Case Study: Virtual Commissioning an Injection Molding Machine

Many engineering organizations face major challenges when designing and delivering new products. This includes the discovery of design issues late in development that bring unbudgeted costs and delays, especially if design issues arise during the prototyping, or integration stages. For companies in the manufacturing industry, staying competitive requires significant cost reductions, increased productivity and innovation, and the adoption of advanced technologies. With the right set of tools for virtual commissioning, companies can explore, test, and validate designs, while reducing the time and money spent on product development.

Cost-Effective Motor Sizing

The injection molding industry is a diverse, competitive market where innovative products must meet demanding requirements. These requirements lend themselves to cautionary approaches to new products, and a robust testing strategy to minimize operational failure. Often, these practices result in a slower time to market and higher development costs. To remain competitive, these companies are adopting model-based techniques that inform design choices with more accuracy than ever before.

A leading manufacturer of injection molding wanted to create a new design that could promise reliable performance at a lower cost. The design, however, had to meet strict requirements for motor sizing, and called for a specialized controller that would offer the same reliability expected from their customers. To ensure accurately sized motors and precise controller design, the company used MapleSim to get model-based feedback during their design process. With virtual commissioning, the company could use a physics-based model of their design to understand the dynamics of their machine and make informed choices for both motor sizing and control design.

By using the company’s existing CAD information, the physics-based model was customized in a matter of days, allowing motor sizing to begin sooner than the company’s traditional processes would have allowed. The motion profile was implemented in MapleSim, and the simulation results were formulated into a common Speed-Torque graph. The machine’s duty cycle was well within the company’s motor requirements. This assured the company that the motor would operate within safe limits, and that the motor was sized without a large margin of error.

Control Strategy Testing

The new machine would split the motor loads in half by using a dual axis closing mechanism, helping reduce the costs of a single, larger motor. A key requirement of the design required that both axes remained in parallel during the opening and closing of the mold. Misalignment of either axis would risk significant damage to the machine; therefore, it was necessary for the control strategy to ensure axis alignment under a variety of conditions. To reduce the risks of machine damage, virtual commissioning techniques were used to test the controller performance against the model.

To prepare the model for virtual commissioning, it was refined to reflect the new dual-axis design. The new mechanism was duplicated and connected to a mold subsystem, which modeled the mold as a spring-damper system. The model was exported as a Functional Mock-Up Unit (FMU), which acts as a standalone, executable model that can be used in a variety of other design tools. The FMU was imported into B&R Automation Studio, where it functions as a variety of inputs (motor torques) and outputs (sensor data) that run in real-time for control testing.

In the weeks following the motion profile testing, the company created a physical prototype of their new dual-axis mechanism. While this prototype could provide them with some testing information, the key piece of information – controller robustness to keep axis alignment – would impose signification machine damage, making repeated testing an expensive choice on a physical prototype. By using a virtual model initially, they avoided these risks.  By testing the controller against the virtual model, countless simulations can be run in a fraction of the time it would otherwise take with a physical machine, saving time and money to ensure a robust, reliable machine.

Going Forward

As part of a growing need to speed development and minimize the inherent risk in developing new, innovative products, virtual commissioning is quickly becoming an essential technology. With the right tools in place, it is now possible for many organizations to adopt virtual commissioning techniques for their machine design projects. They may use virtual commissioning to reduce their overall commissioning time, to reduce development costs, or to create a more reliable time to market.

In this case, the company was able to create a cost-competitive injection molding machine using a new dual-axis design with smaller, inexpensive motors. The precise loading requirements of the motors were simulated, ensuring the company had selected the right motor for the job. To avoid the costs and delays of damaging prototypes for controller testing, they could ensure the controller’s robustness by using virtual commissioning. Taken together, these techniques have given this company a powerful set of design tools, helping them continue to stay one step ahead in an already competitive market.