In order to have correct 3D printouts, we should consider some key points:
Confirm that the model to be printed is only composed of a single element.
Compound models shall be problematic and give as a result failed prints if they are not specifically designed to that purpose (for example, chains or objects designed to have moving parts under strict design criteria).
Either if the model has several parts that touch but are not joined together or if it is one part with surface problems that our software interpretate as different bodies, we should fix it. It is going to be a failed print in almost cases and, if it is visually not, you can trust that this part will break in a very short time.
Analize wall thickness
This issue is mainly spotted when scaling objects, because that reduces all measures and often produce too thin walls. Watch out this, and study the digital model before print to look for missprinting or missing walls.
If they are spotted, you will have to edit the original 3D model. Personal advice: Work in design software with final print scale. This will avoid any chance to have this issue and your model will look as great as you designed it. You will have no doubts when exporting to .STL .
Check that the model is correctly loaded and placed
It can sound ridiculous, but the design needs to be in the printing area of the software (centered is a recommendation unless you specially want to place it anywhere else), touching the building surface and within the printing area. Several slicers do not allow you to export .STL file of a part that excess the printing area, but others do (like Simplify 3D).
I have met people breaking their head because print ran out and failed, and it was as simple as that their model was partially under the printing bed on slicing software, It was not well placed. Please, look carefuly all the details before export (all of us can underestimate this!).
Nowadays, most popular filaments in FDM 3D printing industry are PLA and ABS. PLA offers higher stiffness and stronger bonding of layers, while ABS is much more resistent to impacts and temperature exposure.
Note: Since ABS dissolves in acetone, it can be used in dual printers as supports and print the model in PLA. Submerging the model in acetone will reveal the PLA print and will release it from ABS.
Other filaments are winning presence on the marked such as PETG, which is being reconsidered as one of most suitable home printing materials due to its ease of use, strenght, durability and low warping.
Flexible filaments like TPU are trying to be settled in, but they are not still well placed because of its printing difficulties. Prints have to be done in small scales, with a very low printing speed. They are very sensitive materials and need high specialization to obtain successful prints.
I extensively talk about printing materials in “What material should you use?” post so please, if you need further information about what materials exist for different printing technologies, you can check that post.
The diameter of the nozzle is directly related with printing time, but also to detail.
With same parameters, the print time of the shown element using a 0.4mm nozzle was 2 hours and 25 minutes, if a 0.3mm had were used, the printing time would be extend to 3 hours and 30 minutes.
That’s not the same that happen between diameter and level of detail. The smaller is the nozzle diameter, the better will show out details. Smaller diameters are used for more detailed prints like small reproductions of architecture models or characters.
Standard printing nozzle would be 0.4mm, what works for most projects. If you need to print big-scale elements you can try bigger diameters such as 0.6 or 0.8mm ones. Always keed in mind what would work better for your project and needs, because it is important to keep a good relation between printing time, cuality and detail.