My initial skepticism about 3-D printing’s place in the gear industry took a solid hit during a recent visit to a client. I am used to seeing colorful renderings of Solid Works or Pro Engineer files, but nothing prepared me for a complete one-quarter-scale, WORKING model of the prototype product we were meeting about. Scale models are powerful communication and selling tools. I have built several myself over the years and know the value of putting a physical object in the decision maker’s hands. My first model was for a turret drive mechanism that severely taxed my limited woodworking skills, but it looked fabulous in the mocked-up, full-size mobile howitzer — so good in fact that the vehicle builder “neglected” to return it after giving the contract to a competitor. The project eventually got cancelled, so karma may have been restored to proper balance. Ten years later, my woodworking skills were slightly better and the resulting model helped secure a nice prototype order. But not before it got bounced on the tarmac at the airport and had its paint job touched up with a felt tip pen! Some concepts can only really be understood with a scale model. This client took his model to the next level by 3-D printing the internal components too and assembling it with to-scale plastic nuts and bolts. The fit and finish were consistent with the full-size prototype, save for the gear action being a bit lumpy because the bearings didn’t have rollers. Lots of hand-finishing on tooth flanks and splines got the motion close enough that potential customers couldn’t resist rotating the device. Best of all, the model was made in-house on a low-cost 3-D printer that will get lots of use in the future. I am interested to see if they can throw a shrink factor at the computer models and print their own patterns for the foundry. That savings would more than recover the cost of the printer.