to Mitchell, the cost savings was 50% from a traditional manufacturing process, and it took 24 hours to print the cooling core versus almost a two-week lead time.

HP: How Does AM Complement Injection Molding?

“I am always looking for something new to learn and I like the breakthrough of knowledge; last but not least, I like failing, I like falling just like when I am snowboarding. It hurts when you fall but falling is part of the process if you go for it, you just need to respond,” began David Tucker, automotive strategy and production development manager at HP 3D Printing, during his presentation. In his opinion, moldmakers are very creative, and even if additive manufacturing is new to them, they should think about how to complement their business with AM to create success for their customers.

While explaining HP’s Multi Jet Fusion technology, Tucker used the bulk of his presentation to focus on the question of how AM can complement injection molding, which use cases are appropriate, how the innovation cycle can be sped up and how tooling expenditures can be reduced and controlled using AM. “When tools don’t make economic sense to make, why make them?” he said.

Moreover, AM complements a mold shop’s products rather than replacing them. Tools have business cases, Tucker emphasized, so adopting something that is competing with current technology does not help the business case. AM should be a big complementary, it should enable new products to be created. AM also offers the unique opportunity to create parts without following the rules of injection molding such as mold flow considerations. AM offers the opportunity to create unique designs, to concentrate on part features and to use topology optimization to reach performance breakthroughs.

Since time is every shop’s critical point, moldmakers should adopt strategies that save time. Tucker’s advice is to look at an existing process, eliminate everything that you spend a lot of time on, look at your part and the components and decide which ones can be bought in as standard parts instead of making them in-house. What technologies do you need to speed up? Maybe stamping, wire cutting, bending, or other manufacturing processes. Then think about what AM could offer to speed up your manufacturing process.

“Once you have the AM system set up, it is easier to operate than a CNC machine,” Tucker added. “Design for additive is not easier. But operating the machines is. It’s like click to print. You don't need as much knowledge. Moreover, AM is a great way for organizations to attract young talent.”

Evolve: Is AM Ready for Mass Production?

While AM offers huge opportunities in moldmaking and injection molding, most of the buzz today is all about volume production. But what does it take to print hundreds of thousands or even a million production parts? Bruce Bradshaw, CMO, Evolve Additive Solutions is convinced that a company can benefit from sitting an AM machine or production cell on the shop floor right next to the injection molding production lines—if there is acceptance and advancements across the value chain in these five areas: cost, speed, quality, scalability and materials.

According to Bradshaw, industry is just scratching the surface today. Use cases include customized automotive badging, aircraft cable harnesses and interiors, custom orthotics or hearing aids, molds for dental aligners and jigs and fixtures for manufacturing tools. Some current perceptions of production AM, however, prevent many operations managers from realizing real-world end use applications. They think parts made with AM are expensive, lack materials and quality, the technology is not scalable and reliable and integration on the factory floor is difficult because of propriety software. Other limitations on the adoption of AM are the skills sets and processes within many organizations, high material costs and slow build speeds.

However, in future the operating cost model will shift with volume, Bradshaw said, but hardware alone is not enough for factory integration, it requires standardization: an easy to use file preparation and secure storage solution, a digital twin solution for simulation and optimization such as Siemens NX, as well as automation partners to create new levels of flexibility.

With STEP (Selective Thermoplastic Electrophotographic Process), Evolve offers a viable alternative to injection molding and other traditional manufacturing processes. Designed for automated manufacturing and factory-floor integration, it allows users to utilize production-grade thermoplastics for volume manufacturing applications across multiple industries, including consumer, automotive, industrial and medical.

EOS: Achieving Serial Production with Polymer AM Technology

Fabian Krauss, Global Business Development Manager at EOS also believes that serial production with AM technology is possible and that companies can leverage digital workflow solutions to allow for mass-customization, for instance. According to Krauss, AM serial production is more than prototyping at large scale; prototyping has to be fast, easy and plug-and-play. When it comes to large series, total cost of ownership needs to be considered, technology integration into the production environment, as well as automation and quality control issues.

