Remix of the Spritztruder by Kitemare, for i3 Rework. I also used a modified idler from the compact E3D extruder by Mak-a-Face. Modified to have better support for drive gear. Also uses typical herringbone gears from greg's accessible extruder, so hopefully is a bit easier to incorporate into existing systems. Also modified to fit larger capacity syringes - 30ml ones by Terumo (from eBay), have OD of 25mm and ID of 22.5mm.

I tested Kitemare's Spritztruder and found the gear ratio to be OK when using M221 s1 in marlin to set the extrusion multiplier as 1%. It's a bit of a bad fix, but works OK for now, and I'd rather this that fiddling around with lots of gears to get a better ratio. You also need to fit a thermister to avoid thermal errors - use m302 to allow cold extrudes.

I haven't carried out much testing, but wanted to share anyway. I'll be carrying out some more tests using a clay mix over the next few weeks. This is quite thick, so requires a really high pressure to push through the syringe. I imagine most other pastes (chocolate, sugar, etc) will be fine.

The plunger drive gear is held in place and secured by using a chamfered M8 bolt. You have to take ~1.5mm from one side, and ~2.5mm from the other side with a file. Use a vice and a good file to get a nice flat chamfer on either side of the bolt. I haven't tested much, but this should take the high load required to push paste through.

BOM:
2no. M3x50
4no. M3 washers
2no. idler springs
1no. M3x30
2no. M3x40
5no. M3 nuts
1no. M8 Chamfered bolt
6no. M8 washers
1no. M8 nut
2no. 608 bearings
1no. M4x20 rod
1no. 624 bearing