@Maker6066: Crispy1 is right, too much moisture is your main problem. They probably didn't store it in a plastic bag with dessicant. If they shipped it in a plastic bag with dessicant, either the dessicant wasn't moisture free to start, or they time in the bag was too little and not soon enough after it was extruded. On top of this, the plastic could be contamintated with garbage, or be poorly processed (and turn otherwise good plastic into garbage). The switch to plastic spools from cardboard ones probably means that they switched plastic extruders. Cardboard does have some drying / dessicant characteristics, but only if it is new. EU extruders primarily use cardboard spools (something to do with EU regulations), but American and Chinese suppliers use mainly plastic spools. You should contact your supplier to let them know the bad results you got. I doubt they even use their own plastic, so feedback is important.
@ ohioplastics: I agree to disagree. Although a normal oven isn't optimal, 70° isn't high enough to cause any health problems. The ABS in most cars is tested to over 90° in extended periods of time, and the internal surfaces of a car are a bigger problem because people (especially children) don't wash there hands everytime they touch everything and before they put them in their mouths to ingest the stuff on their hands. Their is probably 40 lbs of ABS and another 50 lbs of PC/ABS in a normal car (not to mention all the vinyl, rubber, Polypropylene, HDPE, Nylon, etc..). Although plastic coiled on a spool isn't ideal at all, it can be done by increasing the residence time of the plastic in the oven.
The problems with most ovens, is that they aren't rated that low of a temp, they have a direct radiation heating elements, they have very limited air circulation, and their moisture removal is by heat only (unassisted by dessicant). Prior to 30 years ago, most small plastic job shops routinely used plastic drying ovens (without dessicant). The ovens used had no direct radiation, a fan for air circulation, venting for VOCs (which normally was just released into the shop), shelves to stack multiple trays of resin, and decent temp controls. For small prototype runs of injection molded parts, I still use one of these ovens, because it makes no sense to load 200 lbs of resin into a small drying hopper, only to run 10 lbs of parts. For drying resin without dessicant in this type of oven, I normally dry it at about half the molding temp. For ABS molding at 440° (227°C) I dry it at around 212°F (100°C) for 2 to 4 hours. For extruding, you don't need it as dry as much as for injection molding. Injection molding uses far higher injection pressures and even the slightest moisture will lead to surface defects on the plastic parts. Extruding only makes the plastic flow at a much, much lower pressure, so slight moisture isn't a big problem.
In normal industrial plastics manufacturing, most processors use a combination drying hopper / dual bed dessicant dryer /auto loader that runs flawlessly 24/7. They have active blowing of heated, super dry air through the material that is stored in the hopper. I have hoppers that can store up to 2000 lbs of plastic that is actively being dried and continuously used so that the hopper is always loaded with 2000 lbs of plastic. The hopper diameter is 4 ft (1220mm)! which means that there is a minimum of 4 ft of plastic for the moisture to be boiled out / dried out in order for the plastic to meet it's drying residence time. The normal household oven isn't even 4 ft wide, so a little 20cm spool with only 4 cm worth of coil depth, which will easily come up to temp pretty quick.
All that said, the safest and best way to have dry material, is to purchase it from a source known for shipping dry filament!!!!
But,.... although not ideal, if someone is still going to use their household oven to try and dry their plastic here are some basic precautions:
1. Have a separate thermometer in the oven and use it to set the temp. Low temps on the oven temp controls aren't accurate.
2. Shield the plastic from direct radiation of the heating elements using aluminum foil. Put the coil on a cookie sheet (with another cookie sheet on the shelf below it for additional shielding).
3. WATCH THE Thermometer (very easy if you have a glass front door or a long thermistor cable to an LCD). NEVER LEAVE THE OVEN UNATTENDED - EVER!!!
4. Don't exceed 75°C, the oven wasn't designed for drying plastic. Without the additional fan circulating air and ducting to remove outgassing higher temps shouldn't be attempted.
5. Don't do it more than a couple of hours. Additional time isn't going to help.
I thought about posting a generic plan for making a cheap hobbiest filament drying oven, but didn't think there would be enough interest. It would cost about $150-250 to save/dry an occasional 5 lb spool of plastic. The benefit would be that it would improve the consistency of 3d prints by making sure the plastic is always super dry. It would be greatly beneficial to people living in hot humid environments. Basically a very scaled down plastic dryer that is fully automatic.
