U.S. patent application number 15/573326 was filed with the patent office on 2018-04-19 for vitreous bond abrasive articles and methods of making the same.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Negus B. Adefris, Thomas J. Anderson, Carsten Franke, Maiken Givot, Brian D. Goers, Steven J. Keipert, Robert L.W. Smithson.
Application Number | 20180104793 15/573326 |
Document ID | / |
Family ID | 57586429 |
Filed Date | 2018-04-19 |
United States Patent
Application |
20180104793 |
Kind Code |
A1 |
Franke; Carsten ; et
al. |
April 19, 2018 |
VITREOUS BOND ABRASIVE ARTICLES AND METHODS OF MAKING THE SAME
Abstract
Methods of making vitreous bond abrasive articles and their
precursors using powder bed jetting are disclosed. Vitreous bond
abrasive articles prepared by the method include abrasive articles
having arcuate or tortuous cooling channels, unitary structured
abrasive discs, abrasive segments, shaped abrasive particles, and
abrasive wheels.
Inventors: |
Franke; Carsten; (St. Paul,
MN) ; Smithson; Robert L.W.; (Mahtomedi, MN) ;
Goers; Brian D.; (Minneapolis, MN) ; Adefris; Negus
B.; (St. Paul, MN) ; Givot; Maiken; (St. Paul,
MN) ; Anderson; Thomas J.; (Cottage Grove, MN)
; Keipert; Steven J.; (Houlton, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
57586429 |
Appl. No.: |
15/573326 |
Filed: |
June 23, 2016 |
PCT Filed: |
June 23, 2016 |
PCT NO: |
PCT/US2016/038902 |
371 Date: |
November 10, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62184695 |
Jun 25, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 64/165 20170801;
B24D 7/10 20130101; B24D 7/02 20130101; B24D 5/14 20130101; B24D
3/14 20130101; B24D 18/0009 20130101; B24D 11/04 20130101; B24D
5/10 20130101; B24D 7/14 20130101; B24D 2203/00 20130101; B24D 3/06
20130101; B24D 5/02 20130101 |
International
Class: |
B24D 5/02 20060101
B24D005/02; B24D 5/10 20060101 B24D005/10; B24D 3/06 20060101
B24D003/06; B24D 3/14 20060101 B24D003/14; B24D 5/14 20060101
B24D005/14; B24D 7/02 20060101 B24D007/02 |
Claims
1-24. (canceled)
25. A method of making a vitreous bond abrasive article, the method
comprising sequential steps: a) a subprocess comprising
sequentially: i) depositing a layer of loose powder particles in a
confined region, wherein the loose powder particles comprise
vitreous bond precursor particles and abrasive particles, and
wherein the layer of loose powder particles has substantially
uniform thickness; ii) jetting a liquid binder precursor material
in predetermined regions of the layer of loose powder particles;
iii) converting the liquid binder precursor material into a
temporary binder material that bonds together particles of the
loose powder particles in the predetermined regions to form a layer
of bonded powder particles; b) independently carrying out step a) a
plurality of times to generate an abrasive article preform
comprising the bonded powder particles and remaining loose powder
particles, wherein in each step a), the loose powder particles are
independently selected and the liquid binder precursor material is
independently selected; c) separating substantially all of the
remaining loose powder particles from the abrasive article preform;
d) heating the abrasive article preform to provide the vitreous
bond abrasive article comprising the abrasive particles retained in
a vitreous bond material.
26. The method of claim 25, wherein the abrasive particles comprise
at least one of diamond particles or cubic boron nitride
particles.
27. The method of claim 25, wherein the abrasive particles comprise
metal oxide ceramic particles.
28. The method of claim 25, wherein the abrasive particles and the
vitreous bond material have the same chemical composition.
29. The method of claim 25, wherein the vitreous bond abrasive
article includes at least one cooling channel.
30. The method of claim 25, wherein the vitreous bond abrasive
article is selected from the group consisting of a unitary
structured abrasive disc, an abrasive grinding bit, abrasive
segments, and an abrasive wheel.
31. The method of claim 25, wherein the liquid binder precursor
material comprises a liquid vehicle having a polymer dissolved or
dispersed therein.
32. The method of claim 25, wherein the liquid binder precursor
material comprises a liquid vehicle having an inorganic vitreous
bond precursor dissolved or dispersed therein.
33. The method of claim 32, wherein the inorganic vitreous bond
precursor comprises a precursor of alpha alumina.
34. The method of claim 32, wherein the loose powder particles
comprise submicron ceramic particles.
35. The method of claim 25, wherein the loose powder particles
further comprise flow agent particles.
36. The method of claim 32, wherein step d) further comprises
burning out the temporary binder material.
37. A vitreous bond abrasive article comprising a vitreous bond
material having abrasive particles retained therein, wherein the
vitreous bond abrasive article has at least one tortuous cooling
channel extending at least partially therethrough.
38. A vitreous bond abrasive article comprising a vitreous bond
material having abrasive particles retained therein, wherein the
vitreous bond abrasive article has at least one arcuate cooling
channel extending at least partially therethrough.
39. The vitreous bond abrasive article of claim 38, wherein the
abrasive particles comprise first abrasive particles and second
abrasive particles, wherein the first abrasive particles and second
abrasive particles are disposed in predetermined different regions
within the vitreous bond abrasive article.
40. The vitreous bond abrasive article of claim 38, wherein the
different regions are layers.
41. The vitreous bond abrasive article of claim 38, wherein the
abrasive particles comprise at least one of diamond particles or
cubic boron nitride particles.
42. The vitreous bond abrasive article of claim 38, wherein the
abrasive particles comprise at least one of silicon carbide, boron
carbide, silicon nitride, or metal oxide ceramic particles.
43. The vitreous bond abrasive article of claim 38, wherein the
vitreous bond abrasive article is selected from the group
consisting of a unitary structured abrasive disc, an abrasive
grinding bit, an abrasive segment, and an abrasive wheel.
44. A vitreous bond abrasive article precursor comprising abrasive
particles bonded together by a vitreous bond precursor material,
wherein the vitreous bond abrasive article precursor further
comprises at least one of: at least one tortuous cooling channel
extending at least partially through the vitreous bond abrasive
article precursor; or at least one arcuate cooling channel
extending at least partially through the vitreous bond abrasive
article precursor.
45. The vitreous bond abrasive precursor of claim 44, wherein the
abrasive particles comprise at least one of silicon carbide, boron
carbide, silicon nitride, or metal oxide ceramic particles.
