Hot Reels, pt.2

1. As I mentioned in my last post, I got a well-regarded filament drier and have been trying it out on a roll of flex-PLA.
   As of late this morning, the humidity reading is a resolute 35% and will not go lower.
   
   

   

   
   Now, I trust the cheap plastic-film hygrometer sensor not at all. If you do those right you can get them into the ±15% range. The metrology field says the claims from the sensor makers are bushwa. A hand-calibrated aneroid hygrometer gets you down to 5%, and a laboratory instrument (not for field use) called a chilled-mirror hygrometer gets you down to 1%. When compared to things we can measure down to one-gazillionth, such as voltage, or length, or time, that is absolute canine feces.
   
   RH is the worst measurement in the field of PMEL/metrology- we are terrible at it.

    

   Anyway, we shall see. I've got one of my "silica gel hamsters" in there with the reel but it's not clear to me that it's helping. It is now nearing the end of its 2nd 12 hour run so things aren't looking good for this reel. Need to bag it up with silica gel and run the unit with nothing in it, and then with a bag of silica gel, for a sanity check.
   
   I wonder if this reel is just a lost cause or if the ambient humidity is just too damn high.
   
   I don't have a hygrometer, but I suspect the latter.

    

   I need to make more hamsters. That sounds weird.
   
   

   1. On the plus side, the dryer turns out to be very quiet, quieter than the printer running a print with the tent closed up, which is pretty quiet.

       

      If the issue is the ambient humidity being too high, I might get an aquarium pump and build a desiccant cartridge and just pump dried air into the drier via its vent port.
      
      It just overheated on me. Which means it stops running until it has cooled off enough, then it starts up again. It's a soft limit, apparently, rather than a TCB, because the control panel stays lit. This heat issue was something several reviewers observed. It is not the interior air temp that is too high, it's the PTC heater housing in the base. When I put my hand on the bottom, it was too hot to hold it there. This has also been observed. The unit comes with no feet to speak of, so no air gets to the bottom panel at all. Good thing it's sitting on a steel-cased UPS which provides a partial heat sink.

       

      

      Freya So I'll add some stick-on rubber feet (I like 3M Bump-On™ bumper-feets because they use everlasting TPU and good adhesive) on the bottom, as soon as new ones arrive; I ran out. 0.4in height tho - I hope that's enough. If not, I'll either swap 'em for higher feet or...
      
      If I get really ambitious, I may fab a new bottom panel out of aluminum instead of plastic. If I get really crazy (like it becomes a problem when drying PETG at 70ºC or whatever) I will consider adding a real heat sink.
      
      I'm not too bent out of shape; everybody gets thermal design wrong, and I knew about this issue going in, and most units from different vendors have similar issues.
      
       And so it goes...
      
      

       ~≈{👁}≈~