1. Glass plays an integral role in science and technology - from liquid
crystal displays (LCDs) to high precision optics. Though technological
advances have made glass with thickness in the micron range, makers
of thin glass still face a ubiquitous challenge of surface waviness.
Surface waviness (or warp) presents a major challenge in all the
industries that utilize thin sheet glass. The problem is compounded even
further by the fact that the thinner the sheets, the larger their waviness.
The proposed approach attempts to solve the problem of surface
waviness by modifying an existing open-loop experimental setup to a
closed-loop system by introducing a mass flow controller (MFC) and
utilizing MATLAB control software. The MFC, in conjunction with the
MATLAB software, will work to keep the pressure gradient of the system
constant during slumping.
Future Work
 Update program to add and monitor different variables
sequentially (e.g. temperature).
 Manufacturing continuously flowing glass
 Obtaining sheets with specific curvatures
Overall Objective
To establish a closed loop between the pressure sensors and the flow
controllers to constantly feed the output of the pressure sensor into the
mass flow controller and adjust flow accordingly.
Experimental Set-up
Sheet Glass Applications:
Slumping of glass squeezed between two porous ceramic plates
Abstract
The addition of a MFC and the MATLAB software changes
the experiment from an open-loop system to closed-loop
system.
The MFC helps to keep the pressure gradient constant on
both sides of the mandrels at the T-connection stagnant line
branch off.
 Filters
 Touch panels
 Sensors
 Masks in the semiconductor industry
 Precision substrate in optical instruments
(e.g. telescopes)
 Cellular phones
 Computer panels
 Flat panel displays
 Hard disk drive platters
A contact-free method that utilizes the use of a thin layer of hot
pressurized gas, such as air, to separate the glass sheet from the
mandrel during slumping to avoid all the difficulties associated with
contact during slumping.
Advantages of Proposed Solution:
 Contact is eliminated;
 Reduces surface warps;
 Absence of the effects of particulates;
 No high-spatial frequency errors;
 Glass sheet maintains its pristine optical qualities after slumping.
Air flow Air flow
Glass
Porous ceramic mandrels
Left pair of porous
ceramics
Right pair of porous
ceramicsGlass sheet
Acknowledgments
 Space Nanotechnology Laboratory
 MIT Kavli Institute
 Tuskegee University’s Aerospace Science Engineering Department
 MSRP
Implementation of a Closed-loop System to Improve the Surface Flatness of Thin Glass
Sheets and Silicon Wafers
Toni-Ann P. Falconer1
, Dr. Mark L. Schattenburg2
, Dr. Mireille Akilian2
1. Tuskegee University, Tuskegee, AL, 36088
2. Massachusetts Institute of Technology, Cambridge, MA, 02139
Slumping glass refers to raising its temperature to a point where
its viscosity is low enough to allow it to sag under its own weight.
Proposed Solution for Improving the Surface
Flatness of Glass Sheets
Results
1 1.5 2 2.5 3 3.5 4 4.5 5
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
Voltage,
V
Number of cycles, N
0 5 10 15 20 25 30 35 40 45 50
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
Voltage,
V
Number of cycles, N
1 2 3 4 5 6 7 8 9 10
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
Voltage,
V
Number of cycles, N
Legend
Set Point Controlled Output
Air flow line 2
Before:
Stagnant Pressure
line
T-connection Stagnant
line branch off
Plenums
Glass sheet
Sensor Outputs
Sensor 1 Sensor 2
Air flow line 1
Furnace
After:
Stagnant Pressure
line
T-connection Stagnant
line branch off
Plenums
Glass sheet
Sensor
Outputs
Sensor 1 Sensor 2
Air flow line 1
Air flow line 2
Furnace Output
to
MFC