Lego Great Ball Contraption (GBC) Balls

thingiverse

GBC stands for a series of LEGO modules passing soccerballs and basketballs from one module to another. Recently, I built several custom GBC modules but struggled to obtain the necessary balls. The only sources available are LEGO or Bricklink, with shipping costs amounting to approximately $1.50 CAD per ball, which is quite steep. To avoid this expense, I decided to create my own balls. Designing them was easy; it took just 5 minutes in Tinkercad. However, the printing process proved more challenging. To work effectively with catapult modules, the balls must have a very similar weight to the originals. Here's what I did to achieve accurate weights and prints. Firstly, run a flow test to ensure that the halves and peg fit together properly. This step is crucial, as explained in numerous online resources, but it will not be discussed further here. Next, adjust your infill settings in your slicer. Turn off all helpers, including supports and brim, then load two halves and a peg. Slice the object and check the estimated weight. The goal is to achieve a weight of around 1.52 grams, with a margin of plus or minus 0.05 grams. Once you've reached this target, add your helpers back in and re-slice the object. Repeat the process until you're satisfied with the accuracy of your print. Keep in mind that most modules don't require such precise weights, but I prefer my balls to be as close as possible. To achieve this level of accuracy, weigh your printed ball on a gram scale and adjust your infill settings accordingly. Continue printing, weighing, and adjusting until you reach the desired weight. Finally, make sure to print at a high resolution, around 0.05mm layer height, so that the balls can roll smoothly. Printing at lower resolutions may cause the balls to jam in certain modules. That's about it; I hope these tips are helpful for creating accurate GBC balls.