Now I have a chance to show some photos of my 3D printer finished and set up. If you haven’t seen one before, this will show you what a MakerGear Mendel Prusa kit looks like once it is assembled. Then go have a look on the web to see how other folks have tarted their machines up. Here are Mendel Bling and Kliment’s Holiday Prusa Mendel to get you started.
This first photo shows the printer complete and ready to print. Everything on the green cutting mat is the printer. It is about 500mm wide, 400mm deep and 400mm tall. Hanging from the ceiling is my home-made filament spool and delivery system. I’ll tidy the wiring up when I’ve spent a bit more time printing.
Photograph number two shows the power supply. Its a 600 watt unit intended for installation in high-powered PCs. So it has way more connections than we need. The two comparatively thin black cords in the bottom right of the image are the only ones we use for the MakerGear machine.
PC power supplies are cheap and mass produced. RepRap printers rely as much as possible on re-purposing stuff that was never meant to print, so as to keep the cost down and make 3D printers available to as many people as possible. Eventually HP and IBM and Apple will produce 3D printers, with weird copy restrictions, ‘walled gardens’ and anti-counterfeiting measures. Just like how they charge you a fortune for bubble-jet printer ink. Open Source Hardware FTW!
The next photo is my home-made meccano-and-foamcore filament holder and delivery system.
PLA filament is surprisingly tough and springy, worse than lawn-trimmer plastic. In the quantities I bought it, it came as a coil held together with cable ties. I could tell it just dreamed about tying itself in knots, and couldn’t possibly just be left on the benchtop. Think about how your coiled up garden hose reacts if you just pull the nozzle away from the coil instead of unrolling it, then imagine it made of spring steel.
So I knocked up a reel system in Meccano. I knew meccano would prove useful for something. The first version failed dismally. The second version seemed to work ok, so I replaced as much as possible of the meccano with foamcore side-panels. Then I mounted it on a ceiling beam using a sliding release mechanism so I could easily take it down when I needed to. And a swivel mechanism to automatically release any twists that might be in the coiled PLA.
When I installed it, I discovered my bearings were too good, and the weight of the 5 feet of PLA hanging down to the printer was enough to spin the reel, potentially unrolling all the coil onto my head. I had expected this, because I’d read of someone else with exactly the same problem. Out with more meccano, and I built a spring-tensioned friction arm, inspired by the brake arm in drum brakes. It presses on the rim of the reel, providing just enough tension to stop the PLA unrolling on its own, but not adding to the workload of the extruder stepper motor. It now works beautifully and I’m quite proud of it!
The next two photos show the printer having its printing bed levelled. The horizontal plywood square covered in blue painter’s tape is the print bed. The object is built up on it in layers of tiny thin extruded plastic that looks a bit like thick spider’s web. The black thing with the pointed base in the second photo is the extrusion head. It squeezes out the plastic while moving from side to side and forward and back. When it finishes one layer, it moves up a tiny amount (mine is set for 0.3mm per vertical layer) and puts the next layer on top op the previous one.
I’m not sure what the ultimate vertical resolution is, but you can manually move the extruder head in tenths of a millimetre, and the bed needs to be level with respect to the nozzle tip to about that order of accuracy. Otherwise the plastic won’t stick reliably to the bed. Levelling is a bit tedious. The key thing for me was remembering that a quarter turn of the adjustment nuts is significant, on the order of 3 tenths of a vertical step. Once I stopped over-adjusting the nuts, the process went much more smoothly. The playing card on the bed is a simple way to measure the gap by how much friction you feel when you try to move the card.
The last photo is of the electronics. The plywood board at the bottom is cable-tied to the frame of the printer.
On top of that is a bog standard Arduino Mega microcontroller board. These are a staple of the electronics hobbyist, especially in the ‘maker’ community. It does all the communication with the PC, and runs the printer control software. It’s way more powerful than the first 3 computers I ever owned, but then I did start back in the late 1970s.
On top of the Arduino is a RAMPS shield (version 1.4 in this case). The RAMPS shield allows the Arduino to control the stepper motors and extruder heaters, which use way more current than the Arduino can handle on its own. It also monitors the thermistors and the limit switches.
On top of the RAMPS shield are 4 tiny boards, each with one stepper motor driver. This way, if you burn up one of the drivers you can replace it without replacing the whole electronics system. And yes, there is enough current running through these things that they can explode in a tiny ball of flame if you really screw up. Exciting isn’t it? Seth Godin, the only marketer whose books I recommend, is quoted as saying ‘If you can’t fail, it doesn’t count’!
Despite that macho statement, I paid extra for the assembled version of the hardware. My eyes aren’t what they used to be, and I didn’t feel like trying to solder components smaller than a grain of rice.
The wiring is twisted together in braids partly for neatness around insensitive stepper motors, and partly because twisting wires together makes them less prone to certain forms of electrical interference. Microcontrollers and stepper motors are noted for their potential to generate interference, so every little bit helps.
Next post should finally show some things I’ve printed on my newly assembled 3D printer.