Mosfet Upgrade - Wanhao Duplicator i3 v2.1

Hey there makers!

Today i decided to do the mosfet upgrade to my duplicator i3, its been on my to-do list for a while but i have some 24+ hour prints to do very soon, so i decided to add this safety feature before i did the long prints where i'll be leaving the printer unattended for several hours at a time.

Just as a point, i consider this a must have safety feature for ANY 3d printer. This isnt specific to just the wanhao duplicator i3, any printer with a heated bed should have a mosfet to take the load from the main board. They are easy to add in and inexpensive for the safety they provide.

Infact, on the Wanhao Duplicator i3 its a failure common failure. The connectors on the main board for the hot bed are cheap and not rated for the current load they see. Theres been numerous reports of these shorting out and damaging the main board, and in severe cases can cause a fire. So for the sake of £10 i consider a mosfet install a must.

Here is the list of items you'll need to buy if you dont already have them, i'll put links to them :)
mosfet
wiring
4 x m3x6 screws/cap head bolts
4 x nylon washers (can get away without)
Mosfet:
This is the mosfet that i used, they can be had for much cheaper from aliexpress or ebay if you dont mind waiting for them.
https://www.amazon.co.uk/gp/product/B01NCYD18Y/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1

Wiring:
I used 16 gauge which is the minimum i'd recommend to use, use 14 gauge if your buying the wire for the mosfet install

16 gauge wire
https://www.amazon.co.uk/gp/product/B01FG2OVJW/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

14 gauge wire
https://www.amazon.co.uk/d/DIY-Tools/YCNK-12Feet-Gauge-Super-Flexible-Silicone-Rubber/B01FG2OUE8/ref=pd_bxgy_60_2?_encoding=UTF8&psc=1&refRID=5XGY52633XYNESDSSZEQ

Tools i used:

M3 hex allen key
Phillips screwdriver
Flat head screwdriver
precision flat head screwdriver
Wire strippers

Extra's you need
You will need to mount your mosfet somehow, i chose to print a mount which piggybacks onto the standoff's for the main board in the control box. You will use your 4 m3 screws to attach your mosfet to the mount. Thingiverse link below

https://www.thingiverse.com/thing:2295820

Lets get started!
Turn off the power on the back of the control box, and move the printer and control box onto a flat work surface.

First you need to remove the back cover on the control box, this is done by removing 4 x m3 screws around the back of the cover

Be careful moving the back cover around as when i first took the cover off a while ago i unplugged the cover fan by accident. Place this gently to one side, and then place the control box with the bottom facing up

Now, starting from the back of the unit, undo 6 screws along its sides and the center screw at the bottom of the picture.

Once you have removed them all, the cover with the power supply on can slide out of the control box, again be careful not to snag any wires

Slide this cover off all the way and place it down carefully to the side with the power supply facing up. Now, you have the main board exposed and we can get to what we came here to do! Here's what you'll be faced with.

Now you can put your mosfet on the mount you printed off, and screw it into place using some m3 screws or bolts, use nylon washers here if you have them.
Then you'll want to remove the main board from the standoffs, undo the 4 m3 screws in each corner of the board

I also unplugged the ribbon cable for the screen so i didnt snag the cable by accident

Then, push your mosfet mount down onto the main board standoffs. Mine were a nice snug fit and had to pushed on to both standoffs at the same time or it wouldn't fit.

Voila! Mosfet installed and job done!
No, but your not too far off finishing! Put the control board back onto the standoffs and screw down into place. Now we can wire in the mosfet

You see the 2 green connectors above the orange 2? The bottom of these 2 green connectors are for the heated bed of your printer, it says "HOT BED" under the wires.

Now you can either pull the connector out or, because mine had a dab of hot glue on the side and i had no more, you can do it in place.

Start by using a small flat head screwdriver to undo the 2 screws on the connector holding the wires in.

On my mosfet, the wire with the solid line was the posetive, and the broken line was the negative. Check the specs of the mosfet you buy if it is different to the one shown here. (yes, i know i spelled positive incorrectly...)

Strip off a little extra of the wire insulation, and bend the exposed wire end in half to double the thickness, this will help the connector "bite" and hold the wire better.

Then put the positive (longer solid line on cable) into the right hand side of the connector, you can use the connector for the hotend next to it for reference on what it positive and negative, and the negative cable into the left hand side of the connector. Then tighten down the screws to hold them in place making sure the insulation of the wires is not caught in the connector, you want to clamp down on the wire, not the insultion.

Next, take the wire you took out of this connector, and attach them to the + and - to the "BED" terminals on your mosfet, and tighten the terminal screws again checking the wire insulation is not catching the terminals.

Now we need to supply the mosfet with 12v power. This is where the wire you bought (or already have) comes in, cut off a length that reach up and down the control box once, like in the picture below. This should give you enough slack if you need to get into the control box again.

Next strip off 1/2 an inch or 12-15mm of insulation from the wire on both end. On each wire twist the exposed wire and then bend in half like you did earlier to the smaller wire.

Then you can attach one of the red wires ends to the mosfet on the '+' side, and the black wire to the '-' side, like so, and tighten the terminal screws

Now on the Wanhao Duplicator i3 v2.1 there are 2 empty spaces on the power supply, 1 COM and 1 +V. Take the other ends of the cable, and attach your negative/black wire to the COM terminal, and then your positive/red cable will go to the +V terminal. Make sure the insulation of the wires are not clamped and these terminals are screwed down tight on the wire (i went back and re-did my supply side wiring), then go along and tighten all of them to be sure there all snug.

Now you mosfet is installed! Before we put all together, first lets make sure the mosfet actually works. Make sure nothing metal is touching, and plug in your power cable to the back cover, and turn your machine on. After checking to make sure no magical pixie smoke comes out of your control box, tell your bed to heat up to 50 degree's, If you have the same mosfet as me a led on the board lights up to let you know the mosfet is active and sending power to the heatbed.
Then monitor the screen to see if it gets up to temp ok.

 

If it gets to temp ok and stays there, now tell it to cooldown, and the led light on the mosfet should now turn off.

Now you get to put your control box back together, I like to put some cable ties in to keep the cables tidy but thats up to you.

Follow the process for opening up your control box in reverse to put it back together and your done! Little tip, i start from near the screen when putting the screws back in on the bottom, and work my way to the back 2. It makes lining up the holes a little easier.

Well there you go, my very picture heavy guide to installing a mosfet in your Duplicator i3 v2.1, but it should be a similar process for most 3d printers. I hope this helps some of you who want to do this mod but think its looks/sounds complicated. Its a very simple mod, and what i consider a MUST have on any 3d printer. As its another layer of security to stop your printer catching fire when you leave in unattended on longer prints, or for printing with abs, petg ect. that requires hot bed temps of 90+

Thanks for reading everyone, hope you enjoying it
Keep safe,
ThatNerd.

Twitter: @ThatNerdChannel
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