CCG Midshore Patrol Vessel 3D Printing Project (and debunking the 3DP hype)

Now what's there to debunk about 3DP?

Well, there is a lot of hype. So much so that there's actually been an investment bubble around the subject, go figure. It IS a neat technology, but you're NOT going to be printing your sneakers at home any time soon, and if you try to fire a 3DP gun, you'll likely get what you deserve.

For modelers, the attraction is obvious- anything you can draw (or obtain a file for), you can make. The drawback? The cost is still high, and the surface finish is nowhere close to what a Fine Scale Modeler needs.

You think you're going to buy a desktop printer? Hah, piffle, and nonsense. Anything you or I can afford makes cr@p... the affordable process is called FDM (fused deposition modeling), which is sort of like building things with a cake decorator... it might be suitable for wicker chairs in GI Joe scale, not much else. Machines that make the best parts still cost tens or hundreds of thousands, not to mention the materials and secondary processes required. And they still make parts that are hardly usable for many fine models.

Or to be usable, the parts need so much hand finishing as to make the process unattractive for most modeling projects. You are NOT going to print anything in the near future that compares to even average quality parts in an injection molded kit.

So why am I undertaking this model in 3DP?

Because the stars aligned. First, it's a commission, so I have a budget that covers the high cost of the parts, and makes it worth my while to "invest" in all the hand finishing. Second, most of the big parts have surfaces that lend themselves to hand finishing, which means a combination of block sanding large surfaces, and/or filling with the heaviest automotive primer-filler I could find (Rustoleum, btw). If the surfaces were riveted panels or such, the detail would be obliterated in sanding and filling.

The little details? Lots of hand work there too... think of the worst cast resin or white metal parts you've ever seen, and trying to rectify them... it's a lot like that.

But, it can be done...

So, even with all the drawbacks, can a respectable model be made?

Well, I'm nearing completion on it, you judge from the work-in-process pictures. Note that almost EVERYTHING is 3D Printed- the hull, cabins, details... it's easier to list what's NOT printed:

Railings (custom PE stanchions and brass wire)
Vertical ladders (HO scale molded parts)
Main deck (simple flattish part in styrene-covered plywood)

...more later...

Patmat-Very impressive and educational..I'll be following this thread for more information.

A prerequisite to doing original work in 3DP is access to good 3D CAD. You can probably not afford to have someone else do this for you! CAD operators know what they and their software is worth.

I wish I could tell you about freeware that is capable of properly modeling things like planes trains & automobiles… but I’m clueless, maybe others can chime in. I’m spoiled because my office gives me a powerful laptop loaded with one of the most powerful pro CAD packages available, CATIA… and I’m free to use it at home for personal stuff.

There may be a market for ready-to-use part files made by others that you can order parts from… for now, you’re unlikely to find exactly what you need for special projects.

Some screenshots of the MSPV model:

Neat-O!

How about some plastic parts then?

I'll start with the hull. At Shapeways, I'd have to print this in SLS (sintered nylon powder) due to its size (almost 2 feet long), which could work... but I had the opportunity to get it done on a large format stereolithography machine, the type that scans a laser across a pool of liquid photopolymer, hardening one layer at a time to make a non-porous part. The hull had to go into the print table diagonally to fit!

One of the drawbacks of this process is that a lattice-like support structure has to be printed under overhangs. This is ripped of by hand after printing but before finally cure in a UV "tanning booth". This leaves nits on those surfaces where the lattice was attached, and for delicate parts, there is risk of damage. Even though my hull wall is 1mm thick, there were some tear-outs that required repair.

But a neat point: Just like with styrene kit hull, you can add features inside. I made a lip to support the deck, ribs to accept stiffening bulkheads (which I didn't print to save on material cost), and built-in seats for the mounting finnials and nuts. 

Another neat trick: There are a bunch of supports inside the forward bulwarks. I drew them "into" the hull by 0.5mm, then did a Boolean subtract to leave grooves in the bulwark wall- perfect for locating the supports later.

The freshly printed hull:

Detail inside the hull. There are some tear-outs at the chine.

Surface finish was not so bad on this part, but the woodgrain-like layers are visible on some of the angled surfaces.

Designing the bulwark supports:

And creating the notches for location: