Saturday, October 7, 2017

Styrene, resin and 3D printing

I got a couple of packages in the mail recently, courtesy my good friend Mr. E. Bay. In particular I got a couple of resin kits and my first batch of 3D-printed parts, so I thought this would be a good opportunity to review the pros and cons.

I am assuming anyone reading this has some familiarity with styrene: large companies like Tamiya or Round 2 crank out large numbers of kits that they think will sell well. This is because styrene requires expensive molds and injection molding systems, so you'd better be able to amortise the cost of a mold over many kits. Parts are usually good fits with minimal part lines or flash, and the best are all doweled together so assembly really is pretty simple. So I won't dwell on styrene any further.

Resin parts can be cast at low temperatures and pressures in your garage. The necessary silicon molds take time to make, and they wear out fairly quickly, so bits will be costly due to the labour and cost of the silicon. There is a huge number of small resin casters out there, typically catering to specialised markets and providing the interesting odd-ball stuff some of us want. The variability from producer to producer, however, can be enormous.

To wit the first of my recent acquisitions: a Rolls Royce Merlin V12 from a Dutch company called Firerods. The $20 kit came in a baggie, with no instructions, and the parts are going to require an awful lot of fiddling to get them right as you can see by the poor fit of the two halves of the block. No surprises here, given the price. The motor will go on the shelf awaiting a suitable chassis.

Next up is a more detailed motor for the Tamiya Subaru STi kits, from Hobby Design. At $100, the kit comes in a cardboard box with a colour instruction sheet and a photo-etched detail sheet. Parts detail is very nice. There will still be large sprue sections to remove, but it looks good and I expect it will fit in the engine bay of a Tamiya kit quite well.

Next up is a complete resin kit of the Jaguar D-Type from the French company Profil 24. At 200 euros (about $250-$300), this is not cheap, but it will build into a complete car. The detail of the lovely Jag six is great and while there is trimming to be done, it should not be huge.

Now we come to the disruptive technology: 3D printing. I ordered some bits from Shapeways (click here) just to see what the quality is like. The site offers 1/24 parts to make a V12 LS3 motor -- essentially a one-off stretched Chevy small block motor -- which includes block, a tree including heads, valve covers, front cover and pan, and a separate tree with two headers, for about $35. I added a couple of transaxles (not Hewland but they look great) and a few other items to come to about $60.

The quality is just astonishing, and I hope the pictures show this. The first one illustrates one interesting point: once a shape exists as a computer file, you can print it, on demand as needed, at any scale. The LS3 is offered in scales ranging from 1/6 to 1/32 (including either 1/24 or 1/25). I accidentally ordered the 1/32 inlet manifold (to the right of the block), and this will be replaced by a 1/24 part.

Pistons, rods and a crank would not be impossible!

The next picture shows the heads, valve covers, front cover and oil pan, all on a very delicate web of 'sprue'.

One last picture shows the 3D V12 block next to a Ferrari V12 made of spun-cast white metal from Model Factory Hiro. The metal bits require drilling out dowel holes and filing of surfaces to make them flat, but the result can be stunning. Nonetheless the complexities of pouring molten metal into a spinning mold make this an unusual and expensive approach.

Obviously I will need to paint and build the LS3, and will report on any challenges. So the next question is quality of an entire body. I am getting my nerve together to order something, perhaps the Ferrari 166 MM Barchetta from TDR Innovations (click here), to see what it looks like. At $90 it is not cheap, but if it is significantly better than the resin stuff, it may well be worthwhile. Surface quality and warping of a thin shell are two items I worry about, as well as how exactly the computer file reproduces the real thing. But look at the upside: no out-of-stock issues because it is print-on-demand; no scarf or flash because there is no mold; cheaper and faster than resin again because there is no mold; and the possibility of making all kinds of really interesting oddball stuff. If I were a resin producer, I would be very worried. Stay tuned!

No comments:

Post a Comment