Alright... With the expiration of some 3D printing patents, cheap FDM 3d printers started to flood the market and I made myself one a few years ago, those printers run a plastic string through a heated nozzle and depozit it onto a heated plate, the result is generaly not good enough to print in warhammer-lookable quality, but making terrain or *some* models is feasible with some ingenuity and ton of handwork. I initialy wanted to try printing some tau themed terrain, but I didn't find any good artwork that i'd like (I'm not much of an artist) and I'm also working on some suit modifications(for shapeways FUD or comparable printer), so here we are.
This is a guide for the Orca, but a lot of this is general information that could be used for other projects. I tried to make it as structured as possible, but some things have to be considered from start to finish.
Step 1: Draw the 3D model
For something like an Orca, I strongly recommend using a 3D "modeling" program like solidworks/inventor/fusion360, not a "sculpting" program like Zbrush/blender. Modeling in "mathematical" shapes and having an ability to quickly modify them instead of having to deal with a buch of polygons is essencial. Also the ability to put a photo canvas, tracing edges on a 2D plane and simply extruding them is very valuable. (Although I'd add that I don't rly know what all the "sculpting" programs I named can do...)
It would be nice to have the original model and measure a few dimensions, but all dimensions can be deduced from one picture showing drone holders and measuring a drone. Without having access to the original model, it'll be an iterative process of drawing, printing, looking at videos/pictures, correcting mistakes and printing it again and I wouldn't do it without quick access to a 3D printer. You can do renders, colision/clearance checks, motion studies, but all that can't rly tell you how the printed part will look&feel like. In pure time spent on drawing and looking at photos/videos, it took me about 80 hours(about 4 times longer than I estimated
) and I still have to finish some features near anthenas, rear door and turret cover.
Here are the parts that are ready to print: https://www.myminifactory.com/object/37751
Step 2: Print it
Slicing the model into separate parts
First of all the model is 370mm long, which wouldn't fit on any common FDM 3D printer(mostly 200mm cube printspaces). Other reasons to separate some detailed parts have to with printability, print quality/print speed tradeoff and ease of reaching a surface with sandpaper or other tools. You can't print into air, but even 5°overhangs and long bridges are doable with correct printer settings. Still, try slicing the parts in a way that reduces steep overhangs&bridges at least on visible surfaces. With lower quality printers, it's better to print one part at a time than filling your build plate with multiple objects just so you don't have touch the printer more often, for well calibrated printer it's not an issue though.
Tau-like armor/hull grooves are printed best when oriented on a horizontal plane (A) which is the reason i separated so many panels from the main hull, (B) can look good under certain printer setting (I found 25% of nozzle diameter as layer height works best, it's also affected by printing temperature/speed/fan cooling...), (C) will never look good unless you print with extremely small nozzle, it's as if you'd wanna draw sharp corner with very thick marker. If you have to print (B) or (C), you'll have to re-establish the groove in post processing, (A) can be just blended a little bit if you can do vapour smoothing correctly(more on that later). I split parts into 3 categories, printing in 0.25mm layers with fan off for the largest parts, 0.1mm layers for medium parts and 0.05mm layers for details (with 0.4mm nozzle). All grooves are modeled 0.6mm x 0.6mm deep.
Some things to consider when choosing printing material:
-Surface smoothing: You can use a combination of chemical disolving(blending), filling with putty or thick paint, and sanding. Out of commonly used materials, the only suitable materials are ABS and PLA. For chemical disolving/blending, ABS is the best material as it can be blended by Acetone(which costs 3€/liter) vapours in about 30-120 minutes. PLA can too be smoothed, but by a different chemical, limonene, which is much more expensive, less availible and takes longer than ABS/Acetone. I would say chemical smoothing is only worth doing with ABS/Acetone. Sanding of course works on both materials. ABS is about the same hardness as the plastit that GW uses and can be "shaved" in the same way as GW plastic, but PLA is much harder and will take longer to sand down, which can be either good or bad, depending on your overall smoothing process, if you just stick to smoothing with spray filler and light sanding, it will hold the intended dimensions better than ABS, but it will take much longer to chemicaly smooth&sand.
- Plastic colorants reduce layer adhesion. If you want ABS, it's better to choose fillament without colorants, for PLA that doesn't matter.
-There's also the issue of printability. When printing such large models, due to thermal expansion, the layers of a print can delaminate when a part of it cools down. This issue affects ABS much more than PLA. Printers with a heated chamber are best suited for this.
-ABS can be glued by ordinary plastic solvent glue. The equivalent glue for PLA is rly nasty and requires protection equipment. CA glue or epoxy works well enough though.
-Also note that PLA is 20% denser than ABS, but the model in PLA can be lighter as it's superior layer adhesion and printability allow lower infill percentage and wall thicknesses.
-Vallejo surface primer works very well on ABS (especialy on sanded ABS), I have no idea what works well for PLA
-All in all, if the printer can handle it without delaminating, ABS is the better choice. Though in theory there are even better materials for this, i.e. I've heard of a company doing a blend of PLA any Styren that's smoothable by acetone vapours, but didn't look into it closer. Would love to hear any opinions on it as neither material I tried is optimal.
Step3: Post-print processing
So... depending on which material you use, the process will be slightly different, but you gonna need some tools either way. This is all I used so far:
The round scalpels are rly amazing for some parts. The lowest grit sandpaper I use is 180, it's "fast" but it leaves scratches, so I finish it with 400 grit after that, not all "X grit" sandpapers are the same, you'll have to test them, but I would say anything higher than 400-600 grit will get covered by the primer anyway. The steel wool I use is "0" grade, but one step lower or higher probably won't matter. What else's worth mentioning is the ear wax scoop I use for grinding grooves, I just sharpened it a bit.
In a few days I'll post detailed explaination how to post-process some parts, for now I'll leave you with an unsorted gallery of blury pictures. http://imgur.com/a/A5OOH