Quality Down to the Last Detail

Optimized Gap Dimensions in Automobile Construction

EDAG - partner for the international mobility industry
The world’s largest independent development partner, EDAG develops customized concepts and solutions, optimized for production, to meet the mobility needs of the future. The company’s holistic understanding of vehicles and manufacturing plants makes EDAG a leading partner who can offer the merger of product and production in development to the realization in plant construction in a value-adding process.

The current situation:
Quality requirements hardly to be met with conventional process

German automobiles stand worldwide for high quality down to the smallest detail. “There is no second chance for a first impression” – that is the motto of the engineers and designers – and in fact, perceived quality is a big factor in the decision to purchase a vehicle. The precise fit of body parts, such as doors, with the smallest and above all most uniform gaps possible, plays a decisive role. That makes the requirements of automotive manufacturers for their production processes all the higher.

In automobile construction, attached components are assembled predominantly using conventional methods with gauges, which keep the attached components is a constant, rigid position for installation. This means that sometimes substantial re-work has to be invested during production for manual adjustment. Uniform distribution of gap dimensions, as required today by both designers and quality engineers is hardly possible using these conventional methods except through correspondingly high levels of expensive labor.
This was recognized by the engineers at EDAG, the world’s largest independent development partner of the mobility industry. The company worked with Allied Vision Technologies to develop an intelligent sensor for use with the EDAG image processing systems Best-Fit and other applications. In the first step, a pilot system was implemented at the main EDAG location in Fulda, Germany, in collaboration with GM/Opel.

EDAG Best-Fit: sensor-controlled assembly
The system known as “Best-Fit” is a sensor-based assembly process, which makes custom-tailored, highly precise assembly of attached parts in automotive production possible. For example, for door installation, sensors first determine the dimensions of the gap and transition for each manufactured door along with the cut-out in the side wall of each corresponding vehicle; then calculate the optimal position of installation of that door with that car body; and finally use robots to target this position precisely. The joining robot then installs the door so that it meets the requirements for a high-quality vehicle, despite the unavoidable geometric variations due to production tolerances. A particular feature of the EDAG Best-Fit system is that it learns and thus independently controls placement behavior in the joining process. Beyond that, a final quality inspection step is carried out and documented, so that downstream measurement stations can be eliminated.


Depending on the design of the attached part, 6 to 11 sensors of the type EDAG VarioGauge V4 are installed on the gripper of the robot. In addition to electronic control and monitoring systems, the intelligent sensor EDAG VarioGauge V4 consists of a laser source and a digital camera from Allied Vision Technologies. With the aid of these sensors, the components, e.g. door and side wall, are measured with each other. The EDAG Best-Fit system detects the current status quo of the alignment along with the width and distribution of the gap dimensions and calculates the optimal position for installation. The software ensures not only the most parallel possible gap dimensions, but also uniform distribution of the gap dimensions at all measurement positions.

Optimal choice for multi-camera operation: AVT Marlin with internal memory
For the Best-Fit process, EDAG depended on digital cameras of the Marlin family by Allied Vision Technologies. For better integration in the EDAG VarioGauge sensor, the housing of the standard camera was removed and the board-level version was selected. With a resolution of 1.4 Megapixels, the cameras permit precise gap measurements. In addition, the cameras are equipped with a digital interface (FireWire IEEE 1394a). This interface can be used to activate all the cameras of the EDAG Best-Fit system via a broadcast trigger. Thanks to the internal memory and the deferred mode, the Best-Fit system can flexibly call up the images of each camera for analysis.

Customer satisfaction with AVT: “Marlin is the best match”
“The deferred mode of the Marlin cameras from Allied Vision Technologies is the best match for the Best-Fit application”, explain Christian Böttcher, Technical Manager for Image Processing Technology and Christian Körbel, Sales Manager System Technology of EDAG. “The industrial suitability of the FireWire interface was important to us in selecting a camera: We were able to design a special hub with fiber optic data transmission from the assembly gripper to the Best-Fit computer (VarioInspector), which makes the image processing technology immune to electrical and magnetic interferences within the system.”

Practical use: Milestone for assembly quality in automobile construction
The EDAG Best-Fit process is a milestone for assembly quality in automotive production. For each manufactured component and each manufactured body, the system calculates the optimal position for assembly - for a consistently uniform and high-quality appearance of the overall vehicle. But in addition to the quality advantage of perfect distribution of the gap dimensions, the EDAG Best-Fit system also achieves economic advantages: The costs of manual re-adjustment are reduced drastically, as the implemented projects have shown clearly.

Assembly is now being done at two European locations with the EDAG Best-Fit system, for instance, for all the attached parts of the Mercedes Benz S-Class and the doors of the Opel Corsa. In addition, the EDAG Best-Fit system is also being used for other applications, such as precise positioning of robot tools, e.g. for punching, stamping, or riveting in automobile production.