Final Design

Overall Design

    In order to achieve the functional requirements specified by the sponsor, the final design solution is a dimple polishing system, which consists of the following components: a 3-axis CNC milling machine (3018 Pro mini CNC engraver), a ball holder device with a dimple locator device, and a custom end bit.

    To initiate the buffing process, a ball is placed in the ball holder with the face of the flash-containing, center pentagons perpendicular to the XY plane and facing in the positive Z direction. The dimple locator device can be used to verify that the ball is in the correct orientation by placing the device in the slot in the side of the ball holder and ensuring that the pin at the top of the device is in the center flash-containing dimple pentagon. Once the ball is in the correct orientation, rubber bands are stretched over the ball and connected to the latches on the ball holder to ensure that the ball is constrained in the axial (Z) direction. The end bit, which is connected to the spindle of the CNC machine, is then lowered a certain depth in the Z direction that ensures the bit is exerting an optimal force onto the dimple. The CNC begins to not only rotate the end bit at 1000 RPM but also maneuver it along the circumference of the flash.  After a certain period of time, the CNC removes the bit from the dimple. The user then rotates the ball to one of the flash-containing hexagons and ensures that the hexagon is facing the positive Z direction using the dimple locator. The end bit and motion profile are also switched to the ones used for hexagonal dimple buffing. 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. This process is then repeated for the four other flash-containing hexagons of that pole group. Once the flash is removed from the pole, the other flash pole group of the ball undergoes the same process.

Figure 1: Full Assembly of Entire Buffing System

CNC Machine:

The CNC 3018 Pro is a 3-axis CNC engraving machine. The CNC is able to conduct movements on the scale of thousandths of an inch in the X, Y, and Z directions. Additionally, the machine runs using G code and a GRBL open source software. The machine also meets functional requirements by being able to fit on a bench top.

Figure 2: CNC 3018 Pro

Custom End Bit:

   Since the pentagonal and hexagonal flash-containing dimples have different geometries, different end bits and circular motion profiles are used. Consequently, when buffing a pentagon or hexagonal dimple, one must ensure that the correct end bit and motion profiles are used. For the pentagon dimple, the end bit has a diameter of 0.115 inches and the bit adheres to a circular motion profile with a diameter of 0.175 mm. The end bit for the hexagon has a radius of 0.1 inches and follows a circular path with a diameter of 0.560 mm. The custom end bits was 3D printed out of VeroClear with the Connex3 Object 350 as the printer. The contours of the tips of the bits were designed to match the curve of the dimples on the golf ball to help ensure that minimal excess material is removed. The end bit is placed in the spindle of the CNC machine.

                            Figure 3: 0.1'' End Bit                                                        Figure 4: Contour of 0.1'' End Bit                       

Ball Holder:

    The ball holder was 3D printed using VeroClear as the material and the Connex3 Object350  as the printer The ball is placed in the holder and friction between the ball holder and the ball is used to impede the rotation of the ball. To constrain the ball in the Z-direction, the holder was designed with latches that allow rubber bands, if desired, to be stretched over the ball and additionally constraining the ball; however, the friction is able to acceptably constrain the ball in the Z-direction. Additionally, the ball holder was designed with a dimple locator device in order to allow for the ball to be aligned in an uncomplicated manner. The dimple locator is placed in the slot on the side of the holder and the pin at the end of the locator is placed inside the desired dimple. The ball holder is attached to the bed using bolts and drop-in fittings.

                                                                 Figure 5: Ball holder with extended flanges                    Figure 6: Extended Alignment Tool                               Figure 7: Final Ball Holder Assembly

Performance:

Video 1: Dimple Location and Buffing Process for 1 Dimple

    The system is unable to remove all flash from a ball in 10 minutes. However, the system is able to keep the variation of non-pin dimples and pin (flash) dimples on a buffed ball within 0.124% and 0.323%, respectively, of the non-pin and pin dimples of a molded (unbuffed) ball; albeit, this result is achieved with a variation of 67.989% for the pin dimples.

Table 1: Comparison of Variation Between Van Mark Method and Dimple Tracing