What it is:

CoreXY conversion for Prusa MK3/S 3d printer. This build is aiming at getting more performance out of your 6 years old machine with the lowest cost possible by re-using most the MK3/S stock parts. Make sure you read the open beta kit notes.

Specs:

• Better performance (check input-shaper in pictures).
• Triple Z (independent or sync based on controller board) 
  
• Single v6 hot end (default) or mixed 2-in-1-out hot end (WIP).
• Optional AUX cooling fan.
• Semi-enclosed (default) or fully-enclosed with top hat (coming soon).
• Our industrial leading SnakeOil technology 😉
  

Notes:

• This mod requires some drilling on the original center frame plate and cutting the original motor leadscrews. This drilling/cutting is easy enough to be done with a hand drill and a hacksaw BUT THERE IS NO WAY BACK. You won't be able to convert back to the original MK3/s machine if you change your mind later.
  
• To keep the cost down and reuse old components, there are some trade-offs I made:
  
• The machine is semi-enclosed by default and will need some printed panels and a top hats to fully enclose it.
• To match the frame height, cutting the motor leadscrew and linear shafts is required.

What's in the Kit

• All new extrusions (drilled and tapped)
• Fastener/Screw/Washer kit with 20% extras *except for a few sizes mentioned in notes below
• 2x HoneyBadger Nema 17 48mm motors
  
• 1x 3rd Z motor w/ integrated lead screw
• 1x Sherpa mini extruder
• 4m Original Gates 2GT 6mm belt
• 1x GDSTIME 120120x32mm 12v blower fan (aux fan)
  
• 4x Rubber feet
  
• 36x F623RS bearing
• 4x 2GT 16T idler 3mm bore
  
• 2x 370mm linear shaft (d=8)
  
• 2x 330mm linear shaft (d=8)
• 3x 260mm linear shaft (d=8)
• 6x linear bearings
• 1x Rubber tape (60x18x0.5mm)
• 14x 2020 corner bracket
• 4x 1515 corner bracket
• 2x Din rail 329mm
  
• 1x Din rail 430mm
• 3x POM T8 nut

Open Beta kit specific notes:

We're offering beta kits at a discounted price for customers who are willing to address the notes below during their build. These issues will be fixed in the production version of the kit.

Things to FIX

• Frame extrusions:
• We found some extrusions in beta kits that were not cut 100% square, but are still usable. Use the included corner brackets to ensure everything lines up.
• Check for "fence burs" in the tapped ends and sand/file as necessary.
  
• Extra wrench hole in two extrusions for easier motor mount access (optional).
  
• Motors:
  • Motor shafts are a little short (23mm instead of 25mm) and only make minimal contact with the support bearings.
  • Also, the support bearings may be too tight to fit properly on the motor shaft. Some sanding/filing may be necessary, or simply install without the support bearings.
• Cut rubber tape into two strips of 5x48mm
  
• DIN rails may be a tight fit. Shorten by ~1mm (if necessary)
  
• Aux fan is 12v (instead of 24v) so be sure to use a buck converter or an MCU with selectable voltage
  

Add

• +12 m3 square nuts
• +12 m3x25mm button head screws
  
• +2 m3x30mm socket head screws
  
• 24v hotend fan and part cooling fans **be sure to use a buck converter or an MCU with selectable voltage if you're re-using your existing 5v fans
  
• Drill bits and m3 tap for drilling front center frame plate (optional)
  
• 2.6mm drill bit
  
• 5mm drill bit
• m3 tap

We also recommend upgrading your MCU and hotend to take full advantage of the increased speed.

Links:
GitHub - SnakeOilXY/ProosaXY: Low cost CoreXY conversion mod for Prusa MK3/S