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Trouble with moisture

A project log for Recycling Household Plastic for 3D printing

I'm attempting to recycle my household plastic into usable 3D printer filament

Ennis MasseyEnnis Massey 03/01/2019 at 21:390 Comments

So, having done some more looking into recycling PETE, it's become increasingly evident that it requires thorough drying before re-extrusion. PET loves to absorb water from the air, and if it's remelted with this moisture still present, it can significantly effect the strength of the plastic. So, having ordered my FilaStruder and winder, my next project is a small, but effective drying cabinet. I'm planning on using the same technique used in the industrial processing of PET, albeit not as complex. The normal method is what's known as a desiccant wheel dryer (example here), where normal air is blown through one section of the wheel, the desiccant (silica gel or similar) removes the moisture from the air, which is then blown through the chamber containing the PET flakes. This extremely dry air leaches the moisture from the plastic. The now moist air is blown out of the chamber and either reused for some other process or just ejected outside. Once the section of the wheel being used is saturated, the wheel is rotated, a new, dry section is rotated into place, and the wet section is moved to a drying mechanism, which blows extremely hot air, often produced from another process such as compression, through the desiccant, removing the moisture and ejecting it outside. The wheel as such constantly recharges itself, leaving little to no downtime. However, I lack the resources to create such a wheel, so my plan consists of instead using a box of rechargable silica-gel, likely compartmentalised so as to allow for better airflow, which air is blown through, then exiting and moving into another chamber where the flakes are contained. To recharge the desiccant I'd place it in the oven at a high temperature to recharge them. Not as elegant, but it should work. 

I could very much use some assistance from those experienced with this portion of the project if possible. Any assistance would be greatly appreciated

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