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Big on 3-D

Additive manufacturing goes big thanks to an American machine tool builder

Maybe your shop bought a Makerbot or similar desktop 3-D printer for the engineers to play around with, building concept models and protype parts or grippers for the new robot you installed last month. Perhaps you’ve gotten a little more serious and invested in industrial-grade fused deposition modeling (FDM) or selective laser sintering (SLS) equipment and use it to make jigs, fixtures and other tooling.

As clearly illustrated here, 3-D printed parts are built one layer at a time.

While the possibilities seem endless, there’s just one thing – and it’s a big one. For manufacturers that make big products, even the largest 3-D printers are, for the most part, limited to producing parts that would fit in a suitcase.

Large-scale needs

But what if there were a 3-D printer able to build parts the size of a Ford F-150 SuperCrew Cab? As it turns out, there is and if you give Randy Adams a call, he could probably arrange to have one of these printers installed for you. The vice president of engineering and general manager of CNC table products at Cincinnati Inc. (CI), Adams is responsible for this century-old machine tool builder’s latest in a long line-up of machine tools, the BAAM, a 3-D printing system.

BAAM is short for Big Area Additive Manufacturing, and it’s the largest of the three models of 3-D printers currently available from CI, boasting a 240-in.-by-90-in.-by-72-in. build area – plenty big enough to print an F-150 along with a host of similarly supersized parts. A quick glance at the CI website shows an additively manufactured submarine hull, a cab for an earth excavator cab, replicas of the Orion spacecraft, an F-22 Raptor and a Shelby Cobra, all printed on the BAAM system’s massive bed. Pickup trucks? No problem.

Of course, the maximum payload of this as-yet imaginary vehicle won’t be anything to brag about because the chassis, drivetrain and everything else in it would be made of thermoplastic – more specifically, glass or carbon fiber-filled acrylonitrile butadiene styrene (also known as ABS, the stuff of Legos and drain pipes) or an engineering grade polymer such as PEEK or Ultem. All are tough materials, to be sure, able to withstand significant impact and mechanical forces, chemical attack, temperature extremes and humidity, but like the majority of 3-D printed parts, are plastic nonetheless.

Printing 101

If you just finished bending a batch of 316 stainless steel cabinets or welding up a few dozen 1018 mounting brackets, you might be wondering: What use do we have for a machine that produces nothing but plastic parts? According to Adams, plenty.

“Generally speaking, we see great opportunities for anyone making large to medium-sized tooling for the aircraft, automotive, marine and furniture industries, to name a few,” he says.

Though the BAAM system is a relative newcomer, its list of completed projects is extensive. It has produced stretch form tools, molds suitable for autoclave use, drill and trim fixtures, layup tooling for aircraft component assembly, and more. In most cases, these are high-dollar tools that once took months or even years to complete, but can now be “out the door” in weeks.

“Many times, we’ve reduced lead times and project costs by half,” Adams says.

If that last part got your attention, you might be wondering how the BAAM works, how it was developed and what it would take to implement it in your shop.

Like its much smaller additive cousins – and indeed like most 3-D printers today – the BAAM builds parts one layer at a time. Starting from the bottom of the workpiece, it extrudes molten polymer in a raster-like fashion, moving back and forth, side to side, completing each 1/8-in. or so thick layer before lifting the print head up to start on the next layer.

Its additive engine, if you will, most closely mimics that of an FDM printer, which to some might resemble an oversized, automated hot glue gun. Instead of using reels of thermoplastic filament to feed the printer’s extrusion nozzle, the BAAM is equipped with a pellet-filled hopper. This makes it much better suited to keep up with the huge material requirements of supersized parts; it can lay down up to 80 lbs. per hour of finger-width beads of plastic.

The BAAM was developed in partnership with Oak Ridge National Laboratories (ORNL). Adams and his team supplied the research organization with the frame and gantry motion system from one of CI’s laser cutting machines and worked with ORNL to add a thermoplastic extruder to the machine along with a heated bed, a feature common with many 3-D printers. This minimizes the distortion that would otherwise occur when hot plastic is laid atop the relatively cold plastic of the previous layer. The result? The world’s first large-scale additive manufacturing machine, the BAAM.

The BAAM can 3-D print a variety of polymers such as Ultem, PEEK and ABS.

Go big or go home

That answers the first two questions; the last one about implementation is a bit more gnarly. For starters, parts don’t come off the BAAM in usable form. Most 3-D printed parts require post-processing to remove support material, finish machine critical features and smooth out the inevitable stair-stepping that occurs with any layer-by-layer manufacturing process. The BAAM is no different. The message is clear: If you’re going to 3-D print big parts, you’ll need a way to machine and finish big parts.

The BAAM can build its own fixturing surfaces and fiducials for use in subsequent machining operations.

The next nut is tougher to crack. For all your shop’s manufacturing skill and experience, learning to design and manufacture 3-D printed parts takes time.

“Not a lot of people out there actually know how to 3-D print large parts,” Adams says. “Consider a simple arch-like structure, such as a car wheel well or door frame. If you don’t design in the appropriate support structures, features like these collapse during the build process. And you need to design the part with enough room so that you can reach in afterward and remove the supports.”

This educational process is something that anyone using 3-D printers or designing parts for them goes through, regardless of the part size. With the BAAM and other large-scale printers, however, the stakes are much higher due to the amount of time and material needed to actually build something.

“Many customers we work with in our service bureau submit parts to us that simply cannot be 3-D-printed,” he says. “We work with them to make their design more additive-friendly, but sometimes you have to throw out everything you know and start over.

“Manufacturers everywhere are faced with retraining their designers and engineers on how to do things in the additive world – not just for our equipment, but for all types of 3-D printing,” he adds. “It’s an industry-wide problem not unlike that of the first CNC machines or learning how to use computers and CAD software. We’ll get through it. It’s going to take some time, but in the end it will be well worth it.”

Cincinnati Inc.