46. A unitary structured abrasive disc comprising: a planar ceramic
base having a working major surface; and precisely-shaped ceramic
abrasive elements extending from the working major surface, wherein
the precisely-shaped ceramic abrasive elements and the planar
ceramic base form a unitary body.
47. The unitary structured abrasive disc of claim 46, wherein the
precisely-shaped abrasive elements are curved around a common
rotational axis.
48. The unitary structured abrasive disc of claim 47, wherein the
precisely-shaped abrasive elements are curved.
Description
TECHNICAL FIELD
[0001] The present disclosure broadly relates to methods of making
abrasive articles having abrasive particles in a vitreous bonding
matrix, and methods of making them.
BACKGROUND
[0002] Traditionally, vitrified bond abrasive articles (e.g.,
abrasive wheels, abrasive segments, and whetstones) are made by
compressing a blend of abrasive particles (e.g., diamond, cubic
boron nitride, alumina, or SiC), a vitreous bond precursor (e.g.,
glass frit, ceramic precursor) an optional pore inducer (e.g.,
glass bubbles, naphthalene, crushed coconut or walnut shells, or
acrylic glass or PMMA), and a temporary organic binder in a liquid
vehicle (e.g., aqueous solutions of phenolic resin, polyvinyl
alcohol, urea-formaldehyde resin, or dextrin). The abrasive
particles, vitreous bond precursor, and usually the pore inducer
are typically dry blended together. The temporary organic binder
solution is then added to wet out the grain mix. The blended mix is
then placed in a hardened steel mold treated with a mold release,
and then heated until the vitreous bond precursor is converted into
a vitreous bond matrix (also referred to in the art as "vitreous
bond" and "vitreous binder".
[0003] There are many disadvantages to this manufacturing approach:
each abrasive article shape requires a specialized mold; the molds
typically are expensive and have a long lead time to make; any
design change requires the manufacture of a new mold; there are
limitations to the shapes that can be molded, complicated shapes
with undercuts or internal structures such as cooling channels are
generally not possible; molds wear out and have a limited number of
units that can be manufactured per mold; while the molds are filled
with the abrasive mixture, separation of the components can occur,
leading to inhomogeneous abrasive components and density variation,
which is easily visible. Moreover, the process is manual and labor
intensive.
[0004] Powder bed binder jetting is an additive manufacturing, or
"3D printing" technology, in which a thin layer of a powder is
temporarily bonded at desired locations by a jetted liquid binder
mixture. Typically, that binder mixture is dispensed by an inkjet
printing head, and consists of a polymer dissolved in a suitable
solvent or carrier solution. In one method, the binder is a powder
which is mixed with the other powder, or coated onto the powder and
dried, and then an activating liquid, such as water or a solvent
mixture, is jetted onto the powder, activating the binder in select
areas.
[0005] The printed powder layer is then at least partially dried
and lowered so that a next powder layer can be spread. The powder
spreading, bonding and drying processes can be repeated until the
full object is created. The object and surrounding powder is
removed from the printer and often dried or cured to impart
additional strength so that the now hardened object can be
extracted from the surrounding powder.
SUMMARY
[0006] In one aspect, the present disclosure provides a method of
making a vitreous bond abrasive article, the method comprising
sequential steps: [0007] a) a subprocess comprising sequentially:
[0008] i) depositing a layer of loose powder particles in a
confined region, wherein the loose powder particles comprise
vitreous bond precursor particles and abrasive particles, and
wherein the layer of loose powder particles has substantially
uniform thickness; [0009] ii) jetting a liquid binder precursor
material in predetermined regions of the layer of loose powder
particles; [0010] iii) converting the liquid binder precursor
material into a temporary binder material that bonds together
particles of the loose powder particles in the predetermined
regions to form a layer of bonded powder particles; [0011] b)
independently carrying out step a) a plurality of times to generate
an abrasive article preform comprising the bonded powder particles
and remaining loose powder particles, wherein in each step a), the
loose powder particles are independently selected and the liquid
binder precursor material is independently selected; [0012] c)
separating substantially all of the remaining loose powder
particles from the abrasive article preform; [0013] d) heating the
abrasive article preform to provide the vitreous bond abrasive
article comprising the abrasive particles retained in a vitreous
bond material.
[0014] Advantageously, methods according to the present disclosure
are suitable for making vitreous bond abrasive articles, either in
large volume or short run production.
[0015] Accordingly, in another aspect, the present disclosure
provides a vitreous bond abrasive article comprising a vitreous
bond material having abrasive particles retained therein, wherein
the vitreous bond abrasive article has at least one tortuous
cooling channel extending at least partially therethrough.
[0016] In yet another aspect, the present disclosure provides a
vitreous bond abrasive article comprising a vitreous bond material
having abrasive particles retained therein, wherein the vitreous
bond abrasive article has at least one arcuate cooling channel
extending at least partially therethrough.
[0017] In yet another aspect, the present disclosure provides a
vitreous bond abrasive article precursor comprising abrasive
particles bonded together by a vitreous bond precursor material,
wherein the vitreous bond abrasive article precursor further
comprises at least one of: [0018] at least one tortuous cooling
channel extending at least partially through the vitreous bond
abrasive article precursor; or [0019] at least one arcuate cooling
channel extending at least partially through the vitreous bond
abrasive article precursor.
[0020] In yet another aspect, the present disclosure provides a
unitary structured abrasive disc comprising:
[0021] a planar ceramic base having a working major surface;
and
[0022] precisely-shaped ceramic abrasive elements extending from
the working major surface, wherein the precisely-shaped ceramic
abrasive elements and the planar ceramic base form a unitary
body.
[0023] In a twenty-second embodiment, the present disclosure
provides a unitary structured abrasive disc according to the
nineteenth embodiment, wherein the precisely-shaped abrasive
elements are curved around a common rotational axis.
[0024] As used herein, the term "vitreous bond" includes inorganic
ceramics, glasses, and glass-ceramics.
[0025] Features and advantages of the present disclosure will be
further understood upon consideration of the detailed description
as well as the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a schematic process flow diagram of a method of
making a vitreous bond abrasive article according to the present
disclosure.
[0027] FIG. 2 is a schematic cross-sectional top view of an
exemplary vitreous bond abrasive wheel 200, preparable according to
the present disclosure.
[0028] FIG. 3 is a schematic cross-sectional top view of an
exemplary vitreous bond abrasive wheel 300, preparable according to
the present disclosure.
