DAC102021

35 www.drivesncontrols.com October 2021 MACHINE BUILDING n Bent on success F ive years ago, Bend-Tech, a US company that makes CNC tube and pipe bending and cutting machines, noticed a spike in field- service calls. It looked for the reason and found that the growing popularity of off- roading and other outdoor motorsports was boosting demand for metal tubes and pipes. Most of Bend-Tech’s business comes from two markets, both of which have been experiencing significant growth. Many of its customers manufacture bespoke handrails for buildings. But its largest growth is coming from workshops that modify vehicles for off- road motorsports. “Our systems enable metal fabricators to cut tubing and pipes with great speed and accuracy,” explains Ted Merry, Bend-Tech’s production manager. “This improves production capabilities and ultimately their bottom line by bringing traditionally outsourced services in-house.” Bend-Tech’s initial machine (the Dragon A250) was not suitable for high-volume production, so it designed the larger Dragon A400 plasma cutting, marking and engraving system, which can handle almost anything thrown at it – but presented another challenge. Although it was well-received by larger customers, it was difficult for smaller users to justify because it cost about three times more than the A250. “What we needed was something in- between,”Merry explains. “We knew what price point we needed and essentially had to halve our machine-building costs without jeopardising production quality.” Three components Bend-Tech’s machines have three main components: a structural frame; a cutting and marking toolhead; and a software- guided actuation system that controls tool movement. After deciding to eliminate some functions for the new mid-range system, Bend-Tech turned its cost-cutting attention to the machines’ linear motion systems. “Thomson Industries made the linear systems that provided the motion control on our A400, so we went to them for ideas on how we could make a production-level system at a lower price point,”Merry recalls. “We explored other linear technology vendors as well but, as they have done for us in the past, Thomson came back with the ideal solution.” This consisted of a smaller, simpler version of the A400 actuation system, with a different drive mechanism. Each A400 uses two 2DB linear slides bolted together in a cross-configuration to control the A and Z axes. One positions the toolhead on the horizontal plane, while the other moves the cutting, marking and engraving tools up and down. Driving each axis is a 610mm ballscrew powered by a stepper motor. Because of its length, the screw needs support bearings on both ends and a special coupling to the stepper. For the new A250 model, a shorter (280mm) leadscrew and 152mm drive were chosen. This meant a motorised leadscrew (MLS) could be specified that does not need to be supported on both ends because the motor’s bearings carry the load. And because the leadscrew and the MLS rotor are one, there is no need to couple the screw externally to the rotor. Merry describes the design as “really slick”. It reduces costs by minimising the number of components. And using a motor with an integrated leadscrew instead of a ballscrew cuts the cost of coupling the screw and motor together, as well as the support hardware The new motion control assembly is smaller than the system on the A400, but it looks similar with round rails, bearings, blocks and a carriage. The actuation system is connected to a Windows PC running CAD/CAM software that stores customer design parameters such as lengths, bend angles, rotations and material characteristics. The motion control system follows a pre-programmed sequence, allowing the tool to switch between plasma- cutting and part-marking activities automatically. For both the A400 and A250 machines, all cuts and markings have a ±0.25mm tolerance. Enforcing this precision are position sensors that establish a zero point and record any variation from it. Contributing to what Merry calls “spot-on” reliability is a pre-loaded Acme-threaded nut. Factory alignment of the ballscrew and the composite polymer nut results in much less play than the original ballscrew assembly, which used a standard moulded nut. On the day that Bend-Tech announced the availability of the Dragon A250, it sold four of the systems. Demand has been steady ever since. Some users who had been relying on manual methods expect to boost their productivity by more than a 500%. n An American manufacturer of CNC tube and pipe bending equipment has developed a machine that caters for the rapidly expanding off-road vehicle market. To make the machine affordable, it chose a leadscrew-driven actuator instead of more costly ballscrew designs. By using a stepper-motor-driven leadscrew instead of a ballscrew-driven linear slide, Bend-Tech has achieved accurate motion control on its plasma cutting, marking and engraving systems, cutting costs.