Automating the Tube Bending Process

Feb. 22, 2006

Unison (, a provider of tube-bending machines and tube benders, integrated Baldor Electric’s motion and machine control hardware and software into its Breeze Uniflex system, which provides modular multi-stage

Unison (, a provider of tube-bending machines and tube benders, integrated Baldor Electric’s motion and machine control hardware and software into its Breeze Uniflex system, which provides modular multi-stage bending with automatic feeding, positioning, and clamping of tube components during the bending process.

The Baldor Electric ( system supports the Ethernet Powerlink networking protocol. Each bend head is powered by a servo motor axis and drive. A single machine controller manages the complete real-time, multi-stage bending process, along with numerous other feed and carriage axes. In the first production version of Breeze Uniflex, a machine Unison configured to produce condenser tubes for diesel engines, the controller manages a total of 15 motion axes, as well as numerous I/O channels. On this application, tubing components progress automatically through four separate bending stages, with operations at each stage happening simultaneously.

The parallel processing multiplies productivity compared with the more typical sequential operation of a multi-head bender. Unison reduced the size of the electrical control cabinet dramatically, by an estimated two thirds from previous models. This benefit was a combined result of much simpler wiring and the ability of the machine controller — Baldor”s NextMove e100 — to manage and synchronize all the motion axes and I/O required via the high-bandwidth (100 MB/second) Ethernet network.

The centralized machine controller offers real-time control of each drive, allowing it to deterministically control parameters, such as motor torque and speed, as tube components move through the machine. Such control would not have been possible with the motion architecture Unison employed on previous machines, which was based on standard servo drive amplifiers managed by a standard Windows PC. The performance of the Windows PC controller, and the basic analog control over servo motor characteristics, would simply not have supported such sophisticated or fast operation without additional hardware and real-time extensions to the operating system.

The machine”s simpler architecture, with its single Ethernet-based controller, also reduced software complexity. In fact, Unison says it managed to get a prototype version of the control program working within just one week of receiving the machine control software (Baldor”s Mint programming language).

Programming speed was aided by the Mint software”s built-in multi-tasking kernel, which allowed Unison”s development team to divide the real-time control program into a number of discrete software modules. Programming the core bending control program was further simplified by using a single bend task throughout the machine, of which there can be several instances. The instances all run concurrently, providing simultaneous control for all required bend stations; the first instance of the machine has four, but a further station could be added by generating code for another axis.

Mint”s keyword programming structure, with high-level commands for motion operations, provided a fast means of developing the motion tasks.

Operation of the machine is set up via a customized variant of Unison”s existing human-machine interface (HMI) package — based on Visual BASIC — which interfaces to the NextMove machine controller via ActiveX calls. Mint”s support for ActiveX also simplified this aspect of the programming. For example, on a previous Unison machine one element of the Visual BASIC front end required several hundred lines of code to manage the complex communication routines. This was reduced to just 25 lines on Breeze Uniflex by referencing the ActiveX control provided.

“Baldor”s Ethernet Powerlink technology provides such a leap in motion control performance that it makes this new multi-stage bending machine feasible,” says Mike Kay, the Unison engineer responsible for the control system. “The machine operates at several times the productivity that would previously have been possible, and in a space that”s probably half the size of the last generation.”

In total there are 15 brushless servo motor axes on Unison”s first machine, each controlled by one of Baldor”s single-axis MicroFlex e100 drives. Four axes perform bending operations on the tube components. The remaining 11 feed, rotate, and clamp tubing components. In addition to these major hardware elements, a number of I/O devices are controlled via the network, including an absolute encoder for automatic bend angle verification on each bend axis. For cost effectiveness, and to maintain the machine”s modular architecture, many of the I/O components are connected locally to the controller using the CANopen fieldbus, an architectural possibility opened up by the decision of the Ethernet Powerlink standards body group to use CANopen device profiles and the availability of a CANopen port on the Baldor drives.

Unison built its reputation for the use of electrical actuation technology for tube and pipe bending in the mid 1990s — delivering machines that operate on a small fraction of the energy used by traditional hydraulic benders, along with other benefits including quieter operation and drift-free accuracy.

“The benefits of all-electric tube bending machinery are now strongly established, and the technology is taking a substantial slice of the market,” notes Alan Pickering, Unison”s managing director. “We believe all-electric technology now accounts for a fifth of the high-end tube bending market — which is around 10 times the share of five years ago — and we expect market share to double again in the next five years.”

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