June 2020

32 n ROBOTICS, AUTOMATION AND MACHINE BUILDING June 2020 www.drivesncontrols.com Blind faith: automated screw feeding cuts reworking T he German company Roma specialises in the production of roller shutters, venetian blinds and textile screens. One of its manufacturing processes traditionally involved drilling and screwing up to three aluminium or plastic profile rails. The process relied on an automatically moving screwing unit with screw feed, but it had no automatic monitoring measures. This meant that with wrought aluminium alloys, the drill screw frequently created chips between the screw head and profile rail. When a visible cap was subsequently placed on top of the screw, it could not be attached properly because of the chips, and operators would repeatedly have to rework the piece by hand. To avoid this problem, Roma wanted to be able to predrill its profile rails in lengths from 710 to 5,710mm, and to mount screws without needing to retighten or perform rework manually. The specialist machine-builder Soga Gallenbach came up with the idea for a system that feeds the screws automatically and screws them in pneumatically. During the process, multiple mounting heads monitor the screw depth and tightening torque reliably. This means that Roma can now operate with much higher reliability, principally achieved by avoiding the need to do any reworking. The new machine is equipped with five mounting heads that move independently of one another on a gear rack in the X direction. Each head is equipped with a Z-axis and drilling axis. Engineers from Soga and the German drives specialist Stober developed the idea for combining a motor, gear unit and helical gear to form one module for the X-axis. Stober supplied its ZVPE rack-and-pinion drives and EZ synchronous servomotors for the X-axis. EZ motors with spindle drives are also used for the Z-axis. “The whole machine concept design is based on calculations for the motor technology,”explains Soga’s managing director, Fabian Gallenbach.“An error in the design could endanger the entire automation system.” To minimise the mass being moved by the five axes, and thus achieve rapid positioning, the drilling spindle needed a motor that could set the speed and torque to any point, from a standstill to top speed, with full torque control. For this, Soga turned to Stober’s encoderless LeanMotor (LM), which is lighter and smaller than an asynchronous drive with the same output, while also more cost-efficient and more rugged than a servodrive. The IE5 motors operate with efficiencies up to 96%. Each head has three motors placed close together. Because the LM operates without an encoder, only a single standard power cable is needed, without any extra cores or shielding. A single Stober ST6 controller can work with up to two axes, and by connecting multiple controllers in series, the number of axes can be scaled without limit. To ensure that the five heads do not collide with one another on the gear rack, there is a three-fold collision-protection process: the controller monitors the relative positions; software limit switches are pre-programmed with the permitted travel range for each X- axis; and a mechanical safety switch is located on each head. While this machine solved Roma’s problem with aluminium chips, the tightening torque profile needed can vary with the material being processed. Further refinements are needed for plastic rails, where the torque during the final tightening process must be no higher than at any other point.“We developed a strategy specifically for plastic screw connections in which our pneumatic screwdriver operates with pressure pulses,” Gallanbech says. The system is also equipped with two drawers for loading the profile rails. As a result, the machine supplies profiles for processing either separately or synchronously. The components are manually inserted and clamped. The drawers move using two Y-axes in automatic operation. Roma’s production processes are now considerably more reliable and the company is avoiding the need for reworking. n A German manufacturer of sun protection systems was having to perform a lot of manual reworking on its products because it was not monitoring its drilling operations automatically. By introducing a new machine that pre-drills profile rails, the company has ended the need for reworking. Roma has reduced the need for reworking on its sun protection products by introducing a new machine that pre-drills profile rails Following the introduction of the new machinery, Roma’s production processes are far more reliable

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