The Chemnitz-based Steinbeis Transfer Center for Drive and Handling Technology has developed a special winding unit for resistance wire. This type of wire has special properties which shouldn’t be affected when it is wound onto customer-specific spools. The new winding unit can be used in the lab as well as in production and can be modified for a variety of applications.
The materials used in resistance wire can vary greatly and demand particularly careful handling. The newly developed winding unit can accommodate resistance wires with diameters ranging from 0.02mm to 1mm, and these can be transferred from a source spool to various processing spools again and again. The wire can be exposed to tensile forces ranging from 20mN to 5,000mN (2g to 500g), and values can be selected and kept constant as desired throughout the complete re-spooling process.
The wire is guided from the source spool to the desired target spool using a force sensor and guidance pole. The source spool is mounted on a motor driven axle. During the re-spooling process, it is readjusted within milliseconds based on the specified tension generated by the electromagnetic dancer on the force sensor.
During this process, the force sensor generates the force specified by the control unit and keeps it constant within its work range, regardless of its displacement. If the dancer arm comes close to a defined limit, the speed of the source spool is adjusted automatically. By combining the synchronized drive shaft with a sensor, the wire can be spooled very gently in a process that isn’t affected by external forces – even when very fine wires are run onto a spool. Using the linear wire guide traverse, radial and cross-winding can be achieved on the target spool. The required pitch is calculated automatically depending on the diameter of the wire being wound.
A laser sensor installed with the wire guide traverse ensures that the target spool edge is measured completely automatically. Readings are then saved in the control unit as limit values for the wire guide traverse. The advantages of this approach are twofold: (1) the point at which the wire guide traverse reverses its direction can be influenced directly by manual adjustment and (2) the direction of cable feeding onto the spool can change very quickly once the spool reaches the limit. The length of wire to be re-spooled and the number of windings, as well as the tension and wire diameter can all be set via a control panel, and these parameters are displayed during automatic winding.
Stepper motors running in closed-loop mode are used to drive the application. The drives are controlled by a microprocessor based controller developed by the Steinbeis Transfer Center for Drive and Handling Technology in Chemnitz. This controller allows to run brushed DC motors, stepper motors and servo motors with a maximum output of 2.5kW.