[0029] FIG. 4 is a schematic perspective view of an exemplary
vitreous bond abrasive segment 400, preparable according to the
present disclosure.
[0030] FIG. 5 is a schematic perspective view of a vitreous bond
abrasive wheel 500, preparable according to the present
disclosure.
[0031] FIG. 6A is a schematic perspective view of a unitary
structured abrasive disc 600, preparable according to the present
disclosure.
[0032] FIG. 6B is a schematic top view of unitary structured
abrasive disc 600.
[0033] FIG. 7A is a schematic perspective view of a unitary
structured abrasive disc 700, preparable according to the present
disclosure.
[0034] FIG. 7B is a schematic top view of unitary structured
abrasive disc 700.
[0035] FIG. 8 is a schematic perspective view of rotary abrasive
tool 800, preparable according to the present disclosure.
[0036] Repeated use of reference characters in the specification
and drawings is intended to represent the same or analogous
features or elements of the disclosure. It should be understood
that numerous other modifications and embodiments can be devised by
those skilled in the art, which fall within the scope and spirit of
the principles of the disclosure. The figures may not be drawn to
scale.
DETAILED DESCRIPTION
[0037] Methods of making vitreous bond abrasive articles according
to the present disclosure include a common additive subprocess. The
subprocess comprises sequentially, preferably consecutively
(although not required) carrying out at least three steps.
[0038] FIG. 1 schematically depicts an exemplary powder bed jetting
process 100 used in making a vitreous bond abrasive article.
[0039] In the first step, a layer 138 of loose powder particles 110
is deposited in a confined region 140. The layer 138 should be of
substantially uniform thickness. For example, the thickness of the
layer may vary less than 50 microns, preferably less than 30
microns, and more preferably less than 10 microns. The layers may
have any thickness up to about 1 millimeter, as long as the jetted
liquid binder precursor material can bind all the loose powder
where it is applied. Preferably, the thickness of the layer is from
about 10 microns to about 500 microns, 10 microns to about 250
microns, more preferably about 50 microns to about 250 microns, and
more preferably from about 100 microns to about 200 microns.
[0040] The loose powder particles comprise vitreous bond precursor
particles and abrasive particles.
[0041] The vitreous bond precursor particles may comprise particles
of any material that can be thermally converted into a vitreous
material. Examples include glass frit particles, ceramic particles,
ceramic precursor particles, and combinations thereof.
[0042] The vitreous bond which binds together the abrasive grain in
accordance with this disclosure can be of any suitable composition
which is known in the abrasives art, for example. The vitreous bond
phase, also variously known in the art as a "ceramic bond",
"vitreous phase", vitreous matrix", or "glass bond" (e.g.,
depending on the composition) may be produced from one or more
oxide (e.g., a metal oxide and/or boria) and/or at least one
silicate as frit (i.e., small particles), which upon being heated
to a high temperature react to form an integral vitreous bond
phase. Examples include glass particles (e.g., recycled glass frit,
water glass frit), silica frit (e.g., sol-gel silica frit), alumina
trihydrate particles, alumina particles, zirconia particles, and
combinations thereof. Suitable frits, their sources and
compositions are well known in the art.
[0043] Abrasive articles are typically prepared by forming a green
structure comprised of abrasive grain, the vitreous bond precursor,
an optional pore former, and a temporary binder. The green
structure is then fired. The vitreous bond phase is usually
produced in the firing step of the process for producing the
abrasive article of this disclosure. Typical firing temperatures
are in the range of from 540.degree. C. to 1700.degree. C.
(1000.degree. F. to 3100.degree. F.). It should be understood that
the temperature selected for the firing step and the composition of
the vitreous bond phase must be chosen so as to not have a
detrimental effect on the physical properties and/or composition of
abrasive particles contained in the vitreous bond abrasive
article.
[0044] Useful glass frit particles may include any glass frit
material known for use in vitreous bond abrasive articles. Examples
include glass frit selected from the group consisting of silica
glass frit, silicate glass frit, borosilicate glass frit, and
combinations thereof. In one embodiment, a typical vitreous binding
material contains about 70-90% SiO.sub.2+B.sub.2O.sub.3, 1-20%
alkali oxides, 1-20% alkaline earth oxides, and 1-20% transition
metal oxides. In another embodiment, the vitreous binding material
has a composition of about 82 wt % SiO.sub.2+B.sub.2O.sub.3, 5%
alkali metal oxide, 5% transition series metal oxide, 4%
Al.sub.2O.sub.3, and 4% alkaline earth oxide. In another
embodiment, a frit having about 20% B.sub.2O.sub.3, 60% silica, 2%
soda, and 4% magnesia may be utilized as the vitreous binding
material. One of skill in the art will understand that the
particular components and the amounts of those components can be
chosen in part to provide particular properties of the final
abrasive article formed from the composition.
[0045] The size of the glass frit can vary. For example, it may be
the same size as the abrasive particles, or different. Typically,
the average particle size of the glass frit ranges from about 0.01
micrometer to about 100 micrometers, preferably about 0.05
micrometer to about 50 micrometers, and most preferably about 0.1
micrometer to about 25 micrometers. The average particle size of
the glass frit in relation to the average particle size of the
abrasive particles having a Mohs hardness of at least about 5 can
vary. Typically, the average particle size of the glass frit is
about 1 to about 200 percent of the average particle size of the
abrasive, preferably about 10 to about 100 percent, and most
preferably about 15 to about 50 percent.
[0046] Typically, the weight ratio of vitreous bond precursor
particles to abrasive particles in the loose powder particles
ranges from about 10:90 to about 90:10. The shape of the vitreous
bond precursor particles can also vary. Typically, they are
irregular in shape (e.g., crushed and optionally graded), although
this is not a requirement. For example, they may be spheroidal,
cubic, or some other predetermined shape.
[0047] Preferably, the coefficient of thermal expansion of the
vitreous bond precursor particles is the same or substantially the
same as that of the abrasive particles.
[0048] One preferred vitreous bond has an oxide-based mole percent
(%) composition of SiO.sub.2 63.28; TiO.sub.2 0.32; Al.sub.2O.sub.3
10.99; B.sub.2O.sub.3 5.11; Fe.sub.2O.sub.3 0.13; K.sub.2O 3.81;
Na.sub.2O 4.20; Li.sub.2O 4.98; CaO 3.88; MgO 3.04 and BaO 0.26.
Firing of these ingredients is typically accomplished by raising
the temperature from room temperature to 1149.degree. C.
