After countless hours of choosing a 3D Printer, I fell in love with the Maker Select (a.k.a. Wanhao Duplicator i3). I read every review on Amazon, Reddit discussion and web article I could find before finally landing there. The one major drawback was a problem from the factory… they are ticking time bombs. Without making some changes, they will either burnout or worse, catch on fire.

Despite being an IT guy, my experience with wiring was on par with that of a 12 year old child. Nonetheless, I was convinced I could figure it out while sustaining minimal injuries. I placed the order for the printer, followed by an extended shopping spree to turn this budget printer into something of beauty.

Thanks to all those at Reddit 3D Printing that helped me figure out how to get this done!

Purchased Parts

Printed Parts

MOSFET Board Mount

MOSFET Mounting Bracket (Better Alternative – See Notes Below)

Note: When this guide was written, the MOSFET Board Mount was used. The MOSFET Mounting Bracket was designed several months later and offers a better alternative. There is no need to purchase the Velcro Pads or Steel Star Drive Screws when using this design, it mounts under the Melzi board and uses M3 8mm screws.

Overview

The problem with these printers is that the Melzi board (basically the motherboard) connectors are not rated for the power used by the 3D printer. In other words, the printer is trying to pull more electricity than the connectors can supply and eventually result in the aforementioned problems.

To fix this, the MOSFET board will handle the power to the heated bed, routing it to the power supply rather than the Melzi board and solving the issue. In doing so, we essentially have 3 steps overall that we will need to do.

Connect the Hot Bed to the MOSFET board

Connect the MOSFET board to the original Hot Bed connectors

Connect the MOSFET board to the power supply

I took the process slow to avoid making mistakes, but it can definitely be completed in less than 30 minutes depending on your experience level.

Instructions

We will start by mounting the MOSFET board to the mount that we printed out. The screws mentioned in the parts list were the only ones I had on hand that fit the mount. You could probably use M2 x 5 or similar but they are considerably small so keep that in mind.

You can then attach one of the Velcro Pads to the bottom of the printed mount. The other half will later be stuck inside of the control box, allowing you to mount the board with ease.

We then proceed to install the 14 Gauge Silicone Wire that will go to the power supply. To ensure a good connection, I recommend using the 14 Gauge Spade Terminals on both ends, which offer a snug fit around the screws.

For this step, I purchased a cheap tool from Home Depot to handle stripping and crimping wire. You can find decent information online if you are inexperienced, however the general idea is to expose around 1″ of bare wire. You then slide this into the spade connector and use the crimping tool to seal it inside. I used the brief guide Working With Wire and had it done in 5 minutes.

Now to the scary part, actually working with the inside of the control box (the black box with the LCD screen). Make sure to to power off and unplug the cord from the 3D Printer that runs to the wall. Afterwards, there are 11 screws that need to be removed, 7 on the bottom and and 4 on the back. Once all of them are out, slide the top of the control box forward until it can be separated from the base.

It will be easiest to remove the Melzi board, taking out the 4 screws placed in each corner. You can leave it in place but it may make working with it more difficult. Locate the orange/green plug combo labeled “HOTBED” and unplug the orange connector from the green. In my case these were super glued together, where you may need to peel this off before doing so.

Once disconnected, we have two steps. First we will remove the wires currently inside of the orange connector and plug them into the MOSFET board. Afterwards, we install the Control Input wire (white one) from the MOSFET board in their place.

If you rotate the orange connector, you will see two flat head screws. Loosen these to free the red/black wire from the connector. These will have straight metal ends called bootlace furrels. You can either use the same spade connectors from earlier to cut these off and replace them, or simply leave them as they are. The spade connectors are a better option but in case I need to revert back, I just kept them as they are.

When connecting the Hot Bed wires to the MOSFET board, the red wire goes where it says “HOT” and the black wire goes where it says “BED”. Make sure they are securely connected and adequate metal contact is being made to avoid shorts and other issues later on.

Now we just need to run the white wire from the MOSFET board to the orange connector and plug it back in. Make sure the positive/negatives are correct, slide them into the openings and tighten the connector securely where they will not pull free.

Note: The end of the white cable did not expose enough bare wire to make a proper connection. I had to use the crimping tool (#20-22) to open these up a bit more.

To finish it off, we just need to connect the MOSFET board to the Power Supply using the 14 Gauge Silicon wires. The red wire is connected to “+V” and the black wire is connected to “COM”, where the spade terminals will provide a simple and secure connection on this end as well.

Image Credit 3DPrinterWiki.info

Final Thoughts

From here, all we have left is putting everything back together. Stick the other half of the velcro pad somewhere within the Control Box near the Hot Bed connector on the Melzi board. You can then reconnect the Melzi board (if it was removed) and stick the bottom of your new MOSFET board to the velcro base nearby.

Slide the top of the Control Box back on to the base and take a few minutes to organize all of the wires inside, ensuring they are not bent in strange angles. Screw the case shut and plug it back in to find out if it works!

If everything was done correctly, it should look like the following…