Table Of ContentA Collection of Papers Presented at the 1978,1979,
and 1980 Meetings of the Materials & Equipment and
Whitewares Divisions
The American Ceramic Society
Cullen Hacider
L.
Chairman, Proceeding@C ommittee
May 6-11, 1978 Cob0 Hall, Detroit, Mich.
April 29- May 2, 1979 Convention-Exposition Center, Cincinnati, Ohio
September 26-29, 1979 Bedford Springs Hotel, Bedford, Pa.
April 27-30, 1980 Conrad Hilton Hotel, Chicago, Ill.
ISSN 0196-6219
Published by
The American Ceramic Society, Inc.
65 Ceramic Drive
Columbus, Ohio 43214
'The American Ceramic Society, 1980
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of
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ex ofpcfo;W iliam J. Smothers, ex ofpcfo;A rthur L. Friedberg, ex oflcio.
EdftorfalA duluory Board: L. J. Trostel, Jr., Chairman; R. L. Berger; W.
G. Coulter; T. Dkstine; R. A. Eppler; E. J. Friebele; F. A. Hummel; W.
R.
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CESPDK Vol. 1, 9-10, pp. 745-922, 1980
NO.
Preface
This issue was compiled by the Proceedings Committee for the Materials & Equip-
ment and Whitewares Divisions, with the cooperation of the program chairman,
session chairman, and the various authors. This publication is designed to serve the
needs of ceramists and engineers in bringing timely, useful information to them.
The papers in this issue may contain some inadvertent inaccuracies. Readers
are encouraged to contact the individual authors in any case of doubt or misun-
derstanding.
As the chairman of the Proceedings Committee for the Materials & Equipment
and Whitewares Divisions, I wish to thank all who helped in writing and in gathering
the papers presented in this volume.
Cullen Hackler
Chairman, Proceedings Committee
iii
Table of Contents
Plastic Pressing of. Cordierite Saggers ............................. 745
William C. Mohr and Michael W. Morris
Process Controls in Pressing of Light Refractories .................. 747
William C. Mohr and Gary A. Kos
A Microprocessor Programmer Controller for Kiln Temperature
Control ......................................................
753
R. I. Gruber
Automatic Application of Color on Whiteware by Banding,
Spraying, and Other Means ..................................... 761
R. J. Verba
Three-Color Glass Decoration ................................... 764
Gene Collard
Pad Transfer Decorating ........................................ 766
David A. Karlyn
The Automation of Hand-Decorating Techniques .................... 767
John Geelen
The Practical Application of Current Automatic Weighing
Techniques in the Ceramic Industry .............................. 771
Kenneth A. Kardux
Ceramic Cements: Their Properties and Their Applications for
Industry ...................................................... 772
Robert L. Trinklein
Rheology and the Ceramic Engineer .............................. 775
J. W. Joudrey
Solving Production Problems with a Computer ..................... 776
Peter P. Nitchman
Fast Firing of Triaxial Porcelain ................................. 780
Nils G. Holmstrdm
New Shuttle Kiln Design for Firing Large Insulators ................. 788
L. E. Bauer
Which Is the Yellow for You? ................................... 789
Cullen L. Hackler and Robert E. Carpenter
Evaluation and Comparison of Peaches, Pinks, and Maroons for
CornJ etitive Color Matching ..................................... 790
E. Sturm
Observations on Brown Ceramic Colors ........................... 791
William G. Loucka
Basic Principles of Ceramic Decals ............................... 793
Richard G. Norsworthy
V
Color Control in Decal Systems and Its Implications for
Decorating Ceramics ........................................... 796
Gary Stevens
...........
Application of Ceramic Decals to Hollowware by Machine 801
Kris T. Brenard
Isostatic Dry Pressing of Flatware ................................ 804
H. Niffka
Dust-Free Loading and Stockpiling of Dry Bulk Material ............. 805
Ron Pair
The Refiring of Sanitary Ware ................................... 807
D. K. Hullock
Use of Wad Mills in Materials Handling ........................... 812
M. A. Zanghi
........................................
