Not every design should be made using additive technology. But answers to eight questions will help you make the right choice between additive, machining, and injection molding for your production needs.
Despite the buzz and attention on additive manufacturing (AM), not every design should be built using an additive process. Just as there are tradeoffs on when to use machining or injection molding, there are tradeoffs with additive manufacturing. Answers to a few key questions will help you determine whether your design is best handled through additive manufacturing.
1. What’s the application?
The final use plays a paramount role in whether a design is built through machining, injection molding, or additive manufacturing. “It’s super important to understand how the part is going to be used,” says Jim Niekamp, President, RPM Fast. “Whether it’s simply for fit, form, and function, or it’s going to be a production part, the application really drives the decision to use additive manufacturing. And the application will push you to certain directions in terms of what type of printer technologies you’re able to use.
2. Are there any critical part features?
Wall thicknesses, tolerances, part size, part complexity, part count reduction, customization—all will influence the choice to use additive manufacturing.
But keep in mind, each additive technology offers different capabilities with regards to part features. For example, each additive technology has different capabilities for wall thickness or accuracies. Thus, if the wall thickness or the tolerances are critical, the part may not be a good fit for additive.
Combining parts into one unit can be a reason to build a part through AM. “But there are costs in taking a part down from X number of components to one,” says Niekamp. One of those costs involves testing. Depending on the industry, the new, lower part count design will have to prove it is as capable as the previous multi-part version.
Sometimes you can offset testing costs with savings in other areas, such as shipping, controlling the supply base, sourcing, eliminating other processes, and better lead times.
“Designers also consolidate parts because certain components are now hard to find when you’re looking at the sourcing chain,” says Jesse Marin, Solutions Engineering Partner, Stratasys Direct Manufacturing. “If you can consolidate parts you’re eliminating the process of having to go out and purchase six different components from four different suppliers. Then there’s lead times and scheduling and ensuring that they arrive on time and are to spec, so there’s a lot of that process that gets eliminated just by part or assembly consolidation.
Another part characteristic that lends itself to AM is the need for customization.
Also consider those design situations where you have a number of parts with slight changes on them,” adds Marin. Some examples include high-end aircraft interior components or custom medical applications where each patient’s uniqueness rules out full standardization of a particular product.
3. Is the design too complex to be made other ways?
A natural fit for additive manufacturing is when a design is too complex to build using traditional manufacturing methods like machining or thermoforming. Additive manufacturing essentially eliminates many limitations in regards to axes of freedom. “Not to say that it’s fully Carte Blanche in how you want, but it makes it a lot easier to make more complex ergonomic designs right off the bat,” adds Marin.
4. What material will the part need?
“Material selection is a critical part of the design process based on the part function. Material class selection can be based on some fundamental operational requirements of the part, such as operating temperature, environmental conditions, mechanical property or physical property needs, or cost targets,” says Dave Chapin, Addworks Design Engineering Leader, GE Additive.
“Additive has been shown to be a true enabler in terms of design freedom that can lead to
truly disruptive ways of solving a design problem,” said a spokesman from GE Additive. “A
design engineer who is able to approach design problems through an additive mindset will
find an amazing level of design flexibility. Then, once designs are fleshed out, a business case
study will highlight the right path to take from a design to manufacturing.” Dave
Chapin,Addworks Design Engineering Leader, GE Additive.
While the availability of a range of materials for AM is improving, today there are still some limitations.
“High heat, certain rigidity or flexibility needs, any really specific material property called out for in a spec that must be matched exactly will limit which parts can go to additive,” says Niekamp.
Depending on whom you listen to, additive materials that are “ABS-like” or “PLA-like” are not going to give you the mechanical features you need. This belief is not always true, and is often more the result of marketing branding.
“There are a lot of proprietary materials that vendors are purposely keeping proprietary, materials that could actually be superior in their features. A “like” material doesn’t mean it isn’t “real” or suitable, says Niekamp.
With additive, a designer often must use a “like” material because it’s been formulated to build specifically with an additive technology. Especially for plastics and resins, for example, many “like” materials have been formulated to extrude or to cure with a specific light process properly.
But the material situation is changing. Additive materials have made strides. Notes Marin, several additive systems actually print in thermoplastic production grade material. Not “ABS-like,” but actual ABS, just processed in filament form so the machine can accommodate the manufacturing process with that material. “We print in polycarbonate, in PC-ABS blends, in Ultem 9085 and 1010 which are also CNC materials. We’re now entering the age of actual materials.”
5. What costs are you looking to reduce through AM?
Many claim additive technology will reduce the cost of a part. There are several types of costs a design can reduce through an AM process, including production, supply chain, assembly, inspection, and so on. Which of these costs is the focus will help determine the most appropriate AM technology to use.
The use of additive in a corporation suggests setting aside resources to think about
additive versus rushing products to market. It will be important to spend some R&D dollars
to address the opportunity to make your company not just one step better, but exponentially
better than your competitors, because your parts are designed in a different way that no
one else can do. Jim Niekamp, President, RPM Fast
Consider whether a design could include internal aspects that cannot be handled through traditional production. Usually, complex designs are best produced through additive technology. Designs that combine functions are also good choices for additive.
6. How many parts must be made?
Additive technologies are making parts faster, but they not necessarily as fast as traditional production technologies. For low quantities, often defined as 10,000 or less, additive can be highly cost efficient, especially if fixtures and tooling are involved.
7. Which additive technology should you use?
Additive manufacturing has grown past the seven different ways to build parts layer by layer from a few years ago. Today there are several versions of stereolithography, several versions of material jetting, laser sintering, electron beam technology, and more. As the additive industry works to build parts faster and faster, new ways to build parts are here and more are coming.
“Knowledge of the design rules for each additive process is a must to be able to capitalize on the benefits of each process for a design,” says Chapin.
In general, designers will find they will need more than one additive technology, for example, they will need both stereolithography and material jetting, and possibly a third option. Answers to the earlier questions will help narrow the choice.
“In some cases, extremes will make the choice clear. For example, extremes like super demanding temperatures or high requirements for energy transfer or loading requirements may give you a clear idea of the best additive manufacturing process to use, but for the most part the choice of the best additive manufacturing process is often a combination,” says Marin.
8. Should you use a service provider rather than go in-house?
Increasingly, the answer is you will want both. Service providers can deliver prototypes or final parts fast. In-house additive benefits and enhances the design skills of the design team. Which ever the direction, consider the following points:
Will multiple departments want to use additive technology? Will there be enough work for the equipment, or too much?
“If you have a line up of products that you know you’re going to need to use, that you can produce with additive over the next three years, and that you can put enough volume on a printer that you’ll have at least 75% capacity usage on that printer, in-house is a good choice,” says Neikamp. “You’ll want enough variety of equipment so as not to limit your creativity.”
Does your company have the resources to implement the necessary additive technology?
“For example,” notes Marin, “if you’re implementing a DMLS system you’re probably looking at upwards of half a million dollars to implement a full system and that includes not only the hardware purchase but the material, the system requirements, the installation, the training behind it, the software behind it, qualification builds to make sure the machine is up and running properly and that can easily extend anywhere from two to five months depending on your expertise in implementing a system so do you have that amount of time?”
Another factor is do you want to develop in-house expertise for the future? Once designers understand how to work with additive technology, it enables them to develop unique parts that can give their company a competitive edge in an industry.
“Many factors can influence this outside of a simple business case evaluation including supply chain strategy, facility availability and suitability, part volume, existing infrastructure, (to name a few). Having said all that, we highly recommend that organizations engage with one of our service bureaus to print sample parts and test part quality,” says Chapin.
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