Peter Wakefield Jackson on mon 30 oct 00
Hi folks,
I have a friend who wants to set up high volume production for extruded clay
cylinders, using a power extruder--either a converted vertical pug mill, or
a hydraulic set up. Is there anyone out there who knows what limits there
are for the velocity of extrusions without the cylinder twisting. I know
that the clay will play a big part in that, and that in general extrusions
will stay more true the slower they are pushed out, but what do you think
the upper limit for speed is?
Any ideas?
Peter Wakefield Jackson, President
P. WAKEFIELD & CO., LTD.
Makers of traditional handmade pottery,
including Guy Wolff Garden Pottery
http://www.pwakefield.com/
Connie Pike on tue 31 oct 00
Hello from Bob Pike
I've been extruding with a pug mill extruder of my own design for the
past 15 years. There are so many variables to your query that it's very
hard to answer. What diameter of cylinder? What wall thickness? How
large of a capacity of machine will you use?
I would recommend using a pug mill extruder over hydraulic if you want
high volume as the process is continuous. With a hydraulic extruder, the
emerging cylinder will wander in different directions as it comes out of
the barrel if the clay is not completely homogeneous (just pugged) and
you will have to continuously shut down to reload the barrel. Very time
consuming.
My Pug mill extruder has a 9" diameter barrel with a 4.5" exit hole and
an 8" square expansion chamber. The speed of the second shaft is approx.
25 RPM. If I were to extrude a 5" diameter cylinder with a 3/8" wall
thickness, I would probably extrude 3 feet every 15 to 20 seconds. I
special order my clay extra stiff (approx. 18% water) with an oil
mixture of 50% Pamak-4 and 50% Faxam-22 added at 0.15%. If you used
commercial pug mill extruder you could extrude even stiffer. This allows
you to extrude horizontally onto a treadmill table which is more
manageable than a vertical set up and the cylinders won't collapse. If
you set up for high production you'd need a 10,000 square foot building
to dry, store all of the pieces in.
The speed of the extrusion has nothing to do with how true it comes out.
If the die is centered properly and the clay is absolutely homogeneous,
the cylinder will be true. If you had a commercial extruder with a
variable speed motor, you could keep increasing the speed of the shaft
to the point where the clay breaks down and starts turning inside the
machine rather than going forward. I have no idea when that happens.
You can see a picture of my set up and how I work in "The Extruder
Book" by Daryl Baird.
Hope this gets you pointed in the right direction.
--
Bob and Connie Pike Pike Studios Ltd.
High River, Alberta.
http://www.pikestudios.com
http://www.pikec@cadvision.com
I have a friend who wants to set up high volume production for extruded
clay
cylinders, using a power extruder--either a converted vertical pug mill,
or
a hydraulic set up. Is there anyone out there who knows what limits
there
are for the velocity of extrusions without the cylinder twisting. I
know
that the clay will play a big part in that, and that in general
extrusions
will stay more true the slower they are pushed out, but what do you
think
the upper limit for speed is?
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