(THIS PAGE IS STILL IN PROGRESS)
I know some of my designs can be quite a torture test for some people. 95% of the issues are related to improving the bed adhesion and dealing with warping/curling. Also, some may find issues with brittle links easily breaking, which is caused by underextrusion on small perimeters.
This has a simple explanation: The articulations I use have small parts with ~45º overhangs. Theoretically, they are perfectly able to be printed without issues. However, as the filament cools down it shrinks slightly and causes it to curl up. As a consequence, the nozzle may collide with the printed part and detach the piece if the bed adhesion is not strong enough.
Fortunately, there are some easy tips that may solve almost all the issues.
Also, I strongly recommend testing my free designs before purchasing the more complex ones. They may help you to understand better your printer, and will teach you a lot about the printing process. You can find them here.
All the following tips are just from my experience and may not work for everyone. Keep in mind that I'm just trying to help 😉
To improve your bed adhesion is really easy in most cases:
Be sure your bed is well calibrated. It may seem trivial, but having a smooth and solid first layer is really important. Here you can find a step by step guide.
Be sure the bed is clean from dust and grease. I use IPA almost before every print, because even if the bed looks clean it may have some residue or grease from the fingers.
Lowering first layer speed, even down to 8-10m/s (or even slower if needed), really improves adhesion. This is about a quality print, not about the fastest one.
Increasing the first layer thickness, around 0.3 mm, helps a lot.
Proper bed temperature (if heated). Each bed material and each filament has its own requirements. Silky filaments, for instance, usually have worse adhesion.
For most of my designs, you may disable the "Elephant foot compensation" in your slicer. That improves the first layer adhesion, and should not affect the print look.
You may use some stick or spray glue. There are several in the market. Personally, I like 3DLAC, which is specially designed for 3D printing and works amazingly well.
As the last resource, you can print using raft. Each printer has its own optimal raft settings, so you can take a look at forums or threads about your printer to get the best result.
To deal with the warping/curling it's more tricky, but these tips are a game changer:
Enable the z-hop/lift Z (~0.4 - 0.6 mm), so you avoid the nozzle colliding with curled parts and loosen them.
Be sure you have a good layer cooling. Check it and be sure the layer fan is set at 100% speed and you have proper airflow. Some printers have really bad fan ducts, which limit the flow or focus it in the wrong direction. I improved my prints a lot just changing the stock fan duct. Fortunately, the 3D printing community is huge and there are alternative pieces for almost all the printers in the market.
Reducing the printing temperature also helps, but this may affect other stuff, such as stringing or proper filament flow. Do it at your own risk.
I designed a curling test file a while ago, and really helps to understand where your airflow needs to improve. You can download it here.
It is probably related to under extrusion on small perimeters. I've seen that in the past and it happens mostly on bowden printers. The first explanation is a partially clogged nozzle, which makes it more difficult for the filament to flow correctly after a retraction. It can be also due to not properly tuned retraction settings. Things you should check:
On the hardware side, check the bowden tube is tight and doesn't have a loose connection.
Underextrusion can be also caused by a partially clogged nozzle. You can try a cold pull, sometimes that fixes most of the extrusion issues. Also cleaning the nozzle with a thin needle may help.
Adjust the "coasting" and "restart" distances on the retraction settings. These values control the amount of filament extruded before and after the retraction. Increasing the "restart" distance usually solves this problem almost immediately.
Print it with 3 perimeters/walls. For this kind of designs, the walls are what give strength to the articulation.
As the last option, check the inner PTFE tube in your hotend (assuming your hotend has PTFE tube). It usually gets damaged over time and needs a replacement.
To test how your printer performs with small perimeters, try printing this simple model with 0% infill. You may want to scale it down a bit, to 70% for instance, to better represent the small articulated links. I use it also to quickly test the stringing.
Prints can be strongly improved if you know how to use your slicer. I'll be posting here all the tips I found (to be finished, with some pics...):
Seams position. Obviously, you don't want your print to have a scar just on the front side, so be careful to position the seams as hidden as possible. PrusaSlicer has the "Seam Painting" feature, which allows you to directly draw over the 3D model where the seams will be located.
"Variable Layer Height". This feature is really handy to give a smooth top finish to rounded models like the octopuses. In PrusaSlicer it's very intuitive and easy to use. I haven't used it with Cura, so I'm not sure how it works yet.
Selective infill. You can set different infill settings for the different parts. This can be done in different ways. One way is to sepparate the model in parts, and assign different settings to each one. For instance in the octopus, no infill for the tentacles and 10% infill for the head. Other way is using modifier shapes, and give some infill just to the areas where you think is needed (to reinforce some articulations, for instance).