Control Quality Control 815
Richard F. Jaeger
Presentation from the Panel Discussion “Taking the Lead Out” ....... 818
R. H. Insley
Presentation from the Panel Discussion “Taking the Lead Out” ....... 819
John E. Jozefowski
Presentation from the Panel Discussion “Taking the Lead Out”:
Reducing Hazards in the Pottery ................................. 821
James R. Platte
Kiln Furniture in a Fuel-Conscious World .......................... 823
D. K. Hewitt
Cordierite Slabs ............................................... 826
William C. Mohr, Bruce E. Dunworth, David B. McCuen,
and Michaei W. Morris
§hock-Resistant Extruded and Hand-Molded Kiln Cartop
Refractories ................................................... 829
Francis B. Rernrney
The Effect on Thermal Expansion of the Addition of Various
Materials to a Cone 01-1 Bright Glaze and Body .................. 838
J. Eleison
What Raw Materials Can Do to Cut Energy Consumption ............ 842
Konrad C. Rieger
The Ceramic Glaze Data Bank ................................... 848
Harold J. McWhinnie
Use of Linear Programming for Reformulation
of Triaxial Ceramics ........................................... 852
Salil K. Roy
vi
Inclusion Pigments: New Types of Ceramic Stains and Their
Applications ..................................................
860
H. D. de Ahna
Cobalt-Free Black Pigments .....................................
863
Richard A. Eppler
Recent Design Changes in Pebble Mills ...........................
871
John M. Rahter
Everything You Want to Know about Semibulk Containers ...........
873
Herbert Bear Rothman
Plastic Forming in the Tableware Industry .........................
877
A. Bradshaw and R. Cater
A Whitewares Dream Comes True: Isostatic Pressing, a Tool to
Complete Automation ..........................................
882
Alfred Dube
Machinery for Hot Molding Ceramic Parts under Low Pressure ........
886
I. Peltsman and M. Peltsman
Combustion Control Saves Fuel, Products, and Money ...............
889
Roman F. Lempa
Energy Management Strategies Using Microprocessor
Instrumentation ...............................................
902
John E. O’Neil
The Thermograph System of Kiln Control .........................
913
D. W. Thomas
Fast-Firing Sled Kiln for Dinnerware ..............................
917
Dietrich A. Heimsoth, Rainier Hoffmann, and William C. Ware
New Roller Hearth Kiln for Vitrified Tile .......................... 920
Dietrich A. Heimsoth, Herbert Spitzbart, and Eberhard Wolf
vii
Ceramic Engineering and Science Proceedings
William J. Smothers
copyright@ The American Ceramic Society, 1980
Plastic Pressing of Cordierite Saggers
c. w.
MOHRA ND MICHAEL MORRIS
WILLIAM
Electro Div., Fern Corp.
Box 151, Crooksville, Ohio 43731
The plastic pressing of saggers made from cordierite-bonded mullite is described in
this paper. Cordierite is a lowexpansion magnesium aluminum silicate, which is
formed, during firing, from mixturesofballclay, kaolin, and talc. Mullite-type grog
is added to control shrinkage and to increase resistance to thermal shock and sag.
The saggers being pressed are 30-38 cm wide by 30-61 cm long, with heights of
10-30 cm. The plant described produces saggers by pressing slugs, which are
extruded from a vacuum pug mill.
The raw ingredients are batched into a skip hoist. A binder, usually a lignin
sulfonate, is added to improve flow during extrusion and pressing and to provide
green strength during drying and the early stages of firing. The skip hoist is dumped
into a muller-type mixer, and water is added until a very stiff plastic state is
achieved. The mixed batch is dumped onto a conveyor belt, which brings the
material to a vacuum pug mill. The pug mill operator controls the movement of the
conveyor, so that the pug mill receives more batch as required.
The design of the die on the pug mill, the design of the nozzle leading to the die,
and the length of the spacer between the end of the auger and the nozzle are all
important factors. Unfortunately, since there are no rules governing these items,
they must be fixed by trial-andemr experimentation. There are two major difficul-
ties that may be encountered in extrusion. The first is an “S” crack, found in the
center of the column of clay. This crack is not always noticeable at the pug mill and
may not appear until the formed article is fired. The “S crack is caused by a lack of
”
healing of the two layers of clay which slide along the auger spiral during extrusion.
This ‘ ‘S crack can often be eliminated by using a longer spacer between the end of
”
the auger and the die. The second major problem of extrusion is “dog’s teeth,”
which occur when the clay column moves irregularly at the comers of the die,
causing a series of curved fractures, in which the clay peels outward from the comer
of the extrusion. The cause of this defect is excess friction at the comers of the die. It
can be remedied by changes in the body composition, by providing lubrication to the
die, or by enlarging the back of the die in the comers.
