Francesco's Short Circuits

3D printer!

I can finally write about my best achievement so far: I built a decent quality and large volume 3D printer. It's an open source design of a delta printer called "Kossel", delta means the three motors have a parallel movement.

The advantages of this kind of printer is that each motor has a similar load. I won't give you instructions about how to build it, there is enough material on the web already.

I will tell you where I bought the components, where to find the instructions, what problems I had and how I solved them. Handmade printers require a lot of calibrations that involve mechanical, electrical, electronic and software adjustment. So if you are not too confident in these fields think about buying one instead of building one. There are some decent quality 3D printers on the market under 1000$ (AUD). Sometimes I'm not patient so I skip some important steps and I end up burning something. This kind of project doesn't allow for mistakes, you have to do things right. These warnings sound pretty serious but I have to say I enjoyed the assembly, wiring and calibrating of this beautiful printer. When I printed the first good quality item, I couldn't stop watching it.

My first advice is to read more than one instruction because I found mistakes and gaps in all of them. Understand that each printer is different, nobody can give you a calibrated firmware, you have to do it yourself and that's the longest part.

I bought the kit from http://builda3dprinter.eu/, they offer good quality components, quick shipment (from Europe), and a website full of information. I found some gaps in their instructions, so I followed this manual too. The most common version of Kossel is the Kossel mini, but the one I've built is Kossel XL. The printable volume of the mini is a cylinder of about 170mm diameter and 240mm high. The volume of the XL is a cylinder of about 250mm diameter and 310mm high. The assembly is exactly the same.

Something I strongly recommend:

1 - Get an heated bed, your printed object won't move and you don't have add anything to the surface of your bed.

2 - With an heated bed, do not put your controller under it or it would get hot. I put it on top, in a case with an extra fan for it (it gets hot in Australia). I build the case with clear acrylic sheet (it can be shaped hot). The extra fan is from my CPU (I just upgraded my PC with an Arctic Cooler).

3 - Get a metal nozzle holder with heatsink: I melted the plastic one twice, before I ordered a metal one. I had to modify the platform and fan holder to fit the metal holder because it's much bigger. I also ground one side of the metal holder's heatsink to allow the probe to go up and down without touching it, because it's 25mm diameter (but there are smaller ones). Believe me, all this work is worth it.

4 - The fan that cools the nozzle holder must run all the time: I suggest you wire it up with the power supply rather then the controller, because if the controller shuts down, you don't want the fan to stop, causing the melting of the nozzle holder (or the extrusion platform in case you have a metal nozzle holder).

5 - When you troubleshoot a problem, if you are not sure of what it is, start looking for mechanical issues. Sometimes I look for the cause in electronics or software, when it's just something very simple, like a loose grub screw on the motor shaft (I spent few hours before I figure that out).

6 - PC power supplies are not always ideal. They are made to supply loads of different voltages: 12 V, 5 V and 3.3 V. If you only pull current from the 12 V rail, it goes down under 12 V, and it might not be enough to heat the bed to high temperatures. In my case it was 10.5 V and the heated bed was maximum 85 degrees, when I needed 100-110 to print ABS. So I applied a load (resistances) on the 5 V rail (which was giving 5.6 V) and the 12 V rail went up to 11.7 V. So I bought a LED strip power supply, which only have 12 V output and can supply 30 A (20 A would be enough). Now the voltage is constant and the heated bed keeps the temperature over 100 degrees.