(2100.degree. F.) over a prolonged period of time (e.g., about
25-26 hours), holding at the maximum temperature (e.g., for several
hours), and then cooling the fired article to room temperature over
an extended period of time (e.g., 25-30 hours).
[0049] The vitreous bond precursor particles may comprise ceramic
particles. In such cases sintering and/or fusing of the ceramic
particles forms the vitreous matrix. Any sinterable and/or fusible
ceramic material may be used. Preferred ceramic materials include
alumina, zirconia, and combinations thereof.
[0050] If desired, alpha-alumina ceramic particles may be modified
with oxides of metals such as magnesium, nickel, zinc, yttria, rare
earth oxides, zirconia, hafnium, chromium, or the like. Alumina and
zirconia abrasive particles may be made by a sol-gel process, for
example, as disclosed in U.S. Pat. No. 4,314,827 (Leitheiser et
al.); U.S. Pat. No. 4,518,397 (Leitheiser et al.); U.S. Pat. No.
4,574,003 (Gerk); U.S. Pat. No. 4,623,364 (Cottringer et al.); U.S.
Pat. No. 4,744,802 (Schwabel); and U.S. Pat. No. 5,551,963
(Larmie).
[0051] The vitreous bond precursor particles may be present in an
amount from 10 to 40 volume percent of the combined volume of the
vitreous bond precursor particles and abrasive particles,
preferably from 15 to 35 volume percent of the abrasive
composition.
[0052] It is known in the art to use various additives in the
making of vitreous bonded abrasive articles both to assist in the
making of the abrasive article and/or improve the performance of
such articles. Such conventional additives which may also be used
in the practice of this disclosure include but are not limited to
lubricants, fillers, pore inducers, and processing aids. Examples
of lubricants include, graphite, sulfur, polytetrafluoroethylene
and molybdenum disulfide. Examples of pore inducers include glass
bubbles and organic particles. Concentrations of the additives as
are known in the art may be employed for the intended purpose of
the additive, for example. Preferably, the additives have little or
no adverse effect on abrasive particles employed in the practice of
this disclosure.
[0053] The loose powder particles may optionally be modified to
improve their flowability and the uniformity of the layer spread.
Methods of improving the powders include agglomeration, spray
drying, gas or water atomization, flame forming, granulation,
milling, and sieving. Additionally, flow agents such as, for
example, fumed silica, nanosilica, stearates, and starch may
optionally be added.
[0054] The vitreous bond precursor particles may comprise a ceramic
precursor (e.g., a precursor of alumina or zirconia) such as, for
example, bauxite, boehmite, calcined alumina, or calcined zirconia
that when fired converts to the corresponding ceramic form.
[0055] Procedures and conditions known in the art for producing
vitreous bonded abrasive articles (e.g., grinding wheels), and
especially procedures and conditions for producing vitreous bond
abrasive articles, may be used to make the abrasive articles of
this disclosure. These procedures may employ conventional and well
known equipment in the art.
[0056] The abrasive particles may comprise any abrasive particle
used in the abrasives industry. Preferably, the abrasive particles
have a Mohs hardness of at least 4, preferably at least 5, more
preferably at least 6, more preferably at least 7, more preferably
at least 8, more preferably at least 8.5, and more preferably at
least 9. In certain embodiments, the abrasive particles comprise
superabrasive particles. As used herein, the term "superabrasive"
refers to any abrasive particle having a hardness greater than or
equal to that of silicon carbide (e.g., silicon carbide, boron
carbide, cubic boron nitride, and diamond).
[0057] Specific examples of suitable abrasive materials include
aluminum oxide (e.g., alpha alumina) materials (e.g., fused,
heat-treated, ceramic, and/or sintered aluminum oxide materials),
silicon carbide, titanium diboride, titanium nitride, boron
carbide, tungsten carbide, titanium carbide, aluminum nitride,
diamond, cubic boron nitride (CBN), garnet, fused alumina-zirconia,
sol-gel derived abrasive particles, cerium oxide, zirconium oxide,
titanium oxide, and combinations thereof. Examples of sol-gel
derived abrasive particles can be found in U.S. Pat. No. 4,314,827
(Leitheiser et al.), U.S. Pat. No. 4,623,364 (Cottringer et al.);
U.S. Pat. No. 4,744,802 (Schwabel), U.S. Pat. No. 4,770,671 (Monroe
et al.); and U.S. Pat. No. 4,881,951 (Monroe et al.). Agglomerate
abrasive particles that comprise finer abrasive particles in a
vitreous bond matrix (e.g., as described in U.S. Pat. No. 6,551,366
(D'Souza et al.)) may also be used.
[0058] In order to achieve fine resolution, the loose powder
particles are preferably sized (e.g., by screening) to have a
maximum size of less than or equal to 400 microns, preferably less
than or equal to 250 microns, more preferably less than or equal to
200 microns, more preferably less than or equal to 150 microns,
less than or equal to 100 microns, or even less than or equal to 80
microns, although larger sizes may also be used. The vitreous bond
precursor particles, abrasive particles, and any optional
additional particulate components may have the same or different
maximum particle sizes, D.sub.90, D.sub.50, and/or D.sub.10
particle size distribution parameters.
[0059] The loose powder particles may optionally further comprise
other components such as, for example, pore inducers, and/or filler
particles. Examples of pore inducers include glass bubbles and
organic particles.
[0060] Next, a liquid binder precursor material 170 is jetted by
printer 150 onto predetermined region(s) 180 of layer 138. The
liquid binder precursor material thus coats the loose powder
particles in region 180, and is subsequently converted to a binder
material that binds the loose powder particles in region 180 to
each other. The liquid binder precursor material may be any
composition that can be converted (e.g., by evaporation, or
thermal, chemical, and/or radiation curing (e.g., using UV or
visible light)) into a binder material that bonds the loose powder
particles together according to the jetted pattern (and ultimate
3-D shape upon multiple repetitions).
[0061] In some embodiments, the liquid binder precursor material
comprises a liquid vehicle having a polymer dissolved therein. The
liquid may include one or more of organic solvent and water.
Exemplary organic solvents include alcohols (e.g., butanol,
ethylene glycol monomethyl ether), ketones, and ethers, preferably
having a flash point above 100.degree. C.
[0062] Selection of a suitable solvent or solvents will typically
depend upon requirements of the specific application, such as
desired surface tension and viscosity, the selected particulate
solid, for example.
