Process Monitoring During Open‐die Forging
Thermography with VarioCAM® HD head 800 in Harsh Environments
Anyone who wants to produce curved or twisted steel
and aluminium components, can rely on bendingforging nowadays. Components with complex
geometries can now be manufactured by means of
this incremental forging variant.

RWTH Aachen
Institute of Metal Forming (IBF)https://www.ibf.rwth‐aachen.de/cms/~owzh/IBF/?lidx=1
Infrared camera: VarioCAM® HD head 800

So far, however, there has been no reliable process stability at this point. The Institute of Metal Forming (IBF) at RWTH
Aachen University has developed an assistance system that eliminates this weak point. The temperature
measurement on the surface of the processed metals during the forging process by means of an infrared camera plays
an important role here.

Historical Shortcoming CompensatedOpen‐die forging encompasses a series of different forming processes. What they all have in common is the fact thatthe final shape of the metal workpiece, which usually has been heated to well over 1,000 °C, does not result from theshape of the tool. An often geometrically simple tool is usually moved relatively to the workpiece and reshapes theworkpiece locally through repeated punches. The whole process occurs gradually, i.e. incrementally. Companies use
open‐die forging to produce semi‐finished products from cast ingots. This offers the enormous advantage of
specifically influencing material properties and shapes. However, thanks to the process, cavities and pores that haveformed after the casting can also be closed. Much of what occurred in the production halls in the past was largely
based on experience. Given the absence of backed‐up data and parameters, the results sometimes fluctuated greatly
regarding the quality of the products. In total, even small, added up deviations could mean that entire components
did not meet the requirements.
At the same time, open‐die forging faces requirements that are well known from many industrial processes. Energy,
time and thus costs should be saved and resources used optimally. In particular, this means using the available heat as
efficiently as possible, creating optimised pass schedules and reducing the heating duration. Such projects will only
succeed if the process can run in a much more stable manner.

Assistance System Records the Geometry, Temperature and Microstructure of Components
The assistance system developed by the IBF ensures the urgently required reliability in open‐die forging. It is based on
the idea of measuring the geometry and temperature of the component and calculating the part properties parallel tothe process. For this purpose, various measuring devices, the forging press and the manipulator can be coupled andsynchronized with fast models. The actual properties are to be compared with the required properties by means oflive calculations. This occurs in a matter of seconds. A simple forging process with four passes, for example, requires acomputing time of just one second. If the result deviates from the target parameters, the robot control for the pressand manipulator must be adapted. This is repeated until the target values have been reached.

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Process Monitoring During Open‐die Forging
Thermography with VarioCAM® HD head 800 in Harsh Environments

Fig. 1:

Systematic structure of the assistance system of the IBF

Temperature plays a crucial role in this complex process. If it is too low, the massively acting forces cause cracks toform in the component. On the other hand, excessively high temperatures produce grain growth of the respectivematerial. However, a microstructure with small grain sizes is desired. The forging window, the range of ideal processtemperatures, depends heavily on the material. "Demanding materials such as nickel‐based alloys have a forging
window of around 50 Kelvin," says Fridtjof Rudolph from the IBF. "The majority of forged products are made fromtempered steels that have a forging window of about 300 K."