To obtain good pressed ware, it is necessary to have wellevacuated clay that
contains no air pockets. Air pockets in the extruded slugs will lead to laminations
and blisters in the pressed saggers. The extruded clay column is tested for effective-
ness of evacuation by cutting a representative sample of thin slivers. These speci-
mens are laid flat on the tray of a vacuum desiccator. Water or kerosene is then
poured into the desiccator, until the specimens are covered with liquid. Vacuum is
applied while the specimens are continually observed. Any swelling of the clay
indicates the presence of undesirable air pockets.
The cross-sectional size of the extruded column depends on the size of the
article to be made. For smaller saggers, vertical wires across the die opening may
split the column into two or three slices. The pug mill operator has an adjustable
745
gage that allows him or her to cut the extruded column to the length required for the
item to be pressed. The operator gages the column and cuts it with a wire; the pug
mill is stopped while the operator measures and cuts. He or she then gets a more
accurate check on the amount of clay in the cut slug by weighing it; if the slug is too
light, it is returned to the pug mill. However, the slugs, if not of proper weight, are
usually oversize, so that the operator trims off a little clay with a knife to bring the
slug to the weight desired. A tolerance of 2 0.4% is usually required. The extruded
and weighed slugs are stacked in a metal-lined cart; the filled carts are covered with
damp canvas to prevent undesirable water loss prior to pressing.
The pressperson applies die oil to the two opposite large surfaces of the slug;
this oil is needed in quantity so that the clay, during forming, can slide easily along
the die surfaces and so that the pressed piece releases from the die after pressing. To
the same end, it is necessary to keep the die surfaces slightly rough so that oil is
entrapped there, facilitating release.
The pressing dies are precision-made to exacting tolerances. A die consists of
an outer casing and spacers, which are made from cold-rolled steel. The actual
pressing surfaces, a liner and top and bottom pads, are made from A2 or 41/50
heat-treated steel. The clearance between the liner and the core is 0.005 cm. This is
large enough to allow air release during pressing but small enough to prevent the
body from extruding through the clearance during pressing. Pressing is ac-
complished on hydraulic presses. During pressing 1.7-3.4 MPa are applied, the
pressure being varied to meet the requirements of each shape. It is important that
each shape be pressed to an even density throughout. Bad density gradients will lead
to warping and cracking during drying.
Although one cannot look into the die during pressing, one can mentally
construct reasonable models of the manner in which the clay moves in the die. The
slug has the form of an orthorhombic prism. When the top punch contacts the slug,
the clay begins to flow outward in four columns from the four vertical faces of the
slug. These four columns move across the bottom of the die and then turn at right
angles and move up the cavities that form the walls of the sagger. Eventually, the
four columns broaden out and join. This joint is a possible area of weakness in the
sagger, especially since the clay columns are oily. For this reason, most saggers are
made in dies that produce a shape higher than that which is desired. In the case of
rectangular saggers, the extra height is usually added only at the comers. After the
sagger is pressed, it is trimmed with a knife to the exact height required. This allows
the poorly knit sections to be cut off and discarded as scrap. All scrap is returned to
the mixing operation, and scrap body usually makes up a limited portion of each
batch charged into the mixer.
746
Ceramic Engineering and Science Proceedings
William J. Smothers
copyright@ The American Ceramic Society, 1980
Process Controls in Pressing of Light Refractories
WILLIAMC . MOHR
Electro Div., Ferro Corp.
Box 151, Crooksville, Ohio 43731
GARYA . Kos
Fern Corp., Louthan Plant
2000 Harvey Ave., East Liverpool, Ohio 43920
This paper concerns the pressing of small refractory articles that in area are not much
larger than 30 cm square and in thickness not much greater than 2.54 cm. The bodies
consist of alumina, mullite, or fused silica grog, bonded with cordierite or mullite.
Relatively inexpensive products are manufactured, such as items for metal casting
and kiln furniture for the firing of ceramics and metals.
The selection of raw materials is based on compromises among cost, quality,
and requirements. In general, the quality of raw materials is good, so that a
minimum of raw material testing is required. Strenuous attempts are made to agree
with each supplier on specifications for each raw material. Most materials are
received in bags, and each bag is required to be stamped with a lot number for ready
reference in case of problems. The particle size of grogs is checked faithfully, and
only properly sized grog is used. No routine tests are run on other raw materials, but
“hold samples” are taken from each shipment. For each raw material, the “hold
sample” inventory consists of a sample from the oldest available shipment, plus
samples from the latest three shipments. This “hold sample” program provides
valuable reference material in case trouble does develop in the form of an undesir-
able variation in the quality of a raw material.
