All pieces seen in photos were printed with a PETG material on a heated glass (90), nozzle 230-235, nozzle diameter 0.4. The material brand was Devil Design PETG, they have this nice six-color filament pack (6X0.33Kg) that worked perfectly for this project, and there was 3/4 of each spool left over after this project was done.
The information about the print time listed is for o-k quality (as seen in the photos), 0.4 nozzle, 3 layer walls, 4 bottom/top layers, infill speed 50, inner wall speed 35, outer wall 22, top surface 20, travel speed 120. First layer speed 15, first layer travel speed 50. Simple 25% infill. The pieces need to have a bit of weight, so you may want to go with a bit denser infill or thicker walls. The use of denser infill helps to properly lay down the last piece layers; alternatively, use more top layers to even them out.
This is my first bigger 3D print, and it was done with PETG on a budget printer, so I will just dump all the info here, which may help, or it may not. There may be many begginer-level things that I know now that I had no clue before, but I feel that 3D printing still is a bit of messy, so take caution and be prepared to fail.
First of all — the PETG filament. It soaks humidity from the environment and it is impossible to print anything nice with a boiling filament. So get a sealed box (hint: ikea) and put your PETG spools there, and dump a bag of silica gel at the bottom. It also helps to put your spool that you are printing from in a similar, but smaller box. Some creativity may be required there.
The printer used was Ender 3 with a heated glass bed (a bit custom mod).
There is a whole story to make the first layer of PETG stick properly to the glass.
First of all, the bed needs to be level. With my luck, I got a warped bed and a glass bed mod did not help. The thing that really helped was a firmware update with the manual software bed leveling enabled. In short, it is possible to manually record the tiny height differences of the bed, and then this printer will use this info when printing the first layers.
Then, I use high temperature (100C for the first layer, 90C for other layers), and cover the bed with a very tiny coat of diluted PVA (wood glue, stuff that glue sticks are made of but without the smell and stickiness). Once the bed cools off (35C), it pops off very easily. Start with something like 1:30 dilution, because it glues things reliably. If too much glue is applied, the usual method of getting razor sharp knife under the sides of the print helps to peel it off (a bit of trial and error as usual). I advise erring on the side of not enough glue, because it is easier to restart when the first layer does not stick instead of getting stuck at the end. Just remember that PVA is easily diluted by water, and especially well by isopropyl alcohol, so get that stuff. A piece of cloth dipped in the isopropyl alcohol will also help to remove the residue of the old glue and prepare the bed for a fresh thin layer of glue. Alternatively, for many small prints in a row, I found no need to clean off the previously used glue; instead, use a wet brush on the heated bed to spread the existing glue out.
It was possible to make print stick to bare glass when I raised the bed temperature to the max (110) and adjusted the nozzle temperature to the max (recommended for the filament). The bare glass is usually tempting because of the shiny bottom you get. However, the glass heats up slowly, and it feels like going from 100 to 110 is almost double the wait to start printing. The max filament temperature may also be not very healthy, if you want to spend time in the same room. Then, there are problems with "elephants foot": the first layers get way too wide at high bed temperature. This design has a slight bevel to compensate for this effect at 100C bed temperature.
Then, finally, go slow for the first layer. My setting now is 15mm per second. Turn off any slicer attempts to move faster than 40mm/s when printing the first layer, because it will cause trouble. For the subsequent layers you may choose higher speeds (like 50mm/s print, 150mm/s travel), depending on your quality needs.
Also, this print has many pieces, so make sure your extruder settings are correct. Print two-pillar pieces to test it out and adjust until you get good-enough result.
The fun does not end! You may also get stringiness between the pieces if your flow rate is too high. What happens is the nozzle touches the sides of printed parts when moving from part to part, and this has nothing to do with extrusion settings.
No, the fun does not end. Each color has slightly different properties, even from the same brand and the same pack. I found blue, green and black very sticky, while white felt like it was mixed with chalk. But generally, they are similar enough. Currently, (when printing other projects) I use printer's ability to adjust the flow rate on the fly.