Anycubic i3 Mega (Ai3M) Conversion to Ender 3 Printbed

With this parts, you can use an Ender 3 Heatbed on the Anycubic i3 Mega (Ai3M).

Requirements

Since the Ender 3 printbed is 24V only, it is a requirement that you converted the printer to 24V before. This requires swapping out the hotend heater and all the fans, the motors or Trigorilla board do not need to be swapped. I recommend a MeanWell LRS-350-24 power supply together with my mount adapter for this conversion.

Also I strongly recommend a bed level sensor (like BLTouch or BIQU MicroProbe) because these cheap heatbeds never are perfectly flat.

Since the printbed carrier is a bit thicker than the original, there may be some incompatibilies with for example Y-tensioner. For this reason, I removed my tensioner and use this kind of belt tensioner instead which works fine for me. 

The advantage of the Ender 3 heatbed are:

• larger (235x235mm instead of 220x220mm usable print area)
• a bit more power (0,4W/cm² instead of 0,33W/cm³)
• thick enough to serve as a stable base for magnetic PEI sheet without ultrabase glass
• less weight (since my heatbed carrier is printed and much lighter, also the ultrabase glass is not needed anymore)

Needed material:

• Ender 3 heatbed (including leveling screws and printbed of your choice, I recommend a magnetic PEI sheet)
• leveling silicon buffers or springs (recommend silicon buffers)
• I recommend bed insulation
• a few wires to extend the heating and thermistor cables (including for example WAGO connector if you do not want to solder it). You can recycle the wires of the Anycubid bed, if you like.
• four M4 nyloc nuts (the large leveling wheels do not fit)
• 6-8 M3x5x5 melt insert nuts, the same as used by most Voron builds (the two on the front side are currently not used but planned for a ADXL345 mount or a handle)
• 3 or 4 LM8UU linear bearings in industry quality (24x15mm with 8mm hole)
• some small but long zip ties to mount the linear bearings on the carrier

With the provided pictures, the build should be self explaining, but I highlight some of the not so obvious points here:

Cable routing of the print bed cable and end stop offset

The cable of the bed heater and the thermistor is not fed through the original feed-through into the inside of the housing. Instead, it goes through the hole with the Y end stop, which has to be moved slightly anyway. You should be able to see from the pictures that there are two pressure parts for the offset of the end stop and for holding down the pressure bed cable.

Fastening the linear ball bearings to the print bed carrier

I used zip ties to fasten the linear bearings on the print bed carrier. Thats the way the Prusa did it for years and it seems to work without any issues.

It is a little fiddly to feed the cable ties back through the holes in the carrier from below, but with a little skill you can do it quickly.

Linear Bearings

You can choose between three or four LM8UU linear bearings on the printbed carrier. In the beginning I choosed four because I was not sure if a printed bed carrier is stable enough and with four bearings the distance between the bearing point and the leveling screw is shorter.

The first printed was printed with PETG-CF and I used a bit less infill, so it had a bit flex but overall was very stable.

I later redesigned the carriage and created the option of using three bearings instead of four. With three linear bearings, the bearing is not overdetermined and it is definitely stable enough for the bed I printed last with ABS-CF, four walls and 40% grid infill.

Print settings

I printed the last version of the parts with ABS-CF, but I guess PETG should be stable enough.

Use many wall lines (I printed with a 0,6mm nozzle and 4 perimeters / top / bottom layers and 45% grid infill and it is very regid and stiff. My first print was with (blue) PETG-CF but only 25% grid infill and less perimeters and therefor is not as stiff als the (black) ABS-CF print.

I cannot guarantee, but I guess a PETG print without CF should be stiff enough if you haven enough perimeters / infill.

I provided all the STEP files for your convenience. Feel free to improve!

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