Cetus Extruder V2

Using PETG and Thermodynamics

I admit that PETG (Polyethylene terephthalate glycol) is one of my favorite FDM printing filaments.

My only issues using it has been from extruder heat control. Those issues have been due to poor dynamic thermal conductance within the heating system. Nothing to do with the PETG material.

The solution for me has been to use a thermal compound on the threads of the extrusion barrel when rebuilding an extruder. Threads can be high resistance areas for heat transfer.

PETG does like to have a very consistent and constant dynamic heat flow and close temperature control. 

The Tiertime Cetus V2 extruder has a design flaw with the extruder barrel. In a stock installation there is a retainer plate on the barrel hex to prevent it from turning when replacing the screw-on nozzle. The index action of the plate prevents full tightening the barrel within the heat block. The threads loosely float within their thread clearance allowance and extremely poor dynamic heat transfer becomes an issue.

I now remove the retainer plate. Apply a high temperature anti-seize compound. Then fully tighten the barrel threads and the barrel head against the heat block. Heat transfer problem solved.

I do not apply compound to the nozzle threads as I don’t want to introduce the material into the interior of the nozzle. The nozzle never “floats” loose-threaded, so heat flow is typically not an issue in this thread connection.

I now produce excellent PETG prints with an extruder heat system that operates as intended.

I believe this issue is the common problem with many extruders. The blame is usually called a “plugged nozzle”. But plugged nozzles are almost never an issue for me. 

Unless one is working within a very dirty environment with airborne dust and zero house-keeping, external debris is not a 3D print issue. I have consumed well over 200 spools of filament and never had contaminated material. Never had an other than a self-inflicted tangle. Both are non-issues for me.

Thermodynamics is a science of heat flow and transfer. Not a common field of knowledge for everyone. But we experience it constantly every minute of our lives. Heat is the basis of all energy.

It also helps make good PETG prints.

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