destroyer2012

Here is my opinion on this, as a user of UM1 for 2 yr and having modified the heck out of my extruder drive to get it to work reliably. Take it or leave it obviously. I think the knurled thing has to go. I was never able to get a good extrusion until i made my own hobbed bolt with sharp teeth and a larger diameter (using a metal "spacer" as the blank like the makerbot mk6 drive gear) I think the 'lack of space' for the spring to travel is actually a good idea. What this does is it creates a stopping point for the travel of the sprung idler. This means that if the drive grinds the filament because of too much pressure needed to extrude, it does not go on ahead eating away at the filament (as the spring idler presses it in towards the drive gear). Also consider the problem of force application. With a totally sprung idler (no stop) the spring is squeezing the filament towards the drive gear, in a direction it totally does not need to. With either a fixed idler (like the first wade's extruder) or a stopped idler, the pressure stops after teeth have been imprinted on the filament, because after that point you don't need to press on the filament even harder. Just another point on this: we don't need the drive gears to accomodate all sizes of filament. The bowden tube already jams if the filament is the wrong size. That is why a minimum travel of the idler wheel should be fine (in fact my extruder currently has absolutely no travel and it works great with ABS and PLA) I think the extruder needs a gear reduction. This allows you to use larger diameter drive gears which I think are absolutely necessary to have enough grip. The goal is to have the extruder motor start skipping before the filament shreds or the hot end gets destroyed. finally, other aspects of the filament drive subsystem are important to consider. For example, the length and ID of the bowden tube, the hot end itself (modified to minimize necessary extrusion pressure?), and of course the diameter of the filament you are feeding into the machine (forget it if the filament ever goes near 2.99-3.01mm). If any of those other things don't fit the specification then nothing you do to the pinch wheels will make a difference.

Alternatively, just swap the axis direction in the firmware. I have done a similar thing in that I have enclosed my ultimaker completely using cut up oven bags to keep the warmth from my heated platform in. I think it definately helps, at least with PLA. I think the fan is still important because what you want is to quickly cool the plastic down to the ambient temperature inside the chamber. Commercial printers do this by basically being a convection oven. So you could keep the fan around the nozzle or mount a big fan on the bottom that blows all around the inside. You definitely don't want your plastic to stay molten after it gets extruded or else it will sag/move around after being printed.

I read somewhere that the belts we are using are not intended for precise back and forth motion, only precise motion in one direction. Switching to belts with a more curved (and maybe slightly bigger) tooth profile like reprap does would probably be one good step to take. The curved tooth profile ensures that the teeth cannot slide on the gear pulley. THe next thing we would need is a good way to tension the belts, ideally with some kind of spring to literally apply tension to the belt (as opposed to the "stretch the belt till it's taut" method). This is the way all commercial 2d printers do it, and it allows the belt to be relieved of stress; that means no belt stretching over time.

Thanks for taking the time to relate your experience! I think this will be very helpful to a lot of people

Can you be more specific? How is it more difficult to work with? What did you have to do differently once you "got the hang of it"?

Whoa awesome! Can we get some videos of this script in action?? Makerbot made some seriously awesome time-lapse footage of an ABP-equipped thingomatic printing out all the mendel parts one by one. Never mind that the ABP never worked for anyone else, it was a pretty awesome vid and I bet you'd get a lot of customers when they see that. Maybe you can put a little printed bulldozer on the side of the print head so the robots are removed more successfully?

NOW if only we had the automated build platform! Then it would really be a factory wall. How many robots do you guys print at once on one of those UMs? I figure you could fit at least nine on each platform, maybe more. What is that box-like object sitting on the lower right blue UM in that picture?

My general experience with ABS is just don't worry about cooling. When I print, I only turn the fan on for making perimeters, and even then only at half speed. I think the chamber helps a bit but it's really not hot enough (since I don't have a dedicated chamber heater/ convection fan) to prevent all warp, so you should be OK with a heated bed + no cooling on the part. I'm glad to hear those parts are solid! I wonder then if you can replicate the 2BEIGH3 results in terms of print flexibility/solidity http://www.instructables.com/id/Combina ... -Overview/ He doesn't even use a heated platform, and he also uses blue tape to make the nylon stick. Definately going to try to make a v3 nozzle myself.

Those prints look pretty good I'd say! Are they flexible? How good is the layer adhesion? Can you make a replacement extruder gear with this stuff? If you are experiencing poor layer adhesion perhaps the answer is a higher extrusion temperature? Are you using a fan when extruding this? I know when I first started printing in ABS I was cooling it too much and all my parts came out brittle, so I increased the extrusion temp (240 now!) and turned down the fan and now my parts come out (dare I say) perfectly.

SWEET CITY! Don't forget to put pictures of the items printed in nylon! Where did you get your nylon filament/feedstock?

I don't think that professional 3d printers use valves, I think cooling is the way to go. A low thermal mass hot end with a thermal break and an active cold end would eliminate oozing. Just turn the extruder down 20 degrees when not extruding, and pull the filament up to the thermal break.

You could try to drill out the stainless steel part in steps. First, use a #31 drill (3.041 mm), then 1/8" drill (3.175 mm), which should be plenty big for extrusion. Sure it won't be as smooth as a reamer but close enough? It's already got a hole in it so alignment shouldn't be too much of a problem. You might need some carbide drills though. Plus, you should only have to drill out the part of the barrel where the filament is still cold. Once it gets hot and liquid it will flow into a smaller opening. So maybe drilling only one cm deep with a 1/8" drill into the stainless steel part is more doable? Another alternative is to drill out a brass bolt to replace the broken V2 heater barrel, and then try to make a thermal break by filing down the threads in the right place. I might try to drill out some stainless steel bolts just to see how insane it is... MAY be doable at home? I hope so because this hot end seems like a really good idea

Awesome! I have two questions though: 1) What exactly is your setup? Do you have the bowden tube float above the metal nozzle's cold end? Are you saying it is cool enough now to just insert the filament up top and not have it form a plug? 2) How fast is "max speed"? What mm/min are you feeding filament to the extruder? So it looks like all we need is an aluminum block to screw on above the heater block, and a heatsink+fan combo to cool it down? That's way better than water cooling, seems like I could make it with only a drill press too. Sweet.

Adrian bowyer made a valve on his extruder back in 2008. See here http://blog.reprap.org/2008/08/extruder-valve.html The conclusion was, it's too hard to build it, and the benefits were later found to be attainable via retraction. Besides the valve hole makes it leak from two places instead of one. Ultimaker retraction is possible, we just need a better extruder with a bigger diameter hobbed bolt for better grip.

Whoa you are turning the whole head assembly into aluminum? That's crazy! Isn't it going to become really heavy now? I thought you were changing only the hot end. Why is it necessary to change the entire head to metal if you are water cooling the hot end anyway?