The geometrical quality of a welded assembly is to some extent depending part positions before welding. Here, a design of experiment is set up in order to investigate this relation using physical tests in a controlled environment. Based on the experimental results it can be concluded that the influence of part position before welding is significant for geometrical deviation after welding. Furthermore, a working procedure for a completely virtual geometry assurance process for welded assemblies is outlined. In this process, part variations, assembly fixture variations and welding induced variations are important inputs when predicting the capability of the final assembly.

The interest for thermography as a method for spot weld inspection has increased during the last years since it is a full-field method suitable for automatic inspection. Thermography systems can be developed in different ways, with different physical setups, excitation sources, and image analysis algorithms. In this paper we suggest a single-sided setup of a thermography system using a flash lamp as excitation source. The analysis algorithm aims to find the spatial region in the acquired images corresponding to the successfully welded area, i.e., the nugget size. Experiments show that the system is able to detect spot welds, measure the nugget diameter, and based on the information also separate a spot weld from a stick weld. The system is capable to inspect more than four spot welds per minute, and has potential for an automatic non-destructive system for spot weld inspection. The development opportunities are significant, since the algorithm used in the initial analysis is rather simplified. Moreover, further evaluation of alternative excitation sources can potentially improve the performance.

This report is written within Spotlight WP5 financed by the FFI programme within Vinnova.

Thermography is a non-destructive testing method based on measurement of the heat distribution by an infrared camera. The method is suitable for automatic inspection since it is a full filed and non-contact method.

A thermography system with an analysis tool developed by Termisk Systemteknik AB is investigated as an inspection method for spot weld. The system is able to detect spot welds, measure the diameter and separate a spot weld from a stick weld. The algorithms used in the analysis are rather simplified and the development opportunities are significant.

A fully automated NDT-cell for spot weld inspection is presented. The automation includes a six axis industrial robot and communication for handling the information flow. This comprised the identification of the inspected spot weld and the reporting to the overall system as to the operator.

A failure modes and effects analysis (FMEA) of the automated NDT-cell is accomplished and the most important actions are reported

A business case for implementing a automated NDT-cell was included in the project. In this business case the most promising quality check concepts for NDT spot weld will be presented and compared with the other identified methods.

In the modern manufacturing industry, quality assurance is important. Over the last few years, the interest in automatic inspection has increased and automatic non-destructive testing (NDT) has been introduced. A general automated inspection cell consists of a mechanized system for scanning and a computer system for automatic analysis of the data. In the manufacturing industry, it is preferable to use industrial robots as the scanning equipment since they offer great flexibility, excellent support organization and the in-house know-how is normally high. Another benefit is that a robot can carry different inspection equipment and an inspection cell can therefore include more than one NDT method. For an automatic analysis, high quality of the resulting data is essential. However, a non-stable condition of the NDT sensor mounted on the robotic arm may influence the results. This paper focuses on the influence of the vibration induced disturbances on the results from an NDT system. Vibration amplitude of a point to point robot movement on the robotic arm is measured. The influence of vibration disturbances on the inspection results are evaluated on the thermal images from a thermography system mounted on a six axis industrial robot. The thermal images taken by the system during the movement and after the stop of the robot are evaluated, and the influence of the vibration in these two situations is considered.

Metal Deposition (MD) is a method to build three dimensional metal geometries by welding using filler wire or powdered metal. NDT of a MD feature is required when the feature is located in an area of high stress or could be a potential hazard to the part. Ultrasonic testing (UT) can be used to detect pores, linear indications and lack of fusion in welds. This method has limitations when it comes to large parts with complex geometries with various shapes and sizes. A flexible method for inspecting complex geometries is to mount an ultrasonic water flow probe (squirter) on a robot. The robot can then follow a pre-programmed path to achieve full inspection of the feature. This paper shows results and functionality from a system where a squirter probe was used together with a standard industrial robot. Results from a scanning of a three-dimensional MD-structure are also presented.

Car bodies are today more often made of high strength steel. In high strength steel spot welds are more friable and it is necessary to have higher demands on the inspections of spot welds. Quality control of spot weld can be either destructive or non-destructive. Destructive testing is still the most common method to test spot weld. The non-destructive methods that are investigete in this project are visual inspektion (VT), penetrant testing (PT), eddy current testing (ET), ultrasonic testing (UT), magnetic paticle testing (MT) and X-ray testing (RT). Other NDT methods are acoustic emission (AE), digital sheargraphy and IR-termography (IRT). These methods are investigated with focus on the possibility to detect Lens Diameter, stick welds, expulsions, porosity and cracks. And the possibility to automation of the method with focus on size and weight of the system, protection equipment, contact or contactless, one or two sided, position accuracy, and result in real-time.

Only tree NDT methods, UT, RT and IRT, can detect all discontinuities that we looking for in RSW. The thermography system has the largest potential to be a NDT system for spot weld in the future, mainly because the method is non-contact, which helps when you have the opportunity to searching on a surface instead of a specific position. The main problem with this method is that there is no software for analysing the results to obtain lens diameter.