When a product establishes itself on the market and demand increases, it is time to increase production. However, it is not always easy to speed up an automated process chain to build more units per unit of time. Increasing the line cycle rate is not always straightforward. Purchasing additional equipment or a complete production line can be very costly. Even if such investments make sense and can be financed, there are practical hurdles to overcome. Free space in the factory may be limited, while on the other hand some processes may be a bottleneck that cannot be solved by purchasing more or larger machines.

To find solutions to these problems, production engineers need to rethink, develop new production technologies or find a combination of both.

A challenge for scaling production

Rotary indexing tables are often used to transport workpieces from one sub-process to the next in a production sequence. They offer high positioning and repeatability and high cycle speeds and can also handle heavy workpieces if required. Their rotary motion can enable complex operations and support seamless transitions between different manufacturing stations. Due to their versatility and ability to handle complex tasks, they are beneficial in situations where traditional transport systems may not provide the required precision.

Nevertheless, increasing production output can be a real challenge. Increasing transport speed to move more quickly between index positions has little effect if the time to complete each operation is long. Introducing a larger indexing table or duplicating the entire line to process more workpieces simultaneously can be problematic, expensive and take up additional space on the factory floor.

Figure 1: Components are tested and inspected individually using rotary indexing tables and offline inspections.

© Yamaha

This is exactly the situation that an electronic component manufacturer recently found itself in when demand for one of its products began to rise and the company sought to increase its production output. In the production area, components were loaded onto a rotary indexing table via a conveyor belt to go through a series of test and inspection processes(Figure 1). For one of the inspection processes, the components had to be switched on. The cycle time for this process step was significantly longer than for other steps in the sequence. To realize this, the team used a SCARA robot to transfer the components from the rotary indexing table to an offline inspection station. After this inspection, the robot loads the components onto the second rotary indexing table so that the remaining production processes can be carried out.

Rotary indexing table vs. linear transport system

As offline inspection is considerably slower compared to the other processes, the team could not easily increase production output. In addition, the team found that the transfer of components from the rotary indexing table to the inspection fixture and back increased the risk of damage and contamination of the component surface by foreign objects. These risks needed to be reduced while increasing production throughput.

The team considered installing a larger rotary indexing table for workpiece carriers, each with four components, to save time by testing multiple units simultaneously in the offline fixture. However, the rotary indexing tables were difficult to align.

Processing directly on the carriage

Figure 2: The LCMR200 traversing unit ensures greater flexibility in eliminating production bottlenecks and carrying out inspections and reworking without stopping the line.

© Yamaha

As an alternative to rotary indexing tables, a linear transport system provides a compact and easily scalable solution with comparable speed and accuracy. With systems such as Yamaha's flexible, modular LCMR200 linear transports(Fig. 2), production planners can design lines up to 25.5 m in length. Configurable slide speeds and stop positions facilitate the transportation of workpieces between automated processing stations, which can be located at any point along the line. The slides offer high rigidity and positioning accuracy with a repeatability of ±5 µm and can carry workpieces weighing up to 30 kg. This means that processes can be carried out directly on the slide without the workpiece having to be transferred to a fixture, which enables shorter cycle times and helps to save development and system costs.

Greater flexibility thanks to traversing unit

The LCMR200 system also offers circulation units that can be installed at both ends of the line. They enable the carriages to be transported in a loop, allowing them to be quickly returned to the start of the process chain. Additional assembly operations can also be carried out during the return.

Figure 3: The circulation and traversing units enable stable production lines with high flexibility to overcome bottlenecks and minimize downtimes.

© Yamaha

A new traversing module now enables even more flexible configurations, including the parallelization of processes to eliminate production bottlenecks and the retraction of workpieces for offline inspections or tests.

Figure 3 shows a comparison between the traversing unit, which can be inserted between the modules and allows slides to enter and exit from both sides, and the carousel unit, which is intended for use at the end of the line.

Traversing unit in action

Figure 4: The traversing unit simplifies the parallelization of industrial processes for greater efficiency and higher throughput.

© Yamaha

With the help of the traversing unit, the component manufacturer's production team saw the possibility of setting up a production line with LCMR200 modules and providing three parallel branches for testing and inspecting the components(Fig. 4).

In addition, the slides can accommodate larger workpiece carriers than the rotary indexing table, so that four components can be inspected simultaneously, increasing production throughput.

The high system speed - LCMR200 slides can move at up to 2500 mm/s - combined with the opportunity to test components in parallel, enabled a significant reduction in overall cycle time. As the components do not have to be removed from the slides for offline testing, they are also protected from possible damage and contamination. This allowed the team to achieve the desired increase in production without having to set up additional work shifts, while also improving product quality by minimizing the potential for damage and contamination.

Higher productivity with factory automation

Common approaches in the development of process automation focus on meeting predetermined targets for parameters such as throughput, accuracy and repeatability. Scalability is often not the focus. Product manufacturers may run into problems later if they need to increase production as market demand increases. A workpiece transport system that offers flexible configuration options and simplifies the parallelization of processes can provide speed, accuracy and repeatability while enabling space-saving, scalable solutions.