Hot end Jamming on new machine

Hi All,
A friend and I are trying to get a kit working that he got some months ago, it's a Reprap prusa i3 with 'Greg's Hinged Accessible Extruder, 3mm filament.

we have been able to print a few small things, but the filament stops pulling in between 5 - 10 mins of running, you cannot pull it back out, instead we need to open the hot end and pull it through.

The issue seems to be that it is expanding in the white block that screws into the hot end, see the picture of the parts.

We have tried adding a fan on to the upper part but then the heater can't keep up!

we are print (or wanting to print) PLA and using a temp of 200c, to high to low?

Googling for days we can find recommendation to increase the temperature and to reduce it! to add a heatsink and others say no cooling is needed!

we think we are close to joining all you successful printers, but we can't seem to overcome this last hurdle!

In the pictures you see the Hot end and also how the PLA is expanding and jamming in the plastic block.


who makes the hot end pictured?

What do all the experts on this forum recommend we try?

here you see another users picture with the same hot end link

thanks for any help...

Edited 3 time(s). Last edit at 03/12/2015 08:43AM by I_Need_Help.

Try cooling the insulator (white PEEK?) with a cooling fan.

Try to make a fan-duct so the fan really only blows on the white part and not on the heater block.

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http://www.marinusdebeer.nl/

You don't really need a high-powered fan to cool the insulator. I have been told that the insulator heats up mainly from convection as the warm air rises form the tip. A small fan to break up this flow of hot air is all that is necessary. I run a small 25mm fan mounted hanging from the side of the X carriage - it just points horizontally across the bottom of the X carriage. The point is that you do not need to have such a high-powered fan that it also cools the tip.

I DO have a switch on this fan so I can turn it off for ABS. The only time I have ever had a jam is once when I switched from printing ABS back to PLA and forgot to turn the fan back on.

Edited 1 time(s). Last edit at 03/12/2015 11:13AM by jbernardis.

Thank you for your replies we will try your ideas and let you know how we get on...

if it does not work we may change the head to a different one, what do you think of hot end

Ive been using one for a few months now 3mm direct drive. Very good hot end.
It was a bit tight on my prusa i2 between the smooth rods and i had to redesgn the xcarriage to get the fan shroud in.
Not had a single jam or problem.
What i also like is you can swap the nozzles between different sizes.

Gordon

thanks Gordon, we have order one, but we are also going to try the other fixes tonight! we just think it looks a better design