Design Engineering

Terminal velocity: Smart conveyor system boosts testing, production

By DE staff   

Automation Motion Control

Smart conveyor system increases testing capacity and throughput of I/O terminal production.


In the fall of 2021, Beckhoff began to completely rethink the way it carried out final inspections of its I/O components. Its aim was to significantly increase testing capacity and throughput, even though the German automation company produces many different types of terminals.

To address this challenge, Beckhoff’s own equipment manufacturing department developed a system capable of programming, adjusting and testing approximately 10,000 terminals per shift fully automatically. The system’s high speed and flexibility are the result of not only a sophisticated system concept, but also the automation company’s XPlanar transport system, PC-based control and the wide range of EtherCAT terminals.

Keeping pace with Beckhoff’s growth remains a challenge for Michael Golz, the head of the company’s demo systems department, and his approximately 40 employees, who are responsible for building the operating equipment. They have taken a completely new approach to the system for final inspection of I/O terminals – with the XPlanar as a transport system, specially developed firmware programmers, and test stations with universal test cabinets.

“On average, a fully tested I/O terminal, that is programmed with the appropriate firmware, leaves the system every 3 seconds,” Golz explains, “regardless of the type of terminal and the order in which they are delivered.”

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Currently, more than 200 different types of terminal can be programmed and tested on the system. The number of different types present also has no impact on the output rate of 10,000 terminals per shift.

It seems like Beckhoff is trying to square the circle, particularly as, depending on the type of terminal – with/without FPGA, a controller or with analog channels – programming and the subsequent function test take different amounts of time.

“It can take up to 30 seconds for the firmware to be installed and all analog channels to be adjusted,” explains Stefan Engelke, who developed and programmed the test cabinets together with his team.

The solution to this time issue lies in the parallelization and separation of the firmware installation on the one hand and the function tests on the other. This is not a groundbreaking idea in itself; the pioneering element is the systematic use of the XPlanar’s degrees of freedom for the entire internal logistics and infeed of the terminals to the workstations.

Due to the free 2D movement of the products, it is irrelevant whether a single bus terminal needs to spend 10 seconds or one minute in a tester. The remaining movers simply go past the occupied stations to the next free station. The overall output of the system is therefore unaffected by individual delays.

 

Transparent handling

“The process is nevertheless very simple,” Golz says. “The operator doesn’t have to set up anything; all they have to do is place a stack of trays with terminals at the infeed station and press a button.”

The stack then enters the picking station, where a delta robot picks up the modules from the trays and places them individually on the waiting XPlanar movers. The system has two main paths, almost like highways, leading left and right to the programming and testing stations. The stations are located at exits, or parking bays, on the side of both lanes. Between the lanes, there is a third path where all movers return to the picker. This symmetrical set-up has the advantage that even if an entire half of the system fails, the other side can continue to operate.

The movers then pass the terminals under a reading station through to the lateral programming stations. The reading station captures the individual Beckhoff Identification Code (BIC) of each terminal by means of multiple cameras and Beckhoff Vision.

“After that, the system knows the terminal type and does everything completely autonomously – programming, adjusting the analog channels if necessary and function testing,” adds Ulrich Brockhaus, who is responsible for system programming. At the same time, the BIC is “married” to the mover via its ID. This means that the mover ID can be used to track the location of each individual mover or terminal, even after a power failure.

When the mover has reached a free programming station, it positions the terminal precisely under its contact pins. Then, depending on the BIC, the corresponding firmware is loaded onto the terminal.

It then moves on to one of the universal testing stations, which in turn calls up the device-specific test sequence based on the BIC. If the software has been loaded correctly and the function test reports no issues, the mover transports the terminal to the picking station’s second delta robot, which places the terminal on another tray, via the middle track. The mover passes through the reading station a second time, only this time in the opposite direction.

“The terminal is booked out via the renewed capture of the BIC on the return track, and the installation of the firmware and the function test of each individual terminal are documented in the central database, including all adjustment values in the case of analog terminals,” Engelke says.

 

Degrees of freedom

The basis for this flexible yet fast process is an XPlanar system consisting of 100 tiles.

