Any body got qu-bd extruder. i have contacted them for selling it without drive gear and extruder block as they are going to need replacement any way.
I have two, spent almost six months trying to make them work, then gave up and switched back to my Makergear drive + J-Head.
At some point I might try using them again with some alternative parts, but most likely I’ll just be recycling the motors for another robot.
They are giving me without extruder block and driver gear with 10 usd discount. Adding mk7 replacement and better drive gear should solve problem.
Can you tell me if you can push filament my hand?
briefly 
It extrude and then it blocks?
Yeah once it gets up to temp you can push it through for a bit, maybe 3cm or so and then it just stops. I thought maybe I was pushing it too fast and the nozzle temp was falling too quickly, etc. but it seems pretty constant regardless of rate.
On the rare occasions where I could get the extruder gear to grab the same thing would happen, the filament would move 1 or 2 cm and then stop.
Like I said I tried for months to make them work, I didn’t fab any alternative parts (because these were for my one and only machine) but I tried everything else I could come up with and even had the extruders replaced.
It’s always possible that I was just doing something wrong, but many of the other owners on their support forums had simular problems, and eventually I decided to try something else, and within a week of getting the parts I was printing again.
Try bdring’s upgrades.
The top of your barrel was probably getting too hot. I haven’t had that problem with mine, but I helped a friend today who was seeing the same behavior. Turning down the motor current so that it did not heat the block helped a lot, and printing my upgrade did the rest. He was also already using a better drive gear than the included one.
I use one with the same configuration on my bot, with the addition that I used a dual-shaft stepper and put the qu-bd drive gear on the other shaft so that I can turn it by hand.
I have one. if it starts extrude but then stops that could be problem with inner hole in stainless steel tube. try to polish it. thats helps for mine.
The qu-bd hotends have a ptfe liner, right? If that gets too hot, it will get too soft and eventually get a kink, making the filament very hard or impossible to push through. Sounds like the problem you’re seeing, @Jason_Gullickson
@Whosa_whatsis i think you are suggesting same upgrades http://www.fabric8r.com/forums/showthread.php?787-My-quick-path-to-successfully-printing-with-PLA turn down current replace gear and add mk7 replacement. they are ready to give me without extruder block and drive gear so i can add these upgrades. are the drive gears used by you available for sale. i am using from http://www.2engineers.com/ works great with my current setup with there motor.
@Thomas_Sanladerer no they don`t
@Karan_Chaphekar we only had a few of the 5mm-bore gears made for our own testing (most are 6mm to fit the geared steppers we use). I’m hoping to get a bunch of them added to our next batch, but for now, we don’t have enough to sell.
@Thomas_Sanladerer the qu-bd hot end is all-metal.
it looks like qu-bd are not reliable.
@Whosa_whatsis Is there anything about it that would rule out polycarbonate printing, then?
@Karan_Chaphekar mine one is morking fine after polishing. I still think that hotend for 34usd is good offer. but of course it doesn`t sute for u if u wish just install and print without any any extra work.
@Thomas_Sanladerer nope. I’ve been meaning to order some to use with it…
@Whosa_whatsis i’d give it a wild guess and say that @Jason_Gullickson 's blockage issues won’t be occurring with PC, then.
Still looking forward to Prusa releasing his hotend - i hope it will somewhat affordable as well.
It’s funny you choose the words “if u wish just install and print” @Taras_Protsiv because that’s almost the exact claim they made on their Kickstarter campaign 
It was a good lesson for me, I had been wrestling with a Makergear hot-end and decided to try something different. I saw the QU-BD pair of extruders for not too much more than the price of just one hot-end and figured I could just buy my way out of my hot-end problems. In the end, I wound up learning a lot about how the whole extruder component of the printer works and while it was frustrating being sidelined for so long, in the end I came away with knowledge and experience which has come in handy since then, even though I gave up on the QU-BD.
I’ll add that part of my frustration came from the company’s attitude toward customers reporting problems. The response was often “there are XXXX people using these extruders and they are working flawlessly” which even if true isn’t very helpful. I was fine accepting that the problems were my fault, but I did all of the troubleshooting they provided to no avail, and when I gave up and went back to the Makergear drive and a new J-head, I was able to get everything working within an hour or so.
At some point I might try and re-use them, I know for sure I’ll be using the motors in another printer project (perhaps as part of a bowden setup) and I’ll probably play with the hot-ends too but I’ve had such good luck with the j-head that unless they are surprisingly cooperative, I’ll probably pick up another j-head or possibly a Prusa if they are available when I get to that point.