Arow Global is a small, innovative US manufacturer of window systems for the transportation industry, and is making their first foray into continuous fibre composite materials—by 3D printing them.

“What we’ve used so far is fibreglass and the carbon fibre. Basically to help make our parts a little more rigid – especially some of our drill jigs,” says Joseph Walters, New Product Design Engineer at Arow Global. “We’ll do carbon fibre inlay around the corners that stiffens the part up to the point that it’s as stiff as aluminium, but it’s also a lot lighter than aluminium.”

Everyday, Walters and the rest of the Arow team know that they made the right call – 3D-printed composite materials can affordably provide the mechanical properties that Arow could previously only obtain with machined metal.

A few months prior, Walters had been faced with a dilemma – to deliver robust, affordable tools and fixtures, as well as to prototype new design concepts for Arow. His best choice was to outsource parts to a CNC machine shop — using Arow’s own CNC equipment would divert essential production resources. Yet, the cost was still too high and the time too long — parts were hundreds to thousands of dollars, and took weeks.

“There’s no good way to do prototyping quickly without spending a couple hundred dollars for a four-inch tall piece.”

3D printing was an attractive solution for Walters, but had many shortcomings. While conventional 3D printers complement engineering effort, at factories doing routine machine fixturing, ordinary plastic 3D printing is often too weak or fragile. Metal 3D printing, on the other hand, is simply inaccessible — most solutions of this type are nearly a million US dollars.

In describing his search for an affordable 3D printer to replace aluminium parts, Walters emphasises: “We wanted parts that were useful, so we didn’t want to have a 3D printer that can do only common plastics like PLA and ABS, which are very brittle. ‘Useful’ was one of our requirements.”

Arow’s fixtures and prototypes need to be not merely inexpensive, but reliable. It’s not surprising that Walters initially overlooked composites to fill the role. Although materials like carbon fibre provide incredible benefits, full composites production automation has been available only to first-rank aerospace companies using multimillion dollar robots capable of ATL (Automated Tape Laying) and AFP (Automated Fibre Placement). Without automation, difficult traditional layup techniques are often beyond the reach of modest manufacturing businesses needing affordable parts. Continuous fibre composites have been exotic for 50 years — too expensive and too elaborate for everyday use. Until recently, Walters would have considered an automatic carbon fibre printer to be science fiction.

However, the world is changing quickly for composites. For several years, 3D printed parts made of reinforced plastics have been available from 3D printing service bureaus using laser sintering to melt thermoplastics. However, since 2015, the availability of automatic, on-site composites manufacturing has exploded. New desktop 3D printers marry the tough, non-marring properties of thermoplastic with short chopped fibres — or in some cases continuous strand carbon fibre, Kevlar or glass — to inject high-end aerospace materials into commonplace shop jigs and tools. Users of these new 3D printers are often unfamiliar with composites, and are not displacing composites in their work or making inroads into historical composites areas. Instead, they are switching away from reliance on metal processes — especially CNC milling of aluminium, as well as forging, moulding, or sheet metal bending.

Arow Global finally settled on one of these new composite 3D printers. The use of a desktop composite 3D printer — a Mark Two from Markforged — has given their engineers more agility in prototyping new concepts in real-world environments. Even machinists on the shop-floor can make their own manufacturing jigs, multitasking in parallel with production work. 3D printing requires no CAM — the parts are simply printed, often while the machinist is doing other work.

“We’re able to take a part that would have cost US$400, with a two-and-a-half week lead time of machining from one of our local vendors,” Walters comments. “Instead we printed it over the weekend, and the manufacturing floor likes it just as much, if not a little better… and they’re using it to this day.”

Some of their jigs have now been extensively used in the assembly process, nearing 1000 cycles.

“We see no visible signs of wear on any of the nylon parts, and it adds the benefit of not scratching the parts that we’re producing, where with aluminium you can get scratching in the extrusion if one is a little harder than the other. With nylon, that’s basically eliminated.

“The last time I did a new outsourced latch design I had six prototype extrusions costing well over US$1,500” adds Walters. “What we’re able to do with the Mark Two is really dial in some of the tolerances and also some of the features to make a feature like snap fitting as simple as possible and easy as possible for the assemblers … before, a lot of that would have been based off of guess work.”

Now with its composite 3D printer, Arow Global can afford the time and money to go through many more rounds of prototyping than before.

“With the 3D printer, we’re now able to do this with three or four revisions in a week whereas before you’d have to cut dies, which takes time and money,” Walters continues. “Overall the printer has helped dramatically in terms of reducing wasted material inventory and time.”

With the Mark Two, the prototypes that Walters designed could be easily printed with high strength reinforcement, without the need for a costly and time consuming third party manufacturer. As a result, the composites 3D printer was able to easily able to pay for itself within 15 jobs.

“I would estimate that we have seen a full return from printing five parts each of three different plastic injection-moulded prototype components, specifically from not having to invest in the soft tooling traditionally used to create injection moulded parts,” Walters explains.

A number of prototypes that otherwise needed to be machined could now be made just as strong for a fraction of the price, proving the Mark Two an invaluable resource to Arow Global.

Marrying carbon fibre composites to 3D printing is not just about cost savings – in some cases it enables the previously impossible. Now Walters and Arow Global are exploring their new ‘superpower’.

“We’re looking at basically rethinking how we can do drill jigs. Now we can do more complicated machining designs that we simply couldn’t do in the past because you physically can’t machine those designs. With Markforged, because it’s an additive technique, not subtractive machine, we don’t have to worry about the limitations of CNC milling.”

Arow Global’s composite 3D printer is capable of printing a wide variety of fibre reinforcement patterns, creating both anisotropic and quasi-isotropic ply constructions. As with traditional composite layups, although each individual layer contains a high degree of anisotropy, the addition of multiple layers of composite with rotating orientations results in a part which is quasi-isotropic as a bulk entity. The printer’s software interface gives users control and optimisation of the layout of internal continuous strand composite fibres – users can adjust the fibre layout pattern, customise fibre orientation codes, and select fibre layer placement in their 3D model. By adjusting fibre orientations and plastic infill, users can emulate traditional unidirectional and quasi-isotropic fibre laminates, and can build dense structures or weight-optimised sandwich panels including automatic honeycombs. Users can also create continuous fibre/plastic structures never before possible, such as concentric loops.

Markforged currently offers the only commercial 3D printer in the world that automatically lays continuous strand fibre — carbon, Kevlar, or glass — into nearly any shape that can be 3D-printed or machined. The printer is also the only commercial 3D printer that combines continuous strand fibre strength and toughness with chopped fibre stiffness, serving worldwide markets. The Mark Two composite printer is a compact desktop printer impeccably designed for ease of use, targeted at engineering and manufacturing professionals, equally in the office or on the shop floor, and in many cases gives a return on investment measured in a few months. Any manufacturing or engineering facility that needs strength, toughness, stiffness, environmental resistance or dimensional stability in everyday tools and fixtures can cost-effectively augment, complement, or replace CNC machining or conventional 3D printing jobs with fully automatic composite 3D printing.

And that’s just the beginning …