Assembling Automotive Control Sensors: How DENSO Robots Enable a Flexible and Precise Soldering Process.
Company: Erwin Quarder Systemtechnik GmbH & Co. KG
Industry: Tool manufacturing, systems technology, automation
DENSO products used: VS 6556G und VS 060
Modern control sensors are essential for today’s automobiles. Supporting safety control features in automobiles, these sensors have an important function. In many cases, their manufacturing has only been made possible with the introduction of automated production systems. Due to the required, highly precise installation of sensors in miniature spaces, a manual assembly is impossible. Their assembly is carried out in an (half) automated wave soldering process of fixating the sensor to a sensor carrier.
The challenge: Despite a pre-set solder wave height, deviations of this value are an unavoidable technical issue that has to be compensated for individually, depending on the varying degrees of deviation. Thus the sensor carrier has to be passed over the wave solder flexibly in order to adjust to the deviation.
The sensors are installed in sensor carriers by using a wave soldering process in an automated production system developed by Erwin Quarder Systemtechnik GmbH & Co. KG for an automotive industry supplier. Quarder is a specialist for automated solutions based on injection molding technology. Relying on innovative engineering know-how and computer science, the company is developing tailor-made production systems. In providing a high level of functionality, quality, safety and usability, these are meeting the requirements of today’s industry.
The automated production line features 12 modules – from the production of the plastic sensor carriers in an injection molding machine, their subsequent transfer onto the assembly line, to the removal and insertion of sensors, the preparation with a fluxing agent and the soldering of the sensors to the sensor carriers and finally to the quality check as well as their palletizing into trays.
In this system, two DENSO robots carry out key functions: First, a DENSO six-axis robots VS 6556G picks a work piece carrier from the assembly line. Each of these hold four sensor carriers with the sensors placed inside, which then have to be installed in a soldering process. In a precise motion, the robot passes the work piece carrier over the fixed wave-solder machine. The challenge: despite a pre-set solder wave height of 4 mm, the actually achieved wave height can deviate by up to 1 mm. This is an unavoidable technical issue. Therefore, prior to the soldering, a sensor monitoring the solder wave height is reporting the actual wave height value to the system, enabling the robot to flexibly adjust its movement of the work piece carrier over the solder wave, thereby compensating the traced deviation. Otherwise, the sensor would not be soldered correctly, making the component part unusable.
The soldering process has to be as precise as possible, and yet needs to be carried out as flexibly as needed in order to not damage the sensors and to avoid plastic deformation of the sensor carriers. Once the soldering has been completed – it takes 30-32 seconds for each work piece carrier –, the robot places it back into the production line for a quality control. At the final station of the assembly line, the second robot (VS 060) carries out a common pick & place task by palletizing the work piece carriers into trays.
Both robots are fully integrated into the system. The remote interface control of the robots is carried out via Profibus, Wago SPS. All figures for the soldering process are being transmitted as integer variables (from the solder angle and deviations to soldering duration, speed and times). The robots as such were programmed in WinCaps using PacScript. Linked by an external VPN connection, the Ethernet-based control can be accessed by users on a touch screen serving as control panel. Here, users can individually adjust all parameters of the soldering process such as the usually pre-set soldering speed, but also all other factors such as the soldering path, duration and angle.
This flexibility not only is a big advantage whenever the assembly of different sensor models is required, but also enables immediate and easy modifications of the soldering process without having to go through the time and effort of re-programming the base settings.
Quarder opted for DENSO robots as the company has had good experiences with them since 2013. They chose the VS 6556G type due to its six axes because the soldering process requires movability and flexibility. In addition, due to the 2 kg weight of each work piece, the robot’s maximum payload of 7 kg was important. In view of the highly precise procedure, both the robot’s cycle time of 0.49 seconds and its excellent repeatability value (+ -0.02 mm) were crucial factors in the decision-making as well. Last but not least, the robots can be calibrated precisely, and are easy to program and to integrate into the existing, automated production system. Quarder was also satisfied with the cost efficiency, longevity and technical reliability of DENSO robots. Currently, a total of five robots of this type are being used in the company.
Thanks to the robots, the production line is fully automated. It’s the robot-assisted assembly of sensors with precise repeatability that makes their application in modern automobiles possible in the first place.
Working in a three-shift operation, the system supplies a total of 10,800 sensors per 24 hours. The error rate of the soldering process is 1 per cent only. Given the complex process, this is an extraordinarily good result. At the same time, the system provides for a highly cost- and time-efficient assembly in a technical quality unavailable without robot assistance.
In the end, car drivers are benefitting with improved vehicle control and driving safety.
More about Erwin Quarder Systemtechnik: www.quarder.de
More about DENSO Robotics: www.densorobotics-europe.com