Structural Bonding of Club Head to Shaft

Taylor Made Golf Clubs

The competition to produce a top-quality metalwood golf club is every bit a fierce as the competition on the course. One manufacturer, Taylor Made Golf Co., has developed a manufacturing process that combines a high performance adhesive with a state-of-the-art epoxy dispensing system.

The Taylor Made design staff, the Sealant Equipment & Engineering Inc. dispensing equipment supplier and the adhesive formulator Ciba-Geigy have co-operated to make the old threaded connection between the club and shaft a technique of the past.

Welcome to the Club

A key facet in manufacturing golf clubs is the head-to-shaft-attachment. Because of the stress at this point, the club needs a connection strong enough to withstand the golfer's swing and impact, and durable enough to last for years.

To verify the durability of the product, Taylor Made's manufacturing technique insures that the shaft-to-head connection withstands a 5,500 psi pull apart test. No manufacturing method has proved as effective as epoxy adhesive bonding in attaching the composite shaft to the head, so the company implemented a rigorous testing process to select a quality adhesive and a dispensing method.

Based on extensive research and testing, the company chose a two component structural epoxy adhesive supplied by Ciba-Geigy. The adhesive formulation, known as Araldite, is used in applications for snow board, ski and golf industries due to its bond strength and resistance to environmental conditions.

The company hit on Araldite after comparative pull and impact tests of almost 50 additional epoxy formulations. Performance testing, based on Taylor Made's stringent requirements, revealed that the epoxy bond was only about 75% effective until the Araldite material was used.

Once selected, the epoxy was mixed in small batches by hand, dipping the shaft into the cup of mixed epoxy, then inserting the shaft into the head - this almost guaranteed that they would not have 100% bond area coverage. It also presented a housekeeping problem, in that the heads would frequently require clean-up. Also, mixing to the specified ratio, 2.5 (Part A) to 1 (Part B), was difficult, frequently inconsistent and completely operator dependent. The finished product, while better than most competitors', was still less than perfect.

In Production

From both the production quantity and quality standpoint, hand weighing, hand mixing and manually applying the epoxy was unacceptable. At 1200 clubs per day, the company's demand was increasing, so choosing an automated adhesive dispensing system with precision volumetric positive displacement and shot size control became a priority. The company began searching for equipment that would dispense the precise volume of correctly and uniformly mixed, air free epoxy for each club and accurately bond the components without mess and costly excess. It was determined that exactly 0.7cc of epoxy dispensed per club was needed. After testing other types of dispense equipment, a SeeFlo® 387 Bench Top Meter / Mix / Dispense System was chosen supplied by Sealant Equipment & Engineering Inc.

The SeeFlo® 387 is a positive displacement volumetric dispensing system with precision shot size adjustment capabilities. The system dispenses at a controlled mixed material flow rate insuring that the mixed epoxy is not dispensed too quickly into the club head and consequently trapping air. The SeeFlo® 387 system accurately dispenses the required 0.7cc per shot, time after time, of the 2.5:1 ratio mixed material.

Using a disposable plastic motionless mixer nozzle insures that solvent flushing is not required in the operation. Seal modifications were made to the SeeFlo® 387 system to make it compatible with the Araldite epoxy and meet the demanding production requirements. With several SeeFlo® 387 dispense systems in place, production has increased from 1200 to more than 4500 clubs per day and continues to rise.

In production, the operator positions the club head under the SeeFlo® 387's disposable mixer nozzle and activates the unit by pressing a foot pedal. The 387 then dispenses the precisely metered epoxy.

The unique Snuf-Bak™ action of the dispense valve ensures that the epoxy does not drip from the nozzle after the dispense cycle is completed. The 387 system's A and B material holding tanks were modified to include heat blankets to lower the epoxy's viscosity and maintain the desired mixed epoxy cure time during cooler weather temperatures.

Once the epoxy is applied, the bonded head and shaft are placed in a fixture which pressure fits the parts together. The finished clubs are tested to ensure that the bond meets the company's standards for impact and tensile strength.

Today's Taylor Made System 2 driver, the result of seven years of research and development, now sets a new standard for golf club manufacturing. While continuously expanding production in the United States, Taylor Made's sister company in Japan, now the home of some of the greatest golf fans in the world, has entered the world-wide market. As the company launches full production, similar equipment and manufacturing techniques will be installed elsewhere.