Today saw the delivery of my most recent 3D print order from Shapeways which contained the Sand Hutton wagons you've recently seen me design. Unfortunately the models were not quite as much of a success as I would have liked, although I don't think the problem is with the 3D model, but we'll get to that later. Let's start by showing you the wagon in it's two basic forms; sorry that the photos aren't very clear but the translucent nature of the prints makes them a nightmare to photograph.
One of the main features of these wagons was that the body could be lifted clear of the underframe (hence the four lifting eyes) and so I modelled the two parts separately. As you can see they fit together quite nicely and they look the part. So far so good. The problem is that what you are seeing here is a bit of a cheat.
Firstly, I should admit that I tried to be clever with this model and that has at least contributed to the problems. In reality both sides of the wagon were hinged to allow easy access to the contents, and I decided to try and model that. My plan was to use 0.2mm nickel silver rod not only to add some of the fine details but also to act as a hinge allowing the side doors to open. In the photo above I've actually glued the sides in place so that I can check the look of the model, as I can't get the nickel silver rod through the holes in the parts. I think this is actually just because I can't clean them out properly and while I thought I had a 0.2mm drill I don't (my smallest is 0.3mm) so until the ones I've ordered arrive I have resorted to glue; something I was going to try anyway as not everyone will want the hassle of fitting the hinges.
Now I grouped the wagons into a number of models when I placed the order, and in total ordered four wagon bodies and eight underframes. Unfortunately when the prints arrived three of the bodies were broken and four of the underframes were also broken. In this photo you can see a complete body and underframe on the left, and then a broken body, and a broken underframe.
Initially I thought the wagon bodies might have broken simply because the sprue I'd used wasn't thick enough. looking closely though it is clear that there is no break and I think what has happened is that Shapeways have deliberately cut the model into two parts for some reason. Given that they placed the break on a sprue it is annoying (I paid for the sprue material which I didn't need to add if they are going to break it) but doesn't render the part unusable (although the support material has ended up in a different orientation than I expected which has obscured some details). The underframes though are a different matter.
The underframes have again been broken into two, and this must have happened prior to printing as the axle boxes, which are joined by the sprue containing the coupling hooks) have been cleanly separated from the rest of the frame. This can't have been accidental. Unfortunately this means I'd have to glue the axle boxes in place and I doubt the model would be very strong as a result. It's unclear why this has happened, especially as some of the parts printed perfectly, but I'm assuming it was human intervention in some way. I've got a complaint in to Shapeways about this as they shouldn't be breaking models at arbitrary points as clearly they won't know what is functional and what is sprue material etc. Hopefully I'll get a sensible answer, but I'll be asking for a refund rather than a reprint while I check the hinges and finalize other details. What this means of course is that these models won't be available for a while as I can't run the risk of them being misprinted for anyone else.
I'll get this model painted up at some point, and when the 0.2mm drills arrive I'll see how the hinges work (if at all), before tweaking the 3D model and trying for a second prototype print.