1. Fall 2016 Senior Design 1 Expo
Replication System for Production of Freeform Optics
from Toroidal Substrates
UNCC FFRP Team: Zachary Geiser (zacharygeiser@gmail.com) & Zachary Mueller (zmueller@uncc.edu)
Sponsor and Mentor: Dr. Matt Davies (mdavies@uncc.edu) & Dr. Joseph Owen (jowen@uncc.edu)
Abstract
Background
Material Testing
System Design Process Flow
Goal: Develop and test a mechanical system for UV
replication as an alternative to diamond turning for the
large scale manufacturing of freeform surfaces.
Work Summary: (1) Conducted material testing and
measurements of test to determine viable materials for
replication. (2) Design of mechanical alignment device
to maintain the desired tolerances of the end product.
(3) Design of a vacuum chamber for the alignment
process to occur in.
What are freeform optics?
• An optic with a surface that has no axis of
symmetry on or off the part.
Freeform optic advantages:
• They provide dramatic improvements in optic
functionality and performance.
• Reduction of sizing of current optical designs.
• Elimination of assembly steps for optical systems.
• Reduction of the waste in lighting applications.
Current Manufacturing Limitations:
• Diamond turning operations are required.
• Costly and time consuming to manufacture.
• Need for cost effective manufacturing process.
Alignment Mechanics
UV and Vacuum Chamber
UV Curing
Summer Optics J-91 UV curable epoxy:
• Form correction material of choice
• Small volume needed
ELC-500 Light Exposure System:
• Intensity: 30 mW/cm2
• Cure time: 5 minutes
• Volume capacity: 150in3
• Turn table: 4in diameter
Form Correction
A cost effective solution for freeform production can be
achieved through form correction.
• Research has been conducted
by A. Sohn and T.A. Down at the
NCSU Precision Engineering
Center[1].
• They achieved high fidelity
replication of a nickel alloy
machined surface with a UV
curable epoxy.
• Replication adhered to glass
substrate and separated from
the alloy.
Mold
Epoxy
Form to be corrected
Material tests were conducted to build upon the results of NCSU Center.
• Tests were conducted on brass, copper and aluminum with 3 surfaces each;
• Sine wave of 10µm P-V and 1mm l with a raised rim.
• Sine wave of 10µm P-V and 1mm l without a raised rim.
• Flat surface with no raised rim.
• 10µm P-V was chosen because this is form correction that the process is expected to make.
• Aluminum was identified as the choice material.
Replication surface roughness and shrinkage were evaluated:
• 5 replications were taken of the aluminum sample with the sine wave pattern with raised rim.
• Scanning White Light Interferometer (SWLI) measurements taken of the 1st and 5th samples.
• Filtering parameters: 80µm and removal of 4th order polynomial (to remove sine wave form).
Results of post processing of SWLI measurements:
• 2% measureable shrinkage in the epoxy  0.25µm shrinkage
• No measureable difference in the surface roughness [(a)(b) above].
• High fidelity replication of grain relief and tooling marks on the aluminum stamper(c) seen in
the cured epoxy(d).
• Verification for the need of a vacuum chamber due to air bubbles found in the epoxy (e).
Orientation System:
• Ball Spline
• Gas Spring
• Slider Plate
• Base Plate
• Top Plate
• Rubber Platform
• Upper Rubber Mounts
• Lower Rubber Mounts
Action System:
• Stepper Motor
• Lead Screw
• End Cap
Coupling System:
• Stamper Mount
• Substrate Mount
• Stamper
• Substrate Lens
Coupling
System
Orientation System
Action System
Kinematic Mounts:
• Fiducials and V-grooves are machined into the stamper
and substrate mount so that when they slot together the
central axis of both parts align.
• In order for the kinematic mounts to correct for any error
there must be 6 degrees of freedom between the 2
pieces.
Rubber Orientation Platform:
• Grant 6 degrees of freedom
to the substrate mount.
• Orients the substrate mount
so that it is within the range
of the kinematic correction
factor.
1. Orients stamper and replicate into axial alignment.
2. Presses Summer Optics J-91 epoxy between the stamper and substrate while within
vacuum.
3. Kinematic mounts correct for any error in the alignment between the stamper and substrate.
4. The two mounts are then locked together once coupled.
5. The mounts are then removed from the apparatus without disengaging the lock.
6. The coupled mounts are then placed into the UV curing chamber and allow UV radiation to
allow for curing of the epoxy.
7. Couple will be removed from the UV chamber and separated via propagation techniques.
8. Application of a thin metal coating via sputtering or e beam evaporation.
Project Specifications
• Weight limit of 10kg
• Occupy a space no larger than 0.5 m3
• Operate within a vacuum of at least 5 Pa to reduce
defects in the optic due to trapped air bubbles.
• Achieving mechanical alignment
• Cartesian coordinates within ±5 µm, clocking and
tilt of ±0.25 mrad.
• Replicate must adhere to base sphere upon
separation
• Toroid will have a diameter of 50 mm – 100 mm
Vacuum Chamber
Construction:
• Chamber walls constructed of PVC.
• Windows constructed of Lexan glass.
• Plumbing to allow for gassing and
degassing of the chamber via pump.
Performance:
• Capable of reaching <5Pa.
• Volume to contain the alignment device.
References
[1] A Sohn, T. D. (1999, March). Removal of Form Error in Replicated Optics. Retrieved from Precision Engineering Center at North
Carolina State University: https://www.pec.ncsu.edu/wp-content/uploads/sites/10/2015/03/aspe_spr1999.pdf
[2] Slocum, Alexander. “Kinematic Couplings: A Review of Design Principles and Applications.” International Journal of Machine (Oct. 2016)
[3] Brar, G. S. (2009). Buckling Load Predictions in Pressure Vessels Utilizing Monte Carlo Method. Charlotte: Ph.D Dissertation of Bara.
Tools and Manufacture 50.4 (2010): 310-327 (Oct. 2016).
Special Thanks:
Dr. Tom Suleski for lending us his UV curing chamber to perform material testing.
Prithiviraj Shanmugam for aiding in the SWLI measurements taken of the material samples.