The key is straight

Despite their individuality, cylinder locks are also mass produced articles that need above all one thing for their assembly: the shortest possible cycle time. The WEISS Linear Assembly System LS280 not only provides enough space for the many process steps, but also features a technology related to indexing tables that changes workpieces considerably faster than conventional transfer systems.

At first glance, the cylinder locks all look alike that run through the fully automated assembly process on a WEISS linear system. Yet locks are nothing of the sort: each is unique, inside and out. Stefan Trommlitz, Managing Director of Aumat in Solingen, knows from experience: “In the lock industry, we mostly have to deal with the exception of the exception.” His company is a wide ranging specialist, also in special purpose machinery for cylinder locks. Also the present system is “no exception”. In a fully automated process, it assembles the complete inner workings of a cylinder lock and seals the housing on an electronically regulated press. Trommlitz added: “The very large number of different pins and wafers that are assembled on the basis of data records give rise to countless permutations.” Despite this diverse range and the precision needed for assembly, cylinder locks are nevertheless mass produced articles. Accordingly, the Aumat designers attached very special importance to “positioning precision” and “short cycle time” when drafting their new system. Both of these are the classical virtues of an indexing table. However, its large number of processing stations – fifteen in total – ruled it out as a candidate from the very outset. Although a transfer system would have provided enough space and – true to “the exception of the exception” – allowed expansion to boot, “positioning and indexing the workpiece carriers needs a lot of time,” is Trommlitz’s objection. “Even 1.5 seconds would still be a full quarter of our cycle time of six seconds.” Aumat ultimately found the solution to this space versus time problem at the Motek stand presented by WEISS. Aumat has known this company and appreciated the indexing tables for decades. Achim Ihlefeld, Head of Engineering, therefore found the linear system LS 280 all the more striking,
which at first glance didn’t look at all part of the program.

An initial inspection revealed established technology and robust workmanship in the characteristic WEISS manner. Paired workpiece carrier “trains” on four rollers run free of backlash on a hardened and ground V shaped guiderail. The workpiece carrier engages in a friction grip, and a guide shoe runs on a toothed belt in the conveyor sections and on a rotating disc at the corner units. Nevertheless, the Linear Assembly System LS 280 is undoubtedly a typical WEISS product, as demonstrated by the locking stations. These are actuated by a cam drive, tried and tested thousands of times in the indexing tables from WEISS. Approaching smoothly on the conveyor section regulated by a frequency inverter, the workpiece carriers wait for the next indexing pitch at the infeed on the transport cam, whose modified sinusoidal motion track guarantees a very gentle and smooth movement at the workpiece carrier. The carrier is then transported and locked in one movement. There is no lengthy stopping, lifting, and positioning as with conventional transfer systems. After just one rotation of the transport cam, the workpiece carrier assumes the next position quickly, securely, and precisely. By “cutting up” so to speak an indexing table, the company has developed a transport system that combines the advantages of an indexing table – short cycle times, high positioning precision, and gentle starting – with the flexibility and the space of a linear transfer system. For Aumat, this “long” indexing table was, in the truest sense of the word, the key to its space versus time problem: the workpiece exchange time of just about half a second was perfect.

Now work could begin on the cylinder lock assembly line. The result is a 12 m long, straight system with two corner units, 15 processing stations, and 42 circulating workpiece carriers. A paternoster feeds pallets each with ten key / lock pairs. At a manual workstation, the locks are then fitted in the receiver on the workpiece carrier. The large number of variants makes automating this operation difficult. While the locks are being assembled, the keys remain in the pallets. An RFID system with data carriers on each workpiece carrier retains the overview and informs the robot at the end of assembly which lock belongs to which key. The circulating preassembled cylinder locks are measured with a laser, fitted with their pins and springs, examined with optical equipment, and pressed with plugs. Stationary cam followers fitted to the bottom of the system support the product devices on the workpiece carrier plates to absorb the vertical process forces.
Aumat appreciates the system’s overall stable design. “The modules of the linear system are delivered completely with a solid machine bed, so we don’t have to build a frame first. Even without the process attachments, the basic machine LS 280 looks ‘complete’, and we can show the customer something without having done much.” The substructure is made of steel and when necessary can be additionally reinforced. It also provides enough space for the switch cabinets of the assembly cells. As a rule, the linear system’s controller is also installed here in the form of a Master PLC. Its Slaves then take over the function of actuating the locking stations to which the upstream conveyor sections are also assigned. On the cylinder lock assembly line, however, the
space in the substructure was badly needed. This was no problem for WEISS – After full function tests and official acceptance at the plant, the LS control components were delivered separately for installation in the switch cabinet on the side of the system. A special version of the WEISS Application Software WAS controls the Linear Assembly System and communicates with the superior machine control. Like on the other WEISS products, WAS.LS comes with preset parameter values that allow the operator to configure and monitor the LS without any programming knowledge. Trommlitz praised the simplicity of the system: “To integrate the LS 280, the it needs solely to enter the control bits for the defined interface signals.” His praise is shared equally by his customer: a second, similar machine has already been sold. When other customers see the advantages this system has to offer, Aumat can hope to control better the “exception of the exception” problem on the sector: “The system’s modular layout and ease of access lends it a high level of flexibility, and when we can link each station skilfully, we could perhaps even create a standard.”



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