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Goals

In order to make the printer a more reliable and useful tool, I have a list of problems and features. Most of my issues with the current printer lie with the smart extruder (jamming, the duct falling off, drowning itself in plastic.) Therefor, the primary objective of this project is to replace it with something more robust. To achieve this, I will use a standard mainboard which will also allow the printer to take gcode generated from modern slicers with much more control than Makerbots slicer. The new board supports klipper firmware which enables faster more precise movement.

Reconnaissance

By removing the panel on the back of the printer I am able to see that both the power supply and mainboard are custom and will not be easily reusable. (you could probably figure out the power supply but I didn't bother.) The motion system is an H bot design and uses standard MOONS NEMA 17 motors, which are high quality stepper motors. There are no endstops on the XY axis, there is an endstop at the top of the z axis. The extruder is connected using an FFC and has a PCB in the carriage and another in the extruder which connect with pogo pins. The extruder motor is another MOONS NEMA 17.

Planning

I will be replacing it with an e3d Hemera XS (most standard extruders would work here.) in order to connect the extruder, the custom mainboard and wiring has to go. My main requirements for the new mainboard are 4 stepper outputs, and drivers capable of sensorless homing as the replicator plus does not have endstops. I chose the BigTreeTech SKR mini e3 for my build. Because I plan on adding a heated bed to this printer, I opted to replace the stock power supply with a 350 Watt 24V unit (Meanwell LRS-350-24.) I also added a BTT Eddy auto bed leveling probe. It should be noted that this probe will not fully work with the stock bed because the aluminum portion is not uniform. I suppose you could use it without the rapid scan function, and find locations on the bed without holes to probe. if you decide to keep the stock bed then maybe consider something like a klicky probe which uses physical contact with the build plate.

Heated Bed (Optional)

The closest standard size bed to the stock bed was 200x300mm (measured 12 1/4 x 8 5/8 inches). I considered a PCB heated bed and a silicone heater with a custom aluminum plate, but figured the ladder would be to much work. I decided on a reprap MK2A PCB bed because of its availability, good size and ease of install. The build surface I chose is a PEI coated magnetic spring steel sheet for good part adhesion and easy removal.

BOM

There is a bill of materials in the root of this project, the screws can be purchased as an assortment for cheap on places like Amazon, just make sure to choose one with all the listed sizes. There is also a section for a custom bed if you decide to make one.