I have used printed parts from rapid prototyping machines for a few projects in the past and they have always made my life a lot easier. This winter I decided to build a 3D printer of my own. I have been following the progress of the RepRap project for a few years now – a RepRap is a 3D printer capable of creating the plastic parts needed to create a copy of itself. The latest version, the Prusa Mendel, strikes a good balance between print quality, cost, and ease of assembly so I figure its finally time for me to jump on the bandwagon!
I did a lot of research before starting the build. The first thing I did was create a Bill of Materials including any modifications I would be making to the basic Prusa Mendel design. I tried to strike a balance between saving cost and keeping my life simple. For example, I soldered together the electronics myself, but I didn’t buy a bare PCB and the components separately, I got the DIY kit from Ultimachine.com.
I got my RP parts from ebay user elderfarrer2hy7. The parts arrived in good condition and they all worked well. It looked like they came straight off the printer, but it only took me about half an hour to clean them up with a sharp knife. I bought a kit with SAE RP parts, lm8uu bearings, nuts, bolts, timing belt, and a laser-cut acrylic Y-carriage/bed (I ended up replacing the bed with MDF). Elderfarrer2hy7 was even nice enough to print me some z-axis stabilizers at no extra cost. Overall I would recommend buying parts from this seller.
It seems like many people have problems with the default Prusa z-couplers. The two alternatives I have seen are Nopheads improved z-axis couplers and some aluminum helical couplers. I bought two aluminum couplers on Ebay from NRG24Seven which have worked very well.
I am confident that the printed gears in the kit would have worked well, but I still decided to invest in some nicer GT2 belts and pulleys. There is a great article here (http://mendelmax.com/tikiwiki/tiki-index.php?page=Choosing+Belts+and+Pulleys) that explains why GT2 belts are preferable to the T5 and T2.5 belts often used on RepRaps. On the Y-Axis stepper I used the 42-tooth pulley recommended in that guide. For the X-axis I used one of the metal pulleys that came installed on the stepper motors I bought on Ebay (lucky break!). The 42-tooth pulley would have been too wide for the x motor mount design.
I also opted to pay a little extra to buy a hobbed bolt from Eckertech for my Wade’s geared extruder. I probably could have hobbed it myself just fine, but it is such a critical component I felt the extra money was worth the time I might have otherwise spent troubleshooting extruder problems. So far it has worked great. I have never had to dismantle my extruder to clean the bolt and any problems I’ve had extruding have been my own fault (more on this later).
I payed the money for a MKI heated build platform (HBP). It seems to work well for me hooked straight up to my Ramps board for power. One (minor) annoyance is that the MKI pcb has very small surface mount pads to solder the power wires too. I think they’ll hold, but I used a few strips of Kapton tape to try help hold it in place. I would prefer plated through-holes for the power connectors or at the very least some holes in the PCB to tuck the wires through for strain relief.
I bought a DIY Ramps 1.4 kit for the electronics. The kit comes with a Ramps 1.4 PCB, an Arduino Mega 2560, all the components for the PCB, and 3 end stops. I bought the optical endstops since I already had some mechanical endstop switches at home. I ended up using a mechanical endstop for the Z-axis and optical endstops for X and Y. I think mechanical endstops are easier to setup and more than reliable enough for the reprap. The kit offers both types at the same price, so buying the opto-endstops is probably a better value.
I bought a J-Head Mk. IV hot end with a 0.35mm nozzle. It has worked extremely well. I have absolutely no complaints. Using PID control in the firmware I am always within 0.2C of my target temperature. I didn’t use any cement to hold the power resistor in place because I know the resistor might fail sometime down the road and I don’t want to have to clean it up. The fit is already pretty tight. The hot end has been one of the most reliable parts of my printer.
I bought my threaded rod at a local Ace hardware store. I bought three of the 6ft 5/16”threaded steel rods for the frame, and a 3ft 5/16” threaded stainless rod for the z-axis drive screw. I bought 8mm precision ground rod at McMaster, part #88625K67. It is important that the smooth rod be 8mm rather than 5/16” if want to get the most out of your lm8uu bearings. All the other parts can be SAE. Since 8mm and 5/16” are so similar, the 8mm rods will fit into any plastic parts designed for SAE rod.
I used an old computer power supply to power the printer.
In Part 2 I’ll describe the construction of the printer, the problems I had (very minor), and I’ll post some closeup pictures of the build.
Suppliers I bought product from:
Ultimachine.com (also a good source for filament)