The PastEtruder is born

In week 17 we had to write a proposal for our final projects.
You can find it here: Week 17

The idea was to Build a Heated, Food-Save, high-precision extruder für paste-materials.

If you warnt to print Paste materials like chocolate or clay there arme some standard extruders in the market or on Open-Source-projects. The Most of them uses a syringe that is actuated by compressed air.

A good example for this is the "FrosTruder" from makerbot:
LINK

The advantage is, that you can easily swap the syringe for a new one if you want to change the material or you want it food-save.
The disadvantages are:

you need compressed air

the pressure in the syringe is not constant and not measured

the "spring-effect" of the material and the compressed air makes it almost impossible to print very precise

If you google a little about industrial extruder, you find very quick that those extruder a a often build with a Archimedes screw that extrudes the material thru a nozzle. The big advantage of this is the constant material flow. And you can easily control the amount of material extruded by setup the speed of the screw.

Beside this, I haven't found a heated extruder. So you are limited to materials that are paste or liquid by normal temperatures. But prints with this materials are not very stable in normal temperatures by nature...

So the idea was born to combine the two extruder-types and heat the hole system to a defined temperature: the PastEtruder!

The hole construction is divided into two stages:
Stage 1 consists of a syringe in a heated aluminum case. The syringe is compressed by a geared dc-motor. The motor-current is measured and so the force on the syringe can be controlled. The pressed out material goes in the second stage.
Stage 2 consists of a screw-extruder also in a heated aluminum-case.
The screw is actuated by a stepper motor to make very fine extrusions, pressed thru a 2mm nozzle from an old 3D-Printer.

Both stages are controlled by some self made-electronics. Here you can set up the temperatures of the two stages (each stage has its own temp), load and unload the material and setup the motor-current of stage 2.

Furthermore the electronic has inputs for a step and a direction signal. This way you can connect the extruder to your normal 3D-printer and it acts like a normal extruder.

To have an overview about my progress and the single steps i planed several phases:

Build the first extruder

Build the second extruder

Build the electronics

Write the code

Throw all togheter

Test it

This plan was good, but when you running out of time it can happen, that you make multiple phases at the same time ;)

I´ve written the documentation in the same style like the phases. That way you can maybe easier understand the whole project ;)