MINI rerouted heatbed cabling

Early-revision MINIs in enclosures ran into heatbed thermistor failures with stock cable routing.

Created a short tube with a 90-degree bend, and a ring to keep it closed and the cable contained.

Modified the top & bottom heatbed covers to accept the tube, and the Z top cover for the alternate cable exit.

Printing notes: 

• Use the slicer to cut the tube in half--orient the cut surfaces on the bed.  Printing without supports is possible.
• Printing the cap is optional--it should print without issue as-is, but the “outside” leg will require removal to allow the cable to pass through (See photo.)

Installation:

• remove the original Z top cover.
• remove the original heatbed covers (note the dovetail fit where the cable exits; slide the top towards the cable end to disengage.)
• disconnect the heatbed power and thermistor connections from the buddy board.
• carefully fit the lockring over the connectors (one at a time) and slide it toward the bed.
• pass the connectors through the modified Z top cover.
• reconnect the heatbed connectors to the buddy board, close the cover and re-secure all other cabling with the original cable clamp.
• reassembling the heatbed cover and tube will require a bit or dexterity & adjustment:
  • place the top and bottom tube pieces over the heatbed cabling--it should fit over the textile cover.  (note that the slight indent in the tube is meant to fit into the heatbed cover assembly, and the longer part points towards the electronics box.)
    • the end of the tube and the textile cover should be relatively close to the heatbed power crimps.
  • Slide the lockring over the tube parts to hold everything in place (See photo)
  • Transfer original M3 nut from original bottom cover to modified bottom cover.
  • Install modified heatbed covers (note modified heatbed covers retain the dovetail design.)
    • Place bottom cover in proper/final installation position.
    • Slide top cover into place (toward heatbed) to engage dovetail.
    • roughly 1cm (¼") of the tube (and tex-cover) should be captured in the end of the assembled modified cover.
    • use the original M3 screw to secure the finished assembly.

The new tube assembly will not be rigid, but the minimal flex remaining (and the resulting new cable motion) should not result in shorted wires.  ("Designed" this solution after 2 failed thermistor wires, no failures since.)