The strength and geometric freedom of fiber-reinforced nylon enables a Markforged senior mechanical engineer to make his own French Horn.
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The Marriage of Music and Engineering 

When not inventing new technology as Senior Mechanical Engineer at Markforged, Keith Durand, PhD is an active, passionate musician performing with groups like the Mercury Orchestra, the Longwood Symphony Orchestra, and Bay Colony Brass. 

Using Markforged’s networked fleet of Mark One 3D printers, Keith has succeeded in combining his passions in precision engineering and music to make his own Knopf-wrap French horn. 

Ultimately, Keith used around 40 nylon modular fixtures printed on the Mark One — some reinforced, others pure nylon — to bend the horn tubing and locate the valves during assembly.

“I realized it was the right tool for the job. Nylon is perfect for this application — it won’t scratch the brass, and the fiber reinforcement makes the parts strong enough to do the job.” 
A Handmade French Horn 

Keith started playing the French horn in the 6th grade, and has wanted to make his own since high school. After playing horn through high school, college, graduate work, and beyond, Keith eventually took a natural trumpet making class. Keith made a natural trumpet using traditional 17th and 18th century techniques. He said, “It was a fun week. I learned new ways to torture metal.” 

In 2013, Keith joined Markforged as employee No. 5 and worked day and night on the first Mark Ones, from time to time letting off steam by machining horn components and modeling tooling in SolidWorks, initially planning to machine the tools from aluminum, plastic, and steel.

Keith with an Early Mark One 3D Printer 

Initially unimpressed with the capabilities of 3D printers in general, Keith became convinced that he could 3D print the modular fixtures to make a horn after an early Mark One successfully printed reinforced nylon. “I realized it was the right tool for the job. Nylon is perfect for this application — it won’t scratch the brass, and the fiber reinforcement makes the parts strong enough to do the job.” 

In designing and printing the tooling, he began with a fixture to locate the valves, then worked outward, making bending fixtures to shape the brass tubing and fixtures to hold tubing in position. As often happens in the design process, the fixtures would sometimes need adjustments. With the Mark One working overnight, most changes were ready by the next morning. 

Keith explained, “The most complicated bending fixture was for the F-branch — it had to be the right shape to bend things around, but had to have clearance so I could get the tube in there in the unbent configuration AND out once the part was bent. I even spent time on vacation in a coffee shop getting the model just right, and the finished part was waiting for me when I got back. 3D printing more or less makes complexity free. Machining this particular fixture would have cost a small fortune.” 

With simple tooling and locating fixtures printed in pure nylon, and more complex bend tools, including a bending tool with a Kevlar-reinforced cheater bar to increase leverage, printed with fiber reinforcement for additional strength, Keith designed and printed about 40 different fixtures to complete his horn construction.

“Machining this particular fixture would have cost a small fortune.” 
Even Artisans Cheat...

While many of these jigs, forms, and fixtures would traditionally have been made of wood, and in the 20th century would have been machined out of aluminum or steel, Markforged industrial strength 3D printing now replaces wood and metals with reinforced nylon, shortens the cycle time, and provides remarkable cost savings. The cost per fixture can be an order of order of magnitude cheaper compared to CNC machining, approximately $500 for a machined fixture compared to ~$42 for a reinforced 3D printed one.

Keith played the homemade horn for the first time in concert with the Longwood Symphony Orchestra in May 2015. According to Keith, “really before it was ready, but I couldn’t wait.” The horn had a 3D printed thumb lever, a little bit of duct tape, and a few missing parts. 

Both Keith and the horn survived the concert, and over the next few weeks, the horn got the finishing touches it desperately needed. Now that the horn is done, he regularly plays it with Longwood and the Bay Colony Brass. In addition to achieving a lifelong dream of making his own French horn, the horn now has a beautiful, clear tone that he is proud to play in concert. 

What’s next for Keith and the horn? “It’s only fitting that my second horn will get new fixtures, of course printing on the Mark Two.” 

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