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Apr 30, 2019, 12:35 PM
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Filament Fridge ?


Gentlemen :

Those of us who use 3D printers for making model parts know that most of the plastic filaments we use pick up moisture from the air . (Agroscopic) Filament manufacturers go to great lengths in their packaging to combat this with the inclusion of a small bag of dessicant and vacuum sealing .

One of my mates was throwing out a small wine cooler fridge as it had a busted door bracket and would not seal properly . I rescued this unit from going off to the landfill and quickly repaired it . Plugged the cooler / fridge into the mains to see that it worked . This cooler uses a solid state PELTIER juction module as its cooling element and has a heatsink and fan to aid the heat transfer process . Knowing that the Peltier junction can transfer heat form its surfaces in either direction by reversing its power connection polarity , immediately suggested an obvious mod to make it either cool or heat the interior . A simple DPST relay of a 12 volt DC coil voltage was chosen for this quick mod . The relay was wired up using 2 sets of contacts and was placed into the circuit where the main power supply feeds the Peltier element . A toggle switch is used to energize this relay for the heating mode . I tested the cooler's operation with this mod in both modes to find that the interior temp reached over 40 degrees C after only an hour in the heating mode .

An overtemp safety problem occured to me which should be addressed . Not wanting to fool around with the existing cooling thermostat circuitry , I decided to add a temperature controlled relay (Banggood.com $6 US) that had a SPST set of contacts that could be used . This relay's temp sensor was mounted inside the cabinet to sense the interior temperature . The placement of this heating thermostat had me doing some head scratching for awhile as its output had only one set of switched contacts . I inserted this switch within the newly added mode relay circuit in line with the toggle switch which selects the modes themselves . As a default with no current energizing the mode relay , the fridge operates per its original design in the cooling mode . In short , the fridge operates in both modes with the cooling temp selected by the original stat while the heating mode is selected by the added on stat / relay . I use heating temp setpoints of 30C for PLA and 40C for ABS filaments .

I tend to save the dessicant from the filament rolls as it can be dried and reused . Filament drying strings filled with dessicant were made from some cheap plastic braid wiring loom that I us for wiring up my quadcopters . These strings were simple attached to the interior drying rack and work well .

This salvage project turned out really well and does keep my 3D filaments free of moisture .

Regards to all of my readers and my Aussie mates . Special shout out to my mates of the CMAC in Cairns , Australia . Cheers !
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Apr 30, 2019, 08:55 PM
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I use Jiploc freezer bags. It works.
Apr 30, 2019, 11:48 PM
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@Bare :

I know what you mean brother . I used to use them all the time but I had this salvage project kicking around the shop for quite awhile . The fridge doubles as a storage cabinet as welll and just solves a bunch of problems in the shop . The deal does work though ! Holds the temps really nice for a $10 investment . Prints are smoother with no 'zits' now .

Rock on !


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