1/24/2018 - I have added the option of using thumbwheels to level the bed. The change to the materials used is minimal (the new setup uses 4-40x1" machine screws for bed adjustments instead of the 6-32x1" used previously) and there are slight edits to all of the parts. Also, I still have the original no-thumbscrews bed holders uploaded here in case you prefer the original style. Make sure you sand the edges of the thumbwheels lightly to know down any extra protrusions as the clearance is semi-tight. Also, A dab of glue on the top of the screws to stop them from spinning when turning the thumbwheel inst a bad idea.
This is a modification to expand the MonoPrice Select Mini's print bed depth to 230mm on the cheap. I am able to utilize a printable area of 130mm x 220mm with just these modifications. The price once built was approximately $60 for me. This is nearly the same price as the unheated version of the "4th dimension modifications" "Maximus" kit but my build includes a heated bed. Note that you will need to upgrade the Select Mini's power supply to utilize the heater but I hope to be making a basic guide for that as well soon.
- No special tools (except a 3D printer) are needed for this project. I used a hacksaw to cut the aluminum, scissors, a drill with 1/8" and 5/32" drill bits, and a measuring device.
- Most of the non-3D printer specific parts (8mm rod, belt, and the bed itself) were purchased from my local Ace Hardware.
- I used a lot of Imperial sized (6-32) bolts instead of Metric (M3 or M4) bolts. Im in the US, so they are WAY cheaper locally. Seriously, like 1/3 to 1/2 the price. Sorry, I'd rather use metric too... M4 will PROBABLY work fine and allow use of the nut inserts.
Note: This link is probably sold out (sorry, maybe my fault) but the bed is appears to be an aftermarket replacement for the FlashForge Pro, so searching for "flashforge pro bed" on eBay seems to turn up desirable results.
Note: this is WAY too much belt. You only need ~30cm and could save money by buying a smaller quantity.
Everything else was locally purchased at Ace Hardware.
A REALLY REALLY BRIEF BUILD GUIDE:
Looking at your printer as it comes apart is crucial. This "guide" is very broad and skips a lot of stuff that you should be able to figure out on your own.
I printed everything with 100% infill and 0.1mm layers with PLA. Time will tell if the PLA holds up tot he heat from the print bed but I am confident. I am able to fit it all in 3 print files on the stock Select Mini. It took a long time but it is very rigid and looks good IMO.
Cut aluminum to 150mm for the front and rear and approximately 2-5mm shorter than your rods for the left and right sides. Its ok for the aluminum to be a few mm short but not a few mm long.
Assemble and square the frame off of the printer. Ensure that the 8mm rods are against the aluminum and are the same spacing as on the printer. Use a 1/8" drill bit to drill through the holes in the 3D printer parts. Expand the holes shown in the pictures in the aluminum only. The expanded holes are to allow for some adjustability in the system.
When the frame is initially assembled on the printer, do not tighten the 2 screws in the front and rear that were drilled oversized. Push the frame to the farthest back point of travel and tighten the front screw and vise versa. This prevent binding.
Installing the bed
When installing the bed, I placed the connector for the electronics toward the outside of the printer. It will bind if placed on the inside.
- Installing the belt:
The belt loops through this frame differently than the stock printer. However, it still goes through the stepper motors the same way and the layout in the frame should be obvious. The ribs in the belt will sit in the ribs on the inside edge of the frame.