jonathan byler on tue 17 jul 12
Is there a trick to making these hollow extruder dies work right? I
want some square ceramic tubes extruded, and am having trouble with
this. I started with a 5/16" (maybe 3/8") piece of aluminum and cut
in in a circle to fit the extruder barrel. Then cut out my shape from
the middle, using the leftover square piece that was cut out as the
center of the die. there is a 1/4" gap all around, with rounded
corners. Finally I welded a piece of 1" x 1/4" aluminum bar across
both pieces to hold the interior piece in the center. should work, no?
I am getting two pieces of channel that are not bonding back
together. do I need to increase the amount of relief under the bar
that holds it all together? currently it looks a bit like this from
the side:
/////////////////////////////////
///// ////////////// //////
[[[[[[[[[[[[[[ [[[[[[[[[[[[[[ [[[[[[[[[[[[[[
there is a 1/4" notch in the connecting bar parallel to the gap
between the interior and exterior pieces of the die to aid the clay
coming back together already, does this need to be bigger, or angled
more along the axis of the extrusion?
-jon
James Freeman on tue 17 jul 12
On Tue, Jul 17, 2012 at 2:15 AM, jonathan byler wrote:
Is there a trick to making these hollow extruder dies work right?
I am getting two pieces of channel that are not bonding back
together. do I need to increase the amount of relief under the bar
that holds it all together?
Jonathan...
Yes, you figured out the problem; you need more space between the bridge
and the die to allow the split in the clay caused by the bridge to heal
before being extruded. I make my bridges by welding three 1 1/2" long
pieces of threaded rod perpendicularly to another piece of rod, threaded or
not depending on what I have laying around. The two end rods go through
holes in the extruder plate while the center rod goes through a hole in the
piece that forms the hollow. I have some similar bridges made by welding
three bolts to a piece of band iron.
I also have some dies made similarly to yours. The bridges are made of
notched pieces of stainless steel 3/4" x 1 1/2" angle iron. The notches
are nearly an inch tall.
I have posted photos of all three types of bridges to my Flickr page:
http://www.flickr.com/photos/jamesfreemanstudio/
Take care.
...James
James Freeman
"Talk sense to a fool, and he calls you foolish."
-Euripides
http://www.jamesfreemanstudio.com
http://www.flickr.com/photos/jamesfreemanstudio/
http://www.jamesfreemanstudio.com/resources
William & Susan Schran User on tue 17 jul 12
On 7/17/12 2:15 AM, "jonathan byler" wrote:
>Finally I welded a piece of 1" x 1/4" aluminum bar across
>both pieces to hold the interior piece in the center. should work, no?
>
>I am getting two pieces of channel that are not bonding back
>together. do I need to increase the amount of relief under the bar
>that holds it all together? currently it looks a bit like this from
>the side:
>
>
> /////////////////////////////////
> ///// ////////////// //////
>[[[[[[[[[[[[[[ [[[[[[[[[[[[[[ [[[[[[[[[[[[[[
>
>
>there is a 1/4" notch in the connecting bar parallel to the gap
>between the interior and exterior pieces of the die to aid the clay
>coming back together already, does this need to be bigger, or angled
>more along the axis of the extrusion?
The dies on our Northstar extruder use a piece of 1"x 1/8" steel mounted
vertically to hold the inner die.
The plastic die are rather thick, 1/2" thick or more and have half circles
cut into the tops,
Where the die and holder meet. These shallow cuts allow compression of the
clay, forcing the clay back together
after it is split by the holder.
I think your inner die holder bar is too thick and too close to the die.
If you are able to mount the horizontal bar of the die holder higher,
This would allow the clay to be compressed back together after being split
by the holder.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Nancy Gallagher on tue 17 jul 12
Hi Jon - I didn't really get that profile ascii thing, but I find the
clay heals by attaching the inside piece of the die with a u-bolt. I cut
mine out of those thin white cutting boards. They come 3 to a pack in
Target for $10. For solid dies, I just make them out of masonite (it's
easier for me to cut) and back it up with a piece of the white cutting
board with a center piece cut out. (yes, the masonite works - I know,
people think it won't but my mentor has been using the same one's for
30+ years and it does).
