Thursday, January 10, 2013

Using Lasers To Build Wagons

While I'm really enjoying this whole 3D printing thing I wish there was a UK based printer I could use. I'm currently printing my items via Shapeways and while their printing prices are fairly reasonable (and seem inline with everyone else) there is a €9 posting and packing charge to add to each order. In fairness to Shapeways this seems a common delivery charge for most of the printers when delivering outside the county in which they are based. This charge means it isn't worth ordering a single small model, such as my TPWS grids, as the postage cost would far outweigh the cost of the model. So each time I've placed an order it has included a number of items, and this time was no different. As well as test printing the mini TPWS grids, I also made two other, more experimental, prints.

I've finally hit on an interesting idea for a layout, one that has even got Bryony interested in the planning, but there are a number of pieces of rolling stock that I'll have to build from scratch. One approach would be to attempt to build rolling stock from plasticard and brass wire etc. but given my success so far with 3D printing I thought I'd give that a whirl first. Printing complete wagons, or at least the major components, will have the advantage that once I can print one wagon I can print as many as I need without having to spend any extra time.

Given that I managed to assemble a Parkside Dundas wagon so that the wheels wouldn't turn, I decided that the hardest part would probably by designing the underframe in such a way that the wheels would fit and turn properly. So one of the prints in my latest order was a simple wagon underframe.

As you can see the wheels do fit, and I promise they do turn quite easily; when weighted appropriately (sitting the mostly full bottle of liquid gravity on it) I can easily push it around my layout. I am, however, going to alter the model slightly. If you look closely you can see that the wheels are actually bending the model outwards quite significantly.

The problem is that while the model is wide enough to take the wheels I didn't make the holes for the axle deep enough. I'm not sure if this is really a problem with my 3D model or with the printing process. All the previous items I've printed have been using Shapeways Frosted Ultra Detail material. This material allows for the smallest of details to be printed, down to 0.1mm, but is also quite expensive (it's the most expensive of the plastics they support). As I wasn't trying to model fine detail but was simply checking rough proportions I printed this model in the cheapest material: White Strong and Flexible. Rather than printing by depositing plastic from a print head, this material is turned into a model using a process known as selective laser sintering or SLS; essentially using a laser to fuse a powder together to form the model. While printing in this way is cheaper it has a much lower accuracy, ±0.15mm, than the Frosted Ultra Detail material, ±0.025, and I'm wondering if this has made the holes slightly shallower than I intended.

Anyway as a test print, to make the postage and package costs worthwhile, I'm more than happy with how it turned out and I'm already working on refining the model ready for the next print run.


  1. Well. I am absolutely fascinated with this Mark. I hadn't realised how far the potential of this process extended and how large the printed item could be. Not that I have any thing in mind but I do feel that one day this could be useful.

    1. It's possible to print some quite large complex pieces. A quick browse of other peoples models on Shapeways shows the range of things that are possible; from espresso cups printed in glazed ceramic through dice printed in stainless steel to a hollow Rubik's cube. It's also possible to print some multiple part objects (ball in a cage style things) that would be impossible to manufacture in one piece. Quite a few people are also using it to manufacture replacement parts for larger items; the parts for the Bugaboo are probably the most famous in this category.