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Aluminum Extrusion Temperature Measurement

Temperature Control for Aluminum Extrusion

The goal for any extruder is to maximize throughput while maintaining quality products. Increased throughput means that each press can produce more products and be more profitable and time efficient. Aluminum extrusion temperature control is a critical component of the extrusion process. Running the presses based off of temperature control will allow the customer to maximize their press efficiency while also completely eliminating temperature-related quality defects.

Williamson Wavelength Technologies

Aluminum is a non-greybody material that has complex emissivity characteristics that vary with alloy, surface roughness, and oxidation, making it a particularly difficult material to measure with ordinary infrared pyrometers. Traditional single-wavelength and ratio aluminum infrared temperature sensor solutions are not able to accurately measure aluminum. Williamson’s multi-wavelength pyrometer uses application-specific algorithms to compensate for these unique emissivity characteristics of aluminum. These algorithms allow the Williamson multi-wavelength pyrometers to achieve accurate and repeatable aluminum extrusion temperature measurements at multiple points during the extrusion process.

Download the Complete Set of Aluminum Extrusion Application Notes

Billet Measurement

Application Overview

Billet temperature at the entry of the extrusion press is a critical process control parameter. A high billet temperature limits the maximum speed of the extrusion press and can result in quality defects. A low billet temperature can freeze in the die to create a sticker or cause the die to break. A consistent billet temperature is required to assure consistent process conditions, high extrusion speed, and highly repeatable product quality.

New alloys for automotive and aerospace products also require more precise control of billet temperatures at temperatures in excess of 500°C/925°F. At these high temperatures, oxides on the surface of the billet vitrify gradually over time changing the surface characteristics of the billet. This more complex surface condition requires the use of Williamson’s more advanced MWx Technology.

Williamson offers two different multi-wavelength technologies for billet applications.

Williamson Multi-Wavelength Technologies

Pyrometer Type MWxAB MW-20
Description Multi-wavelength with Dynamic ESP Technology


Automatically compensates for changing surface character conditions

Accurate across ALL relevant temperature ranges

Multi-wavelength with Static ESP Technology


Assumes reasonably predictable surface character conditions

Accurate for temperatures below 900°F/500°C

Temperature Ranges 550-1100°F / 285-600°C 400-1100°F / 200-600°C
Measurement Locations Cut Billet


Side Billet

Shear Billet

Cut Billet


Side Billet


Williamson pyrometer aimed at aluminum extrusion billet
Williamson Wavelength Advantage

Both single-wavelength and ratio pyrometers are affected by the non-greybody emissivity variation associated with aluminum and copper. Williamson multi-wavelength pyrometers accurately compensate for non-greybody emissivity variation to produce a highly accurate measure of temperature.

Pyrometer Benefits
  • Assure desired product properties
  • Establish consistent operating conditions
  • Maximize press speed
  • Reduce downtime and thermocouple maintenance
Wavelength Technology
  • Multi-Wavelength technology assures accurate measure of temperature for any billet surface.
  • Measure any billet surface from a distance

Press Exit

Application Overview

Aluminum Profile Temperature at the exit of the press is used to optimize extrusion speed while also eliminating cracks and surface blemishes and establishing highly repeatable mechanical properties and dimensions.

Williamson pyrometer at the aluminum extrusion press exit
Williamson Wavelength Advantage

Williamson’s multi-wavelength technology uses an ESP algorithm to correct for the low and varying emissivity of an extruded aluminum profile. This algorithm works across all different alloys and does not need a full field-of-view (FOV) to make an accurate measurement. This ability to tolerate partially filled FOVs means that the pyrometer can be mounted in a fixed location and can tolerate multiple-holed dies and small extruded profiles.

Pyrometer Benefits
  • Increase extrusion speed, typically by 20% or more
  • Eliminate surface blemishes and cracks
  • Maintain consistent mechanical and dimensional properties
  • Assure repeatable process conditions
  • Reduce downtime
Wavelength Technology
  • MW technology automatically corrects for non-greybody emissivity variation associated with extruded aluminum profiles
  • Press Exit algorithm tolerates partially-filled (12%) FOV
  • Self-aligns to the small, wandering hot profile
  • Automatically corrects for profile shape, size and alloy change

Quench Rate

Application Overview

The mechanical properties of the metal are established by the rate of cooling within the critical range of about 950°F / 510°C and 600°F / 315°C. A fast rate of cooling through this span will produce small crystals, resulting in a harder metal. A slow rate of cooling within this span will produce larger crystals, resulting in a more malleable metal. A pyrometer placed at or near the 600°F / 315°C point can communicate with the press exit pyrometer to calculate and confirm the desired rate of cooling.

Williamson pyrometer making quench rate measurement in an aluminum extrusion plant
Williamson Wavelength Advantage

There are two different pyrometer options for the quench rate measurement. Just like at the press exit, our multi-wavelength technology can also make an accurate measurement of the profile with a partially full FOV. However, the MW technology is not that reliable at temperatures lower than 600°F / 315°C because there is just not enough infrared energy being emitted from the profile. The short-wavelength technology can measure lower temperatures, but it requires a full FOV to make an accurate measurement and there will be some error due to emissivity variation.

Pyrometer Benefits
  • Assure desired product properties
  • Provides temperature and quench rate (degrees per second) values with optional IMQ quench module
Wavelength Technology
  • MW technology provides greatest precision and self-alignment for profile temperatures above 600°F / 315°C
  • SW technology provides exceptional precision for installations where the temperature drops below 600°F / 315°C and a broader temperature span is desired

Quench Confirmation

Application Overview

Aluminum must be below 400°F / 200°C when exiting the quench zone to assure that established mechanical properties are maintained. Low and variable emissivity values and often narrow profiles dictate the use of a short-wavelength pyrometer with precision optics. Williamson offers the shortest wavelengths for the greatest accuracy, and the only low-temperature pyrometers able to view clearly through steam without interference. The SW technology requires a full FOV to make an accurate measurement.

Williamson pyrometer making quench confirmation measurement
Williamson Wavelength Advantage

Short-Wavelength (SW) technology assures an accurate measure of temperature for this low-temperature, low-emissivity application. The Williamson SW-2A wavelength set offers the shortest wavelength and the strongest performance for unequaled stability and accuracy. The SW technology requires a full FOV to make an accurate measurement and there will be some error due to emissivity variation.

Pyrometer Benefits
  • Assure desired product properties
Wavelength Technology
  • Short-Wavelength technology for precise temperature values
  • SW-2A wavelength set can view through steam

Die Measurement

Application Overview

Die temperature is confirmed for each die change before entry into the press. An infrared pyrometer provides a simple way to make this reading quickly, accurately, consistently and reliably.

Williamson Wavelength Advantage

The pyrometer used for the die measurement is a short-wavelength pyrometer that is designed to minimize errors due to emissivity variation. As the die is a high-emissivity steel, the emissivity is fairly high and consistent, but there are hundreds of different dies that might slightly vary in their emissivity. Using a short-wavelength pyrometer will minimize the temperature error due to emissivity variation especially when compared with a long-wavelength general purpose pyrometer.

Pyrometer Benefits
  • Prevent die damage
  • Assure process consistency
  • Eliminate problematic thermocouple readings
  • Eliminate measurement delays
Wavelength Technology
  • Short-Wavelength technology provides a high degree of accuracy for the steel die temperature.

Consult With One of Williamson’s Temperature Experts

We would love to discuss your temperature measurement application with you.

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