extruder heads
David F. Flanders
coming up with a more common solution? /dff
Martin Ling
>
> we need to sort extruder heads, either finding more suppliers or
> coming up with a more common solution? /dff
I have given myself a headache looking at all the umpteen extruder
components from various designs scattered across the web and trying to
figure out what we should do.
It is clear that the extruder hot end is the most troublesome part of
the whole RepRap concept and so I am rather reluctant to go with earlier
designs, which have known problems that newer ones are supposed to
address.
Hence it seemed what we really wanted was indeed this hot end kit:
http://www.mendelfactory.com/product_info.php?cPath=35&products_id=233
...but the supplier is out of stock, snowed under and not taking new
orders.
I've looked around and haven't found anyone else offering suitable
parts. So I think we should look into machining the necessary stuff
ourselves, following Adrian Bowyer's later design version:
http://reprap.org/wiki/Geared_extruder_nozzle
Some of that can be done on the Edinburgh Hacklab's CNC mill, which is
up and running fully as of this week. But I think a lathe is going to be
required too, we're unlіkely to be able to cut the round parts with
sufficient accuracy on the mill. Does anyone have access to a lathe?
Martin
Graham Klyne
It seems to me there are two key components:
- the heated brass tube/nozzle, which apparently can be made with a bit of
lathe-work on an M6 brass screw.
- the heat-resistant plastic block that protects the printed plastic carrier for
the extruder from the hot end itself. AFAICT, this too is lathe-formed, but
maybe can get away without machining?
Apparently, a simple design which has the brass hot-end sitting in a recess in
the plastic block has the problem that as the temperature rises, the plastic
expands more than the brass, and the nozzle then comes off under the pressure of
filament being pushed into the barrel. Hence some kind of positive retainer is
needed.
(The mendel-parts extruder cleverly has the brass hot-end screw on *over* a
threaded nipple on the plastic part, neatly avoiding these problems.)
#g
--
Graham Klyne
I can see if I can get a price from the workshop here in the Zoology Department
at Oxford - if it's reasonable, I'd be tempted to ask for a batch of (say) 10 or so.
On the topic of extruders, I have my RepRap mostly working, but am having
trouble with getting Skeinforge to generate the required E values (Extrude
distance) [*]. It generates values that appear to be too small by a factor of
about 5-10, but I can't see what parameter to change in Skeinforge to change
this. Does anyone have any insights? [**]
#g
--
[*] I've finally figured out that the new "5D" firmware is so-called because it
generates G-code in 5 dimensions: X, Y, Z, feed rate (speed) and extrude
distance, eliminating the need for separate extruder start/stop commands in the
GCode. The advantage of this is that it allows the extrude rate to be
controlled along with varying head movement rates, which in principle should
allow for faster, cleaner prints.
[**] there's a proposal for new GCode commands to control this and other
parameters, but as yet they are not implemented (as far as I can tell) in the
Gen6 electronics firmware - certainly not in the source code they publish.
Martin Ling
end design, with the help of a friend who has a lathe:
http://reprap.org/wiki/Geared_extruder_nozzle#PTFE_sleeve_nozzle
We plan to start work on this Tuesday evening, I'll post an update to
the list to say how it goes.
Martin