1. • Dr. Eric Stelter • 22 April 2004 • Heidelberg Digital LLC.ppt • page:
1© Heidelberg Digital L.L.C.
Dr. Eric Stelter, Dr. Pat Lambert, and Mr. Michael Frauens
Heidelberg Digital L.L.C. Rochester, New York USA
Application of
Rotating Magnetic Brush Technology
in New Powder Coating Markets
ICC 2004 22.04.2004

2. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
2© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 2
Fixed
Magnets
Explanation : What is Rotating Magnetic Brush Technology?
Rotating Magnetic Brush
Magnetic roller with 2 moving parts
• Rotating metallic outer shell
• Rotating magnetic core
Conventional Magnetic Brush
Magnetic roller with 1 moving part
• Rotating metallic outer shell
• Stationary magnetic core
Rotating
Magnets
S
S
S
N
N
N
N
S
S S
N
N
N

3. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
3© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 3
Explanation : What is Rotating Magnetic Brush Technology?
Rotating Magnetic Brush
Magnetic roller with 2 moving parts
• Rotating metallic outer shell
• Rotating magnetic core
Conventional Magnetic Brush
Magnetic roller with 1 moving part
• Rotating metallic outer shell
• Stationary magnetic core
Rotating
Magnets
S
S
S
N
N
N
N
S
Fixed
Magnets
S S
N
N
N

4. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
4© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 4
Characteristics of Rotating Magnetic Brush Technology
• Direct deposition of powder to substrate
• Intermediate rollers not required between magnetic brush and
substrate of any classification, including magnetic material.
• Non-contact roller (Gap between roller surface and substrate)
• Coating thickness adjusted by changing voltage applied to roller
• Efficient handling of small particles 9µm and larger
• Minimal environmental controls required
• Powder particles contained between roller and substrate
• Particles not dispersed into air
Performance of Rotating Magnetic Brush Technology
• High speed greater than 2,5 m/s
• Laydown range with 1 roller: 10 g/m2
to 40 g/m2
(adjustable)
• Uniformity better than 10%

5. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
5© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 5
• Magnetic carrier particles
form a brush on the
development roller.
• The powder (-) is attracted to
the carrier particles (+)
• The rotation of the outer roller
and the magnetic core impart
motion to the chains of
developer
• Bias voltage applied to
metallic shell moves powder
to substrate.
Substrate
N SS
+
+ + +
+
+
+
+
+
+
+
+ + +
+
-
- -
- - --
-
-
-
-
-
- --
-
-
-
-
- -
-
-
-
-
-
-
-
-
-- -
-
-
-
-
-
-
-
-
-
-
-
-
--
-
--
- - - -
Rotating Magnetic Brush:
Roller with rotating outer metallic shell and rotating
inner magnetic core.

6. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
6© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 6
The Powder Coating Process: Experimental Equipment
• Metallic substrate
• Coating apparatus
with magnetic rollers
and drive motors
• Power supplies for
bias voltage to roller
• Motors and motor
speed controllers
• Powder reservoir and
feed mechanism

7. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
7© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 7
The Rotating Magnetic Brush
• Modified Imaging/Coating Module
(~ 48cm x 15cm x 15cm)
• Single, non-contact roller
• Deposition onto ferromagnetic
substrate. (Reasons Include:
high field gradient, demagnetize
substrate with rotating core)
• Used in thousands of existing
printing machines.

8. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
8© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 8
The Rotating Magnetic Brush: Carrier Particles
• Strontium Ferrite particles
• Permanently magnetized
• Polymer coated
• Can accommodate a wide
range of powder paint
materials.

9. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
9© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 9
Magnetic Brush Types
Rotating Magnetic Brush
Technology
Conventional Magnetic Brush
Technology
Rotating
Magnets
"Dynamic/Flipping" Chains
Rotating Smooth Shell
S
S
S
N
N
N
"Static/Less Dynamic" Chains
Rotating Rough Shell
N
S
Fixed
Magnets
SS S
NN
N

10. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
10© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 10
Initial stage of deposition
Simulation of Deposition
• Magnetic brush moves, creating a
uniform powder coating without streaks.
• Carrier particles are large (26 microns)
• Powder particles are small (9 microns)
• Particles are deposited in areas of
substrate with electrostatic charge
• Particles are colored based on their final
location at the completion of deposition
(final state coloration)
Red particles will end up at the top of the
development zone, blue particles at the bottom

11. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
11© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 11
Magnetic Brush and Powder Coating: History
Powder coating from a magnetic
brush to an intermediate transfer
member and then to a substrate.
(U.S. Pat. 3,306,193)
Powder coating directly from a
magnetic brush to a metallic
substrate.
(U.S. Pat. 4,041,901)

12. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
12© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 12
• Deposition of Paint Particle (Toner
Particle) to Substrate (Photoconductor)
occurs only during 3-body contact
events
• Describes development with a
stationary magnetic core
Equilibrium Theory of Development
(from copier technology)
Λ
=
νε
MQ
V
A
M 0
Schein, "Electrophotography and Development Physics" 1996
Substrate
Paint Particle

13. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
13© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 13
• Roller speeds were set
and substrate speed was
varied
• Deposition of particles is
greater with rotating
magnetic brush
• Imaging toner (polymeric
particles) were used in
this test. This toner is
used in Heidelberg Digital
printers.
Comparison of Equilibrium Theory for Conventional
Magnetic Brush with Rotating Magnetic Brush
Comparison of
Actual Data to Equilibrium Theory
0
10
20
30
40
0 1 2 3
Web Speed m/s
PowderAreaDensity
g/(sqm)
High Setpoints Black D1
Equilibrium Theory

14. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
14© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 14
Deposition of powder paint
behaves similarly to
deposition of imaging toner.
Modified Powder
• particle size for thin films
• powder flow aids
Rotating Magnetic Core Development of Modified
Commercially Available Powder
Powder Area Density
vs. Web Speed
0
10
20
30
40
50
60
0 1 2 3
Web Speed m/s
PowderAreaDensity
g/(sqm)
High' Setpoints Gray

15. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
15© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 15
• Deposition of powder with
rotating magnetic brush
has exponential behavior
• Extrapolation to high
speeds is straightforward
• Powder area density can
be increased by increasing
bias voltage applied to
magnetic brush.
Rotating Magnetic Core Development vs Web Speed
Powder Area Density vs. Web Speed
(Log Plot)
1
10
100
0 1 2 3
Web Speed m/s
PowderAreaDensity
g/(sqm)
High Setpoints Black D1
Lower Setpoints Black D1
Expon. (High Setpoints Black
D1)
Expon. (Lower Setpoints
Black D1)

16. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
16© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 16
Advantages of this technology for coil coating and other
applications include
• High deposition rates, high process speeds.
• Uniform coatings with controllable coating thickness.
• Wide range of powder particle sizes.
• Manageable hardware tolerances.
• Direct placement of material on ferrous metals. (In many cases no
intermediate is necessary.)
• Low chance of arcing to conductive substrates (intrinsically non-conductive)
• Alternative and textured surfaces using projection coating (no contact of
brush with substrate, non-metals)

17. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
17© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 17
Future Direction – Emphasis on Systems Integration
• Integration into existing coating line.
• Development of control strategy, thickness measurement, powder
feed.
• Testing and certification of powders and related coatings.
• Optimize curing to take advantage of high coating speed.

18. • Dr. Eric Stelter • 22 April 2004 • Heidelberg
18© Heidelberg Digital L.L.C.
Heidelberg Digital LLC Page 18
Acknowledgements
• We would like to acknowledge the assistance of Joseph Guth, Vern Lincoln, and Bret
Johnston of Heidelberg Digital L.L.C. Rochester, New York USA.
• Several figures in this presentation were used with permission from L. B. Shein:
Electrophotography and Development Physics, revised 2nd
ed. (Electrostatic
Applications, Morgan Hill, CA 1996).
• Patents that were shown are from http://www.uspto.gov
• The simulation work was done by Ulrich Mutze, Eric Stelter, and Thomas Dera of
Heidelberg Digital with John Zollweg of Cornell University, Ithaca, New York USA.
This research was conducted using resources made available by CTC High
Performance Solutions, a Dell, Intel, Microsoft and Cornell Theory Center (CTC)
alliance that is bringing high-performance computing to the enterprise. CTC also
receives funding from Cornell University, New York State, federal agencies,
foundations, and other corporate partners.