[Zabco]

Some more interesting questions Wombii. Would require some more testing, which I'm not going to do, to answer the relative strength question. However, I think that a 100% infill printed part and a matching part made of solid layers of styrene would probably perform comparably. There are a number of variables involved:

Type of plastic used
Printer settings
Filament orientation
Thickness of styrene / number of layers
Quality of glue joints
etc.

So would really require a lot of testing to know for sure. The type of plastic used in printing would be important. I used nGen in my testing which is an amphora copolyester made by Eastman and ColorFabb. It is a bit stronger than ABS, especially in flexural strength (9717 psi vs. 8820 psi). I think it might fare a little better than a comparable solid styrene part. Whereas a part printed from 100% ABS and a solid styrene part might be a toss up. If somebody tests this, let us know.

Cost wise, looking solely at material costs, the laminated styrene part will be a little bit cheaper. I did take some time and ran some numbers based on the size of the 100% infill printed part I used in my testing. That part has a surface area of 3.8825 in^2 and is 0.394 in thick for a total volume of 1.5297 in^3.. When printed with nGen it weighed 29 grams. Plastic filament used in 3D printers is sold by weight and that nGen cost me $38.95 for a .75 kilo spool or $0.0519 per gram. So that part cost 29 x 0.0519 = $1.51 to make. (For the sake of comparisons I am not including shipping or taxes in material costs).

If I had used ABS instead the cost would have been a little cheaper. ABS is lighter than nGen, so the part would have been lighter. 'nGen weights 1.20 gm/cm^3 and ABS weighs 1.03 gm/cm^3. So the same part in ABS would weigh 24.9 grams. ABS filament is currently going for about $0.04 per gram. Thus this same part printed in ABS would cost 24.9 x 0.04 = $1.00.

I recently bought some sheet styrene in a thickness of 0.040 in (about 1mm). My cost was $0.023/in^2. If I were to duplicate this part in this thickness material I would need 10 layers. So, 3.8825in2 x $0.023 x 10 = $0.89 for the styrene. There would also be the cost of whatever glue was used to do the lamination, but this would probably be minimal.

Remember that these are just the bare minimum material costs. In reality there are also other costs with the biggest being time. Now if you are just a hobbyist like me my time is for whatever I want to do with it. I enjoy the process of designing parts and willing spend the time to do so, but hate the drudgery of making multiple copies of the same thing over and over. If I am printing parts I can do other tasks while the printer is running. If I am cutting out and gluing parts together than that is all I can do. There is some time involved in creating the original CAD drawing of the part, making the .stl file, slicing the file and creating the gcode for the printer. But once that's done I can create as many of those parts as I want by just loading the gcode file back into the printer. If I am going to use sheet styrene then I am going to have to layout every single layer, cutout every single layer and then glue them all together while keeping everything in alignment, then clamping and waiting for glue to cure. And I have to do this for every single part I want to make. Yes it could be automated to some degree by using a CNC mill of some type which would eliminate a lot of the layout and hand cutting work. But my experience with cutting styrene on a mill is that it is difficult to do. Styrene really tends to want to melt instead of cutting cleanly and you usually have to do a lot of cleanup of parts before they can be used.

So my opinion is that while the material costs may be a bit higher, the 3D printed parts end up being the better value. Again this is only one example. There may be situations where the reverse is true. Strength wise, speaking again without real world knowledge, I don't think either method will be able to make a lowboy trailer that can carry a real heavy load. Anyone else with info/experience to share along these lines please chime in.