I just wanted to share my experience with the V2 hotend, and see if anyone
has similar.

First off, it solves the plug problem. Excellent. Been running near 24h a
day for a week now.

With PLA, it prints really well. Can't see a difference to how if did
before.

With ABS (which is most of my work) it prints well, but the speed has
dropped significantly. at 0.1mm layer height, with the V1 hot end I could
print (with kisslicer) boundaries at 40, fill at100. With V2 I can only
achieve 60 mm/s before the extruder drive starts slipping and then grinding.

It seems to be that the change to thin the 'neck' of the V2, has prevented
so much heat in the upper parts of the brass tube in order to improve
things for the PEEK, but this has reduced the ability to melt the filament
so fast. I have tried running the hot end hotter to compensate, up to
270deg from my normal 250/255 for ABS, and it doesn't help much, in fact at
that temp the material starts to degrade and turn to toffee if not kept
moving.

Also as I side issue I pushed a calibrated thermocouple meter inside the
molten plastic inside the nozzle when I had it apart, and it seems the
Ultimaker is about 12degrees C below, so my setting of 270 is actually 258.
Is this usual? I checked the voltage output from the thermocouple pre-amp
and it reads the same as the Ultimaker sees, i.e. 2.70v. so the fault (if
any) is in the thermocouple or pre-amp chip which seems unlikely.

Your thoughts and experiences appreciated.

Andrew

To accurately measure the temperature you need a thermocouple with an open
junction and skinny wires.  I usually use AWG #36=  0.005 Inch= 0.13mm.
Most probes are way too big and they conduct away heat from the measured
object and often they do not make proper thermal contact.  More TC info at:

http://www.vinland.com/blog/?p=138

Bertho

From:  am001  Sent: Thursday, September 20, 2012 05:56

-----< snip

Also as I side issue I pushed a calibrated thermocouple meter inside the
molten plastic inside the nozzle when I had it apart, and it seems the
Ultimaker is about 12degrees C below, so my setting of 270 is actually 258.
Is this usual? I checked the voltage output from the thermocouple pre-amp
and it reads the same as the Ultimaker sees, i.e. 2.70v. so the fault (if
any) is in the thermocouple or pre-amp chip which seems unlikely.

Your thoughts and experiences appreciated.

Andrew

Anyone else? I'm not sure if it will help with my problem - popping bowden.

W dniu czwartek, 20 września 2012 11:55:42 UTC+2 użytkownik am001 napisał:

The new clip is better, so it should work against bowden poping.

But, from personal experience, I installed it on a machine with just the
old clip, and it did not fully resolve the popping problem. It did
eliminate the plug that would normally happen when you have a bowden pop.
(This machine sees a lot of abuse, as it is transported a lot, and used in
workshops with kids)

We threaded the bowden tube with M7 thread, and added an M7 nut below the
wooden plate. This solved the popping for good for us, with the V2 hotend.

Hi,

The thin neck part in the brass connection to the peek in the V2 design has been introduced to act as a heat transfer barrier to the peek and to the alu plate, which remains much cooler now.
Consequently this part of the brass inside the peek is somewhat colder than the alu block and the nozzle itself, especially when a lot of cold filament is transferred into that part as well.

The Teflon part in the V2 is well fixed because of the 10 mm wide rim between the wood and the peek and that is major reason why previously occurring unmovable plugs are not being formed anymore.

The Teflon part with an inner diameter equal to the bowden diam. (3,2mm) or preferably slightly less (3,1mm) should be the place where liquid and solid filament exists side by side.  
(In fact that is the movable plug inevitably being formed (pressure induced back flow,  filling the full 'diameter' of the Teflon insulator).
It is movable because of the low friction of (well drilled) Teflon inside surface.
The length of the this movable plug and the place where in the insulator this is formed depends on a number of parameters like the local temperatures and  the feed-in and flow out of filament.
It will be close to the brass end and shorter with average fast extrusions. It will move to the bowden end and gets longer with very slow average extrusion.
But that movable plug is easily pushed out from the Teflon part into the brass part where it melts again and also fully.

