SPOTline spot weld inline inspection system

Production-accompanying inline inspection system for spot welding, which monitors the welding quality already during the weldings process by means of sensors in the welding guns.

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Fully Integrated

Automated 100% spot weld inspection

SPOTline is an ultrasonic inspection system for the direct inspection of spots while the welding process is still in progress. SPOTline is integrated directly into the production line and controlled automatically. Thereby a 100% inspection is realized.


The system is suitable for the reliable inspection of spot welds of two- and three-sheet metal joints. The welding process is monitored by two ultrasonic probes integrated in the welding guns. The inspection results are evaluated and communicated in the ultrasonic client. Based on these inspection results, the inspection system can immediately initiate corrective actions to ensure the quality of the spot weld, if necessary, and optimize the production process. The basis for this is a decision matrix for the spot welds, which is set up in the system setup. For this purpose, the ultrasonic client can communicate with the robot or welding system controller via standardized interfaces in order e.g. to request a change in the welding parameters or cap milling, or alternatively to suggest a production stop. It also transmits the measurement results to the communication unit for statistical evaluations.

The advantages

Outstanding features of the SPOTline ultrasonic testing system

  • Automated 100% inspection of all spot welds is possible

  • Inspection already during the welding process

  • Integration of SPOTline is possible independent of the welding machine manufacturer

  • Immediate reporting of irregularities

  • Regulation and control of the welding process

  • Networkability with higher-level customer system

  • Avoidance of subjective manual quality assessments (manual inspection / chisel test)

  • ISO-VDA-compliant, complete documentation

  • Reduction of production costs due to less scrap

  • Reduction of personnel costs due to less rework

  • Reduction of inspection costs through automation

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this is how it works

Principle of operation

Ultrasonic probes are integrated in the welding guns of the welding robots. These probes are connected to the cooling water channel of the welding guns in order to use this as a coupling medium or transmission medium for the ultrasound. For this purpose, the SPOTline ultrasonic client generates a longitudinal ultrasonic wave via the probe in the form of a short, highly attenuated ultrasonic pulse. This wave is transmitted via the cooling water into the welded joint.

The system operates either in the transmission or pulse-echo mode. In transmission mode, one probe acts as a transmitter and the other as a receiver. A part of the ultrasonic wave energy is transmitted from one probe to the other. The result is a transmission signal. The multiple reflection echoes as well as the transmission signals are evaluated with regard to their amplitude (intensity of the received signals) as well as their transit times (sound paths of the ultrasonic signals). These data enable a reliable statement to be made regarding the weld quality. In the pulse-echo method, on the other hand, each probe is a transmitter and receiver in its own right.

The information thus recorded is passed to a SPOTline ultrasonic client, which evaluates it in seconds while welding is still in progress with the aid of intelligent, learning evaluation. The data is then communicated via an interface with the welding controller, the robot controller and a server for data management.


Integration of SPOTline in production plants

The integration of the system is possible in newly planned plants as well as retroactively in existing production plants. It includes the following issues:

  • Integration of the ultrasonic probes into the guns
  • Insertion of the data lines from the probes to the SPOTline ultrasonic client via the robot hose assemblies
  • Installation of the network infrastructure for the data line between ultrasonic client and communication unit
  • Optional: Interface installation between ultrasonic client and robot/welding control unit
  • Optional: Connection of the data communication unit to the internal customer network
immediate correction

Communication with the welding and robot control

To ensure a control and regulation process, the ultrasonic client also communicates with the welding and robot control system. Optionally, with appropriate software and hardware adaptations, as well as a standard interface to the welding control system, it is possible to regulate the welding parameters, such as the welding power, or to control cap milling if the spot weld quality decreases. A production stop can also be initiated. A decision matrix defined in advance by the customer determines the triggering of the actions. Here, not only the spot weld quality is decisive, but also other criteria such as the sequence and the number of certain spot qualities on a component as well as the quality of certain safety spots. The SPOTline ultrasonic client takes into account the respective decision matrix, which can also be defined individually for individual spot welds, and initiates the action associated with the result.


Evaluation of quality data and system monitoring

All inspection results are forwarded to the plant control room, welding departments and the administrator via a corresponding interface. 

The result of the quality of the spot weld is stored in the -communication unit in an SQL database in relation to gun, component, date and time.

In addition, the communication unit supports the ultrasonic client in self-monitoring, parameter setting and the definition of evaluation criteria. The inspection results can be forwarded via information software, e.g. to the plant maintenance department, welding departments and administrators. Optionally, all data can also be transmitted to a data management server. This serves to document all inspections and can represent the interface to the internal customer network. Via a modem interface, there is the possibility of continuous remote diagnosis and fast remote maintenance.

Everything in view

Visualization of inspection results

The inspection software clearly displays the inspection results. The individual results of the weldings, frequency representations as well as the trend information of the welding quality. This makes critical spots quickly visible. Trend information and the respective current status of a robot, or a welding gun, or the individual spot welds are clearly visualized. This makes it easy to quickly identify any deviations or malfunctions that occur and to initiate targeted measures. OK spots are displayed in green, ok spots with spatter are displayed in blue, medium (critical) spots are displayed in yellow (warning limit), and NOK spots are displayed in red.

that's how it works too

The alternative: spot weld inspection after the welding process with PHAsis ultrasonic inspection systems

For the subsequent inspection of spot welds, we have developed the PHAsis spot weld inspection system family. The PHAsis family includes both the PHAsisNEO manual inspection system and the PHAsisBLU inspection system, which was specially developed for automated inspection with robots. PHAsis inspection systems use phased array ultrasonic technology. This provides a very high resolution of the diameter of the spot weld lens as well as an imaging representation of the spot weld quality..

Both inspection options – manual and automated – can be combined with PHAsis through the common software and a common database and linked to the customer’s QA system. This means that the customer always has an overview of the complete inspection process for spot welded joints.

PHAsisNEO is designed for fast and safe manual inspection of spot welded joints. In addition to the intuitive user interface, PHAsis as an imaging inspection system, makes the spot weld quality visible to the operator at a glance. An automatic evaluation proposal and documentation increase efficiency and inspection reliability.  


PHAsisBLU is the solution for automated spot weld inspection with robot technology. Due to its compact design, it can be mounted directly in an automation cell and operated from the outside with a PC. Thus it ensures an optimal signal quality. By connecting it to your QA system, quality deviations can be identified and corrected immediately.

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