Machine Design

New Job for Robots: Tube Bending

An innovative new automatic cell for manufacturing tubular automotive parts exploits an articulated robotic arm to manage intervening movements and transfers.

The arm eliminates the need for the conventional carriage of a tube-bending machine. It also promotes manufacturing precision by retaining the part for the entire process.

The machine, called Uni-vercell, was developed by Unison. A Powerlink system controls four motion axes, plus the I/O needed for continuous operation. This involves tube bending and end forming, and general operational control of the cell. A NextMove e100 controller from Baldor Electric Co. manages four MicroFlex e100 servomotor drives which control the tube-bending head’s clamp, pressure die, and bend-arm axes, plus actuation of the end-forming tool for flaring and compressing. In addition to these core functions, the controller manages all of the cell I/Os, plus the link to the front-end user interface.

Unison estimates the daisy-chained nature of the high speed Powerlink network reduced the size of the electrical system and the wiring and system building tasks by about 50% compared to conventional analog motion control.

The 100-Mbits/sec network provides enough bandwidth to dynamically control each motor’s position and torque parameters. This helps make the bending process precise. Some I/Os sit directly on the controller while the rest sit on distributed servodrives, yet still get controlled in software as if they were local. Remote I/Os are CANopen I/O modules.

There is no front-end user interface. It is on a laptop that connects as needed to the cell’s NextMove e100 controller for downloading production programs. But the cell can connect to a local man-machine interface through a standard Powerlink gateway to a PC or Ethernet.

The Uni-vercell can fabricate parts to an overall accuracy of 0.1 mm. Although the cell is optimized for high volumes, Unison says its robotic arm can handle batch production as well. With typical energy consumption of around 1.5 kW (measured using an example part with three bends and one end form, including stacking at the end of the process and 100% inspection), electricity costs about 7 Euros per day.

Software control of the bending lets operators adjust torque and movement profiles to improve bend quality. Complicated shapes that might be difficult to make on conventional hydraulic machines are no problem because the machine can make intervening adjustments or moves between stages to avoid collisions.

Operators program bends and end forms by inputting data such as position, angle, rotation, and torque. Simply positioning the arm manually and capturing the data program the robot’s intervening movements.

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Watch a video of the cell:
Baldor Electric Co.,

A view of the Unison cell shows the articulated arm.

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