“We built the two main paths with two outbound lanes and the return track in the middle from six XPlanar base sets, each containing 3 x 4 tiles,” Golz explains.

For the add-ons (programmer and tester), the remaining 28 tiles are screwed onto the side of the basic system. Each mounting position has a standardized interface with power supply (400 VAC), safety, Ethernet, as well as EtherCAT. “The interface and the system layout enable future expansions without major conversion work,” emphasizes Golz, who is responsible for the mechanical design of the system and the specific details for terminal contacting.

XPlanar makes machinery modular while also simplifying mechanics in many sectors. For example, the programming stations use XPlanar’s XY precision positioning. Therefore, immediately after reaching the exact position, programmers can lower their pins onto the terminal contacts and start loading the firmware.

At the test stations, XPlanar’s variable flight height feature reduces the design work. When it arrives at the test station, the mover first lifts so that the slide-in unit of the test station can move under the terminal. Then, the mover lowers its hovering level again, and the terminal then rests on the slide-in unit and is drawn into the tester. The benefit is that all contacts are freely accessible and can be contacted. After the test, the terminal is then placed back on the mover in reverse order.

The option to rotate the movers comes into play again during insertion and removal. It is used to rotate the movers by 180°, depending on the side of the system used.

“This feature has also significantly reduced the mechanical complexity and has made space-saving configuration of the tester and programmer on both sides possible in the first place,” Golz points out.

 

Electrical and optical functions

The testing stations don’t just check the electrical properties and functions of a terminal. “For terminals with analog signals, the corresponding test sequences and calibrations are included too,” Engelke says. An integrated vision system also checks that the prism is present and in the correct position and measures the colours and intensity of the LED.

A very wide range of EtherCAT Terminals, with their diverse functions and measuring ranges, can be tested automatically on the system, and this is all thanks to the universal test cabinet. Its measurement and testing capabilities are based on Beckhoff technology, with a focus on the precise measurement terminals from the ELM series.

Mounted in mobile cabinets and coupled to the system by means of a plug connector, the test cabinets can be replaced quickly, without shutting down the entire system. This needs to be performed regularly, since the ELM terminals are measurement devices which must be re-calibrated and certified in specific cycles.

The strengths of PC-based control are also evident in the overall coordination and evaluation. If a tester detects a discrepancy on a terminal, this is registered via the BIC while the tester sends the terminal back to the programming stations for reconfiguration. However, if error messages accumulate on a programmer or tester, this indicates a malfunction.

“In this case, the tester is reported to the system as unavailable and this position is no longer approached by the movers until the tester has been examined and, if necessary, replaced,” says Brockhaus. Although the system will then run with one station less for a short time, it is still up and running and not significantly slower. “An I/O terminal that could cause any problems for a customer would not leave our system,” Golz adds.

The system is a prime example of how PC-based control can be used to perform a wide variety of tasks and functions. In addition to a C6670 control cabinet industrial server, which coordinates the 33 movers on the 100 tiles, a total of ten compact C6032 Industrial PCs control the other system components. The delta robots are automated with the AX8000 multi-axis servo system and AM8000 servomotors.

“We use the AMI8100 integrated servo drives to infeed and eject the trays because they are extremely compact and only require EtherCAT and 48V voltage to operate,” says Brockhaus. AA1000 linear actuators are used by the programmers to contact the terminals; AA3000 electric cylinders are also used by the testers to feed in the terminal carriers. The entire safety technology is implemented with TwinSAFE. TwinCAT Vision captures the DataMatrix codes.

Around 40 EtherCAT measurement terminals from the ELM series are installed in each of the four test cabinets. In addition, a wide range of EtherCAT terminals from the EL series are also used. “PC-based control has made a lot of things easier for us in this project and leaves us the option for further expansions,” Golz says.

“Our I/O terminal portfolio comprises a wealth of products, from 2-channel digital input terminals to compact drive technology, with differing levels of complexity, which are produced in annual quantities ranging from a few thousand to hundreds of thousands of units,” Michael Klasmeier, Beckhoff’s head of I/O production. “All of our products are produced locally in Verl, East Westphalia. Our objective is increase production output with our current employee numbers and in the space available, which is impossible without automated testing.”

This article was submitted by Beckhoff Automation.

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