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I've made a paste extruder(plunger type), in which a plunger will push the syringe to extrude. Plunger movement is controlled by a stepper motor. In that arrangement, for g-code generation I've used inside dia of syringe as the filament diameter and inside dia of needle as nozzle diameter and to calculate extruder steps per mm, I"ve used the lead of threaded rod which controls the movement of plunger.

But it had several issues like air bubbles and unable to print thick pastes.

Later I've seen this video on Youtube. In which he later changed to a Auger bit mechanism and I've seen WASP LDM already made a successful one.

I'm trying to make one of these. But in this mechanism how to calculate the steps per mm for Extruder?

Is it same as the lead of Auger bit?? What about the filament diameter in slic3r settings?? Anyone have any idea??

Thanks

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To be precise we shall have all physical parameters of extruded material to calculate extrusion parameters. In that case, my approach will be to use try and check approach, as that will give a systematic problem-solving.

To set the steps/mm, we will focus only on the measured length after extrusion.

  1. let's set the extrusion length to 10 cm, extrude and check the extruded length.
  2. if we measure a different value, then we can use a formula to fix that newStepsPermm = currentStepsPermm*(requestedExtrusionLength / measuredLength ) That need to be repeated as long as we will get requested length and this is a standard calibration procedure.

The minimal layer thickness will be connected with the way how the pasta behaves (how it is sticky, water amount etc) - so for that there is a need for a patience. My approach will be to create a sheet where I would store the ingredients ratio and a note about extruded material behavior.

To remove bubbles in the extruded material - the syringe shall be filled with caution and continuously to avoid material stacking as that produces air pockets.


Addon: To calibrate clay you can print a single line using manually prepared gcode. Amount of extruded material could be estimated by weighting conteiner/bottle or extruded material and that will give you an orientation of flow like gramms/mm or mm3/mm.

let's try this:

  1. we have our steps//mm untouched
  2. try to set printing speed for single line, so the clay will looks nice
  3. if we have over/under extrusion - change feedrate by 5% up/down.
  4. when the extrusion looks ok, then note all printed parameters

so if we end-up with printing speed 10mm/s and feedrate 140%, then we know that the steps/mm need to be multiplied by feedrate factor (1.4 in this case).

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    $\begingroup$ In short, "always calibrate." Good plan. $\endgroup$ – Carl Witthoft May 3 '18 at 14:51
  • $\begingroup$ In case of a filament exturder I could tlll the printer to extrude certain mm of filament, and by taking the length of extruded material i could calibrate e_steps. But hoe could I measure the length of clay??? The advantage of auger paste extruder is, it wont have air bubble problems. But I'm confused about the filament diameter calculations??? $\endgroup$ – Athul May 4 '18 at 9:14
  • $\begingroup$ please see edit @Athul $\endgroup$ – profesor79 May 4 '18 at 9:46
  • $\begingroup$ How could I know if I am under/over extruding. For filament extrusion I can Check this by measuring extrusion width for a single perimeter print and comparing it with the extrusion width in that I've given in slic3r. Also you've any idea about filament diameter setting?? If I couldn't find a staring point in that everything would mess up, inclusing extrusion $\endgroup$ – Athul May 4 '18 at 10:22
  • $\begingroup$ the main thing is that the process needs to be started and then observation will derive calculations, as there is to many unknown parameters. as you provided a valid comparison example - then same approach need to be used with clay. Stabilise one factor, then next one and so on up to the point that you will be able set all things. $\endgroup$ – profesor79 May 4 '18 at 10:35

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