How Bowling Balls Are Made
For anyone wishing to understand a little about how bowling balls are made, it is useful to focus attention on the two key components of all bowling balls, the core and the coverstock. Since the core is the first principal component of a bowling ball assembled at any given manufacturer's factory, we should first address the core component as an initial step in discussing how bowling balls are made.
It all begins with which type of ball motion a given manufacturer visualizes or plans as the next bowling ball to be introduced into the market. Over time, manufacturer's typically develop strategies to offer performance and diversification in each line of bowling balls for each brand manufactured. It is important to note than each manufacturer will use their own procedures making bowling balls.
The core design process is the first step in planning a bowling ball to fit into the given product line. For example. if a given company wishes to introduce a very aggressive ball to combat heavy oil and fit into a certain line of bowling balls, then the first step is to design the core with an intent to achieve a pre-planned, low RG rating so the ball will "rev" quickly and respond on the front end of the lane. By means of a Computer Animated Designs (CAD's), ball designers generate special computer programs to design and develop a very stable reacting inner-core concept, known as a symmetrical core, which encourages a strong ball reaction on the front end of the lane for the heavy oil condition.
Of course, the engineers will design a less stable core if the intent is to produce a ball with a medium or high RG for use on medium or medium dry lane conditions. These types of core designs are known as an asymmetrical cores and they typically create a longer skid and greater flare potential than symmetrical cores as the bowling ball clears through the front ends before reacting in the mid-lane.
Manufacturers will design inner-cores made of urethane and polymer based products in varying density ranges, shapes, and number of pieces to also vary the mass density of the core and achieve an end result which will influence the overall ball motion predictably. Cores with the most mass density placed closest to the center of the bowling ball will tend to roll soonest and skid less than cores with the mass placed furthest from the center of the bowling ball and closer to the coverstock location. In our heavy oil example, ball core designs which includes a shape which places mass in specific areas near the center of the ball and also places mass to the top of the ball by means of an additional weight block component and by means of a special shape to the principal inner-core will promote early roll to combat front-end excessive oil coupled with a strong back-end reaction (high differential and flare potential) from the break point to the pocket.
Other core designs will produce somewhat different results in ball reaction capabilities based upon the core design principles planned by the engineers. Varying shapes, numbers of pieces in the core designs, and mass distribution in multiple core locations will enable the manufacturer to produce pre-planned ball reactions.
The cores come through the core room assembly conveyor after being molded and shaped into the size and mass density forms predetermined by CAD designs. Once the cores are finished off into their final form, they are placed into the injection molds and supported with a urethane stem, known as the pin, positioned in the weight block to hold the core in place as the coverstock is poured into the ball mold during the injection process. The pin represents the top part of the weight block and is usually identified by a colored dot on the ball surface. There are certain optional procedures which may be used to wrap an outer-core around between the inner-core and the urethane material injected into the ball mold.
It is helpful to know that the industry refers to coverstock urethane blends in the following way: plastic, urethane, reactive resin, hybrid reactive, and particle materials. Each of these coverstock material variations yields to the performance range capabilities intended for the given bowling ball. Since there are no tolerances provided for coverstock texture, the manufacturers offer a variety of textured coverstocks to match with varying oil lane conditions. Coverstock materials vary chemically and use a variety of additives merged in the mixture of basic urethane liquid compounds. These additives are used to produce a solid, pliable coverstock or a stiff, pearl coverstock, all of which will be versatile and will allow the factory finish to be altered after drilling as needed for ball reaction capabilities. Multiple dyes are used to create the desired color effect planned for the bowling ball.
Often times mixtures of urethane compounds are used to vary the molecular fiber make-up of the final mixture of material. The specific mass density of the urethane material is also calculated to ensure the overall ball weight will be achieved. Added particles may be introduced into the mixture to reinforce the material as the urethane hardens and is cured into its final state and surface appearance.
Once the injection process is completed and has cooled, the bowling ball is removed from the molds and is placed on a conveyor assembly for the purpose of honing the shape and size of the ball into acceptable tolerances by use of lathe-like devices which remove rough and bumpy materials from the ball surface. Sanding and screening procedures will then be applied to the ball surface so the ball begins to take a uniform shape within acceptable USBC tolerance ranges.
After the screening procedure is complete, the ball will be cured and polished to achieve the desired level of surface texture by means of high-speed screening devices and by use of Abralon-type pads which ultimately finish the coverstock to the intended surface texture. When the bowling ball surface is complete, then the process of spinning the ball to determine the preferred spin axis and identifying the bowling ball center of gravity are completed.
The ball will then be marked pinpointing the location of the CG and mass bias on the ball surface. The bowling ball will be stamped with the company logo and brand labels and with serial numbers indicating the ball is U.S.B.C. approved for use. The final step is placing the ball into the ball box accompanied with any given literature. The ball box is labeled with the bowling ball weight information and manufacturing information as deemed appropriate by the manufacturer.
Bowling Balls Being Made