Over the summer, students moving our 3D printers to and from the AggieSTEM summer camp sessions accidentally dropped three 3D Printers into a pit due to on-campus construction they were trying to lift the cart over, resulting in various types of damage to the MakerBot Replicator, RostockMax delta and MendelMax cartesian printers.
In order to prepare to give the free 3D Printing classes for Element14, I began repairing the three printers to get one into operational shape. The first printer to be fully recovered to operational status has been the MendelMax cartesian-format 3D printer based on the Prusa Mendel RepRap design. The first few items were visible as obvious damage to the printer itself - the LCD controller was knocked off, while the bed level probe was crushed, the hob was damaged by impact with a stronger material (the hob was made from brass), while the extruder hotend's nozzle was crushed by impact that closed the 0.4mm aperture.
The hob was replaced after my wife's observation of metal debris jamming the grub screw, which was ferrous and wiggled free using strong rare-earth magnets, allowing replacement with a spare hob.
Because the J-head's nozzle cannot be separately replaced, I was able to obtain an all-metal E3D v5 hotend that was compatible with the J-head's mounting flange with some shimming.
Once replaced, the original hall-effect (magnetic) Z axis endstop was revealed to have been damaged as well, but after discussion with the original designer, I was able to replace it with a mechanical endstop using locally-available switches and a simple 3D printed replacement bracket shared with me via Git.
After replacing the endstop, during test of the new extruder's elements, the filament slipped and yanked the spool holder from the top of the machine, shattering the borosilicate glass (Pyrex) build plate. While waiting on the replacement glass, my wife tried to bend the extruder's lower guidler and snapped it in half, revealing an internal break that was flexing as the extruder advanced and allowing filament to twist up in a void created by the broken extruder's guidler bracket being partially hollow.
Through judicious use of plastic-compatible epoxy, Super Glue and spare washers, I was able to return the printer to basic operation while I designed a thicker lower guidler that includes the shim needed by the v5 E3D hotend and ordered a copy from a 3D Printing service while I waited for the epoxy to harden.
After the temporary repair, I was able to create a replacement for the flawed part. Once the new thicker lower guideler was installed together with an adjustable tension adaptation to the spring, I also fabricated a replacement for the upper guideler.
This allowed easier alignment between the filament and the new extruder hob, while I also reprinted Z axis caps to make everything the same color when I talk about additions to the printer (students noted the previous purple was hard to identify).
While repairing the more solid extruder guidler components, a washer fell out, rolled the length of the replacement build plate, bounced off the frame and through a tiny slot in the power supply where it bridged 110VAC with the DC supply for the electronic control board, "letting the smoke out" of the chips and requiring a replacement.
To prevent further such issues, I sealed all of the power supply's vents using mesh screens for case fans.
I first tested an Arduino MEGA + RAMPS + Pololu stepper motor controllers, but settled on an alternate RAMBO controller board so that my replacement LCD could connect properly to the alternate bus structure.
After re-wiring the auto bed leveling probe to reflect the board's reversed and poles from a Servo standard connection, I was able to get the new electronics and auto bed level probe re-installed.
After printing a case and mounting adapter for the GLCD, I was able to get this installed and working together with the 3D Printer so that the printer can operate stand-alone from the SD card without needing the host computer for basic operation.
Expanding beyond this, my students wanted to install one of the new Raspberry Pi B+ boards configured with OctoPi, WiFi and a Web-cam to allow wireless management and monitoring.
After designing and printing a case for the model B+, I was able to get this configured and installed, allowing remote access and control of the original MendelMax. Finally, after many steps, the "mildly damaged" 3D printer was returned to full capacity plus new capabilities and is used in my 3D Printing classes for demonstration of the use of 3D Printers in creating cases for Arduino, RasPi, and other electronics. Now, to get the other printers repaired in turn!