Latest Issue: Extruder Not Extruding

We let a print run all night and woke up to a giant mass of angel hair ABS. After a doctor's visit, some errands, and lunch, my husband decided that he really needed to try his hand out at printing some female stormtroopers. This all resulted in nothing. No, really, nothing. Prusa, our Makerfarm 8" Prusa i3, was refusing to extrude. There are a variety of reasons why this can happen, so let's explore some of those reasons:

• Tension on the filament clamp spring(s) too strong
• Tension on the filament clamp spring(s) too weak
• Tension on the filament itself (ie. Not unwinding/feeding freely)
• Extruder motor malfunction
• Hotend not hot enough
• Hotend too hot

Each of these situations can and will cause issues with extrusion, however we've missed one insidious possible cause of error: the hotend nozzle being too close to the print bed. Betcha didn't think of that one! The reason why this is such a pain in the ass is because with the way I troubleshoot, I generally go through the above checklist first before checking the nozzle to bed distance. This is a problem is because it doesn't allow the filament to freely escape the nozzle, which results in the hobbed bolt chewing up the filament, the nozzle grinding the print bed, and a lack of extrusion. The solution to this problem is to recalibrate your Z-stop and to make sure your print bed and X-carriage are level. If you've already calibrated everything else, and you are definitely too close to the print bed, you more than likely only need to recalibrate the Z-stop.