Lemontron belt extruder MOD

Reason:

I found the stock extruder of the lomontron under-powered so i made my own that is stronger.

Printing:
The mid- and top-plate should be printed as instructed by the lemontron build the pully gear needs to be solid but PLA is fine.

Other parts:
you need a extruder gear set, with bearing, idler and drive gear and a 16mm button head screw (or better a custom 17mm one).
Also you need a 2mm polyurethane round belt.

(optional) a quick connect fitting)
 

Modifications:

Cut both the drive and idler gear right aboth the gear (not the one engaging with the filament), take extra care on the idler to cut as straight as possible.

To complete the pully gear, take the cut idler gear press it into the printed pully gear.
the pully gear has a flat side with a beveled entrance that's where the idler gets inserted. the hole itself is undersized so it needs quite some force. But take care not to overshoot or bend the printed part.
 

The best way to get this done, i found, is to use an M5 bolt, a fitting nur and somthing to spread the load (washer, m5 pully) and put the bolt thru the gear and pully. Then ou can easely get the gear pressed in by tightening the nut. The pully assembly should have a total height of 11-12.5mm.

Now is also a good time to roughen up the outer surface of the pully that will engage with the round belt for more grip.

Build:
Install the midplate as instructed by the lemontron page, just without the inner screw for the extruder motor, as the pully gets installed there.

then take the screw and put on both bearings, then add the pully, making sure to have the gear pointing up (when the screw is inserted).

When you want to do a test fit you can continue with the build but for a permanent solution i would recommend adding some thread locker into the motor mount hole.

Then you can screw the assembly into the inner extruder motor mount, and check if everything spins, there could be some resistance becouse the PLA got squished out and is pressing on the bearing but this will break itself if its not too much resistance, but you can also try to file it off.

Now you can install the drive gear on the motor, take care that the part that the set-screw is on-top. 

now you need to make your own belt loop, for that you first need to measure out how much you need. I found a slightly loose loop around the motor shaft and the installed filament gear (not the pully, the gear on the pully) gives you the right length. But this might very with how stretchable your round belt is.
 

Just as a disclaimer:
You will need you some tension or the belt will slip later during use and the extruder wont work.

How to weld the belt:

Get a felt metal object (preferably something you don't mind getting dirty/ruined) and a blowtorch or a lighter (blowtorch would be better, a small kitchen one would do too).
 

You will want to secure the metal somewhere so that it stands up vertically and then heat it up with your preferred method. hotter is better get it glowing if you can.

Then, holding one side in each hand, sightly press the ends on the oposide sides on the metal and when fully melted (1-2s) quickly press them together. you need to be very very quick there and it might take some experimenting to get it right. you want a clean strong bond with as little of a bump as possible (but a small amount is fine, it will be way less once its stretched).

Now just stretch your belt over the drive gear and pully, install the top-plate (but first install the quick cone ct fitting if you want).

you will need to calibrate the e steps for your extruder new mine are ~9 with might be a start but will wary.