Composite materials have been used in the golf industry for nearly 20 years to make golf club shafts and the club heads. However, it might be argued that composites used in a multi-material approach might better optimize club performance. That proved to be the case when Mark Kronenberg founded custom golf club manufacturer Krone Ltd. (Dallas, TX, US) in 2012.
Determined to create the world’s most advanced high-performance golf equipment, Kronenberg wanted to go beyond conventional composite mass-manufacturing techniques to a more innovative and customizable approach. Although Krone had tested direct metal laser sintering of titanium and 3D printing of master casting patterns for metal, it ultimately approached for guidance the CRP Group (Modena, Italy), which had long experience with 3D printing in Formula 1 racing. CRP Group companies CRP Technology, which produces additive manufacturing materials and technology, and CRP Meccanica, with high-precision CNC machining experience, were involved in the project.
Developing a golf driver is complex, because the US Golf Assn. (Far Hills, NJ, US) and the R&A, a spinoff organization of the Royal and Ancient Golf Club of St. Andrews (St. Andrews, Fife, Scotland) formed in 2004, which now functions as the ruling authority of golf except in the US and Mexico, both limit the maximum size and volume of a driver head. Plus, golfers have expectations about not only driver performance (ball distance, loft, speed and spin) but also nuances such as “feel” and balance, which are tough to engineer in, say Krone and CRP. The three companies (Krone, CRP Technology and CRP Meccania) worked together to develop the KD-1, a composite driver club head consisting of an additively manufactured body, using selective laser sintering (SLS) and employing Windform SP, a sinterable carbon fiber/polyamide powder; a Ti6A14V titanium strike face, CNC-machined from billet material, followed by sandblasting and cleaning; and a brass weight, also CNC-machined and sandblasted.
Printable in hours, the hollow body’s lattice geometry optimizes its stiffness, while the carbon/polyamide exhibits high ductility and impact absorption. The machined titanium face fits over and is adhesively bonded to the body. Four Helicoil inserts in the body, opposite the face, accept fasteners that attach a brass weight.
According to Krone, the AM process coupled with CNC reduces the touch labor otherwise required for conventional composite driver heads made with prepreg, and produces parts with tighter tolerances than those made from cast and forged metals, without time- and labor-intensive secondary operations.
Concludes Kronenberg, “In our working experience with CRP so far, we have seen outstanding part quality, consistency and accuracy, in both CNC machining and 3D printing.”
See a video that demonstrates the multi-material club head manufacturing process: