ThermaViz® - The Innovative Two-Wavelength Imaging Pyrometer
The integration of advanced optical diagnostics and intelligent materials processing; success in sophisticated electro-optical instrumentation systems in harsh environments.
Advanced Imaging Sensors For Temperature Measurements and Process Control
THERMAL SENSOR TECHNOLOGY
"Control and Monitoring of Laser Deposition Processes" Abstract Oral Presentation
"Initial Developments in Monitoring and Modeling of Laser Additive Manufacturing with Titanium" Abstract Oral Presentation
"On-line Imaging Pyrometer for Laser Deposition Processing" Abstract
"Experimental and Numerical Study of the LENS Rapid Fabrication Process", L. Wang, S. Felicelli, J Craig, Metallurgical and Materials Transactions A, Sept 2007
"Particle Temperature and Velocity Characterization in Spray Tooling Process by Thermal Imaging Techniques" Abstract
"Particle Temperature and Velocity Measurements by Two-Wavelength Streak Imaging" Abstract
"Investigation of the Thermal Behavior during the LENSTM Process" Abstract
"Particle Temperature Measurements by Spectroscopic and Two-Wavelength Particle Streak Imaging" Abstract
Stratonics, Inc. Patent # 5 963 311, October 1999, United States Patent Office, entitled "Surface and particle Imaging Pyrometer and Method of Use"
"A Two-Wavelength Imaging Pyrometer for Measuring Particle Temperature, Velocity and Size in Thermal Spray Processes" Abstract
"Two Color Imaging Pyrometer Temperature Measurements of the Kerf Front During Laser Cutting" Abstract
"Measurements of Particle Temperature, Velocity, Trajectory, and size in Thermal Sprays", J.E.Craig, R.A.Parker, D.Y.Lee, Presented at ASM International Materials Solutions, November 1999, Cincinnati, OH
"An Imaging Pyrometer for Monitoring the Surface Temperature of a Spray Formed Steel Billet" Abstract
"Thermal Spray Coatings Workshop: Sensors, Modeling, and Control Strategies", J.E. Craig, Summary of workshop held at NIST/DOC, November 1998, Gaithersburg, MD
"Temperature Imaging Measurements with a Two-Wavelength Imaging Pyrometer" Abstract
"Control and Monitoring of Laser Deposition Processes"
Richard Grylls and David Keicher (Optomec, Inc.), James E Craig, (Stratonics, Inc.),
Oral Presentation at MT&S 2011 Conference and Exhibition, 19 October 2011, Columbus, OH
Abstract
The first Laser Engineered Net Shaping (LENS®) metal additive manufacturing system was installed thirteen years ago at The Ohio State University. That first system relied entirely on the skill of the operator to ensure a successful deposition - no automated controls were available at that time. Since then, laser deposition technology has become an established industrial process, and the requirements for process control have been better defined. In this presentation we will discuss when process control is needed, how it can be achieved, and the future directions in this area. Particular attention will be paid to temperature measurement, melt pool size, toolpath generation, and atmosphere control.
"Initial Developments in Monitoring and Modeling of Laser Additive Manufacturing with Titanium"
James E Craig, Thomas Wakeman (Stratonics, Inc.), Richard Grylls (Optomec, Inc.), Shawn Kelly (Penn State Univ.)
Oral Presentation at MT&S 2011 Conference and Exhibition, 19 October 2011, Columbus, OH
Abstract
We will describe a set of experiments using LENS to
deposit
"On-line Imaging Pyrometer for Laser Deposition Processing"
James E Craig, Thomas Wakeman (Stratonics, Inc.), Richard Grylls, James Bullen (Optomec, Inc.)
Presented at TMS 2011 Annual Meeting and Exhibition, 3 March 2011, San Diego, CA
Abstract
An online imaging pyrometer has been developed to monitor the temperature distribution of the melt pool in laser additive manufacturing processes. The imaging pyrometer uses two CCD cameras with “long and short” wavelength filters in the NIR waveband. The intensity ratio is formed and the two wavelength temperature is determined from a calibration, relating the ratio to the temperature. In the experiment, deposit strips are formed over a variation of laser power levels, ranging from standard levels for a superalloy to about half the initial level. As the power is lowered, the deposit efficiency is reduced, as is its dimensions. Melt pool temperature distributions are measured in the final 6 through 10 passes and their properties will be presented and described. Peak temperatures of about 1800°C are noted for standard power levels, and in general lower temperatures are observed at lower power levels.
"Particle Temperature and Velocity Characterization in Spray Tooling Process by Thermal Imaging Technique"
P. S. Mohanty, R. Allor, P. Lechowicz, R.A. Parker, and J.E. Craig
Presented at ITSC 03, ASM International, 1 May 2003, Orlando, FL
Abstract
A two-color imaging pyrometer system is employed to examine twin wire arc spray gun used in Spray Tooling Process. Key aspects analyzed in this study include particle temperature, particle velocity, and particle distribution. The influence of process parameters such as gas flow rate, type of gas (N2, and air), voltage and current, as well as, spray cap design has been studied. Influence of a super atomizer called the arc jet has also been investigated. The measurements were taken at 80 mm, 160 mm and 200 mm from the gun tip. Finally, the influence of the material on the spray characteristics has been examined. The material list includes 0.8% carbon steel, 0.8% Carbon steel with B, stainless steel, Molybdenum, Ni, Ni-Al and Copper. The type of gas used for atomization significantly influences the particle temperature and velocity. Lowest temperature is observed with nitrogen gas and the highest temperature with the arc jet. Arc jet also produced particles with significantly higher velocity. The flow rate did influence the particle velocity where as temperature wasn’t affected noticeably. The wire material has considerable impact on the particle temperature and velocity. Lower melting point alloys showed higher temperature whereas the velocity has complex dependence on the density and viscosity of the material. Cap type affects the temperature and velocity of the particle. As cap opening increases the temperature and velocity decrease.
"Particle Temperature and Velocity Measurements by Two-Wavelength Streak Imaging"
J.E. Craig, R.A. Parker, D.Y. Lee, T. Wakeman, J. Heberlein, and D. Guru
Presented at ITSC 03, ASM International, 1 May 2003, Orlando, FL
Abstract
A two-wavelength particle imaging sensor has been developed to measure temperature and velocity of individual particles in most thermal spray devices. The sensor provides continuous updates to particle condition profiles, histograms and correlation’s. The software locates particle streaks, determines the intensity ratio and dimensions of each streak, and calculates the particle temperature and velocity. Many forms of advanced materials processing technologies, such as thermal spray, spray-forming and atomization have considerable need of process control sensor technology. These measurements provide the basis for application of the sensor to many of these processes. Particle temperature and velocity measurements of plasma-sprayed ceramic powder were obtained using the sensor. The average temperature varied from 2800 K to 3000 K as the current to the plasma was increased from 700 amps to 900 amps. The average velocity varied from 85 m/s to 99 m/s over the same range. These results compare favorably with similar measurements, reported in the literature. With its full-stream field of view, the vision-based particle sensor can be applied to control strategies for the purpose of providing stable particle temperatures and velocities over long duration plasma spray processes.
"Investigation of the Thermal Behavior during the LENSTM Process"
W. Wei, Y. Zhou, R. Ye, E.J. Lavernia (Dept of Chemical Engineering and Materials Science, UCI) D.Y. Lee, J.E. Craig, (Stratonics, Inc.) J.E. Smugeresky, (Sandia National Laboratories)
Presented at the 2002 International Conference on Metal Powder Deposition for Rapid Manufacturing, MPIF, 8-10 April 2002, San Antonio, TX
Abstract
Laser Engineered Net-Shaping (LENSTM) is evolving as a promising manufacturing technique that ensures significant reduction of time between initial concept and final component. A thorough understanding of the thermal history during LENS processing is a pre-requisite for dimensional stability, microstructure design and property control. In this paper, the thermal behavior of the LENS process was investigated experimentally and numerically. Thermal images of LENS processed areas were recorded using a two-wavelength imaging pyrometer system for temperature and distribution analysis. Morphology and size of the stationary melt pool were evaluated under different laser power conditions. Thermal history of the moving melt pool, at the beginning stage of part fabrication, was also recorded and analyzed for different processing conditions. Temperature gradient distribution and cooling rate in the melt pool and the surrounding area were derived from the temperature profile along the centerline of the pool. Preliminary results obtained using Finite Element Method (FEM) simulation of the temperature distribution around the pool area and the entire part (during deposition) showed reasonable agreement with the experimental results.
“Particle Temperature Measurements by Spectroscopic and Two-Wavelength Streak Imaging”
J.E. Craig, R. Parker, F. Biancaniello, and S. Ridder
Presented at the “ASM International Thermal Spray Conference”, Montreal, Canada, May 2000
Published in Edoxica Report on Thermal Spraying, No. 20, April 2000, France
Abstract
A two-wavelength particle imaging pyrometer has been developed to measure temperature, velocity and size of individual particles within a field of view and a depth of field that spans the entire particle stream in most thermal spray devices. The pyrometer provides continuous updates to particle condition profiles, histograms and correlations. The software locates particle streaks, determines the intensity ratio and dimensions of each streak, and calculates the particle temperature, velocity and size. Many forms of advanced materials processing technologies, such as thermal spray, spray-forming and atomization processes, have considerable need of process control sensor technology. These measurements provide the basis for application of the pyrometer to many of these processes. Particle temperature measurements of plasma-sprayed ceramic powder were obtained using a spectrometer and the pyrometer. Comparisons of the measurements show that the vision-based pyrometer has excellent accuracy. The standard deviation of the measurements was 40 K or about 1.3 %. Additional pyrometer measurements were used to determine its minimum detectable temperature and velocity change, which were 12.4 K and 2.77 m/s, or 0.4 % and 1.5 %, respectively. The vision-based particle sensor can now be applied to high performance control strategies to provide stable particle temperatures and velocities over long duration plasma spray processes.
"A Two-Wavelength Imaging Pyrometer for Measuring Particle Temperature, Velocity and Size in Thermal Spray Processes"
J. E. Craig, R.A. Parker, D.Y. Lee, F. S. Biancaniello, and S. D. Ridder
Presented at CIM, Quebec, Canada, 22 August, 1999
Abstract
An imaging pyrometer was developed to measure surface temperature of hot metal objects and particle temperature, velocity and size in thermal spray, spray-forming and atomization processes. Two-wavelength imaging provides true, high-resolution temperature measurement, even with emissivity variation caused by roughness or oxidation. The system, having a field of view that spans the entire particle stream in thermal spray devices, provides continuous measurement of the entire particle stream. The software locates particle streaks in acquired thermal images, determines the intensity ratio and dimensions of each streak, and calculates the particle temperature, velocity and size. Measurements in the National Institute of Standards and Technology thermal spray facility are described.
“Two-Color Imaging Pyrometer Temperature Measurements of the Kerf Front During Laser Cutting”
K. J. Woods and R. Parker
Presented at ‘International Conference of Applied Laser and Electro-Optics (ICALEO ’99)’, 15-18 November, 1999, San Diego, California.
Abstract
Temperature measurements of the kerf front during steady state laser cutting have been recorded with an imaging two-color pyrometer. This allowed spatial resolution of the temperature profile across and along the kerf front, independent of oxidization level and consequent changes in surface emissivity. Experimental conditions included thin (3-mm) and thick (9.5-mm) mild steel with oxygen assist, as well as 3-mm 304 stainless steel with both high-pressure (1500 kPa) nitrogen and low-pressure (150 kPa) oxygen assist. The measured temperatures can be compared with calculations based on heat conduction modeling and the molten layer thickness predicted from a fluid dynamic model.
“Imaging Pyrometer for Monitoring the Surface Temperature of a Spray-formed Steel Billet”
R.A. Parker and R. Allor
Presented at the ‘AeroSense SPIE 15th Annual International Symposium on Aerospace/Defense Sensing, Simulation and Controls’, 15-18 November, 1999, San Diego, CA
Abstract
A two-wavelength, imaging pyrometer was developed for real-time measurement of the surface temperature distribution of a spray-formed steel billet. This new spray-forming process is used to deposit bulk steel on a ceramic substrate in a surface temperature range of 300°C to 400°C, using four, twin-wire arc plasma torches. These steel billets are used as tools in metal forming processes, injection molding and die casting tools, and other processes that may need hard tooling, such as the automotive industry. The steel billet must be formed with a uniform, surface temperature distribution to minimize the thermal stresses within the steel, throughout the process.
The imaging pyrometer uses a near-IR InGaAs CCD camera with high quantum efficiency from 0.95 to 1.75 microns. The wavelengths of 1.40 and 1.65 microns were selected to sense the low temperature billet. The camera has a format of 320 x 240 pixels with a pixel spacing of 30 microns and an integral 12-bit A/D converter with both video and digital outputs. The design of the pyrometer provides a working distance of 2.2 meters and a field of view of 0.6 meters.
This technical paper describes the calibrations and initial measurement results obtained in a spray forming facility at the Ford Research Laboratory. The calibration provided intensity ratio measurements for surface temperatures ranging from 200°C to 300°C, the expected range of operation. The initial measurements described here depict the surface temperature distribution of the steel billet throughout the spray forming process, typically lasting several hours.
“Temperature Imaging Measurements with a Two-Wavelength Imaging Pyrometer”
R.A. Parker, D.Y.Lee, F. Biancaniello and S. Ridder
Presented at the “Heat Treating ’98, The 18th Heat Treating Conference and Exposition”, 12-15 October 1998, Rosemont Convention Center, Rosemont, Illinois
Abstract
An innovative two-wavelength, imaging pyrometer with analysis software provides a method to monitor process uniformity, improve quality and reduce cost in advanced materials processing techniques. The design has achieved high imaging quality and the system measures true surface temperatures of hot objects including surfaces with roughness or emissivity variation. The measurements were made in a material processing lab and calibration results are described. Two wavelength measurements were found to achieve high accuracy, 1.0 % of the measured value, over the range of 1000 to 3000°K.