Plywood Cube, Heated bed possible? Firmware update?


#1

I have the plywood cube kit, bought from Amazon.

I would like to implement a heated bed, to make it easier to print with ABS or PETG. In order to do so, I am guessing that the Marlin firmware would need to be told that there’s a thermistor for the hotbed so that it can control it. There appears to be all the connections on the motherboard for a heated bed, but I don’t know if the provisions are there in the firmware. Also, while on the topic of firmware, a maximum temperature of 245C causing the machine to shut down and need to be reset makes me a little crazy when trying to work with ABS, which I’d like to extrude at 240 deg C. (Even using the built in Preheat ABS in the Prepare menu will cause this more often than not. I’d like to bump that parameter up, but the UI won’t allow me to set it higher than 245.)

So for construction of a heated bed, there are a couple of issues. One is the heated bed itself. The print surface for this seems to be very specifically formed to allow the 3 point leveling, and I’d like to preserve this. I can think of 2 ways to do this with a new bed. Sink the heated bed into a formed platform which matches the original shape of the one that comes with the kit. This seems pretty straightforward, and given the dimensions of a heated bed that I can buy (275mm X 220mm, 220mm X 220mm, or 300mm X 220mm) this is possible, as all will fit within the Y axis. This is probably going to be my approach, to make the platform, copying the original shape, with some rare earth magnets fit in the original configuration unless I just include mounting bolts/springs to the aluminum platform. Alternately, raised platforms could be made for the 3 Z probe locations, and then set a negative offset, which it seems happy to allow.

I’m also concerned about the power supply. The included 24V power supply is rated for 5A, which ought to be plenty adequate for the hotend and motors. Hot beds are usually ~40W or so, which is another 2A demand. Probably it’s not too much of an issue once it’s reached temperature, but I like to plan for worse case. A hotbed controller and separate power supply is an ugly solution, but one that I would probably be willing to tolerate, as I don’t plan on the printer moving around much from its regular home.


#2

In the event that anyone cares…

I’ve started work on the heated bed. I purchased an aluminum headed bed with dimensions 220mm by 275mm by 3mm. The build platform is 235mm by 270mm, so this hangs over the end a little, and is a little tight for allowing the 9.5mm (3/8"?) indentations for the bed leveling system. There seems to be a little bit of wiggle room there with the print head, so I don’t see much of a problem, so long as I can still level the bed.

My problem now is that I need to update the firmware to allow the heated bed controller. I can see that the printer is running Marlin, and I’m certain that I can eventually figure out an appropriate Configuration.h file, but I’d rather start with the one that it’s running now, in order to have the fewest things that can possibly go wrong.

I have tried contacting support, and am getting no response. I’m starting to think that this is an abandoned project, which bothers me so far as replacement parts are concerned.

So far so good though, I have a heated bed built, and it functions, so long as I have something else control it.


#3

Well, I rebuilt the heated bed. It’s a chunk of 8mm MDF cut 275mm by 235mm with 3 .5" rare earth magnets glued to the underside, and a Hictop 275mm X 220mm heated bed screwed to it with some #6 wood screws. The bed is 5mm wider than the one that was supplied with the printer, so I moved the magnets over by 2.5mm. I have a set of 3 5mm pads which I placed at the locations that the Z probe comes down, for auto leveling the bed, which comes out perfect with the 2mm of glass that I have over the heated bed, allowing a more or less appropriate Z offset the same as when I use the acrylic bed with tape. The pads remove the need for the cutouts for bed levelling, since the nozzle misses the heated build platform and glass. Makes construction and duplication simple.

I’d supply plans, but that really is about it. The bed works perfectly and is a direct substitute for the standard bed. The only gotcha is that the power and thermistor feed must go to the left hand side of the printer, as the motor will hit it if it’s on the left.

I’d really like to get my hands on a Configuration.h file for this printer, but I plan to start working on converting it. the plan is that I’m going to temporarily connect this up to a modified 2560/RAMPS setup (To keep the 24V power) and play with it until I get a working Marlin 1.1x with heat build platform control. I also want to once and for all get rid of the stupid “Heating…” hang. It’s probably my biggest complaint with this printer, including the heated platform support.