Tugboat's 3D Printer Build

Slower is okay. My high-detail setting is 20-30mm/sec. So if you max out at 25mm/sec, run it at 20mm/sec and accept slower print times with minimal scarring. Of the printed object. LOL

Seriously think that it'd be better to embrace a full-on 3D printer (even if it's a little one), you'd get much faster prints and a bit more flexibility, as the software has gotten fairly sophisticated in the past few years, while remaining pretty user-friendly on the front end.

I'm torn between building another Mendel for increasing production speed, building a Rostock (vertical tripod 3D printer, much taller build volume, which would mean that I could print ships in sections vertically, up to 16" long), or building a big gantry-style 3D printer from scratch which would allow wholse ships to be printed in one go. Sounds really involved, but apart from the physical construction, the only differences are changing a few settings in the firmware for steps/mm and maximum travel in each direction. The third one is most tempting; A 3D printer that can do a 1.8m ship in one (very long) go. Of course, if the hull is to be clad in balsa, you can run the print speed up at 60 or 70mm, knowing that it'll be structurally sound, and that you won't be cutting out any windows. Very tempted.

 

I will be doing extended testing with the SS of Malaya, and Brian's QE. David Ranier also went and bought a printer, although he bought one ready-to-go, with already-set-up proprietary software, and he printed new barbettes for his and Don Coles' Iron Dukes. David went thin with his (5mm on barbettes), but made them solid. I make the outer 3-4mm solid, with a honeycomb interior, then 3mm solid on the inside. I wanted more surface area for the epoxy to hold them to the deck. David's plan for the future is to add a rim around the bottom of the barbette that fits into a hole of known size in the deck, which is a pretty good idea that I may steal going forward

I know that non-printed ABS 1/8" thick will withstand a LOT of BB fire without issue. I will be subjecting my extrior ABS printed parts to an acetone vapor bath, which will lightly melt the surface, which will get rid of a lot of the microfractures that can result from uneven cooling. It also reduces the visual cue of the layers on the outside surface. You just have to be careful not to overdo it or you'll lose detailing.

 

Mk1 pump in PLA... Still working on fine-tuning the setting to get rid of the little blebs on the surface. But totally functional for demonstration purposes. Printing an impeller tonight. But anyhow, in this drawing, you can see the lip that lets the two parts align and seal...

In the pic below, I flipped the motor mount plate. The breakaway support material was easier to remove, which was vindication of some of my tweaks in the software. Still needs to be cleaned up, and the uptube drilled out (for some reason, the 'cleanup' software thought I wanted a floor in the miiddle of the uptube, and thus put in support material and a floor), but you can clearly make out how the motor mount plate meshes with the pump body.

I am reasonably happy with my progress and the plastic is cheap! Lots of room for trial and error, although this particular print took a hair over 2 and a half hours.

 

PLA is biodegradable (technically). Really, really, slowly. It's the same plastic they use for orthopedic implants in humans. One of Th eblogs I read tested the biodegradability of PLA, and left a printed object outside in the sun, rain, etc, and it was not much degraded after a year.

The reason that I will be making pumps from ABS and not PLA is that ABS is much more tolerant of heat without warping, which is important in a tight-clearance pump. The impeller blade-to-volute clearance in this pump is about .5mm.

 

If a particular pump fails to prime, I do the following:
1) make sure that the pump is level with the waterline
2) make sure that the boat sinks flat, at least staying flat until the pump is 1" deep (1" of water in the bilge).
3) if running pump via ESC, try lowering the initial speed (mine start at 25% throttle and ramp up), and then lowering the throttle profile to a less-aggressive one.
4) drill a small (1/16" or smaller) weep hole in the top half of the pump cavity from the outside. This will allow air to leave the top of the pump, but only let out a little bit of water. Some people use tubing to direct the weep-hole water so that it cools the pump motor.

Design-wise, I use a combined-flow impeller instead of the standard cast one that is only centrifugal. The combined-flow bit means that I have the blades near the pump inlet bent so that they have a kind of a 'scooping' action that draws water up into the pump. I think it helps organize the flow, but that is NOT based on deep knowledge or secret science Just seen some mud pumps that had the feature and it's seemed to work for me. Now that I can print pumps, I may do some experiments to see what different impeller designs (angles, blade count, etc) do for pump capacity/efficiency. Something to do over the winter when Malaya is finished and while I flirt with 4 or 5 other hulls

 

If anyone wants to submit an impeller design for testing, the rules are:
1) diameter 35.0mm
2) height (including the disc with collar) 12.8mm
3) angles on the blades out of vertical no greater than 60 degrees (once I get the dissolvable support medium, that may change)
4) files must be in either .skp (sketchup) or .stl format.

Anything deemed rediculous will be declined Or printed and displayed in the forums for general mockery.

Hub size specs to follow after I get home and measure the collar.
Testing will be this winter, with all the impellers using the same motor and ESC. We're going to measure flowrate(unrestricted, and with 1-unit and 1/2-unit restrictors), current, and anything else that sounds fun/reasonable.

 

I PRINTED A 5-BLADE 1.25" KORT PROP IN ABS!!! IT'S GOING TO BE BATTLE TESTED TOMORROW!!!! BANZAI!!!!!

BETTER PIC OF THE PROP COMING SOON (TONIGHT)!!!!

 

The metal collar fit into the prop nicely with a little trimming, and it slipped onto Lil Scharnie's propshaft like it was made to go there! Well, it WAS made to go there, so that's especially good. FIVE BLADES ON 1.25" DIA!!! BANZAI!!!!!


So, um, anyway, it's getting tested tomorrow. If it explodes into tiny fragments, the old brass prop that has served well for years is in the top of the toolbox with the allen wrench, ready to be swapped in between sorties. If that happens, I'll add a millimeter thickness to the blades, print another one tomorrow night, and try it on Sunday! Banzai!!!

 

Prop performed well under combat conditions! No problems with durability, which was my biggest concern. It did give off a huge side thrust, which hindered turning to port. I intend to make a lower pitch version which should reduce the paddle wheel effect. But it definitely helped with acceleration (slowing to a stop from full ahead was dramatically improved).

 

@Jeff - the idea is practical, and I'm way ahead of you My current print volume is 8"x8"x5.5", but I and several others have been kicking around the idea of printing a small hull in sections that get chemically welded together, with features as you described above, but going further with a printed pump to fit in the pump well, printed gearbox, printed props, printed stuffing tubes that accept bronze sleeve bearings, etc. Even printed decks and SS in appropriate colors. But then the Madness struck me (as it is wont to do) and I realized that the only software change between my desktop printer and a big one is to tell the software the measurements of a bigger one. So the only thing that requires heavy lifting is engineering a bigger frame and the machinery to move the print head around. Which as intellectual heavy lifting goes, pretty dang straightforward. So I'm saving money for The Big One... one that can do a medium sized hull in one go. The big battleships could be done in 2 sections, but I do smaller ships, and fiberglass hulls exist for the big ones, and the people building Yamatos and Iowas can probably lay out their own water channeling

Material cost for something like a Gearing or Z-boat would be around $30-40, plus whatever I'd charge for machine time (taking ~50 hours for a full QE superstructure (guessing based on how long smaller objects like pumps take, and from the 7 hour time for the 01 level of the QE fwd SS)

Just sold one of the hulls from my shop today, so we're on the way! When the Tirpitz hull sells, I'll be able to start buying parts. Not enough to finish, but enough to build the frame.