[0063] The liquid vehicle can be entirely water, or can contain
water in combination with one or more organic solvents. Preferably,
the aqueous vehicle contains, on a total weight basis, at least 20
percent water, at least 30 percent water, at least 40 percent
water, at least 50 percent water, or even at least 75 percent
water.
[0064] In some embodiments, one or more organic solvents may be
included in the liquid vehicle, for instance, to control drying
speed of the liquid vehicle, to control surface tension of the
liquid vehicle, to allow dissolution of an ingredient (e.g., of a
surfactant), or, as a minor component of any of the ingredients;
e.g., an organic co-solvent may be present in a surfactant added as
an ingredient to the liquid vehicle. Exemplary organic solvents
include: alcohols such as methyl alcohol, ethyl alcohol, n-propyl
alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol,
t-butyl alcohol, and isobutyl alcohol; ketones or ketoalcohols such
as acetone, methyl ethyl ketone, and diacetone alcohol; esters such
as ethyl acetate and ethyl lactate; polyhydric alcohols such as
ethylene glycol, diethylene glycol, triethylene glycol, propylene
glycol, butylene glycol, 1,4-butanediol, 1,2,4-butanetriol,
1,5-pentanediol, 1,2,6-hexanetriol, hexylene glycol, glycerol,
glycerol ethoxylate, trimethylolpropane ethoxylate; lower alkyl
ethers such as ethylene glycol methyl or ethyl ether, diethylene
glycol ethyl ether, triethylene glycol methyl or ethyl ether,
ethylene glycol n-butyl ether, diethylene glycol n-butyl ether,
diethylene glycol methyl ether, ethylene glycol phenyl ether,
propylene glycol methyl ether, dipropylene glycol methyl ether,
tripropylene glycol methyl ether, propylene glycol methyl ether
acetate, dipropylene glycol methyl ether acetate, propylene glycol
n-propyl ether, dipropylene glycol n-propyl ether, tripropylene
glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene
glycol n-butyl ether, tripropylene glycol n-butyl ether, propylene
glycol phenyl ether, and dipropylene glycol dimethyl ether;
nitrogen-containing compounds such as 2-pyrrolidinone and
N-methyl-2-pyrrolidinone; sulfur-containing compounds such as
dimethyl sulfoxide, tetramethylene sulfone, and thioglycol; and
combinations of any of the foregoing.
[0065] The amounts of organic solvent and/or water within the
liquid vehicle can depend on a number of factors, such as the
particularly desired properties of the liquid binder precursor
material such as the viscosity, surface tension, and/or drying
rate, which can in turn depend on factors such as the type of ink
jet printing technology intended to be used with the liquid vehicle
ink, such as piezo-type or thermal-type printheads, for
example.
[0066] The liquid binder precursor material may include a polymer
that is soluble or dispersible in the liquid vehicle. Examples of
suitable polymers may include polyvinyl pyrrolidones, polyvinyl
caprolactams, polyvinyl alcohols, polyacrylamides,
poly(2-ethyl-2-oxazoline) (PEOX), polyvinyl butyrate, copolymers of
methyl vinyl ether and maleic anhydride, certain copolymers of
acrylic acid and/or hydroxyethyl acrylate, methyl cellulose,
natural polymers (e.g., dextrin, guar gum, xanthan gum). Of these,
polyvinyl pyrrolidones are preferred for use with liquid vehicles
that are predominantly water. Other organic polymers than those
listed above may be used instead or in addition if desired.
[0067] The liquid binder precursor material may include one or more
free-radically polymerizable or otherwise radiation-curable
materials; for example, acrylic monomers and/or oligomers and/or
epoxy resins. An effective amount of photoinitiator and/or
photocatalysts for curing the free-radically polymerizable or
otherwise radiation-curable materials may also be included.
Examples of suitable (meth)acrylate monomers and oligomers and
otherwise radiation-curable materials (e.g., epoxy resins) can be
found in, for example, U.S. Pat. No. 5,766,277 (DeVoe et al.).
[0068] In some preferred embodiments, the liquid binder precursor
material is essentially free of (e.g., contains less than 1
percent, less than 0.1 percent, less than 0.01 percent, or is even
free of) metal nanoparticles and/or metal oxide nanoparticles. As
used herein, the term "nanoparticles" refers to particles having an
average particle diameter of less than or equal to one micron; for
example less than or equal to 500 nanometers (nm), or even less
than or equal to 150 nm.
[0069] Alternatively, or in addition, the liquid binder precursor
may be an aqueous sol comprising a ceramic precursor for alumina
and/or zirconia. Examples include aqueous boehmite sols and
zirconia sols. In such cases, after firing, the liquid binder
precursor may have the same or different composition as the
abrasive particles. Details concerning zirconia sols can be found,
for example, in U.S. Pat. No. 6,376,590 (Kolb et al.). Details
concerning boehmite sols can be found, for example, in U.S. Pat.
No. 4,314,827 (Leitheiser et al.), U.S. Pat. No. 5,178,849 (Bauer)
U.S. Pat. No. 4,518,397 (Leitheiser et al.), U.S. Pat. No.
4,623,364 (Cottringer et al.), U.S. Pat. No. 4,744,802 (Schwabel),
U.S. Pat. No. 4,770,671 (Monroe et al.), U.S. Pat. No. 4,881,951
(Wood et al.), U.S. Pat. No. 4,960,441 (Pellow et al.) U.S. Pat.
No. 5,011,508 (Wald et al.), U.S. Pat. No. 5,090,968 (Pellow), U.S.
Pat. No. 5,139,978 (Wood), U.S. Pat. No. 5,201,916 (Berg et al.),
U.S. Pat. No. 5,227,104 (Bauer), U.S. Pat. No. 5,366,523
(Rowenhorst et al.), U.S. Pat. No. 5,429,647 (Larmie), U.S. Pat.
No. 5,547,479 (Conwell et al.), U.S. Pat. No. 5,498,269 (Larmie),
U.S. Pat. No. 5,551,963 (Larmie), U.S. Pat. No. 5,725,162 (Garg et
al.), and U.S. Pat. No. 5,776,214 (Wood)).
[0070] The jetted liquid binder precursor material is converted
into a binder material that bonds together the loose powder
particles in predetermined regions of the loose powder particles to
form a layer of bonded powder particles; for example, by
evaporation of a liquid vehicle in the liquid binder precursor
material. In these embodiments, heating the binder material to
sufficiently high temperature causes it to volatilize and/or
decompose (e.g., "burn out") during a subsequent firing step.
