One does not necessarily need an oven to cause such a catostrophe.
This was my first attempt at pushing the DIY limits of bed drying. I had weeks of testing and a lot of great results at 70c. So I got a little cocky and decided, well… if 70c is good, 100c must be better…right?
This is what happens to regular plastic filament spool when in direct contact with a 100c bed for 8 hours.
BTW: This DIY setup proves that you don’t need an expensive drying machine, a $7 USB fan and filament box works just as well albeit much slower and you tie up your printer for a few hours. But if you’re heading to bed anyway, what difference does it make? Just remember that your spool may not tolerate the higher temps.
The key to any drying whether it’s oven or anything is to make sure air is always circulating or the spool is always moving so that hot spots don’t build up. The thing is, I know this fact by heart because my other hobby, system building, everyone knows to keep air flowing over hot components if you want to achieve high reliability and lessen component failure during overclocking. But did I listen to the little Angel:angel: on my right shoulder? No… instead I listened to the Devil 
on my other shoulder that said… go ahead… what could go wrong? 
My second design borrowed from two different designs and I added a small fan with a downspout into a filament stand with air outlets. It didn’t need much to make 100c bed temps to work very well. All that was needed was that small stand to raise the spool off of direct contact with the bed and vent holes out the bottom for airflow to circulate inside the PETG hatbox.
