Golf is a global sport that attracts and engages millions. At the highest levels, the money and business involved with golf is mind-boggling. A significant part of the attraction to the game of golf is its centuries old traditions, but one company is looking to bring the game into the 21st century, specifically in terms of the advanced development and manufacturing techniques for golfing equipment.
That company is Krone Golf, recognized as a world leader in the production of custom engineered golf equipment. To maintain and further its reputation in this respect, Krone has been working with partners to utilize advanced manufacturing techniques and materials to produce state-of-the-art smart golf clubs.
According to Krone Golf’s chief executive officer (CEO), Marc Kronenberg: ‘We do something revolutionary in the golf industry and design a superior product through the use of intelligent design, innovative materials and hi-tech manufacturing methods.’ Marc’s biography is an impressive one. He is renowned as a golf club designer, most notably with the TaylorMade R7—arguably the world’s best-selling driver—and the RBZ fairway woods.
Krone Golf, with its partners CRP Meccanica and CRP Technology—both part of Italy-based CRP Group—have been involved in a fascinating evolution of golf club development that has resulted in the new commercial, high-performance driver: the KD-1. Since the launch of the KD-1, the evolution has continued and resulted in a functional prototype of a truly smart golf club that was introduced to the market for the first time at CES a couple of weeks ago.
This development project highlights some recurring industrial themes, including when and how to best apply additive manufacturing techniques alongside more traditional methods such as CNC machining. This is where CRP’s expertise came into play, with the ability to supply its unique Windform powder materials for additive manufacturing and CMM dimensional controls to guarantee the total and complete traceability of every part, from the certification of the metal alloy to the certification of final testing.
Titanium and composite materials have been used in the golf industry for nearly 20 years. However, very little has been done to take full advantage of how they are used to optimize the design or part performance. Most efforts have been dedicated to reducing costs and increasing output. It’s also important to note that for this application titanium parts are typically cast, stamped, or forged, while composites are laid up by hand using ‘pre-preg’ and cured by compression molding or in an autoclave.
Following extensive research and testing of different AM processes, Krone initiated a collaboration with CRP Group, not least because of its vast experience in the highly demanding motorsport sector and its longevity in the AM sector where it has been active since 1996.
There are a lot of metrics used to evaluate golf club performance: most commonly distance and launch conditions like loft, spin and ball speed that are easily measured and quantified. There are also more nuanced ones like ‘sound’ and ‘feel’ that are more of a personal preference and take time to fine tune and customize. Performance is also critical. That is why golf club design and development is quite similar to high-performance automobiles in that acceleration and top speed are easy to measure, but getting the balance, handling and exhaust note just right ‘require a blend of art and science’, as CRP points out.
The engineering behind a great golf driver involves optimizing the thickness of each surface, controlling total weight of the head, and tuning the center of gravity of the assembly and getting the balance between all three exactly right. What is more, the development process is constrained by regulations and standards—the USGA and R&A (Rules Committee for Professional Golf) have placed limitations on the maximum size and volume that a golf driver can be.
Traditional methods of manufacturing golf clubs have not been well suited to complex geometries. These methods are also labor intensive and unsuitable for small runs or customized parts, while both casting and forging operate within wide tolerances, part-to-part variations, and require secondary operations. Other issues include casting or stamping titanium components too thinly, and the post-process welding operations create a heat-affected zone that can cause deformation in thin areas.
However, by combining high-performance CNC machining and additive manufacturing, many of these issues can be overcome, as the CNC process enables tight control of the thicknesses in critical areas, while AM with functional materials produces very stiff yet lightweight lattice structures. The primary result of the collaboration between Krone and CRP was the KD-1—a composite driver clubhead where the different materials have a specific structural function.
The KD-1 body structure was manufactured using the laser sintering process and Windform SP material. This is a highly ductile material with high mechanical resistance which minimizes high stress fatigue over time and when subjected to vibration or shock. The elasticity of the material absorbs these mechanical stresses. The body of the KD-1 also features four Helicoil M4 inserts to fasten the weight. The KD-1 face (the striking surface of the head of the club) is constructed from Ti6Al4V, CNC machined from solid and sandblasted to clean the external surfaces—processes also applied to the club’s weighting mechanism, but using brass billet.
The entire production process for these parts is lean and direct, bringing advantages that include improved lead times, increased precision, design flexibility and part optimization.
Since the success of the KD-1 golf driver, work has continued to further improve the functionality of the golf driver, resulting most recently in a new concept—the first fully integrated smart golf driver. A fully functional prototype version of this driver was introduced at CES recently and demonstrated the integration of dual 9-axis motion sensors in the head and the grip together with a launch monitor.
The motion sensors are able to monitor a player’s swing and detect inefficiencies. This data is collected in real time and can be fed back to an app via a tablet or smartphone. Metrics that can be measured by the Krone Linked system include: the location and speed of the club head and grip during a complete swing; club path at impact; face angle; angle of attack; ball speed; launch angle; spin rate; carry distance; and total distance.
The partnership continues, and it is a fascinating insight into how to maximize the benefits afforded by the additive manufacturing ecosystem.