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Callaway Golf Company
Flash-Removal System
Spring 2019 MAE 156B Sponsored Project
University of California, San Diego
Background
Currently, the Callaway Golf Company uses an injection molding process to manufacture golf ball covers. In this process, the golf ball core is suspended by pins in a cavity mold that is injected with a polyurethane thermoplastic. When pins retract, in order to leave the core suspended within the plastic, excess, which is referred to as flash, is left in the dimples of the newly formed cover of the golf ball. There are twelve instances of flash per ball; these instances are separated into two groups of six that exist on two poles of the golf ball. Each pole group is similar with a flash in a pentagon dimple with the other five instances in hexagonal dimples that surround the pentagon dimple. Each dimple is constructed from a hexagonal lattice, which is also known as a tube. These irregularities impact not only the aerodynamics but also the aesthetics of the ball. Current methods, such as the Van Mark Method, of removing this flash are imprecise and alter the structure of other parts of the ball, and, as a result, influence the flight of the ball in unpredictable ways. The objective of this project is to improve the aerodynamics and aesthetics of the golf ball by developing a system that accurately and precisely removes flash without modifying the rest of the structure of the ball.
Figure 1: Flash on inside of a dimple on a golf ball Figure 2: Schematic of side-view of dimple and flash
Objectives:
The primary objective of this project was to design a bench-top device that would remove the flash completely without significantly altering the dimples that contain flash or their associated tubes more than 2.54%. Additionally, the system should be able to expunge the twelve instances of flash on a ball in a period of 10 minutes.
Final Design:
From experimentation results and safety considerations, it was determined that the most feasible and effective method of removing the flash would to buff the “flash.” In order to implement this method, the final system is comprised of a 3-axis mini-CNC engraving machine, a custom metal end bit, a ball holder integrated with a dimple locator. To initiate the buffing process, a ball is placed into the ball holder and manually rotated such that the flash-containing dimple is facing the positive z-direction. The orientation of the dimple is verified with the dimple locator. The custom end bit, which is being rotated by the spindle of the CNC engraver, is then lowered a prescribed amount. The CNC translates the bit to follow the outline of the “flash.” After a period of time, the end bit is raised. The user then rotates the ball to one of the flash-containing hexagons. The end bit and motion profile are then switch to the bit and profile needed to buff a hexagon dimple. The end bit is then lowered the same working distance as that of the previous step and follows the “flash” outline for a certain period of time before. This process is then repeated for the four other flash-containing hexagons of that pole group.
Figure 3: Full Assembly of Buffing System Figure 4: Full Assembly of Ball Holder with Dimple Locator
Video 1: Dimple Location and Buffing Process for 1 Dimple
Results:
The primary objective of being able to remove all instances of flash within a 10 minute period was unable to be achieved. The other primary objective of the buffing system of being able to spot treat the flash affected dimples while keeping the overall variation of dimples low and maintaining a consistent tube height was able to be accomplished. This result was somewhat achieved as the buffing method kept both the non-pin and pin (flash) dimples tube height variation within the tolerance. The percent difference between the non-pin and pin dimples of the buffed balls and those of the unbuffed (molded) balls are 0.124% and 0.323%, respectively. The current Van Mark solution leads to a larger change in tube height throughout the golf ball with a 1.994% change for non-pin dimples and a 4.328% change for pin dimples.
Table 1: Comparison of Variation Between Van Mark Method and Dimple Tracing
*Note: Information is proprietary to Callaway Golf Company
One drawback incurred by the buffing method is that it introduces a larger variance in the tube height of the pin (flash) dimples of 67.989% when compared to a molded ball. This large variation is due to the failure to consistently align the drill bit head to the center of the dimple, thus resulting in more tube contact than desired. Another reason for this large variation is the depth at which the drill bit goes into the dimple. Figure 6 illustrates what a section view of two dimples between a tube looks like, and it can be seen that some dimples have been buffed too deep as multiple lines dip steeper into the middle of the graph. However, these golf balls contain 332 dimples in total and pin (flash) dimples only contribute 12 to this total, resulting in a larger variation for only 3.6% of the dimples while, on the other hand, the Van Mark solution brings a relatively high amount of variation to all dimples, as seen with Figure 7.
Figure 5: Tube height v. Tube radius - Molded Figure 6: Tube height v. Tube radius - Buffed Figure 7: Tube height v. Tube radius - Van Mark
In order to get a visual understanding of the difference between a molded dimple and a buffed dimple, one can look at Figures 9 and 10, which are ball scan images of golf ball dimples. In Figure 8, there is flash on the right dimple. This dimple then undergoes the buffing process, and the result can be seen in the right dimple of Figure 10. One can see the circular motion profile that the bit followed while buffing the dimple.
Figure 8: Molded (Left) vs. Molded(Right) Ball Scan Figure 8: Molded (Left) vs. Flash (Right) Ball Scan Figure 10: Molded (Left) vs. Buffed (Right) Ball Scan
Thanks
We would like to give special thanks to the following people for their guidance and support throughout the entire project:
Sponsor:
Callaway Golf Company
Sponsor Contact:
Petra Petrich
Senior Engineering Manager
Golf Ball Research and Development
Callaway Golf Company
Course Instructors:
Professor Maziar Ghazinejad
Professor. Nicholas Gravish
James Lynch
Engineering Staff at Callaway Golf Company
Nick Lannes
Julie Caterina
Engineering Staff at UCSD:
Ian Richardson
Stephen Roberts
Chris Cassidy
Thomas Chalfant
Colleague:
Woo Jae Lee
Thank you again for the mentorship, aid, and input that made this project viable.
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