bdring wrote:I worry how these guys can make any money. They only got about $80k from the Kickstarter. It sounds like they have at least 3-4 people working there for 4-5 months with expensive machines and materials.
I think they're all young. They can eat ramen. On Saturday, after shipping a thousand extruders that week, they can celebrate with a trip to Taco Bell.
I haven't installed my QU-BD extruders yet, and I suspect a lot of people haven't, which is why we aren't seeing a lot of online QU-BD extruder news yet.
I've read all of the real world reports that I could find from actual users, mostly at the Fabric8r forum, and based on the problems reported, I'd dare to recommend a few possible suggestions:
1) Opposite the filament drive gear, use a spring loaded bearing, possibly with teeth of its own to grip the filament. Less friction in the drive system. More tolerant of changes in filament diameter.
2) Increase the mass of the hot end aluminum block. There are reports of filament that extrudes fine for a few inches before the filament jams and the gear strips out the filament and the gear is plugged with filament chips. I think the aluminum block's low thermal mass is capable of melting only a small amount of filament before the temperature of the aluminum block drops to below the melting point of the filament. Also contributing to this problem is....
3) Drill a hole and put the thermistor as close to the filament as possible, opposite the heater. The thermistor is currently taped to the outside of the aluminum block on the hot end. This design bothered me as soon as I saw it. There is too much lag time in responding to dropping temperature in the hot end core when the heat is used to melt the filament. It's too slow to respond, as the controller is trying to keep the outside of the aluminum block at a constant temperature, when it should be trying to keep the filament melt zone at a constant temperature. You need to measure what you're trying to control.
4) It sounds like there may be too much heat creeping up from the hot end and possibly softening the filament under the drive gear. If so, add some insulation (preferably with a radiative reflective barrier) and/or increase the spacing between the hot end and the drive section. Take a design tip from the McDLT. The hot side stays hot and the cool side stays cool.
http://youtu.be/UTSdUOC8KacBefore the QU-BD extruder shipped, QU-BD published a picture showing an orange piece of filament with very deep gear tooth embossing, to allay any concerns of stripped filament. I wondered if those deep valleys and ridges would result in variations in the amount of material that was extruded. I'm still not certain about that issue.
On the plus side, this is an open source design. If there are problems, they're fixable! I bet even the most serious problems that could exist will be cheap and easy to fix. I'm a little bit disappointed that my unreasonable expectations of hundreds of giddy 3D printing enthusiasts extolling QU-BD extruding nirvana haven't immediately been realized, but the installed base immediately reached critical mass so I'm confident that there will be improvements and optimizations over the next month or so. Hopefully, that will coincide with me wrapping up other projects and getting back to my 3D printers.