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Could use some suggestions ... feed issues sad smiley

Posted by zomie 
Could use some suggestions ... feed issues sad smiley
October 27, 2011 07:17PM
I put together my Prusa Mendel but I am having some bad feed issues. I am trying to use 1.75mm filament, and have a J head IV setup for that. The only catch is the wades extruder has wider holes for 3mm filament but I don't think that is the issue.

If I run 100mm through the extruder it will slow down and stop then the bolt will grind out filament and won't feed any more. I then have to take apart the extruder and pull out all of the shredded pieces and abs powder sad smiley

I tried to change the tension and upped the temp. of the hotend through a range from 230 - 260. It just continues to eat it sad smiley

Are my feed rates to high? Does anyone have any other suggestions?

More data:
Ramps 1.2
Sprinter Firmware
Pronterface Host
Nozzle is .5mm
Attachments:
open | download - Configuration.h (7.7 KB)
Re: Could use some suggestions ... feed issues sad smiley
October 27, 2011 07:25PM
The nozzle size and filament size has everything to do with it.
The pressure of the filament pushing on the hot end pushes extruder material out of the end and thus your printing.
the pressure creates a "buffer" as i call it.
And that buffer melts incoming filament, while also pushing out the hot end.
With out that pressure the filament runs right into the end of the hot end, and cant melt fast enough.
Basically the 3mm filament heats up beginning deep inside the nozzle.
The 1.75 mm filament isnt and can get to the hot end directly = not good.
thus stripping out on the filament driver.
No buffer, no print.
Just me 2cents
-Erik
Re: Could use some suggestions ... feed issues sad smiley
October 27, 2011 07:44PM
Quote

Are my feed rates to high? Does anyone have any other suggestions?

I don't know if anyone can really answer this question since you didn't state how fast you were extruding. smiling smiley We also don't know how good your hobbed bolt is. Since you mention that you're using a standard Wade extruder with 3 mm holes, it probably also mean that you're using a hobbed bolt that was designed for 3 mm and not 1.75 mm feed. I would guess that it's not going to be as good with a 1.75 since it won't have as good surface contact with it.
Re: Could use some suggestions ... feed issues sad smiley
October 27, 2011 11:21PM
Try setting the temperature between 205'C and 220'C. Don't go higher.

When the heater block first reaches melt temperature, the thermal barrier is much lower, but after some time, the temperature creeps closer and closer up. If you run the extruder far beyond the melting threshold, it enables the barrier to also exceed the melting point and thus jams the filament.

This might explain why you are able to extrude 100mm before the jam. I recommend that you find the the threshold of your hot end, and don't go too much higher.
Re: Could use some suggestions ... feed issues sad smiley
October 27, 2011 11:59PM
Hmm interesting ideas ...

I didnt' realize the hobbed bolts come in different sizes? I figured it was all about the pressure between the bearing and bolt. It is certainly strong enough to tear apart the filament and strip it.

Yeah I apologize. I have the feedrate set in Pronterface at 300mm/min which I thought was pretty standard.

It doesn't actually make it all the way through 100mm. I meant to say that it will tear into the filament about 75mm in or so. It is just a test run and fails.
Re: Could use some suggestions ... feed issues sad smiley
October 28, 2011 12:04AM
Try 100mm/min and see if it doesn't work better.
Remember this is filament in not extruded filament out.


Bob Morrison
W├Ârth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
Re: Could use some suggestions ... feed issues sad smiley
October 28, 2011 03:07AM
I think you guys may be on to something about the hobbed bolt. It is actually pulsing on extrusion. It will pull 1/3 of the time and then it won't move. I am guessing the bolt has a flat spot in it. My huxley just provides constant force on the filament. I am thinking that as it is pulsing it provides extra pressure striping the filament.

I am going to print out a new wades accessible extruder and order a new hobbed bolt and just be done with the damn thing.
Re: Could use some suggestions ... feed issues sad smiley
October 28, 2011 04:41AM
I can only extrude at most 50mm@300mm/min (PLA@160C) from pronterface because of the aforementioned buffer. I can still print fine at 100mm/s (40mm/s perimeter), because the small retracting and head movements during printing gives the hot end time to build up the buffer.

If it's pulsating when extruding, check the the hobbed bolt for clogged teeth.


--
-Nudel
Blog with RepRap Comic
Re: Could use some suggestions ... feed issues sad smiley
October 30, 2011 08:51AM
A good hobbed bolt will get you far but I would look at temp. I have noticed that heat will build up and cause transport issues in decent size prints. My J end came with the aluminum heat dissipaters and if I put a fan on it the issues go away. If you mismatched filament and tube sizes you may be more susceptible to flexing and a temperature issue. When I change filament I can easily see how the PLA has swelled near the end.
Re: Could use some suggestions ... feed issues sad smiley
October 30, 2011 09:43AM
I think the hobbing issue might not have been understood as what it was meant for. The dent created by the taper in the bolt for a 3mm filament, could be pretty big, and could eat the entire 1.75mm inside it, and roller bearing could get more or less stopped by the bolt itself preventing it to apply enough pressure. Maybe something like that. If thats the case, no way to fix it other than either using either 3mm filament or get a hobbed bolt with a smaller dent in it.
Re: Could use some suggestions ... feed issues sad smiley
October 31, 2011 05:02PM
Hi Zomie,
That J Head IV hot end you're using... Is this the what you have (see link) [reprap.org]
The wiki spec says it has a 1/8" internal diameter PTFE sleve, within the PEEK insulator. That's designed to take a 3mm filament. If that's what you have then feeding a 1.75mm filament into it could be the problem. I don't think there is a problem with the hobbed bolt, (even if it's designed for 3mm and it's feeding 1.75mm. My hobbed bolt has fed both filament sizes over time. If cut it originally for 3mm)

Do you have any 3mm filament? Have you tried 3mm in your rig? Might be worth a go, if you could get even a small sample.

Can you verify the internal diameter of the PTFE liner within the PEEK?

Can you post a pict of some jammed filament you have removed? That will tell a lot of the nature of the jam.
Does the jammed filament pull back out?

In my experience, once filament jams in the tube it doesn't matter how good the feed mechanism is. If it's shreading plastic, the problem isn't with the feeder. It's just pointing to a problem further down.

Let us know how it goes.
Regards,
NumberSix


[numbersixreprap.blogspot.com]
Re: Could use some suggestions ... feed issues sad smiley
November 01, 2011 08:58AM
Hello,

I am sorry I didn't see this posting earlier.

Do you have the adapted liner for the 1.75mm filament? If you don't that will be a major problem as the filament will not have proper support and may not be able to build up enough pressure to extrude properly. If the liner is red, it will be the 3mm liner and have a hollow metal set-screw for a liner retainer. The white liners are for 1.75mm and will have a tan PEEK liner retainer, on the cold end, that the filament passes through.

Also, I noticed that you mentioned setting your temperature up to 260 degrees C. PEEK tends to soften somewhere around 250 degrees C. So, there exists a possibility that you will melt your nozzle holder.

Regards,

Brian
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