Cooling may be accomplished by any means known to the art (e.g.,
cold quenching or air cooling to room temperature).
[0071] Referring again to FIG. 1, the jetted liquid binder
precursor material 170 is converted (step 190) into a binder
material that bonds together the loose powder particles in at least
one predetermined region of the loose powder particles to form a
layer of bonded powder particles; for example, by evaporation of a
liquid vehicle in the liquid binder precursor material. In these
embodiments, heating the binder material to sufficiently high
temperature causes it to volatilize and/or decompose (e.g., "burn
out") during subsequent sintering or infusion steps.
[0072] The above steps are then repeated (step 185) with changes to
the region where jetting is carried out according to a
predetermined design resulting through repetition, layer on layer,
in a three-dimensional (3-D) abrasive article preform. In each
repetition, the loose powder particles and the liquid binder
precursor material may be independently selected; that is, either
or both or the loose powder particles and the liquid binder
precursor material may be the same as, or different from those in
adjacent deposited layers.
[0073] The abrasive article preform comprises the bonded powder
particles and remaining loose powder particles. Once sufficient
repetitions have been carried out to form the abrasive article
preform, it is preferably separated from substantially all (e.g.,
at least 85 percent, at least 90 percent, preferably at least 95
percent, and more preferably at least 99 percent) of the remaining
loose powder particles, although this is not a requirement.
[0074] If desired, multiple particle reservoirs each containing a
different powder may be used. Likewise, multiple different liquid
binder precursor materials may be used, either through a common
printhead or, preferably, through separate printheads. This results
in different powders/binders distributed in different and discrete
regions of the vitrified bond abrasive article. For example,
relatively inexpensive, but lower performing abrasive particles and
or vitreous bond precursor particles may be relegated to regions of
the vitrified bond abrasive article where it is not particularly
important to have high performance properties (e.g., in the
interior away from the abrading surface).
[0075] Generally, vitreous bond abrasive articles made in such ways
have considerable porosity throughout their volumes. Accordingly,
the abrasive article preform may then be infused with a solution or
dispersion of additional vitreous bond precursor material, or grain
growth modifiers.
[0076] Powder bed jetting equipment suitable for practicing the
present disclosure is commercially available, for example, from
ExOne, North Huntington, Pa. Further details concerning powder bed
jetting techniques suitable for practicing the present disclosure
can be found, for example, in U.S. Pat. No. 5,340,656 (Sachs et
al.) and U.S. Pat. No. 6,403,002 B1 (van der Geest).
[0077] Advantageously, methods according to the present disclosure
are suitable for manufacturing various vitreous bond abrasive
articles that cannot be readily or easily fabricated by other
methods. For example, inclusion of internal voids is possible as
long as an opening to the exterior of the abrasive preform exists
for removal of unbonded loose powder. Accordingly, cooling channels
having tortuous and or arcuate paths can be readily manufactured
using methods of the present disclosure. Cooling channels are open
to the exterior of the vitreous bond abrasive article. In some
embodiments, they have a single opening, but more typically they
have two or more openings. A cooling medium (e.g., air, water or
oil) circulates through the cooling channel(s) to remove heat
generated during abrading.
[0078] Referring now to FIG. 2, exemplary vitreous bond abrasive
wheel 200 has arcuate and tortuous cooling channels 210,
respectively.
[0079] FIG. 3 shows another exemplary vitreous bond abrasive wheel
300 that has tortuous cooling channels 320.
[0080] Vitreous bond abrasive articles preparable according to
methods of the present disclosure include essentially any known
vitreous bond abrasive article; for example, unitary structured
abrasive discs, grinding bits, abrasive segments, shaped abrasive
particles (e.g., triangular abrasive particles), and abrasive
wheels as well as many hitherto unknown vitreous bond abrasive
articles.
[0081] FIG. 4 shows an exemplary vitreous bond abrasive segment
400. In typical use, multiple vitreous bond abrasive segments 400
are mounted evenly spaced along the circumference of a metal disc
to form an abrasive wheel.
[0082] FIG. 5 shows a vitreous bond abrasive disc 500 has two
regions 510, 520. Each region has abrasive particles 530, 540
retained in a vitreous bond matrix material 550, 560,
respectively.
[0083] FIGS. 6A-6B and 7A-7B, respectively show various unitary
structured abrasive discs with precisely-shaped ceramic abrasive
elements 610, 710 formed integrally with ceramic planar bases 620,
720.
[0084] FIG. 8 shows a rotary abrasive tool 800 (a bit for a
handheld motor driven shaft such as, for example, a Dremel
tool).
[0085] The foregoing vitreous abrasive wheels shown in FIGS. 2 and
3 can be prepared by firing corresponding green bodies (i.e.,
having the same general shape features, but comprising a vitreous
bond precursor particles held together by a temporary binder).
SELECT EMBODIMENTS OF THE PRESENT DISCLOSURE
[0086] In a first embodiment, the present disclosure provides a
method of making a vitreous bond abrasive article, the method
comprising sequential steps: [0087] a) a subprocess comprising
sequentially: [0088] i) depositing a layer of loose powder
particles in a confined region, wherein the loose powder particles
comprise vitreous bond precursor particles and abrasive particles,
and wherein the layer of loose powder particles has substantially
uniform thickness; [0089] ii) jetting a liquid binder precursor
material in predetermined regions of the layer of loose powder
particles; [0090] iii) converting the liquid binder precursor
material into a temporary binder material that bonds together
particles of the loose powder particles in the predetermined
regions to form a layer of bonded powder particles; [0091] b)
independently carrying out step a) a plurality of times to generate
an abrasive article preform comprising the bonded powder particles
and remaining loose powder particles, wherein in each step a), the
loose powder particles are independently selected and the liquid
binder precursor material is independently selected; [0092] c)
separating substantially all of the remaining loose powder
particles from the abrasive article preform; [0093] d) heating the
abrasive article preform to provide the vitreous bond abrasive
article comprising the abrasive particles retained in a vitreous
bond material.
[0094] In a second embodiment, the present disclosure provides a
method according to the first embodiment, wherein the abrasive
particles comprise at least one of diamond particles or cubic boron
nitride particles.
[0095] In a third embodiment, the present disclosure provides a
method according to the first or second embodiment, wherein the
abrasive particles comprise metal oxide ceramic particles.
[0096] In a fourth embodiment, the present disclosure provides a
method according to any one of the first to third embodiments,
wherein the abrasive particles and the vitreous bond material have
the same chemical composition.
