“We are in regular contact with SOGA during all projects. This makes it easier to down to the details immediately for new orders,” said STOBER expert Guido Wittenauer, who supports SOGA. The drive specialist has often supported the machine manufacturer when it was seeking the right motor/gear unit combination.
In this project, the teamwork began as early as the bidding phase. The two sides discussed the critical points and worked them out together. “Before we could get started, we validated possible components during an initial project meeting and tested them in the designed installation situation,” said Gallenbach. “Due to the size of the project, we had to have some adjustments made, which the STOBER experts handled very well.”
Previously, employees had to assemble the modules by hand. This took time and was prone to errors. The new machine, on the other hand, can autonomously produce 150 parts in one piece without the intervention of a worker – and with reproducibly high accuracy. An employee only has to provide the components at the beginning of the process and transport the completely assembled sleeves away in the mesh boxes afterwards. The shortest possible setup times were important during development.
From servo motors to rack and pinion drives
The heart of the machine is a six-finger gripper. In order for it to pick up the individual parts accurately, the system must position them precisely. Threaded rings and cover washers are stored in magazines in the front part of the system. “We supplied our servo helical gear units with brakes for the high-precision lifting motion of the magazines,” Wittenauer said. Due to the helical toothing and low-friction bearing, their efficiency is particularly high.
The second part of the system contains the magazines for the threaded rings, 40 millimeter high elastomer rings and cover washers. A three-axis gantry takes over these components and uses a sensor to rotationally align them stacked on top of each other on a rotary table. “An orbital drive lets the six-finger gripper handle all components of any size – without retooling,” explained the STOBER expert. “We also supplied a synchronous servo motor for this drive.”
In the third part of the system, there is another three-axis gantry. It picks up an M6, M8 or M10 screw – depending on the size of the sleeve to be installed – with the corresponding washer and conveys it to a station that coats both components with copper. STOBER supplied the rack and pinion drives for all axes of the two gantries.
A screw-driving robot developed by SOGA takes the coated screw and screws it into the module consisting of threaded washer, cover washer and elastomer ring. It must be able to overcome fluctuating forces due to the plastic. “Our encoderless Lean motor is used for this task,” said Wittenauer. After all, highly dynamic motor controls are required for this application. The Lean motor enables speed and torque to be set variably, from a standstill to maximum speed with full torque control. The Swiss fitting manufacturer can easily retool the screw driving system with the different screw heads.
A rotary table then guides the completely assembled module to the removal station. Here, too, SOGA installed a rack and pinion drive. Wittenauer said: “Because the partially or completely assembled modules are relatively heavy, both in the removal station and in the three-axis gantries, it was necessary to design them in such a way that they could also move the heavy weights dynamically.”
Finally, the removal unit feeds the component to a marking laser. It then goes into a mesh box for pickup.