The High Spatial Resolution of the Infrared Camera Facilitates Edge Detection
Such framework conditions do not pose a serious challenge for the infrared camera that Fridtjof Rudolph and hiscolleagues use. The VarioCAM® HD head 800 used with (1,024 x 768) IR pixels from InfraTec has very good thermal
sensitivity with which the finest temperature differences can be characterized – thanks to the multi‐characteristic
temperature calibration with a measuring accuracy of ± 1 %. The precision optics with a high light intensity of f / 1.0,
first‐class transmission, a special coating and minimal distortion prove to be an advantage. Thanks to the combinationof a stationary camera, high‐quality optics and image processing software specially designed by the IBF, temperature
measurements at a distance of about two meters on the components heated up to 1,200 °C with geometriccalculations can be carried out easily with over 20 frames per second. The industrial‐grade light metal housing (IP67)
provides excellent protection for the camera against the dust caused by the scale and the steam from hot lubricants.
The VarioCAM® HD head 800 is installed in such a way that the workpiece is located as frontal to it as possible. Whenmeasuring the surface temperature, the IBF is accommodated by the large‐scale IR detector with over 786,000
measuring pixels of the camera. The enormous resolution ensures that the geometry of the respective measurement
object is recorded precisely and the number of measurements can be kept as low as possible. The measured values
flow into the calculations of the comparative form changes and a temperature model in sync with the forging process.
This temperature model considers factors such as the thermal conduction of the component, convection as well asradiation and cooling of the component due to contact with the tool. The process monitoring is completed by the dataon the microstructure of the workpiece calculated for the respective measurement time. In the end, everything resultsin visual information that the press operator can use to determine how he should further control the forging process.
Page 2© InfraTec 10/2020 (All the stated product names and trademarks remain in property of their respective owners.)
Headquarters

InfraTec GmbHInfrarotsensorik und Messtechnik
Gostritzer Straße 61 – 6301217 Dresden / GERMANY

USA officePhoneFax
E‐mail+49 351 871‐8630+49 351 871‐8627
thermo@InfraTec.de
www.InfraTec.eu

InfraTec infrared LLC
5048 Tennyson Pkwy.
Plano TX 75024 / USAPhone
E‐mail+1 844‐226‐3722 (toll free)thermo@InfraTec‐infrared.com
www.InfraTec‐infrared.com

Process Monitoring During Open‐die Forging
Thermography with VarioCAM® HD head 800 in Harsh Environments

123Fig. 2:

4
Sequence of the calculation steps for generating an image for edge detection
1.
2.
3.
4.

Thermal imageConversion to RGB format
Morphological closing by means of a structuring elementEdge detection with Sobel filter

With the assistance system of the forging industry, the IBF hopes to be able to offer an effective instrument that willfurther advance the development of open‐die forging. The previous tests of the system have made the scientists
optimistic that this project will succeed.

Page 3© InfraTec 10/2020 (All the stated product names and trademarks remain in property of their respective owners.)
Headquarters

InfraTec GmbHInfrarotsensorik und Messtechnik
Gostritzer Straße 61 – 6301217 Dresden / GERMANY

USA officePhoneFax
E‐mail+49 351 871‐8630+49 351 871‐8627
thermo@InfraTec.de
www.InfraTec.eu

InfraTec infrared LLC
5048 Tennyson Pkwy.
Plano TX 75024 / USAPhone
E‐mail+1 844‐226‐3722 (toll free)thermo@InfraTec‐infrared.com
www.InfraTec‐infrared.com

Process Monitoring During Open‐die Forging
Thermography with VarioCAM® HD head 800 in Harsh Environments

Fig. 3:

The temperatures of the component can be read on such a thermal image. The saddle position, lengths and heights as well as the areathat has already been forged are also recognisable.

This research and development project is funded by the Federal Ministry of Education and Research(Bundesministerium für Bildung und Forschung – BMBF) within the framework concept "KMU‐innovativ" under thefunding code 02P17K560.

Page 4© InfraTec 10/2020 (All the stated product names and trademarks remain in property of their respective owners.)
Headquarters

InfraTec GmbHInfrarotsensorik und Messtechnik
Gostritzer Straße 61 – 6301217 Dresden / GERMANY

USA office

Phone
Fax
E‐mail+49 351 871‐8630+49 351 871‐8627
thermo@InfraTec.de
www.InfraTec.eu

InfraTec infrared LLC
5048 Tennyson Pkwy.
Plano TX 75024 / USAPhone
E‐mail+1 844‐226‐3722 (toll free)thermo@InfraTec‐infrared.com
www.InfraTec‐infrared.com