Photos and Features

Okay in order for me to go through the details of the Prusa i3 MK2, like with most 3d printers it all stems from the RepRap community. Prusa originally created the Prusa Mendel and then from there, the revisions have been the Prusa Mendel i2, the Prusa i3, the Prusa i3 Plus, the Prusa i3 MK2, and most recently the Prusa i3 MK2S. The design has been extremely popular and because of that in the RepRap community there have been many derivatives and in the market, there are more i3 clones and derivatives than you can possibly count. That is why they push the “Original Prusa” branding. The i3 really took off because of its solid structure, ease of assembly, and its low material costs. Unlike the SeeMeCNC machines I’ve had in the office in the past this machine is a cartesian design. That is the coordinate system used in the X, Y, and Z Axis. There are a few variations on designs but the way this one works is the Y axis (forwards and backward) is all in the bed's movement. Then the hotend moves the X axis (left and right) while floating on the Z screws that move the hotend up and down.

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So when we look at the Prusa from the front we have a few main thing going on. There are two main structures, the Z axis structure is the steel plate that has been cut out, on it on both sides is a stepper motor with a long screw and then a smooth bar to keep everything aligned.

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The print surface is 250mm by 210mm and you can print up to 200mm in height. The bed itself is heated and supports the temperatures needed to print ABS. Prusa advertises that the heated bed also has corner compensation that helps make sure the outside corners run just as warm as the middle of the bed. Then on top, they ship it with a PEI film on It that should help with adhesion. The bed itself is made of a composite material from the looks of it and they have placed metal across the bed in 9 spots for the auto calibration. It connects with the controller out of the back and there is a small red status LED indicator that lets you know when the heated bed is warming.

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The hotend has a direct drive design. That means the extruder is mounted directly above the hotend where on the Deltas they use a Bowden design that puts the extruder away from the hot end. The shorter distance keeps movements tighter so less retraction is needed and it works better with softer filaments. A lot of the hotend is constructed out of printed parts, anything in orange in the pictures below is printed. They are using two screws with springs to keep the pressure on the extruder gear. There are two fans, one small fan on the side that blows across the hotends heatsink to keep the heat just down in the hot end to prevent jams and then a blower style fan that blows down on the parts you are printing. One of the main features of the Prusa i3 MK2S though is that they went with an E3D brand V6 hot end. E3D is very popular for their performance. I eluded to it before but Prusa has also integrated an auto calibration into the MK2S and to accomplish that they have the 9 metal dots in the build plate and then a PINDA probe on the side of the hotend. This is what detects the location of those metal plates, making sure everything is true and then setting the nozzle height.

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So the vertical frame was the thick metal plate, it comes down and bolts to the Y-axis frame. This frame is constructed completely out of thick threaded rods with printed junctions on each end. Then up on the top edge, the smooth rods are zip tied down and the built plate runs forwards and back on them with linear bearings. To move everything the Y-Axis stepper motor is at the back of the machine and it uses a belt with pulleys.

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At the front of the bottom, frame is the control panel. This is a standard LCD screen, just like our Rostock MAX v3 uses only with a bright orange casing around it and Original Prusa branding on the front. I love how bright the screen is. The knob design isn’t my favorite but I’ve been getting used to it, then just below is it a cancel button in case of an emergency. On the left side, the screen also has an SD slot. Prusa also includes an 8GB SD card with the printer as well along with a few prints pre-loaded.

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The Z-Axis is driven by two steppers, one on each side mounted down on the bottom. Unlike the other two axes, this one uses screw drives. The entire X-Axis is hung from the two steppers including the extruder on the hot end and the stepper motor on the left side of the X-Axis so the two steppers help with the additional weight and also allow for some small compensation for a miss aligned bed.

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To control everything Prusa went with a RAMBo board from Ultimachine. While there are a few new options on the market the RAMBo has been the golden standard for high-quality controller boards for a while now. It's really good to see that Prusa went with a quality board, not a cheap knockoff. Also interesting was the mounting solution. They have built a 3d printed enclosure that hangs off the back of the top frame. The enclosure has a single bolt that locks it closed but you can open it up and have full access to hooking everything up. You can see that going out the back of the enclosure are the cables for the heated bed, also inside of the cable wrap is a thick plastic line to keep the line from bending too tightly and causing issues with the cables. Then out of the top all of the cables for the extruder run out of a similar setup with cable wrap and a solid line. That one has a few additional cables for the extruder stepper motor, cables to power the hot end, a thermistor, and the PINDA cables for the auto calibration. Out of the side, the cable for the X-Axis stepper motor and an end stop switch. Then last but not least the rest of the cables run out the bottom. This covers the LCD screen, the Z-Axis steppers, Y-Axis Stepper, and the power coming from the other side of the printer in the vertically mounted power supply. The top of the enclosure has the USB port out of the top as well along with a small hole for the result button.  

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So here is the power supply. This is exactly the same power supply our Rostock MAX v3 runs only Prusa has taken a little bit of the work out of everything. When they ship the kit the power supply comes with the printed end already on it. They have pre-wired up the outlet and switch along with all of the cables that run over to the RAMBo. It’s weird seeing this on the outside of the printer but I like the endcap solution that keeps all of the connections hidden and keeps the wiring that someone could actually hook up wrong hidden from inexperienced users. This open design should also keep the power supply cool and unlike the Rostock does not require a fan because it’s not enclosed so that should help with sound.

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