The body compositions are controlled by the plant ceramic engineer, who
issues batch cards to the plant superintendent (Fig. 1). The superintendent, in turn,
issues the batch cards to the mixing room foreman, who assigns the cards to the
claymakers. The superintendent, on the basis of production requirements, decides
which mixes are to be made and how many batches of each are to be prepared. The
water content and the mixing times are specified by the plant ceramic engineer, in
accordance with the requirements of the item to be made.
It will be noted that the batch card contains six columns headed “Tank #. A
”
“Tank” is a hopper that holds one mixer batch ofprepared body. As the claymaker
prepares each batch, he or she writes the lot number of each raw material on the
batch card in the space opposite the given raw material and in the vertical column
pertaining to the “Tank” that will be filled with the batch being made. This method
provides a record whereby each tank of prepared body can be traced back to a given
set of raw materials. Having the claymaker fill in the lot number, as he or she
batches, is an aid in directing his or her attention toward batching the proper amount
of the proper material. When the claymaker has prepared all the batches to be made
on a single batch card, he or she signs the card at the bottom, attesting that the job has
been done properly. The mixing room foreman then countersigns the batch card,
indicating that proper batching has been done under his or her supervision.
747
The bodies are compounded with sufficient raw clay and water to flow well
under pressure, so that fairly intricate pieces can be produced with even densities, at
forming pressures of 3.4-6.9 MPa. The mixes are prepared muller-type mixers,
in
and pressing granules produced by pulverizing the wet batch.
are
The standard operating procedure for claymakers allows time for the adjust-
ment of each batch to the proper water content, as specified by the plant ceramic
engineer. A scale and a forced-hot-air dryer are used by the claymaker to determine
water content. The claymaker makes every effort to have the batch come out with the
correct moisture, without the need for adjustments. He or she attempts to keep the
tolerance on the dry side, so that if moisture adjustment is necessary the adjustment
will usually require more water, which is an easy addition to make. Of course,
overly wet batches sometimes result; in such a case the claymaker must then add a
small amount of dry batch to bring the moisture content down to specification.
The fired size of refractories pressed in a given die is governed mainly by the
moisture content of the pressing granules. The proper control of moisture content is,
then, a primary process control function. For process control purposes, batches are
divided into three categories, based on the size tolerances required in the finished
product: A-tight control, B-standard, and C-loose control. The QC laboratory
always checks the moisture content of all category A batches to ensure that there are
no slipups. The lab checks the moisture content of some category B batches; if
significant errors are found, they expand the moisture checking to more or to all
category B batches. The lab checks category C batches only when time is available.
In this way, the amount of offsize ware is held to a practical minimum. The QC Lab
and the claymakers use the same type of moisture determination equipment.
Pressing is accomplished on hydraulic C-frame presses. The plant described is
a specialty shop that has no standard shapes but that manufactures hundreds of
different items, according to the varying requirements of individual customers.
With so many shapes to be made, it is imperative that an accurate record be kept of
all the parameters that affect the manufacturing of each individual item. This record
is provided on a 21 39 by 27.94 cm (8% by 11 in.) card that is printed on both sides
to enable all the necessary information to be catalogued. This card is illustrated in
Fig. 2. The mixing parameters should be self-explanatory, in view of the foregoing
discussion. In the forming parameters section, the press to be used is specified,
along with the gage pressure (tonnage) required. The term “bumps” refers to the
number of times the pressure is to be momentarily released and then immediately
reapplied. If a vacuum is to be used to eliminate laminations, the necessary negative
pressure is given. The item ‘‘gage dimensions” refers to the thickness of the pressed
part, which is governed mainly by the depth of die fill. A “go-no go” gage is made
for each pressed shape, and the press operator is required to check pieces at regular
intervals, which vary according to the tolerance requirements of the particular
application. The press room foreman is required to make counterchecks of thickness
at regular but less frequent intervals. A quality control technician makes frequent
trips through the press room and alerts the foreman to any deviation from standard
practice.
In Fig. 2 the column headed “QC Dimensions, refers to those dimensions of
”
the piece which are critical to the customer. The dimension designations “A,”
“B,” “C,” etc., are marked on the blueprint showing the piece. The QC operator
has a copy of the marked print, or a suitable sketch thereof. The QC operator checks
these critical dimensions when the pressing of that item begins. If any of the
dimensions are supercritical, the QC operator will make hourly checks to see that
748
