On-the-Fly Polishing: An Advanced Automated Die Polishing System Without CAD Models and Part Registration

We present an Automated die polishing system, developed in CONVERGING for and with Ford Spain. This system is capable of on-the-fly polishing. It requires no part registration or CAD models; just inspect the part and polish, as a skilled operator would do, enhanced by the precision and force control exclusive to robotic capabilities. Employing mixed reality we can train operators, designate polishing zones, and manage process parameters.

The Challenge

The journey began with the objective of automating the repair process for stamping dies used in stamping machines. This process encompasses numerous steps, ranging from defect detection to material addition, followed by sanding with stones and sands of varying granularities. The final step is polishing. Our focus is primarily on this last step, not only because it is most suitable for automation due to its repetitive nature and lesser need for dimensional checks compared to the preceding steps, but also because it is the most tedious task for a human operator to perform.

Numerous meetings were held between the teams at Ford and Tecnalia to understand the key challenges, and an exhaustive literature review was conducted. The review revealed that nearly all automated polishing processes rely on an accurate CAD model of the die. However, experience has shown that the CAD model does not always accurately represent the actual dies. This method of automation introduces an additional challenge: the need to perform part registration to align the physical die with its corresponding digital representation, the CAD model. Achieving this alignment with high accuracy is not trivial. It is time-consuming and depends on an exact match between the real part and the CAD model.

The Technology

To address these challenges, the Tecnalia team began developing a new technology that was named Watch and Work. This technology encompasses a set of tools that facilitate the planning and execution of robotic trajectories in real-time. It relies on 3D acquisitions and reconstructions to cover entire surfaces for continuous contact operations such as polishing, painting, and welding. Watch and Work overcomes the limitations of traditional robotics in applications that present the following conditions:

• • A large number of different references and short series, making manual programming impractical.
  • Unavailability of CAD models of the parts.
  •  Parts where the real geometry deviates from the theoretical path, making CAD-based programming not feasible.

Traditional robot programming requires the intervention of expert personnel who perform offline programming. This limits the ability to react to changes in the process. The Watch and Work technologies offer the following advantages:

• Elimination of manual programming: The operator simply has to indicate tasks and can also rely on Extended Reality (XR) tools to give instructions to the robot.
• Dynamic flexibility: These technologies allow for agile and flexible adaptation to modifications in the geometry or presentation of the parts without human intervention.
• Dynamic trajectory generation: Adaptations can be made in real-time based on process feedback.
• Accurate force application: By adding the input from the robot’s force sensor to the control strategy executed on a separate PC, we are able to exert precise control over the force applied by the robot to the surface of the die being polished.
• Operator Training, Defect Marking, and Simulation with XR: A training procedure has been developed using XR tools, which facilitates operator learning on system usage. The operator can also identify locations of defects with the help of XR tools, either by marking the area with a finger or using  other natural ways of interaction, such as the concept of a "smart pen" to mark directly on the part. Another significant feature is the ability to simulate the polishing process in XR before initiating the actual robot movement. This feature proves to be very useful.

Deployment Technology and Strategies

To facilitate the workflow, we maintain two production cells. One is installed at the laboratory of Tecnalia and the other at the die repairing area of Ford. The Tecnalia team has made several visits to Ford for the initial installation and setup of the system in their robot cell.

To maximize interactive development and minimize reliance on physical trips for each new feature, a deployment system has been implemented. This system allows for remote updates to the Ford system whenever a new feature is developed at the Tecnalia laboratory work cell. This efficient approach not only enables faster collaboration but also significantly contributes to reducing the amount of travel.

Close communication has been established between the two teams. Ford uses the system to refine new die references and suggests beneficial features to be added. Meanwhile, the Tecnalia team continues to advance the technology while simultaneously incorporating the suggested features.

Daily Operation

When a new die needs polishing at Ford, the monitoring and work system captures the 3D surface scan and automatically calculates the trajectories that will enable the die’s polishing. The polishing process, with precise force control, is then carried out. Ford assesses the quality of the polishing and compares it with the data they have on manually polished items. Conclusions are drawn, and information for further development and enhancement of the system is provided to Tecnalia.

Upcoming Challenges

 As we look to the future, we are concentrating on the following challenges:

• • Automatically selecting the diameter of the polishing tool head based on the curvature of the die.
  • Detecting surface roughness.
  • Performing a dimensional quality check.

This collaboration between Ford Spain and Tecnalia within the CONVERGING project is a testament to the power of innovation and the endless possibilities that technology brings to the industrial sector. We look forward to continuing our journey towards more efficient and precise polishing results.