Graphite Golf Clubs & Composite Shaft Technology

Composite Golf Club Shafts & Graphite Shafts Manufacturing Processes

Aug 25, 2009

Questions of how to make a graphite golf club shaft arise frequently. Now, an overview of a manufacturing process for graphite composite golf shafts provides an answer.

Many golfers believe the shaft makes the club. Graphite composite shafts are more popular than ever, particularly for the driver, or #1 wood. Design variables, such as quantity of fiber, number of layers of fiber and orientation of the fiber in each layer should be considered and will define the lay-up process as well as the attributes and performance of a finished shaft. Four segments of a manufacturing process will be addressed in this overview. They are, material & preparation, lay-up & cure, cut & grind and finishing.

Graphite Material and Preparation

Graphite fiber material which has been impregnated with resin is called "graphite prepreg". This material, commonly called broadgoods, will typically arrive from the vendor in a roll of poly about three feet wide. The poly has the prepreg fiber laid onto it. The strands of fiber are all oriented to meet design criteria when laid on the poly.

The fiber preparation is to orient the broadgoods according to the predetermined angle and cut a triangle shape from the sheet. This triangle shape may be called a pennant or flag by some manufacturers. The orientation of the fibers for each layer, or ply, is determined by the design. The number of layers, or plies is also determined by the design for each shaft.

Fiber Lay-up and Cure Cycle for the Graphite Prepreg

A mandrel is a tool which is a mold form for the inside of the hollow golf shaft. Think of it as a solid metal pencil-like tool which is over four feet long and slightly tapered. The mandrel surface is treated with mold release and placed into a rotating machine where the fiber triangles are applied.

The cut graphite triangles are sequenced by size and fiber orientation for each ply, as called out by the shaft design. The triangle for the first layer is oriented on the mandrel and the mandrel is rotated while the graphite fiber triangle is compacted around the mandrel. This process is repeated until all of the fiber triangles are applied in the sequence noted in the design. After all of the plies have been compacted on the mandrel, the layup is then over-wrapped to hold all of the fibers in proper position during cure. At least one manufacturer uses cellophane for this over-wrap as it creates a vacuum effect during the cure and mandrel expansion.

Note: The strength of each fiber layer, as well as the orientation of the fiber in each layer, will determine the stiffness and torque (resistance to torsion) of the completed shaft.

The cure cycle depends on the resin utilized in the design as well as the thickness of the fiber build up. A typical cure cycle for a graphite golf shaft might be around 300-325 degrees F, for two hours or more at the elevated temperature. Upon completion of the cure cycle and removal from the oven, the over-wrap is removed and the mandrel is extracted from the cured shaft.

Cut to Length and Surface Grinding of the Graphite Shaft

Once the mandrel extraction is complete, the cured shaft is placed into a cut off saw. Typically this saw will position the shaft in the machine and cut the shaft to length, cutting both ends at the same time. Club makers, as well as some shaft manufacturers, call this process "trimming".

The shaft is then removed from the saw and placed into a grinding station. The external surface of the shaft is then ground smooth, to the proper outside dimensions. This is typically accomplished utilizing a pair of opposing grinding heads.

Final Finishing and Inspection of the Graphite Golf Shaft

Inspection of the shaft should be performed throughout the remainder of the process. The surface should be inspected for any voids or imperfections and the shaft should also be tested for the proper frequency that is associated with the stiffness for which the shaft was designed.

The final finishing of the shaft starts with painting and passing through a bake cycle for curing. Once the painted shaft passes inspection it will have the graphics applied and finally the shaft is sealed and given one final inspection prior to packaging and shipment.

Graphite Composite Clubs a Part of the Evolution of Golf Equipment

The game of golf and the equipment used has evolved tremendously over the years. In the last 25 or more years, graphite golf club shafts have been a part of that evolution. Although the details of the fabrication processes for graphite shafts may vary from one manufacturer to another, this basic overview should provide a general understanding as to how graphite shafts are manufactured. An article is available which explains golf swing speed and shaft stiffness that may also be of interest, as well as the article about the physics of swing tempo.

The copyright of the article Graphite Golf Clubs & Composite Shaft Technology in Manufacture Engineering is owned by Jake Crum. Permission to republish Graphite Golf Clubs & Composite Shaft Technology in print or online must be granted by the author in writing.