Within my career, I have been using rapid prototyping for about 20 years now, starting in the mid-90’s with a SLA machine. Over the years, I’ve had various aerospace-oriented components modeled, mostly for form and fit samples, but there are a couple which are flying in in prototype aircraft at this time. In addition to presenting a clinic on the design of my future layout at MARPM, I also spoke at the Mid-Eastern Region NMRA convention this year on rapid prototyping.
One of the tools I use in judging the capabilities of any rapid prototyping house or process, as they are always changing, is a gauge, which includes several holes, bumps, thin walls and internal and external radii, all starting at 0.010″, increasing in 0.010″ increments. This gauge is very helpful in determining the minimum feature size a machine or process can produce, which I then adjust my design to.
Rapid Prototype Gauge
Shapeways offers brass casting as part of their suite of material options, so I have started down the road towards designing and manufacturing a set of brass locomotives. I choose the start with the smallest, because if I can fit all of the capabilities I want into that loco, I can use the same system across all locos, rather than starting with the biggest and finding out later on that I can’t squeeze a particular control card into the smaller vehicles.
After acquiring a brass gauge from Shapeways, I referenced the item as well as their online design guides to produce the smoke box door for B&SR No.s 1 and 2 as a sample. There were a number of iterations, five I believe, between myself and the Shapeways team to get a green light to produce the trial piece.
As you can see in the image below, the door includes the hinges and all bolts modeled. The piece also includes a stem on the back side for turning the door down to the scale thickness. One item of note is that the lower hinge was molded in a skewed position. The error likely occurred in the mold making process. For reference, the door is a little larger than 1/2″ in diameter.
First Brass Rapid Prototype Locomotive Smoke Box Door (B&SR #1/2)
Shapeways has a guarantee to re-manufacture any faulty piece they gave an OK to proceed free of charge, so I took them up on this. The second piece arrived a few weeks after submitting a “damaged goods” statement, accompanied with a photo indicting the error. This one looks much better with regards to hinge alignment.
Improved Brass Rapid Prototype Locomotive Smoke Box Door (B&SR #1/2)
As mentioned, this is a trial piece, and will not be used in the models. Final layout of the internal mechanisms will dictate the assembly of the shell and it is unlikely that I will have a removable door…time will tell.