Model Locomotive with 3D Print Technology

With retirement in February 2011 an interest in model building using 3D printing technology was undertaken.

Initial Project - 1/2" scale model of USRA 2-8-2 Mikado steam locomotive

Recently a BFB-3000 3D printer was ordered from the manufacturer, Bits From Bytes, a subsidiary of 3D Systems located in Bristol, UK. In January a 3D CAD program Alibre Design Pro was purchased from Alibre Inc. in Richardson Texas to provide the necessary 3D CAD drawings in the required .stl format.

Between January and now two samples were built, one by Bits From Bytes using their FDM (Fused Deposition Modeling) technique and another from 3D systems using their V-Flash ultra-violet liquid fusing technique. Both showed promise of being suitable to make interesting and detailed models. Due to the price differential, the BFB-3000 was selected, being some $8000 lower cost. Also, the FDM process may use various colors of base material and is somewhat stronger. The disadvantage of the BFB-3000 is a somewhat greater resolution increment which translates into a lower degree of fine detail. It appears to still be suited to model building provided the resolution is taken into account.

1/2" scale was chosen as a compromise between level of detail that can be modeled and the overall size of parts that can be built in the printer (9" x 10 3/4" x 7 7/8"). The locomotive (less tender) is 51 1/2 ft long which scales to 2 ft 1 /34". The model is not intended to run on any particular guage and will not be powered, however, the wheels and drive mechanisms will rotate as the model moves along. A short section of modified G scale track will be made for display purposes. A suitable tender from another set of plans will be fabricated to complete the overall model.

As of this posting, 3D CAD designs for the main drivers, axels, wheel bearings, two parts of the engine frame and the locomotive trailing truck have been complete. As the project proceeds, suitable alterations are made to either improve the assembly, level of detail or suitability for 3D printing.

Once the printer arrives in the next couple of weeks the real test of design suitability will begin as various parts are built in the printer. The material will be ABS (Acrylonitrile butadiene styrene) plastic for the most part by may also include parts made from PLA (Polylactic Acid). The PLA is generally used as a support material for overhangs and cantilevered portions of a part during the printing process as the ABS is very soft when initially deposited requiring support until it cools and hardens.