The picture above shows all the failed parts printed for PAROL6 robot. It was not the printer that failed but the engineer. I will write a short entry on how to reduce waste when 3D printing by doing the right design choices and checks. 

* Do not rush to start printing your (LARGE) parts! If printing something bigger like 24h+ prints double-check all the features you need for your part to have are there.

* With small prints you don't need to worry about failing, they take 30 mins to print and in the same batch you can place several different versions of the same part and test what is a better fit or what works best.

* If printing large parts that need to mate with a lot of other parts first print some segments of that parts where tolerances need to be hit to a spot. For example, I have a print that will take 30h and one of the things that NEEDS to work is that bearing that that part holds is a tight fit. What I usually do is print just a hole that holds a bearing from the original part and test the tolerances. This will save you a ton of time trust me

* Top-down design and bottom-up design.

Top-down modeling involves generating and designing the geometry exclusively within an assembly, a technique often referred to as "in-context design." In this method, all elements are crafted within the assembly's framework. 

Conversely, the alternative approach is known as bottom-up assembly modeling, where each individual part is conceived independently.

These are 2 methods you can use to design your complex assemblies. I usually go with Top-down design since I have more control over the project as a whole.  For example, for PAROL6 the design was from the wrist to the base. So the first part I designed was the wrist part and then in the context of an assembly, I designed the forearm, then the elbow... Then I printed every part as I was designing it ( after designing the next part it mates too) So after designing the wrist I still did not print it, it was printed after the forearm was designed. 

By printing part by part like that you can see if you did a mistake somewhere and just redesign that part and print a new one. You will not need to disassemble the whole robot that way to replace that part.

* Place all the screws and mechanical parts in your assembly! I know it is boring and you want to print your part as soon as possible but placing parts you did not draw (like screws, bearings, nuts...) really helps.