Automation of spiral tubing manufacture
Until recently, the manufacture of spring-reinforced tubing was considered to be so complex as to be beyond the scope of automation. Elettrosystem, a system integrator based in Italy, has taken on the challenge and realized the world’s first production line for this sophisticated process, incorporating four Stäubli 6-axis robots.
Intubation is a standard medical procedure for airway management and protection. Medtronica, a leading equipment manufacturer uses four-layer composite tubing with an integrated spiral made of thin spring steel to ensure a balance between rigidity and flexibility.
The composite nature of this material presents a technical problem in production, primarily the layering of the spiral tube from the inside to the outside. The complicated handling and the quality requirements of the two flexible components (PVC liner and steel spring) represent a major hurdle for automation. The intricate winding of the spring onto the liner was regarded as beyond the scope of automation until now. Elettrosystem has made the impossible possible.
Four robots make the impossible possible
Specifically, the automated aspect of this cell involves drawing a fine coil spring made of steel onto a PVC tube and then applying an adhesive sheath. The unique challenge lies in he strictly defined uniform distribution of the spring windings as well as in the handling of the two flexible components.
The automated production of four spiral tubes simultaneously is facilitated by the use of two cells in mirror-image layout; Stäubli’s RX160 and a Stäubli TX90 are responsible for the flexible handling. The complicated winding of the spring takes place in an integrated process circuit, which is linked by linear systems. The big advantage of the Stäubli robots is that, even in standard configuration, they already comply with cleanroom class ISO 5, meaning that Elettrosystem did not have to bring in dedicated cleanroom-compatible models.
At first sight, the Stäubli 6-axis RX160 looks large for the setting, but there were good reasons for its selection: this robot has an impressive range of 1,710 mm and has sufficient load capacity for the complex gripper system. The two-part, pneumatic double gripper allows for the simultaneous handling of two tubes with spring sheath already fitted and two without. In addition, the distances between the gripper jaws can be varied by means of an overhead track system and thus adapted to the different dimensions of the workpieces. Retooling for any one of the seven tube variants is therefore accomplished in around 15 minutes.
With this one universal gripper, the Stäubli RX160 performs all handling operations to a high level of precision. The paired pick-up of PVC liner and feeding onto carrier rods transfer to the "tipping station" and then to the station where the spring is wound on. The collection of the spiral-sheathed PVC tubes and transferred to the adhesive application station are then given a visual quality inspection and ultimately in vertical suspension in the drying chamber. Everything else, i.e. the cutting to length and the final quality inspection is then performed by the smaller Stäubli TX90.
Increase in capacity and quality
Elettrosystem desgined the system to be so adaptable that it allows the production of seven different variants with diameters from 5.0 to 9.5 mm as well as tubing of different lengths and degrees of flexibility. This broad spectrum of variants is necessary for the intubation of patients of all ages and sizes.
By using the world’s first robot cell for this task, the Medtronic plant in Ireland is setting new standards in the production of this vital device. At the same time, the manufacturer is benefiting from a significant increase not only in output but also in flexibility and process security.