The task was clearly defined: For the production of sensors within a production line, various individual parts must be fed quickly and assembled precisely one after the other in order to feed them back into further production as a finished assembly in a short cycle time. For this purpose, different components are fed individually depending on the processing step and assembled into finished assemblies in six processing steps such as pressing, screwing or gluing. "We didn't have much space available - the required handling system had to be accommodated in a cell specified by the customer," reports Andreas Hirt, sales representative in the linear axes division at IEF-Werner. "The customer approached us with these requirements."

More compact design with direct drive
Initially, the engineers envisaged independent X-Y-Z handling for each station. "The original concept envisaged six separate three-axis systems based on spindle drives," says Andreas Hirt. However, this solution would have been too large, especially in the material flow direction (X-axis). The engineers came up with a different idea: with a direct drive as the X-axis, the six slides required can be accommodated on a single axis base body. This makes the entire system much more compact - exactly enough for the specified cell, without the system losing any of its precision.

The IEF engineers developed a positioning system with a total of 18 axes. A linear unit from the Euroline series is now used for the X-axis. In this ready-to-install system, the drive is equipped with an iron-core linear motor and an optical absolute value measuring system. This eliminates the need for referencing. The repeat accuracy is plus/minus five micrometers and the speed is up to five meters per second. The stroke of the linear unit is 2,457 millimeters.

The IEF technicians installed spindle axes from the Profiline series for the Y and Z axes. "The spindle-driven linear rails with recirculating ball bearing and guideway assemblies are ideal for the precise handling of small parts," explains Andreas Hirt. As the customer works with a control system from Siemens, the spindle drives in the series were equipped with Siemens motors. The connection of the Euroline linear motor to the specified control components was also ensured via corresponding connection cables. "In order to achieve the safety level required by the customer with the system, the linear motor was also equipped with a special absolute encoder, which allows operation at a safely limited speed," says Andreas Hirt.

In order to achieve maximum flexibility in the axis system and to be able to fully utilize the existing stroke, the developers did not use energy chains. "We would have had to attach them to the side of the stations. That would have restricted freedom of movement and taken up unnecessary space," says Andreas Hirt. That's why the cables are routed upwards centrally.

Same structure, less design work
Andreas Hirt points to the cell in which the 18-axis positioning system is housed. "Each station is set up in the same way, which has a positive effect on the design effort," he explains. Depending on the processing step, the components are fed individually to the stations where they are assembled into modules. A cover is glued on at the last station. The travel range per station is 150 x 510 x 80 millimetres, the travel times for the various processing steps are four to eight seconds, depending on the task, and the weight of the mass to be moved on the Z-axis is up to five kilograms. The quality of the individual steps is monitored by a camera system. "With the 18-axis positioning system, we have implemented six handling processes in a very small installation space, which can be carried out quickly and precisely," says Andreas Hirt, describing the result. as