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Robotics meets THT electronics production

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System expansion through robot-supported process interlinking

 

A fully automated extension to an existing THT production line was put into operation at one of Europe's largest mechatronics service providers. Together with the special machine and system manufacturer haprotec GmbH from Kreuzwertheim, the project team developed a concept to expand an existing system with a fully automatic placement line consisting of a combination of automatic placement machines and robot placement, as well as two test and potting stations.Power electronics, primarily for e-mobility, have been produced on the existing production line since 2013. The system combines two soldering systems with manual placement workstations, buffer and AOI systems. Even back then, the two companies took bold steps in linking several process machines, controlled and monitored by haprotec's newly developed central system control system. Over the years, thanks to the foresighted planning of the two partners, the system was repeatedly expanded and further developed.

Then came the go-ahead for the next, most innovative and forward-looking expansion step to date. The responsible team had laid the foundations in advance in extensive planning discussions and determined the feasibility of the project. The resulting requirements for variants and cycle times were no less challenging than the requirement for "THT assembly without people". It was clear from the outset that control and traceability were to be realised exclusively via haprotec's central control system (ZLS), which was already established worldwide. It was also agreed early on that the system concept should be based on the high flexibility of 6-axis robots.


"Such a project is groundbreaking for our industry and will demand everything from the project team, despite years of successful and trusting collaboration. Both the technical requirements and the time frame for this project are exceptional," says Peter Helmstetter, the sales representative responsible at haprotec.

 

Loading, material feed & hold-down handling

Most THT components are assembled using an integrated pick-and-place machine, although some components can only be assembled using an additional haprotec robot due to their nature. Placement is carried out by both the automatic placement machine and the placement robot, exclusively inline, i.e. directly in the workpiece carrier on the transport system.

To make this possible, a downholder handling system had to be developed that removes the downholders from the workpiece carrier at the start of the placement process and places them back at the end. This resulted in two gantry systems with grippers and an additional transport system for the hold-down devices. In order to optimise space, the downholder handling system was installed above the placement line with the aid of two towers.

 

In order to achieve the required system autonomy, the placement robot is provided with a material feed system based on an automatic tray system. Using appropriate vision applications, the robot identifies the product, selects the correct component, checks the alignment of the up to twelve pins and places it on the PCB. The challenge here was to correct the position before placement. The choice of a 6-axis robot over a classic gantry system proved to be a major advantage here.
 

 

Christian Happ, Managing Director of haprotec, summarises why his company is suitable for this challenge.
 

"As a rule, our customers' concepts in the field of THT automation provide for the placement of components at manual placement workstations. In recent years, haprotec has focussed in particular on the development of assistance systems for worker guidance and placement control. In this case, we were able to rely on our experience from the company's second division, special machine construction for assembly and testing technology, to meet our customer's more demanding requirements. High-precision component handling in cycle times of just a few seconds is the order of the day here. We can therefore serve both high-volume low-mix and high-mix low-volume areas of the industry."

 

Tray handling, tester & dispenser

The eight different basic products are fed into the overall system in tray stacks. A robot removes the individual PCBs from the tray and places them in the empty workpiece carriers on the placement line. After a tray has been emptied, the robot picks up the empty tray and places it on an intermediate transport and then places the finished soldered blanks in the trays. Thanks to the development of a specific double gripper, all products and all tray variants can be gripped with the same gripper system. The product is transported to the second robot via the intermediate conveyor. This robot removes the circuit boards and places them in one of the two testers, depending on their assignment. After successful testing, the robot places the product back into the tray and transfers it to the next robot in the system. This transfers the soldered and tested products to one of two dispensers and then to an outfeed station with the entire tray.

 

The project manager on the client's side explains the complexity of the task. "As planners, we always face the same challenges. Evaluating the best processes for our products and linking them together as efficiently as possible. In this case, the efficiency is demonstrated by the amount of space required, the high product variance with a short cycle time and all without having to retool the system manually. In our collaboration with haprotec, we see their expertise as an integrator of all kinds of processes as particularly valuable."
 

Communication, traceability & line control

The entire system can be operated according to the chaotic principle. To load the programmes, the MES communicates directly with the process machines via the haprotec control system. Each process step is queried and verified via RFID and DMC. Conversely, all production-relevant data is written back to the MES via the central control system. This ensures complete traceability along the production line.

 

"Due to the complexity, the high volume of data and the need to maintain production operations during the commissioning of the expansion, we agreed with our customer in advance to replace the existing control system from 2013 with the latest version. Thanks to continuous further development in recent years, we were able to keep the functions of the ZLS up to date with the latest technology, which enabled us, for example, to test all interfaces by simulating the customer-specific MES before the actual commissioning. This enabled us to smoothly integrate the new system into the existing line," says Alexander Rose, Project and Development Manager at haprotec, summarising the advantages of a modern system control.

 

Following the successful realisation of the project, the go-ahead was given almost immediately for the planning phase of a sister plant. Everyone agrees that the originally developed concept has proved its worth and is the right way forward.

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