Anyway, getting back to the hollow dies - I notch the ubolts because I
was told that helped the clay heal better. The jury is out on that, as
some I have aren't notched and they work, too. I'm not very tool saavy
but have a rotozip I use to notch the bolts...I use a circle saw thing
that attaches to a drill to cut the die. If I can make them, anyone can.
Here's a photo
http://www.gallagherpottery.com/images/hollowdie.jpg
Nancy
--
Nancy Gallagher
http://www.gallagherpottery.com
Want to adopt a basset hound? Visit http://www.dailydrool.com
Snail Scott on tue 17 jul 12
On Jul 17, 2012, at 1:15 AM, jonathan byler wrote:
> ...I want some square ceramic tubes extruded...I started with =3D
a...piece of aluminum and cut
> in in a circle to fit the extruder barrel. Then cut out my shape from
> the middle...I welded a piece of 1" x 1/4" aluminum bar across
> both pieces to hold the interior piece in the center...
> I am getting two pieces of channel that are not bonding back
> together.
There are a couple of ways to deal with this.=3D20
One is to use thinner, deeper stock to bridge the=3D20
die and hold the core in place. (Flat stock, not bar=3D20
stock.) Just as with the beams that hold up a building,=3D20
it's the depth (vertical thickness) that counts for rigidity,=3D20
not width (horizontal thickness. The brace that holds=3D20
the core can be quite thin if it is deep. (1/16" by 1" or=3D20
so, or even thinner.)=3D20
Another method is to have the brace raised quite high=3D20
above the die itself, leaving the clay at least an inch (or=3D20
more) in which to get re-joined after pushing around=3D20
the brace. Some people like U-bolts; other weld a=3D20
cross-bracket onto straight threaded bolts.
Thicker dies, like those made of plastic, can be filed to=3D20
create a 'funnel' effect below the die, which helps push=3D20
the clay back together in those areas. With a thinner
die (like your 5/16" one), there is less thickness to do=3D20
this, but even a little filing will help a bit. Just widen the=3D20
shape at the top surface, leaving the bottom edge with=3D20
the exact shape of your extrusion.
Softer clay is also more forgiving and likely to stick=3D20
back together more readily than stiffer clay. You may=3D20
have to wait longer before using such a soft extrusion,=3D20
but it might give a little extra help with the issue.
-Snail=3D
jonathan byler on tue 17 jul 12
thanks for all of the tips everyone!
On Jul 17, 2012, at 9:32 AM, Snail Scott wrote:
jonathan byler on tue 17 jul 12
so with the advice taken, I beveled the edges of the aluminum plate to
help force the clay into the die rather than shear it at the top.
Also gave about 3" of space between the cross bar and the die plates.
still used heavy aluminum for all of this, I like things rigid. The
test run worked out great, at least with our stoneware. I made this
to extrude some mullite tubes to use in an experimental heat exchanger
for a kiln chimney. I am still confirming that the recipe I used, 3
parts kyanite, 1 part ball clay is going to hold up well to the
possible thermal shock before I go too far with this. I want to see
what I can do with the stuff that marvin bartell did to recapture
waste heat.
Ideally these would be made from silicon carbide tubes, as they have a
much greater ability to transmit heat through them than mullite tubes
would, on the order of 10-20 times more heat per unit or more. But
silicon carbide tubes cost a lot of money, making the whole thing less
doable on a small budget. Maybe I can convince some supplier of SiC
tubes to donate a few to me to experiment with. one would probably
need a lot fewer SiC tubes to get the job done than mullite tubes, so
maybe it wouldn't end up costing that much more. Imagine firing an
anagama for seven days but only using half the wood...
Des & Jan Howard on wed 18 jul 12
Jonathan
Some helpful words on the subject.
The Energy Efficient Potter
Regis C. Brodie
Watson-Guptill Publications 1982
ISBN 0-8230-1614-5(pbk)
On 18/07/2012 8:30 AM, jonathan byler wrote:
> I made this
> to extrude some mullite tubes to use in an experimental
> heat exchanger
> for a kiln chimney.
If one wanted to wood fire efficiently, ie, saving
wood, one would not use an anagama.
One would use a 'fast-fire' kiln or the very efficient
Bourry box. An anagama is for effect, not efficiency.
> Imagine firing an
> anagama for seven days but only using half the wood...
Des
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624
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