PQS weld process monitoring system for resistance spot welding
The basic principles for quality assurance, as well as the requirements for a quality assurance system, are laid down in DIN ISO 9000 “Quality management and quality assurance standards, guidelines for selection and application”. It also emphasises process quality and customer satisfaction: Product testing is good, process monitoring is better, controlled manufacturing is best. The quality assurance system and its functionality must be checked within the framework of an audit. Quality cannot be tested into a product; it has to be designed into it, – engineered into it and – produced into it. The quality of a company’s products determines its image and the trust prospective buyers need to make a purchase decision.
The usual determination of point diameters or shear tensile forces by taking a random sample provides very accurate measured values if appropriate care is taken, but these are only snapshots of past conditions. Furthermore, data obtained in this way are only meaningful, i.e. representative, if
- a controlled process
(free from systematic interferences between sampling)
- a capable process
(process that is statistically safely within the specification limit)
are available.
This means that every operator of a production process is already required to provide this evidence. Process control and its verification is, therefore, a prerequisite for consistent quality.
The desire to obtain a complete image of a running process, which completely records random and spontaneously occurring changes and also allows long-term trends and developments to be recognised at an early stage, is only met by continuous measurement = inline measurement.
In order to ensure consistently high quality at reasonable costs in a continuous process and to exploit existing potential for reducing errors, seamless metrological recording is becoming increasingly important.
The data obtained in this way must, therefore, provide a realistic picture of the course of a manufacturing process.
The PQSweld system from Harms Wende QST GmbH offers all the necessary functions in the required quality. Depending on the respective welding process, various electrical and mechanical measured variables are continuously recorded and permanently compared and evaluated with previously determined references. The evaluation is carried out on the basis of signal progressions. From the resistance curves, for example, the mean value and the standard deviation are determined for each individual spot weld in the current process and displayed as an overview graphic. This can provide the degree of process reproducibility on the basis of which the quality of a welding process can be assessed. In this way, it is possible to react to changes in the process at an early stage, but also to work systematically on improving production processes.
The system supports the user right from the determination of the correct welding parameters, accompanies the production start-up, identifies potential for improvement and seamlessly monitors the ongoing production.
In order to ensure consistently high quality at reasonable costs in a continuous process and to exploit existing potential for reducing errors, seamless metrological recording is becoming increasingly important.
The data obtained in this way must, therefore, provide a realistic picture of the course of a manufacturing process.
The following tasks are covered by PQSweld:
- Assessment of the process flow during weld spot creation including the
- Control interventions and evaluation of the point quality. (single point assessment).
- Assessment of the quality of all points on a component (group assessment).
- Evaluation of the process behaviour (deviation from learned reference, spraying, overheating) of the single point and the last points.
- Assessment of the condition of the joint (interaction between component and tool).
- Statistical evaluation of welding processes (process control, process stability)
- Single point and tool (pliers)
- Providing information for necessary interventions also in upstream
- Process sections and processes
- Analysis functions
- Documentation of the results