For all who don't want to read the whole blogpost: Watch this video (link).
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At the beginning of this year we made experiments with paste extrusion.
First we tried it with a big syringe extruder connected to a bowden cable.
But the bowden cable was not the right decision.
Most power gets losts inside this bowden cable and though the paste inside has to be very fluid to get through.
Even bigger transmisson doesn't solve the problem: The syringe also has it's limits and may burst by the pressure.
So time passed and we dropped this project because the new 3D printer wallace arised.
A while ago Richrap posted it's genius solution for paste extrusion: The universal Paste Extruder for 3D printers
This approach seemd to work, so we made some research ourselves.
The mechanism is very simple. A timing belt is used to squeeze a syringe. The power is boosted by a transmission.
The problem: Richraps model is non-parametric. It only fits to 10 mm syringes.
So we decided to improve this idea by creating a parametric version of a syringe extruder.
We've got plenty of 20ml syringes in stock, so we made it suitable for those syringes.
2Printbeta proudly presents: A heavy duty universal syringe extruder
Because 20ml syringes are much harder to extrude than 10ml syringes, we had to change the tramsission of the gears.
We added another gear to get enough torque.
The prototype is very gigantic but works perfect.
Insted of a metal pulley we tried to use a printed one.
Therefore I modified greg frosts script for pulleys suitable to T5 belts by iteration.
Against all assumtions: The pulley is strong enough to told the torque of the gears.
The additional gear forced us to place the idler on the other side, right above the motor.
It doesn't need to resist much pressure. It is only meant to force the timing belt in place.
If it would be screwed on tight, the pulley would move very hard.
A zip tie on opposite side of the idler pushes the timing belt away from the extruder.
This prevents jamming with the incoming timing belt.
The other side of the belt is clamped by the syringe itself.
Like the richrap model it fits to a standard Prusa x-carriage. It has the same mounting holes as the universal wades extruder
The nozzle is something special:
First tries with a 0.5mm cannula failed because always some larger sugar crystals remain in the sugar powder and block the hollow needle.
The used nozzle is a M5 cap nut with a hole through the cap. For rough prints it's enough just to drill a hole through.
In our case we drilled a 2.5mm hole and cut a M3 thread into it.
To get a small hole without 0.5mm drill we used 8mm hexagon socket M3 grubscrews. The hexagon socket is conical shaped and quite deep.
Simply cut the top with an abrasive wheel and remove material until you can see a little hole.
By removing more you can widen the hole.
Being very careful, you can make tiny holes with a diameter <0.5mm
The screw is now only as long as a M3 nut.
To secure the short M3 screw we used a M3 nut cut into halves.
This way you can screw it into the M5 cap nut and still secure it from dropping out.
The pastruder works just fine. It passed heavy duty tests with frost, hazelnut spread and marzipan without any problems. We used the same motor as for the wades extruder and the torque was high enough.
Here you can see a pictures of our very first extrusion test:
The second test with hazelnut spread was successful using a hollow needle as nozzle.
Since you can not print with high speed we tried to print on something else than our printbed - fixed only by mass inertia:
To get better results, we printed on a butter raft:
The third test was again heavy duty:
Driven by the good printing properties of our very viscous frost, we tried to print marzipan.
The cannula blocked, but the 1.5mm and also 0.8mm nozzle didn't.
The results are awesome:
I hope you enjoyed the perspective of printing you own thread candy :-)
Greetings from the lake constance
BonsaiBrain
