Six processing steps in a very small space
Various individual parts have to be quickly fed and precisely assembled in a total of six work steps in succession to produce sensors. For this purpose, IEF-Werner GmbH developed an 18-axis positioning system that feeds the various components to the sensor. Due to the machine layout specified by the customer, only little installation space was available. The technicians therefore used a direct drive (linear drive with linear motor) as a basis. This allows several slides to be moved on one axis to save space.
Furtwangen, 06.07.2020 – The task was clearly defined: For the production of sensors within a production line, various individual parts must be quickly fed in and precisely assembled 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 a lot of space available - the required handling system was to be housed in a cell specified by the customer," Andreas Hirt, sales representative in the linear axes division at IEF-Werner, reports. "The customer approached us with these requirements.”
More compact design with direct drive
At first, the technicians planned an independent X-Y-Z handling for each station. "The original concept envisaged six separate 3-axis systems based on spindle drives," Andreas Hirt says. But 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 required six slides can be accommodated on a single axis base body. This makes the entire system much more compact - exactly sufficient for the specified cell without the system losing 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 ± 5 micrometers and the speed is up to five meters per second. The stroke of the linear unit is 2,457 millimeters.
For the Y and Z axes, the IEF technicians used spindle axes from the profiLINE series. "The spindle-driven linear rails with linear recirculating ball bearing and guideway assemblies are ideal for the precise handling of small parts," Andreas Hirt explains. Since the customer works with a control system from Siemens, the spindle drives of the profiLINE series were equipped with Siemens motors. The euroLINE linear motor was also connected to the specified control components via appropriate connecting cables. This is a special feature of the automation specialist: They do not only sell solutions with their own motors, but also use third-party equipment at the customer's request. "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 for safely limited speed," Andreas Hirt says.
In order to achieve maximum flexibility in the axis system and to be able to fully use 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," Andreas Hirt says. That's why the cables are routed centrally upwards.
Same construction, less design effort
Andreas Hirt points to the cell that houses the 18-axis positioning system. "Each station is constructed 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. At the last station a lid is glued on. The travel range per station is 150 x 510 x 80 millimetres, the travel times for the various processing steps are between four and eight seconds, depending on the task, and the weight of the mass to be moved on the Z axis is up to five kilograms. A camera system is used to monitor the quality of the individual steps. "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", Andreas Hirt says, describing the result.