[0097] In a fifth embodiment, the present disclosure provides a
method according to any one of the first to fourth embodiments,
wherein the vitreous bond abrasive article includes at least one
cooling channel
[0098] In a sixth embodiment, the present disclosure provides a
method according to any one of the first to fifth embodiments,
wherein the vitreous bond abrasive article is selected from the
group consisting of an unitary structured abrasive disc, an
abrasive grinding bit, abrasive segments, and an abrasive
wheel.
[0099] In a seventh embodiment, the present disclosure provides a
method according to any one of the first to sixth embodiments,
wherein the liquid binder precursor material comprises a liquid
vehicle having a polymer dissolved and/or dispersed therein.
[0100] In an eighth embodiment, the present disclosure provides a
method according to any one of the first to seventh embodiments,
wherein the liquid binder precursor material comprises a liquid
vehicle having an inorganic vitreous bond precursor dissolved
and/or dispersed therein.
[0101] In a ninth embodiment, the present disclosure provides a
method according to the eighth embodiment, wherein the inorganic
vitreous bond precursor comprises a precursor of alpha alumina.
[0102] In a tenth embodiment, the present disclosure provides a
method according to the eighth or ninth embodiment, wherein the
loose powder particles comprise submicron ceramic particles.
[0103] In an eleventh embodiment, the present disclosure provides a
method according to any one of the first to tenth embodiments,
wherein the loose powder particles further comprise flow agent
particles.
[0104] In a twelfth embodiment, the present disclosure provides a
method according to any one of the eighth to eleventh embodiments,
wherein step d) further comprises burning out the temporary binder
material.
[0105] In a thirteenth embodiment, the present disclosure provides
a vitreous bond abrasive article comprising a vitreous bond
material having abrasive particles retained therein, wherein the
vitreous bond abrasive article has at least one tortuous cooling
channel extending at least partially therethrough.
[0106] In a fourteenth embodiment, the present disclosure provides
vitreous bond abrasive article comprising a vitreous bond material
having abrasive particles retained therein, wherein the vitreous
bond abrasive article has at least one arcuate cooling channel
extending at least partially therethrough.
[0107] In a fifteenth embodiment, the present disclosure provides a
vitreous bond abrasive article according to the thirteenth or
fourteenth embodiment, wherein the abrasive particles comprise
first abrasive particles and second abrasive particles, wherein the
first abrasive particles and second abrasive particles are disposed
in predetermined different regions within the vitreous bond
abrasive article.
[0108] In a sixteenth embodiment, the present disclosure provides a
vitreous bond abrasive article according to the fifteenth
embodiment, wherein the different regions are layers.
[0109] In a seventeenth embodiment, the present disclosure provides
a vitreous bond abrasive article according to any one of the
thirteenth to sixteenth embodiments, wherein the abrasive particles
comprise at least one of diamond particles or cubic boron nitride
particles.
[0110] In an eighteenth embodiment, the present disclosure provides
a vitreous bond abrasive article according to any one of the
thirteenth to seventeenth embodiments, wherein the abrasive
particles comprise at least one of silicon carbide, boron carbide,
silicon nitride, or metal oxide ceramic particles.
[0111] In a nineteenth embodiment, the present disclosure provides
a vitreous bond abrasive article precursor according to any one of
the thirteenth to eighteenth embodiments, wherein the vitreous bond
abrasive article is selected from the group consisting of a unitary
structured abrasive disc, an abrasive grinding bit, an abrasive
segment, and an abrasive wheel.
[0112] In a twentieth embodiment, the present disclosure provides a
vitreous bond abrasive article precursor comprising abrasive
particles bonded together by a vitreous bond precursor material,
wherein the vitreous bond abrasive article precursor further
comprises at least one of: [0113] at least one tortuous cooling
channel extending at least partially through the vitreous bond
abrasive article precursor; or [0114] at least one arcuate cooling
channel extending at least partially through the vitreous bond
abrasive article precursor.
[0115] In a twenty-first embodiment, the present disclosure
provides a vitreous bond abrasive precursor according to the
twentieth embodiment, wherein the abrasive particles comprise at
least one of silicon carbide, boron carbide, silicon nitride, or
metal oxide ceramic particles.
[0116] In a twenty-second embodiment, the present disclosure
provides a unitary structured abrasive disc comprising:
[0117] a ceramic base having a working major surface; and
[0118] precisely-shaped ceramic abrasive elements extending from
the working major surface, wherein the precisely-shaped ceramic
abrasive elements and the planar ceramic base form a unitary
body.
[0119] In a twenty-third embodiment, the present disclosure
provides a unitary structured abrasive disc according to the
twenty-second embodiment, wherein the precisely-shaped abrasive
elements are curved around a common rotational axis.
[0120] In a twenty-fourth embodiment, the present disclosure
provides a unitary structured abrasive disc according to the
twenty-third or twenty-fourth embodiment, wherein the
precisely-shaped ceramic abrasive elements are curved.
[0121] Objects and advantages of this disclosure are further
illustrated by the following non-limiting examples, but the
particular materials and amounts thereof recited in these examples,
as well as other conditions and details, should not be construed to
unduly limit this disclosure.
EXAMPLES
[0122] Unless otherwise noted, all parts, percentages, ratios, etc.
in the Examples and the rest of the specification are by weight. In
the Examples: .degree. C.=degrees Celsius, g=grams, min=minute,
mm=millimeter, sec=second, and rpm=revolutions per minute.
Table 1, below, lists abbreviations for materials used in the
Examples.
