20 | 04 | 2021
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Film: Non-contact detection of ovality and errors in the flange profile with MEL M2-iLAN laser scanners. With the collected data, the bending process is parameterised. The MEL software then takes complete control of all components involved in the process.

Industrial Ethernet in the geometric control of cast iron pipes

In order to check the ovality and the flange geometry of cast iron pipes, MEL has implemented a system solution with M2-iLAN laser scanners. The system is able to achieve an accuracy of 0.1 mm. The flexible Ethernet cable, moved by the robotic arm, has a great influence on achieving this precision.

Image 1: Non-contact detection of ovality and errors in the flange profile with MEL M2-iLAN laser scanners. With the collected data, the bending process is parameterised. The MEL software then takes complete control of all components involved in the process.



Image 2: Bending press with the robot-guided laser measuring system. The measuring equipment is driven by the robotic arm into the pipe to be measured.



Image 3: The MEL system solution is implemented, despite the complexity of the task and control, at a reasonable cost. The evaluation and control electronics for the whole process is located directly at the measuring equipment in protective housing with IP64 protection. The administration and measurement data is transmitted over the Ethernet.



Image 4: Detection of the diameter within the limits and ovality at 29.3°.

The manufacturing of steel pipes is usually subject to a thermal process. Duktus manufactures pipes complete with flange and connection profile using centrifugal casting. Upon the cooling of a pipe, different material distortion often develops, giving the pipe an oval shape. So that the pipe meets the high quality requirements, it must be measured accurately after cooling and, if necessary, be mechanically reworked. In addition to ovality, the flange and the connection profile are also checked at the pipe ends for errors and chips. Until now, the measurement has been made with a manually operated contact measuring system at individual points. The subsequent bending process has been manually initiated and controlled. Duktus now uses a system based on two MEL Mikroelektronik GmbH M2-iLAN scanners. The system solution has been integrated into the automated manufacturing process and controls the entire measuring and bending process fully automatically with its own logic. The operator’s long-standing experience, along with its empirical findings, is incorporated.



The pipes to be measured are moved by a PLC-controlled transport system into the holding device of the hydraulic bending press, which serves as a measuring station. The measuring device consists of a linear table with precision drive, which adjusts the spacing of the two scanners, depending on the pipe diameter to be measured. The linear table itself is attached to a robotic arm and is guided by the latter into the pipe end to be measured. The pipe diameter is determined prior to the insertion of the measuring device in the pipe with an M10L laser sensor, allowing the pipe inner diameter and the geometric centre of the pipe to be determined. During the measuring procedure, the linear table is rotated 180°. Both scanners detect, during a measuring period of about two seconds, the ovality of the pipe as well as the geometry of the circumferential connection profile. The data collected by the scanners is sent in real time via Ethernet to the evaluation PC. The MEL software calculates the deviations from the nominal dimension and also the resultant bending parameters. The software then controls the rotation of the pipe into the correct bending position. The bending machine is addressed with the necessary parameters, and the bending process follows. After bending, a control measurement is made in order to record the success of the bend.


Flexible measuring system

Different pipe diameters as well as differences in the flange and connection profiles require a flexible measuring system to be used. The system solution used is able to detect pipes with diameters ranging from 350 mm up to 1,100 mm. Different flange profiles can be stored in the software. The operator can therefore customise the system to changes in the production line. The MEL Software arranges and coordinates the individual components involved in the process with one another. Initiated by the material control, which moves the pipe to be measured into the holding device of the bending machine, the MEL software controls the entire measuring and bending process. This is possible since the acquisition of the measured values and their evaluation both take place within the software.


Integrated empirical values

Each pipe is different. Sometimes it is necessary to process a pipe up to four times from different directions, until the desired result is obtained. Occasionally pipes show atypical deformation, where the normal processing routine proves unsuccessful. Here, the insights of the operator gained from many years of experience are often required, so that the pipe can successfully be brought into shape. These empirical values have been stored as ‘intelligent’ automatic routines in the software. Where the geometry of a pipe satisfies the conditions of one of these different routines, this will be executed instead of the normal procedure.

Meaningful statistics

The system solution produces extensive statistics of each pipe checked. These show many more measuring points compared to manual or simple contact systems. Inaccuracies also occur due to subjective assessment in manual measuring. The knowledge thus obtained can now be much more precise and reliably compared with the values derived from the mixture of materials in the blast furnace. Clear conclusions can therefore be drawn on material properties in relation to the nature of the deformation of the pipes. The manufacturing process can be optimised, even in the mixing of the casting material with regard to the manufacturing quality.


Simple Ethernet wiring

The flexible Ethernet cable has been moved by the robotic arm. The two laser scanners, the motor control unit of the linear adjustment and an encoder are only connected via a flexible Ethernet cable. The power supply, data traffic and also the angular position of the pipe per encoder are transmitted over the cable. The MEL M2-iLAN laser scanner series already contains all the electronics in the sensor head. The camera recorded data is thus evaluated in the sensor head and processed into consolidated data. This data shows a drastically reduced volume compared to conventional frame grabbers and can be transmitted without significant network traffic over the integrated Ethernet port. The connection to the PLC takes place over an RS232, the encoder for the motor control unit over a manufacturer-specific interface.