If the feed-in of filament of the system is very high or requires a lot of heat for temperature increase and melting (perhaps with ABS more that withPLA) this movable plug tends to shift into the colder brass part inside the peek, where it melts too slow and sticks to the brass surface. Hence too much resistance and consequently grinding of the filament feeder.
It is also important that the Teflon insulator is well supported by the peek. Peek material has better mechanical strenght characteristics than Teflon (so a snug fit of the Teflon part in the peek is required).
It should not be possble to blow up the teflon part.
It also is important that the Teflon passage and the brass passage are nicely concentric and that the plug from the Tefon part fits nicely into the brass tube (3,2mm) .
I have got such an Teflon insulator in the hot-end in my Ultimaker for over a year now and had to replace it recently because the teflon passage increased to > 3,2 mm. (Blown up or some wearing?)
I tapered in the lathe the entrance to the brass pipe slightly from 3,2 mm to 3,4 mm, in order to have an easier entry of the brass tube.  

A further inprovement to my mind, expecially for very fast printing or ABS would be a less thin neck (e.g. 5mm diam.) but at the same time a shorter thread of the brass in the peek (currently 11 mm).
Mechanically 5-6 mm length would be sufficient and I applied this in a few Ultimakers.
The higher heat transfer in the thicker neck is compensated by the shorter thread length.
The temperature of the peek and of the Teflon part should be low while preventing a too cold brass end in the peek.  

May be you have to reread this contribution a few times to fully understand what I wanted to say and what I think is happening in our hot-ends.

wim

Good detailed description!

Thanks!

Bertho

From:  WThM de Groot   Sent: Wednesday, September 26, 2012 06:48

Hi,

The thin neck part in the brass connection to the peek in the V2 design has
been introduced to act as a heat transfer barrier to the peek and to the alu
plate, which remains much cooler now.

Consequently this part of the brass inside the peek is somewhat colder than
the alu block and the nozzle itself, especially when a lot of cold filament
is transferred into that part as well.

The Teflon part in the V2 is well fixed because of the 10 mm wide rim
between the wood and the peek and that is major reason why previously
occurring unmovable plugs are not being formed anymore.

The Teflon part with an inner diameter equal to the bowden diam. (3,2mm) or
preferably slightly less (3,1mm) should be the place where liquid and solid
filament exists side by side.  

(In fact that is the movable plug inevitably being formed (pressure induced
back flow,  filling the full 'diameter' of the Teflon insulator).

It is movable because of the low friction of (well drilled) Teflon inside
surface.

The length of the this movable plug and the place where in the insulator
this is formed depends on a number of parameters like the local temperatures
and  the feed-in and flow out of filament.

It will be close to the brass end and shorter with average fast extrusions.
It will move to the bowden end and gets longer with very slow average
extrusion.

But that movable plug is easily pushed out from the Teflon part into the
brass part where it melts again and also fully.

If the feed-in of filament of the system is very high or requires a lot of
heat for temperature increase and melting (perhaps with ABS more that
withPLA) this movable plug tends to shift into the colder brass part inside
the peek, where it melts too slow and sticks to the brass surface. Hence too
much resistance and consequently grinding of the filament feeder.

It is also important that the Teflon insulator is well supported by the
peek. Peek material has better mechanical strenght characteristics than
Teflon (so a snug fit of the Teflon part in the peek is required).

It should not be possble to blow up the teflon part.

It also is important that the Teflon passage and the brass passage are
nicely concentric and that the plug from the Tefon part fits nicely into the
brass tube (3,2mm) .

I have got such an Teflon insulator in the hot-end in my Ultimaker for over
a year now and had to replace it recently because the teflon passage
increased to > 3,2 mm. (Blown up or some wearing?)

I tapered in the lathe the entrance to the brass pipe slightly from 3,2 mm
to 3,4 mm, in order to have an easier entry of the brass tube.  

A further inprovement to my mind, expecially for very fast printing or ABS
would be a less thin neck (e.g. 5mm diam.) but at the same time a shorter
thread of the brass in the peek (currently 11 mm).

Mechanically 5-6 mm length would be sufficient and I applied this in a few
Ultimakers.

The higher heat transfer in the thicker neck is compensated by the shorter
thread length.

The temperature of the peek and of the Teflon part should be low while
preventing a too cold brass end in the peek.  

May be you have to reread this contribution a few times to fully understand
what I wanted to say and what I think is happening in our hot-ends.

wim

Kudos on the upgrade, works like a charm!
No more plugs, no more filament grinds, and easy to check/maintain.
Really happy here.