One use case Krauss cites is what he calls the “world’s most accurate custom orthotic” from a company called Aetrex. Aetrex has been renowned for comfort footwear since its inception in 1946 and for foot scanning since 2002. The 3-D-printed orthotic can be produced in under two weeks, from scan to receipt. A scanner captures the complete foot data, which is sent to the EOS printing facility. There, it is manipulated into a 3D CAD drawing that takes into account the level of support that each individual foot will need in each area. The final design is then fed to the 3D printer, and the finished item is shipped to the recipient.

Sounds simple but the process is highly technical. The material, for instance, was specifically engineered for Aetrex (it uses recyclable materials that can be reincorporated into the production process). Applications drive materials; AM responds and adapts, Krauss said, which is one way of how materials are constantly optimized and developed in the additive world. Aetrex prints their orthotics on EOS P400 machine platforms, which are open to optimize processes for individual customers and to develop lattice specific scan strategies as required by Aetrex. EOS can also provide full IQ, OQ, PQ validation and even incubate serial manufacturing cells as the Aetrex production at EOS in Texas.

In automotive applications, AM can also save cost in low and mid-volume production, such as at Rolls-Royce, where there is increasing demand for complex plastic components (less than 50,000 pieces per year). According to Krauss, the luxury car maker 3D prints more than 100,000 parts with 10-20% cost savings per transferred component. Daimler, too, optimizes its aftersales supply chain by transferring spare parts from physical to digital. More than 380 components are qualified for AM in cooperation with EOS Additive Minds, Krauss said and concluded that it is all about the application and the right mindset.

Forecast 3D: A Practical Application for 3D Printing in Production

A new mindset is also what is required to transition from providing prototyping services to high-volume production services, Justin Swartz, Advanced Manufacturing and Technical Solutions Director, Forecast 3D, emphasized in his presentation. For more than 24 years, Forecast 3D has been providing industrial 3D printing, short-run manufacturing, and high volume production services with meanwhile 45 industrial 3D printers to empower companies to speed their product development cycle. Forecast uses HP MJF for high-volume production with Nylon materials, Stratasys FDM for low-volume production with a variety of thermoplastics and SLM (DMLS) for low-volume production with metals.

While prototyping is all about creating the best part possible with responsive turnaround times, production parts require a repeatable, controlled production flow meeting customer expectations. For quality control, Forecast uses smart, in-process monitoring including a layer control system (a photo analyzes each layer for defects), sensor monitoring, melt pool monitoring and QC reporting of compiled data.

Comparing HP MJF with injection molding, Swartz pulled up a slide comparing manufacturing costs. Injection molding requires very expensive molds and tools, that MJF does not. Injection machine set-ups and mold removal times are eliminated, so are costs for tool storage. Yet the MJF process has drawbacks that need to be addressed, including some part requirements such as surface finish, feature precision, dimensional accuracy and the material range.

Carbon 3D: Designing for AM vs. Designing for Injection Molding

But not everything is a fit for AM, and not everything is a fit for injection molding, Jason Lopes Production Development Engineer, Carbon, said in his presentation. Parts need to be either designed for injection molding or AM; but there are differences. While the injection molding design phase includes part design, design for injection molding, building the tool, testing it and refining it (which can take between 6 and 23 weeks, Lopes noted), creating parts with 3D printing technology such as Carbon Digital Light Synthesis (DLS) only requires a part design and design for DLS, printing and refining—taking a maximum of four weeks. Tool design considerations are significant for injection molding, Lopes said and the major difference is that DLS is focused on part design, whereas injection molding focuses on tool design.

Of course, depending on the requirements, everyone has to make their own choice of either designing a part injection molding or designing it for additive manufacturing. But there are parts that simply cannot be injection molded, and one example could be found right on Lopes’ feet. He and his team were wearing Adidas Alphaedge sneakers during the workshop featuring a unique 3D printed midsole geometry with variable properties to improve shoe performance for different sports. Leveraging Carbon’s Digital Light Synthesis technology the companies have developed the first mass production process that makes previously impossible midsole geometries with new 3D printable materials.