Friday, January 1, 2010

Printing a 1920's Drive-In Market

I've been doing less work on the layout for a bunch of reasons, but one of the larger offenders is a new tool, a Makerbot 3d printer. This squirts out threads of styrene plastic to build up three-dimensional objects.

I've been bitching lots about the lack of Spanish Revival-style buildings in HO, and fabricating the curves of these models is a pain to do by hand. I've also been eager to build a 1920's drive-in market, and Spanish style was insanely popular during the '20's and '30's, so this seemed like a great project to try. My best luck in the past with such buildings was the Campbell storefront. In that case, I used a metal milling machine to cut a Plexiglas sheet for the facade - not the easiest of jobs, and a lot of trouble to remake.

This model (still, obviously, in the process of being built) is a combination of sheet styrene and printed parts. The main facade is made of four identical arches, spliced together. The storefront doors and windows are separate printed pieces. The back walls were made with sheet styrene, and I'm using door castings from my scrapbox for the back doors for the stores. The central tower is an interesting mix; I knew printing such a large object would be slow, so I made the body of the tower out of 1/16" sheet styrene, but printed the top decorative piece. Note how I had to make a tab that glues to the back of the styrene to get a good joint; edge-gluing printed pieces doesn't work well, probably because the pieces are hollow and somewhat rough.

What I've learned about 3d printing from this project:

* The Makerbot's great for making duplicate parts. It's perfect for the main building arches, and it was really easy to borrow the middle section of each facade for the tower's false front. I mentioned on my printing blog about the trouble I had keeping the arches from warping; the smaller pieces for the tower were much faster to print and less likely to warp.

Like the Cricut cutter, the 3d printer is a bit less interesting if you're only making one object, for it might be easier just to make the piece by hand. But see my note about making roofs before assuming a 3d printer only helps when making lots of identical pieces.

* The Makerbot's reasonably good at doing curved edges, but it's not great at doing finished surfaces. The extruded plastic is 0.13mm diameter (or about 1" HO), and the gaps between the extruded noodles makes the surface stripey. With the building facades, I covered the face with spackle, gesso, or acrylic medium to try to smooth out the edges.

The storefront door and windows shows what things look like without filling. These are printed pieces straight from the printer, and were only spray-painted. I wasn't sure if these would be acceptable, so I printed them out quickly to see how they'd look. They turned out better than I hope, but they're still pretty coarse, and not quite good enough for a model. These were all printed with a 45 degree angle fill; I'm hoping to print some storefronts with a vertical or horizontal fill pattern in hopes that'll look more like clapboard or another typical material.

* My big discovery today is how great the 3d printer can be for parts that are difficult to fabricate. For the tower, I wanted to have a low, tar-and-gravel roof behind the false fronts. I knew that doing a pyramid hipped roof (where all four sections of the roof meet at a single point) can be a pain to build. I've done them by building up forms for the roof line and carefully cutting and fitting each roof piece, but it's tedious work.

Instead, I just went to Sketchup, drew out a 14 foot square base, found the center of the base, drew a vertical line 3 feet high, then drew lines out to each corner. I then printed the object, and got my perfectly-sized pyramid. I'll glue some simulation of tarpaper on top, and no one will ever know how easy it was to build the roof.

More photos as I finish assembling and painting the model...

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