Since the invention of Scara robots, they have been synonymous with high speed and very good (relative) repeat accuracy in the automation industry. Thanks to their four axes, they also have a simple, robust design and a good price-performance ratio. All this explains the success of these machines. However, the strong diversification and reduction in the batch sizes of components to be produced, particularly since the beginning of the 2000s, also led to customers placing higher demands on the flexibility and adaptability of their production systems. Between 2011 and 2016, the Scaras market grew by an average of 12% per year [1] and now accounts for an important part of the overall robot market - and the trend is still rising.

A system from Camas in Rovato (Lombardy, Italy) demonstrates what Scaras can do and how companies can use these machines to ensure a high degree of flexibility in their systems. Founded in 1981, the company specializes in the design and construction of assembly and testing systems. A total of eight Epson Scara robots are used in a highly modular, flexible assembly and testing line developed by the company for safety valves used in car tanks.

In addition to the short cycle time (≤3.6 s per valve to be produced), the 15 possible valve variants, which can only be produced alternately with a short lead time in various large batch sizes, were a particular challenge for the customer. The use of the four-axis machines gives the system its high adaptability to rapidly changing tasks. They play a key role within the entire production line for "pick & place" applications. The robots make it possible to produce different variants of the component without the need for additional hardware components or compromising on execution speed.

The production line

The system comprises a total of five stations, consisting of four rotary tables and a free-running pallet conveyor, where the various sub-assemblies of the valves are constructed and finally assembled. The last station is a test station, which tests the finished valves for certain parameters. The design requires a number of constructive measures to make switching between different variants easier and more efficient. It is therefore possible that one station is busy constructing variant 1 while variant 2 is running at another station.

"A line of this complexity contains a number of stumbling blocks in the design," explains a Camas representative. "Fast and efficient handling systems like Scara robots help us a lot to be competitive in this demanding market. That's why we decided to have Scaras handle all the pick & place processes at this plant. Firstly, unlike other solutions, they allow us to process two components in parallel and secondly, they simplify the entire programming and coordination process. In addition, thanks to their simple design, the maintenance effort for the system is reduced without compromising performance and speed. After all, we must never forget that the system has to produce a finished part in a maximum of 3.6 seconds."

The first stage of the system deals with the component that controls the opening and closing phase of the valve. Here, various very small workpieces have to be picked up quickly and precisely in the correct orientation and reoriented. The choice of Scara robots for this segment makes it possible to process two components in each cycle instead of one. In the next part of this section, the pre-assembled part is quickly and accurately placed in the desired orientation. With the Scaras, the machine becomes smaller, as no mechanical aligner is required for the respective valve variant. The Scaras are also reliably fast and precise.

In the two subsequent stations, other sub-assemblies of the valve are assembled, which ultimately make up the entire component. Here, two Scara robots remove and assemble the relevant components from a supply.

"A central PLC monitors the entire line," explains Camas. "All of the machine's production data, including the batch of each individual component, is automatically tracked, stored and archived. If required, we can also provide our customers with IT support and help them manage their production data."