Filament melting above hotend and jams

I replaced the hotend with a new J-head and I had loads of good prints. I changed the filament and it clogged half way through the print. I cleared it and changed the filament back to one I've used in the past in a different colour and tried printing but it keeps on clogging after a few layers. I've never had this problem before. It got to a stage where I couldn't get the filament to go up or down, upon taking it apart I see the filament had fused to the wades block above the hotend. I have attached a pic of this. Any idea what could be happening?

Quote
999dom999
.... Any idea what could be happening?

I suspect that heat is rising from the hot end of the JHead and warming the filament towards the cold end of the JHead. This is likely to make it too soft for the extruder to push it through the JHead and instead, it starts to buckle.

Are you .....
1. Using self amalgamating tape around the heater block?
2. Using the latest version of the fan cowl which has a hole in it through which air from the fan flows to cool the top of the JHead?

If not, I suggest you install those.
If so .... do you have the fan switched on after the first layer? Is the first layer taking so long to print that heat is getting to the top of the JHead before you switch on the cooling fan (usually after the first layer)?

Why this is happening now after you have had your printer working well in the past with the same set up and same filament ...... not a clue, sorry!

Alan

Edited 1 time(s). Last edit at 12/22/2014 09:56AM by Alzibiff.

I'm using a replacement hotend recently supplied by Nophead a week or so ago, this comes with the red tape around the heater block.

I'm printing ABS so I'm not using a fan. I read that the fan is only for PLA is that right?

I just ran another print and it started to get clogged again halfway through. I pushed down hard on the filament and it started to come out again. I tightened (more than hand tight, used pliers for a couple of turns) the bolts with the springs that push the filament into the hobbed bolt and I'm trying another print. I had also cleaned the hobbed bolt in acetone as I could see bits of filament stuck in it, but that was before the last clog. Do the hobbed bolts need replacing, its had a lot of use in the last year and never suffered any clogs before and I have never tightened the bolts with the springs this much?

My next print failed too, same thing filament stopped extruding, I pushed down again hard on the filament and it started coming out again. I think the bolts with the springs were too tight so I loosen them a bit, switched off the motors and pushed down on the filament, it comes out ok. If I then try to extrude from pronterface it starts coming out then stops. Sometimes I can get it working but never for long enough to complete a print. I have 5 x 6 hour prints I need to print.

I was assuming that you were printing PLA and not ABS which means that my response is unlikely to help
My usual extrusion temperature for ABS filament is 245C - what are you using?

Alan

I think the problem is that you think you are using ABS, but it is actually PLA. ABS can't melt above the cold end. If it was hot enough there the Wades block would melt.

Pour some water from a boiled kettle into a cup. If the filament softens in it, it is PLA, not ABS. PLA will become like jelly in hot water above 55C.

Edited 1 time(s). Last edit at 12/22/2014 03:58PM by nophead.

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The extruder part is printed? I used this one design, but finally I give up. Because it is a problem when melting PLA/ABS, the printed part also melting.
If possible, change a acrylic part and mental one. Or finally you change another extruder.

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No the extruder isn't melting. The filament is melting above the hot end where it is not hot enough to melt ABS. So my conclusion is the OP is trying to print PLA with ABS settings, thinking it is ABS.

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