Continuous Jamming/Blocking
modfab...@gmail.com
I Backed the Pico project on Indegogo as the extruders looked like perfect replacements for the ones on my CreatBot DH-02. After having them sit around for a year or more, I took the plunge and made up a mounting and ducted cooling setup for them to retrofit them to the printer. I had a boatload of problems from the outset with blocking and jamming. I searched around and discovered people were using 0.7mm retracts on the Pico. This is an almost useless amount of retract but I tried it anyway.
The result was less jamming during printing and I actually got a couple of prints done in ABS. The stringing was awful though and required a lot of cleanup. I then switched to PET-G and all my troubles started again. First off I was in the situation where I have to clear a clog every time I want to start a print job which added time to every setup which is massively irritating when you're doing commercial printing.
Things have progressed to the point now where, regardless of plastic, I preheat the printer, dismantle the hotend to get to the push on fitting above the extruder and unscrew it. I push the filament down into the hotend and extrude a total of around 30-40mm of filament. Then I reassemble everything with the filament in place (praying all the time) once I have it all done I use the motor to extrude some filament down the bowden tube. If the gods are smiling, I get an extrusion but more often i am just getting a jam. If I pull the filament out I have a melted but clubbed end on the filament and by my judgement, the filament is only going down to the beginning of the solid section where the clog has formed due to the temperature differential.
In other extruders, this kind of effect is caused by heat soak but I'm thinking, with the very long melt area in the Pico, the transition area is longer and no matter how much I heat the extruder, within reason, I cant un-block it, especially with the ducted air blowing over the cooling fins. Another massive no-no appears to be reversing the filament at any stage, this will leave behind enough plastic in the transition zone to ensure a blockage.
I don't want to brag but I have printed literally thousands of objects in the time I have been into 3D printing as a hobbyist and now as a business. I REALLY wanted to like the Pico but even if it printed well, I can't deal with the stringing on prints that I'm doing for clients. The issue with the retract distance tells me that the transition zone in the pico is not working. I tried normal retract settings (2mm) and the extruder jammed very consistently.
Temps are very stable on my machine and the hotends reach temperature quickly as I have the correct 24V heaters. Another issue I have with the picos is the fact that the heater is not retained in any way, it really needs a set screw to keep it in place.
Here are some images of my forced cooling setup
http://www.modfab.com.au/wp-content/uploads/2016/01/DuctedFans1.jpg
http://www.modfab.com.au/wp-content/uploads/2016/01/DuctedFans2.jpg
http://www.modfab.com.au/wp-content/uploads/2016/01/DuctedFans3.jpg
Not sure if B3 can offer any advice but I have ordered a set of E3D V6's with an eye to swapping the picos out. I can't have my machine out of action for any length of time.
