**4. Infrared thermal control of elastic abrasive cutting**

There is a qualitative and quantitative non-contact thermographic temperature control. Qualitative control does not require obtaining an accurate surface temperature, but it is sufficient to obtain thermal signatures, which are characteristic models of relative temperature phenomena at different combinations of the abrasive cutting process control factors values. The relative temperature values of the objects in the cutting area to the temperatures of the other equipment objects with similar conditions are used. Quality visual inspection is appropriate for collecting a large number of detailed data and transmitting them for easy interpretation. It is suitable for controlling the efficiency of the process by monitoring the temperatures of the cut-off wheel, workpiece, cut piece, and chip under certain conditions of the abrasive cutting process.

In quantitative thermographic measurement, the ambient temperature is the reference. The observation of the abrasive cutting is established by measuring the absolute temperature of the studied object, under the same environmental conditions. As the reference temperature must be measured, this requires even better knowledge of the variables affecting the radiometric measurement, as well as taking into account the limitations.

The transition from qualitative to quantitative thermographic control is associated with the need to solve four tasks:


The aim of the study is first to develop a methodology for monitoring the evolution of surface temperature to identify the process of elastic abrasive cutting by IRT. For this purpose, a modular thermographic measuring system is proposed to monitor the process from different positions.

The illustrated in **Figure 3a** and **b** setup is a part of the more complex experimental framework, which is not the object of the present study [13, 25, 31, 44, 45].

Special attachment is developed, which is fixed to the main carriage of a combined lathe, having a device for step-less adjustment of rotational frequency workpiece to perform the elastic abrasive cutting process [46, 47]. In this way, a constant rotational frequency of the cut-off wheel can be provided and adjust the amount of *Remote Nondestructive Thermal Control of Elastic Abrasive Cutting DOI: http://dx.doi.org/10.5772/intechopen.103115*

**Figure 3.**

*Elements of workstand for elastic abrasive cutting, (a); setup for remote thermal control of cutting process, (b); a thermogram of the abrasive cutting made from the direction to profile of the cut-off wheel, (c); a thermogram of the abrasive cutting made from the direction to full-face of the cut-off wheel, (d).*

compression power *F* of the cut-off wheel (2) on the workpiece (1). High-speed reinforced cut-off wheels 41–180 22.2 3.0 A30RBF have been used during counter-directional cutting. Steel cylindrical rods with a diameter of 30 mm of C45 (1.0503) and 42CR4 (1.7045) were processed. **Figure 3c** and **d** shows the raw thermograms and the regions of interest (ROI) for the IRT control.


Unlike previous studies, thermographic measurement of the surface temperatures is performed simultaneously with two factory-calibrated FLIR SC660 infrared cameras (3) and (4), which work synchronously with the same or different frame rates and are located orthogonally. The cameras have a temperature range from 40°C to +2000°C, temperature sensitivity (NETD) <0.045°C and IP-link using FireWire. Matlab, FLIR ResearchIR Max and SDK softwares are used for thermal analysis and supporting cameras communication with the computer (6). The PASCO PS-3209 wireless sensor (5) is used in data collection mode for ambient temperature and relative humidity during thermographic measurements.

LabIR @ thermographic high-temperature applications paint, with high mechanical resistance for long-term uses and high emissivity is sprayed to cover the entire

work surface of the workpiece, the cut-off wheel, and exposed metal parts of the equipment. The layer paint thickness is measured by TROTEC BB20. Infrared cameras are located in isolating boxes with IR windows (shown in **Figure 3**). The outside of the boxes is also coated with paint to minimize the reflections from cameras.

A problem in the quantitative thermographic control of elastic abrasive cutting is the identification and suppression of thermal reflections in thermograms. The approach for thermal measurements of the process at an angle from 40 to 60″C was applied. Cold image subtraction and/or background subtraction is used as image processing methods for reflection reduction in thermograms.

After conducting the experiments for thermographic measurement to verify the calculated maximum temperatures of the cut-off wheel, workpiece, and cut piece and derive the corresponding correlation dependencies, the need to use a second infrared camera was eliminated. For the needs of elastic abrasive cutting online thermographic quality monitoring, only one camera is sufficient (camera (3) in **Figure 3b**.

Thermographic measurements were also performed with other approaches, which is not part of the present study. These relate to quantity thermography, such as the use of IR polarizing filters and deep learning to assess the condition of the elastic abrasive cutting process.

IRT used to detect the cut-off wheel wear can help abrasive cutting process automation and dynamically control.

The introduction of an online thermographic inspection system allows continuous monitoring of temperature evolution and thus prevents damage to the workpiece or machine. The following are illustrated possible information criteria for use in such a system.

**Figure 4** illustrates the possibility of the IRT system to measure and record the surface temperatures (optional maximum, minimum, average values) in the camera field of vision. Areas (regions of interest—ROI, lines, polygons, etc.) can be selected to identify the temperature distribution and evolution in the process of abrasive cutting in the form of graphs. Such a local inspection of the change in surface temperature significantly increases the visual resolution of the selected area. This visualizes the momentary disturbances from the spark's temperatures. **Figure 4a** shows the temperature curves for the marked lines on the workpiece and the cut piece in a direction transverse to the workpiece axis and close to the cutting area. The temperature profile longitudinally on the axis of the workpiece in the area of the marked line is shown in **Figure 4c**. The temperature profiles for different lines passing through the axis of the cut-off wheel show the change in surface temperature near the cutting area and at the farthest end from this area. **Figure 4d** shows the regions of interest (ROI) for the workpiece, the cut-off wheel, and the cut piece whose maximum temperatures are measured.

Due to the lack of a standardized format for reading IR images, software for processing and computer analysis of thermographic images has been developed. So thermal images can be processed regardless of what type of camera they were shot. The wear of the cut-off wheels has been checked. For this purpose, they are divided into four categories: standard (new cut-off wheel, as a reference), slightly worn, critically worn, and worn, which can no longer be used. One or another classification can be prepared on the basis of different criteria for different applications of elastic abrasive cutting. During data processing, areas with elevated temperatures and possible causes of wear are identified. Thus, on the basis of the initial thermal histograms, criteria for diagnosing and evaluating the resources of the cut-off wheels are formed.

The thermal histogram family (according to the camera view of vision) of the entire thermogram or the thermal histogram family of a selected ROI can be used to account for deviations in the quality of the elastic abrasive cutting process relative to a pre-selected optimal process.

#### *Remote Nondestructive Thermal Control of Elastic Abrasive Cutting DOI: http://dx.doi.org/10.5772/intechopen.103115*

#### **Figure 4.**

*Thermograms image with chosen regions and temperature distribution along with selections. (a) Thermogram from camera (3) (b) thermogram from camera (4). (c) Thermogram from camera (3) (d) thermogram with chosen ROIs.*

**Figure 5.** *Infrared image captured with a standard thermal camera.*

**Figure 5** shows (according to the camera's view) a raw thermogram with selected ROI (rectangular area), and the area of the cut-off wheel marked with a black outline. **Figure 6** shows a raw 3D thermogram of the selected ROI. **Figure 7** shows the family of thermal histograms for the same ROI.

There are three density modes of temperature calculation in the histograms:


**Figure 6.** *3D thermogram of the selected ROI in Figure 5.*

#### **Figure 7.**

*3D layered thermal histograms (a family) for IR image sequence of the selected ROI with the workpiece, cut-off wheel, and cut piece.*

Medium and Low approximations automatically exclude any garbage colors detected inside the camera apertures.
