Issues with bowden feed

Hi all,

I built my i3 a few months ago - I had it running using gregs extruder and was printing pretty good parts. I then decided to switch over to a bowden feed as my E3D supported it and having read a few articles it seemed like a decent upgrade - certainly makes sense that the x-carriage would benefit from not lugging a stepper motor around.

Anyhow - I printed the required parts and have put it all together but I cannot get a good print out of it. I switched back from ABS to PLA as I'd had much better and more consistent results using PLA with gregs extruder plus I don't mind wasting PLA while setting up. I ran the suggested calibration e.g. adjusting the E steps until I get the requested length of filament fed through the bowden tube.

The problem I have is that it seems like it's not feeding enough filament through the hotend. I don't think the nozzle is blocked (when switching back to PLA I burnt out any remaining ABS, cleaned with a wire and soaked in Acetone for half an hour). I have tried temporarily increasing the E-steps by a small amount (+0.5%) but it made no difference at all. I could increase a lot more but that seems to defeat the point of having calculated the E steps. At the moment the first layer seems to go down 'ok' but subsequent layers are struggling. The first layer is set to 200% in slic3r.

I haven't adjusted my stepper driver at all - I'm not sure that it's required? It doesn't get hot/warm so I figured no need but I guess it might not be pushing the filament with enough torque?







Any ideas on what I should do? It's very frustrating :/

It's best to set the e steps while extruding through the nozzle and printing temps. You'll know when it's skipping steps, you can hear it clearly. Make sure the filament isn't slipping. The bowden tube shouldn't be too long. 50-55 cm should be long enough.
Also measure the filament diameter and set the slicer accordingly. Set the extrusion multiplier to 1 for now. Slow the print down to 30mm/s and set retraction speed to 60mm/s and retraction length 5mm. If all works you can ramp up the speed.

Well I attempted to calculate the E-steps a few times, while extruding, I found that I was forever going back and forwards so it must have been slipping. I removed the mk7 gear and found it hardly has any bite on the filament not even with quite a lot of pressure. I tried to clean out with a wire brush but I don't think it's clogged up.

Have had to put the direct extruder back in to action - at least I can print now. I'm not sure whether it's worth buying a new MK7 gear or should I look for a different bowden extruder design - perhaps using a bolt like the direct extruder.

What design were you using? I use an adapted wades extruder with a hobbed theaded rod I bought from reprapworld. It works very well. I don't have any experience with direct drives so can't comment on that.

I was using this design (http://www.thingiverse.com/thing:767951). The mk7 drive gear was not really sharp at all - nothing like the hobbed bolt which came with my 'Gregs' extruder. I'm going to order another hobbed bolt and build a geared bowden extruder.