Classroom 3D printing is expensive and time-consuming. There's always more demand than capacity. It's the slowest step in the innovation cycle. Yet all too often students choose to print more versions of their designs than necessary rather than waiting to submit a job only once it's been sufficiently refined and a print is necessary in order to test and confirm their working assumptions. Another common classroom challenge is how to motivate students to move beyond their comfort zones and how to reward them for doing so. Forget Bitcoin. We're 3D'ers! So we use 3DBucks to optimize printer demand and motivate students to maximize their progress through each lap of the cycle. 3DBucks are credits that students must spend in order to print something. The cost of each print job is based on the amount of filament it consumes. Available denominations are 1 gram, 5 grams, 10 grams, 25 grams, and the special Dual credit. The cost of a job that uses both extruders on the dual-headed printer is based both on the amount of filament it consumes as well as a Dual credit. You can give students some 3DBucks at the start of the semester, when a project is assigned or at some other point that makes sense in your classroom. 3DBucks encourage healthy saving, spending and design habits.They can also be used as rewards for good behavior, perseverance, helping others, winning a design contest, or any other deserving achievement. Version 1.1: Made several changes based on users' input. The heads and tails of all denominations are separate STL files. A zip tie slot has been added in the upper left corners. Thanks to Ollie & Mei-Mei for all your great ideas, feedback and refinements!I print 3DBucks on our Makerbot using ABS. Temperatures are as expected; 230 at the tip & 100 on the bed.