RepRapPro Mendel HotEnd/Extruder Issues

Just finished the main build of my RRP Mendel and having serious issues with the hot end. I have followed the instructions to the letter and now when it prints it will sometimes print my test piece fine, but more often it fails.

The problem is with the hotend. I have checked everything is tight (heating it and tightening it more as instructed). It is up to temperature but will simply stop working. A print will start to work and then it is like something has jammed the hotend. I am at a loss and the end of my patience with it all!

What I don't understand is that this is a very similar system to my eMaker Huxley, which works great, but has been changed with a PTFE insert for the 'neck' connector and screw fittings for the bowden tube. Some of the things I have thought it may be, the screw ends consruct the end of the tube causing excess friction - i opened that up with a 2mm drill bit as the instructions say and there seems to be little resistance to the passage of the filament. The bowden tube seems to be pinched as it goes though the X axis shuttle - again I reamed that out a little to reduce the pressure on it. I noticed that when I manually fed the filament in as it went past the hot end side tube connector it seemed to get stuck and not go in any farther. Also the tube seems to bend an awful lot as it comes out of the shuttle.

I have its fan running all the time (same as my Huxley) do I need to have it running constantly?

Anyone else have a suggestion as to what I have done wrong? I mean is must work as I have seen it working in the videos on the RRP site.

it seems that it is 'bunching up' in the hot end somewhere. I have just removed two bits of filament and both have the same lump on the end. You may be able to see from the picture that the lump looks like it has be folded over.

[dl.dropbox.com]

I may have found the problem with the hotend. There is a PTFE insert that goes into the connector between the hotend and heatsink. It looks as though I may not have pushed it in deep enough when I installed it. That means it moves in the connector and allowed a plug to form.

Now asked RRP for a new piece so I can try again and hopefully that will fix all the ills have have

Just thought I would update incase anyone else has a similar issue.

Hi,

I had nearly the same problem and solved it using bit longer PTFE tube. I got the plug everytime i tried to get anything out of the hot end.

Mine I have bought in local store here.

It was that which was the problem. Now all sorted and printing fine! Final thing is to stop the bed-judder when the Y-Axis changes direction.