Simultaneous straightening, cutting and deburring of thin tubes

International machine manufacturer, Ravni Technologies, has specified a complete drive system from Stober for a machine that straightens, cuts and deburrs thin tubes.

The combination of planetary, helical bevel and offset helical gear units, in combination with Stober’s servo and Lean motors of the EZ and LM series, has enabled Ravni to benefit from robust precision components that can be installed in tight spaces and reduce manufacturing costs. Stober has also supplied compact drive controllers that can control both simple and complex axes.

The unique Ravni system with the Stober drive, straightens, cuts and deburrs thin tubes used in refrigeration and is in operation at one of the world’s largest copper companies in New York, and is the only one on the market that can cut up to 100 of these thin tubes per minute and deburr them at the same time.

To increase performance, the machine manufacturer wanted the drive technology for this system to come from a single source, which is why it turned to Stober at the design phase. Modern manufacturing requirements place high demands on the motors used – both with and without gear units – and as the system requires a total of 18 driven axes, loads on the motors vary widely.

What’s more, copper is an expensive metal which made it very important to remove the potential for rejects, plus, the precise operation of Stober’s equipment overcame Ravni’s concerns about waste reduction.

Cost savings and energy efficiency

The starting material is wound on a spool. The spool, weighing about 2.5 tons, is located on a winding station that unrolls the copper tube and feeds it to the next station, using a control system to ensure that that no tension is created during the process. The Stober Lean motor from the LM series was specified to do this.

To obtain a perfectly straight tube, the machine has horizontal and vertical straightening rollers and helical bevel geared motors, with helical gearing ensuring that the system transports the material precisely.

The Stober components feature a high-power density and gear efficiency of 97 percent. They are dynamic, lightweight and extremely compact owing to the angular transmission. This means they also fit perfectly into very tight installation spaces, as required in this application.

Exact position detection

An encoder installed on the straightening line records the exact position of the tube, the information being transmitted directly to the downstream flying saw, comprising three saws arranged in parallel. To separate the material, the system pushes it forward and positions it accurately to the nearest hundredth, using Stober EZ series synchronous servo motors for this task. The synchronous servo motors are extremely compact and offer maximum torque, high dynamics and low torque ripple. They have a mechanically robust design and are extremely reliable in demanding applications.

Finished tube sections are stacked to the left or right of the conveyor line, a task that needs precise movement and a robust, compact drive design. The Lean motor fulfils both these requirements as it can be used at high temperatures and its windings can withstand up to 155 degrees Celsius.

Speed and torque can be controlled infinitely from a stalled position to maximum speed with full torque control – and the Lean motor operates completely without Encoder or sensor. This means that only a single-shielded standard power cable is required, which reduces installation effort considerably. And because neither sensors nor fans are installed, it is also significantly more robust. With an efficiency of up to 96 percent, this series achieves energy efficiency class IE5.

Costs are reduced further by using multi-axis S16 drive controllers that reduce the space required in the control cabinet. These drive controllers are suitable for high-efficiency multi-axis applications, among others, and at a slim 45mm, the highly dynamic drive component works inconspicuously and reliably in the background, even during demanding movements.

STO (Safe Torque Off) and SS1 (Safe Stop 1) functions are integrated in the SI6 series, being certified for PL e, cat. 4 in accordance with EN 13849-1 and can be used without function tests that interrupt production. A single drive controller can control up to two axes.

Stober expert Fabien Marinier, explains: “With three double-axis drives and one single-axis drive, for example, we can control seven motors. By stringing together several of these components, the number of axes to be controlled can be scaled as needed.”

Quick DC-Link modules connect the individual devices with each other and with the PS6 central supply module quickly and easily. This highly dynamic series achieves short recovery times with fast set value changes and load jumps.

Romain Forgeron from Ravni is enthusiastic about the solution: “Stober supplied us with the right motors for all 18 axes of the overall system, right down to the drive controllers – for both simple and complex axes - as well as for the winding station.”

Stober provided full technical support from the selection of components up to commissioning on site, with their technicians carrying out final adjustments to make the production line even more efficient.