MonoPrice Select Mini Bed Expansion (150mmx230mm)

by YourDrunkle Jan 19, 2018
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Has anyone actually wired up the bed? Does the stock board's MOSFET handle it, or did you wire an external SSR / MOSFET for it?
(I understand that the power supply is inadequate and needs to be replaced with a more powerful one)

Matthew Upp (the Monoprice Mini guru) provided me with this link:

It turns out the stock MOSFET has a capacity of 6.5A continuous, 20A pulsed with a <2.0% duty-cycle, so I'll be wiring up another MOSFET to drive this bed (this bed is 1.5 ohms so will draw 8A).

Edit 2:
This may only be for the later V2 models, according to Matthew. I'm not sure what the V1 and early V2 have (nor do I know when the transition was between early and late V2 was).

Edit 3:
Matthew kindly also provided this information for the owners of the earlier minis (copied from another forum):
V1 and first few batches of V2's:
Original part is discontinued by the manufacturer. Part number AOD484.

A suitable replacement is:

infineon.com - https://www.infineon.com/dgdl/irlr7807zpbf.pdf?fileId=5546d462533600a40153566db03d26c7

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Thanks for making and sharing this, it's been great!

I couldn't find the bed you went with, it looks like it has an aluminum surface. I searched AliExpress for "230 150 heated bed" and found this one goo.gl/LhVo2B . I thought I might need to add an aluminum plate on it for more even heat but it's been working great with just a glass bed surface. The one I linked came with wires and the connector even though it doesn't mention them. I couldn't tell what length the rods are you went with were so I got 300mm. Assembled with 300mm rods I only got about 190mm of range, so I feel like I did something wrong, but with a few tweaks I got it to 240mm of range.

Anyway, great work, thanks again!

The bed is available with the aluminum plate here: https://gulfcoast-robotics.com/collections/3d-printer-parts/products/flashforge-monoprice-3d-printer-heated-bed-kit-t15x23-12v-alu-plate-cable

I'm working on putting mine together this weekend. How did you wire it up? It doesn't seem to be a direct wiring swap.

I am also trying to use this bed to make this expansion. I was wondering where the 5v input on the bed connects to since on the stock board, there is only 2 wires for the thermistor. Did you ever end up wiring this bed up to your printer because I realise this was a year ago?

I see the bed is available again. How did you run your wires? I see this bed has them coming out the side instead of the back. Or did you route them under the bed and go through the OEM hole to the main board?

I removed the connector sticking out the side and soldered the wires directly to the board toward the center and ran the wires out the back. I secured the wiring to the bottom of the bed with some tape and covered the contacts in kapton tape for now. The wires are secured to the frame with a zip tie.

this looks real interesting, but apparently, the bed is no longer available. Does anyone an alternate source?

Hmm, I wonder if that is my fault.

I think the bed I used is an aftermarket replacement for a Flashforge Pro, so searching for that should work:

well the one that you linked is no longer available.
However, I did find a manufacturer that makes a flexible heater with the same dimensions and built in thermistor.
The only issue is that it does not come with mounting holes.
So I contacted them and they said they will add the mounting holes per the specification.
Once I get confirmation that they are in the correct spot, I will post the manufacturer and part number for all to use.
The one caveat is that it does NOT come with the build plate. So that will need to be sourced elsewhere.

Judging by the threads on reddit, I think RepRap Champion went out of business.
They have upwards of 300 items listed on Amazon, but only a dozen or so stocked by Amazon. Their website has nothing available, and they don't respond to emails.
This sucks, as what you found was fantastic, I'm kicking myself for hesitating as when I went back, they were gone.
I also bought other stuff from them, used one of their V6 clones to upgrade my mini.

That's a bummer. The bed holders could be redesigned pretty easily to accommodate a different bed as long as it was semi-close to the same dimensions. Id be willing to do some collaborative design work if someone found an alternative and had the screw hole dimensions. I just dont want to spend any more money when I have a working bed.

Ive also been throwing around ideas for how to make a bed holder for just a glass bed. Although, in that case it would probably be easier/cheaper to do the cheapus maximus, so idk.

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So idk if it’s just me but I just finished printing out all the peices and 2 of the corners do not match what’s in your diagram. All four corners are basically the same size and have 2 holes in the side where in the diagram the corner only has 1 hole. Am I missing something?

Its possible I had mixed up when uploading and uploaded duplicates. I'm not really sure how that would have happened, but I apologize if it was my error. I have just posted an update and they are not duplicates now and using the viewer on here will confirm that.

How's your bed expansion working? Any issues thus far?

I actually have it apart for some fine tuning and have been printing on the stock bed. I did a few basic prints on it though and it works really well.

What fine tuning are you going to do? I'm considering ordering parts now to make this mod in a few days.

Nothing that directly relates to functionality but it should add convenience. I'm trying to make the bed leveling doable with thumbscrews from the side/bottom, similar to iBigNTastyi's remix. I've got my first draft printing right now. The only difference in parts will be from the hardware store using (I think) 4-40x1 flat head machine screws and a regular 4-40 nut instead of the 6-32x1 machine screw and square nut. When are you planning to start printing?

I just saw your new uploads. Looks great! Let me know how it works.

I ended up having issues with using really brittle clear PLA when I made the thumbwheel bed holders so they didn't stay on long. The issue was 100% my material though. From my limited time with them, they work decent but not great. Good enough to make small adjustments and make a glass bed usable but they were cumbersome for the first time leveling where you are likely moving several turns at a time. Really, the whole bed holder would have to be redesigned for them to work much better because the current design cant allow them to be big enough to be easy to reach while still being strong.

I plan to try printing another set soon, but between school, work, and other hobbies I dont get as much time to tinker with this stuff as I would like.

Im going to order the parts tonight. It will be either this weekend or next before I do the mod.

Did the PLA hold up ok?

please reply back after you complete the mod. I am very interested in this as well but wanna hear from another person on how it holds up.

PLA seems to be holding up for now but I haven't heated the bed yet. PETG would probably be better for the bed holders but I haven't figured out how to use it yet so I will be trying my luck with PLA. Realistically, its solid on the print bed so it should be ok at slightly lower than the print bed temps at the bottom of the print bed screws.

Can you upload the files in .iges or .stp? I'd like to see if there's a way to integrate thumb wheels for bed leveling.

Yeah, that would be cool if you could make it work. I uploaded the full drawing as on .iges file. Failing that, I'd be happy to share a .dwg as I draw all of this in AutoCAD.

I've posted a remix of your design. Check it out! http://www.thingiverse.com/thing:2764100

MonoPrice Select Mini Bed Expansion V2 (150mmx230mm)