TABLE-US-00001 TABLE 1 ABBREVI- ATION DESCRIPTION PDR1 200/230
Mesh, D76 CMD diamond, from Pinnacle Abrasives, Santa Rosa,
California PDR2 ALODUR BFRPL aluminium oxide particles, grade P320,
from Treibacher Schleifmittel AG, Villach, Austria PDR3 SP1086
glass powder from Specialty Glass Inc., Oldsmar, Florida PDR4 A mix
of 98.5% vitrified bond VO82069 from Reimbold & Strick,
Cologne, Germany and 1.5% color stain for glazes K90084 from
Reimbold & Strick, Cologne, Germany PDR5 MB-M1, 2-4 micron
diamond powder from WorldWide Superabrasives, LLC, Boynton Beach,
Florida PDR6 A mixture of 22.2 wt. % of silicon carbide, 280 grit,
8.8 wt. % of boron carbide, 280 grit, from Washington Mills Electro
Minerals, Niagara Falls, New York and 70 wt. % of PDR3 PDR7
CAB-O-SIL CT-1221 fumed silica from Cabot Corporation, Boston,
Massachusetts PDR8 PWA 4000, 3 micron aluminum oxide powder from
Fujimi Corporation, Tualatin, Oregon PDR9 A-16 SG thermally
reactive superground alumina powder from Almatis Company,
Frankfurt, Germany PDR10 Cornstarch powder, obtained from ConAgra
Foods Inc., Omaha, Nebraska AG1 Diamond agglomerate made from
agglomerating PDR5 according to the Agglomeration Procedure
described herein below AG2 Aluminum oxide agglomerate made from
agglomerating PDR8 according to the Agglomeration Procedure
described below BIN Ether solvent-based polymer binder, obtained as
PM-B- SR1-04 from The ExOne Company, North Huntingdon,
Pennsylvania
Agglomeration Procedure
[0123] Abrasive particles (PDR5 or PDR8) were agglomerated with the
binder matrix PDR3 to form agglomerates (AG1 or AG2, respectively)
with sizes that ranged from 5 micrometers to 45 micrometers using a
spray drying atomization method described as follows. A mixture
containing the following components was blended with the help of a
laboratory ultrasonic bath: 123.0 grams (g) of a 25 wt. % aqueous
dextrin solution, 100.0 g of PDR3, 90.0 g of PDR5 (to make AG1) or
PDR8 (to make AG2), 295.0 g of distilled water, 1.9 g of
N-octadecyl sulfosuccinamate (obtained as CYANASOL AY from American
Cyanamid Co., Wayne, N.J.). The mixture was then atomized in a
centrifugal atomizer (Mobile Minor from Niro Inc., Columbia, Md.).
The atomization wheel was running at 20000 rpm. Air supplied at
200.degree. C. into the atomization chamber was used to dry the
particles as they formed into droplets. The particles were then
collected using a cyclone equipped with the atomizer and sieved
through a 45 micrometer sieve to remove the coarser particles.
Example 1
[0124] A print material was prepared by mixing, based on the
mixture weight, 80 wt. % of PDR1 and 20 wt. % of PDR3. The print
material was filled into the build box of an X1-LAB 3D printer,
obtained from The ExOne Company, North Huntingdon, Pa. The binder
supply bottle of the printer was filled with BIN. 3D printing
according to design parameters shown in FIG. 8 (OD=13 mm, ID=3 mm)
was executed using printing protocol and procedures according to
the manufacturer's operating instructions using the following
operation parameters: layer height=100 microns, spreader speed=1
mm/sec, printing saturation=70% level, and drying time=45 sec at
90% heater power. After printing was finished, the printed object
and the powder bed were extracted from the printer and placed into
an ambient atmosphere oven to cure for 2 hours at 195.degree. C.
After cooling down to 23.degree. C., the printed object was removed
from the powder bed and loose powder was removed using a soft
bristle brush. The object was then placed into a furnace and burned
out at 400.degree. C. for 2 hours, followed by sintering at
700.degree. C. for 4 hours, resulting in an abrasive bit suitable
for use with a handheld rotary tool device (e.g., Dremel rotary
tool for Robert Bosch Tool Corp., Mount Prospect, Ill.).
Example 2
[0125] A print material was prepared by mixing, based on the
mixture weight, 85 wt. % of PDR2 and 15 wt. % of PDR4. The
procedure generally described in Example 1 was repeated, except
that: spreader speed=10 mm/sec, printing saturation=130% level,
drying time=55 sec at 90% heater power, and furnace sintering
temperature=900.degree. C. for 4 hours.
Example 3
[0126] A print material was prepared by mixing, based on the
mixture weight, 80 wt. % of AG1 and 20 wt. % of PDR3. The procedure
generally described in Example 1 was repeated, except printing
saturation=150% level, drying time=25 sec at 90% heater power, and
furnace sintering temperature=at 630.degree. C. for 4 hours.
Example 4
[0127] A print material was prepared by mixing, based on the
mixture weight, 83.0 wt. % of PDR6, 16.9 wt. % of AG1, and 0.1 wt.
% of PDR7. The procedure described in Example 1 was repeated,
except that printing saturation=125% level, drying time=60 sec at
90% heater power, and furnace sintering temperature=600.degree. C.
for 4 hours.
Example 5
[0128] A print material was prepared by mixing, based on the
mixture weight, 80 wt. % of AG2 and 20 wt. % of PDR3. The procedure
described in Example 4 was repeated, except that the furnace
sintering temperature was set at 630.degree. C. for 4 hours.
Abrasive Performance Evaluation
[0129] The vitreous bond abrasive articles from Examples 1 to 5
were evaluated for abrasive performance against a variety of
materials, such as aluminum, a microscopy glass slide, and a piece
of wood. In some cases, rotary tools were assembled on a mandrel
and tested with a Dremel handheld rotary tool. All the objects were
effective for abrading the materials.
Example 6
[0130] The procedure described in Example 1 was repeated, except
that: the article design was an equilateral triangle (3 mm sides,
0.6 thickness); the print powder material was prepared by sifting
PDR9 first through a sieve with 180 micron openings, then through a
sieve with 62 micron openings; layer height=100 microns; powder
ratio=1.6; spreader speed=15 mm/sec; printing saturation=160%
level; drying time=60 sec; after cooling down to 23.degree. C., the
printed object was removed from the powder using a 300 micron sieve
instead of a brush; and the object was then fired in a furnace
heated at a rate of 5.degree. C./min to a final temperature of
1500.degree. C. where it was held for 20 min.
Example 7
[0131] A print powder material was prepared by mixing 80 wt. % of
PDR9 and 20 wt. % of PDR10 (percentages based on the mixture
weight) and sifting first through a sieve with 180 micron openings,
then through a sieve with 62 micron openings. The procedure
generally described in Example 6 was repeated, except that:
spreader speed=1.0 mm/sec, printing saturation=140% level, drying
time=40 sec, and the furnace was heated at a rate of 5.degree.
C./min to a final temperature of 1555.degree. C.
[0132] All cited references, patents, and patent applications in
the above application for letters patent are herein incorporated by
reference in their entirety in a consistent manner. In the event of
inconsistencies or contradictions between portions of the
incorporated references and this application, the information in
the preceding description shall control. The preceding description,
given in order to enable one of ordinary skill in the art to
practice the claimed disclosure, is not to be construed as limiting
the scope of the disclosure, which is defined by the claims and all
equivalents thereto.
* * * * *