Problem pulling in filament

Hi Folks

I have a Prusa i3 Box frame, which has been printing pretty well without much maintenance. Recently my prints started to get a bit stringy and perhaps under-extruded so I bumped up the extrusion multiplier and all was well. However, it's got to the point now where I started to investigate what was wrong. Without an extrusion modifier on, I'm only using about 60mm of filament when requesting 100mm. I've been recalibrating by e-steps, but I can't seem to get close to the value I need to hit requested == actual.

I've been looking closely at what goes on, and I've discovered that my filament doesn't seem to be getting ingested into the extruder smoothly. My first thought was that my nozzle must be blocked, so I've just replaced it with a brand new one. However, I can still see that the filament still isn't been taken down as I'd expect it to be. I've taken a couple of vids which i've uploaded to Youtube to show you what I mean.

[www.youtube.com]

and

[www.youtube.com]

however, if you look at what is coming out of the hotend you can see:

[www.youtube.com]

it looks fine to me, and indeed I did a 2 1/2 hour print last night that I was fairly happy with the quality of, despite knowing my e-steps are way out of whack. I've suspected my hobbed bolt might now be gripping, but it looks fine, although needs a bit of a clean now and then. The hotend and barrel have been stripped down and the nozzle replaced and the barrel cleaned.

My principle concern is that I can't seem to get my e-steps calibrated. I used to run a figure of 696.60 but now even as high as 1000, I'm still not getting more than 60-70% of the extrusion length that I request. Does anyone have any ideas what might be going on here?

notes:

- Printing with 3mm PLA at 185oC
- Prusa i3 Box frame
- 0.35mm Nozzle
- RAMPS 1.4 board
- Latest Marlin F/W (as of last week)
- Pronterface for control. Repiter for big print jobs.
- Slic3r (not that it's relevant in this case)

Thanks!
Jim

Edited 1 time(s). Last edit at 04/21/2015 05:10AM by Jimthree.

Sorry cant see your video seems to be private.

Sorry if im misunderstanding how you are calculating your e-steps for the extruder.

You say what goes in doesnt match what comes out?
When setting your e steps you are only concerned with what goes in to the extruder.
You measure how much filament goes in the top and then compare that to what you expected to go in the top and then adjust the e-steps.
You should do this without the hot end in place.

Again sorry if i misunderstood and you are doing the e-step calculation correctly.
It sounded from your description you were comparing what went in to the extruder with what came out of your hot end.

Gordon

Thanks for pointing that out! I've made the video public now.

No, it's OK, I've calibrated E-steps before, I think i've got a pretty good handle on the process. The problem is with the Filament being fed into the extruder, it's getting blocked or slipping somewhere, and I can't for the life of me work out where! Have a look at the videos, it should help to explain what I'm seeing.

cheers
Jim