Modra Technology, a manufacturer of carpet sample machines based in Warragul, Australia, has chosen to base the motion control system for its innovative Mtuft range of machines on Powerlink technology from Baldor Electric Co., Fort Smith, Ark. By using this deterministic networking technology for real-time multi-axis synchronization, Mtuft machines have set a new industry standard for speed, accuracy, and flexibility: They can produce a new tufted carpet sample in just 20 minutes, including setup time — a task which takes at least a day on conventional carpet sample machines or on production machines.
Modra Technology, founded in 1991, initially produced error-detecting sensors for increasing the efficiency of Axminster looms. At the time, carpet samples were either produced by hand — a slow and arduous process — or on volume production machines, which was expensive and disruptive. Modra’s first machine, known as the Kibby, was designed to produce high-quality samples of Axminster and woven carpets, and was an immediate success; to date, the company has sold more than 150 units in 24 countries. The latest versions of these machines can accommodate very high needle insertion rates of 5 per sec, and are capable of producing a complete 19.7 x 19.7 in. sample of Axminster carpet in just over an hour.
When the company decided to develop a machine to produce samples of tufted carpet, Modra initiated the Mtuft project and set some design goals. Prime among these was the need for a design that flexible enough to simulate as wide a range of carpet-production machines as possible, so that samples would provide an accurate representation of finished carpets produced by various manufacturers' machines. To this end, the company selected an all-servo design, with a sophisticated control system based on Baldor's Ethernet Powerlink-based products.
According to Tim Modra, Modra’s managing director, "Complex, high speed, multi-axis applications such as this traditionally involve a huge amount of wiring, mainly on the control side, and especially for encoder feedback. Over the years, we have been keeping an eye on trends in decentralized motion control and various strategies to help reduce the amount of machine wiring, but we had dismissed non-deterministic Ethernet as being unsuitable for critical real-time automation control purposes. So when Baldor launched its Ethernet-based motion controller and servos, designed specifically to overcome real-time data transmission limitations of standard Ethernet, but with standard Ethernet cable between the controller and the drives, we were keen to try them out.”
By managing message exchanges in a precise and defined sequence to ensure that only one node communicates at any one time, Powerlink adds determinism to Ethernet communications; the protocol guarantees that all time-critical data is transferred within configurable, isochronous bus cycles. This prevents the type of data collisions associated with standard Ethernet and dispenses with the need for bus arbitration schemes, thereby reducing data transmission time overheads significantly.
The Mtuft carpet sample machine uses a combination of pneumatic and electrical actuation technology. There are nine axes of electrically-operated movement, all controlled by a NextMove e100 real-time motion controller. Seven axes are driven by MicroFlex e100 single-phase ac servo drives and BSM servomotors, using Ethernet Powerlink for all communication between controller and drives; five of these axes use interpolation, handled entirely over Powerlink. The remaining two electrically driven axes use small dc motors.
Mtuft machines feature a built-in host computer that runs the machine control software and NedGraphics' Vision Tuft software for creating new carpet sample designs. Each design is exported by the Vision Tuft software in OpenTuft format, and downloaded via Ethernet to the NextMove e100 controller line by line. The machine holds the web — the backing material for the carpet sample — in tension on two backing drums driven in ratio gear mode. Two reciprocating heads, positioned above and below the web, traverse the width of the material. The needle motor provides the reference signal for all interpolated axes, and the top head employs a large servo for needle actuation, using a driven-spline arrangement to save weight on the head itself. Each head is driven in synchronism, and they can also be moved in a way to simulate production of carpet samples with needle shift “zigzag” patterns.
Tim Modra points out that high-speed interpolation on the two main head drive servos provides a key advantage over conventional mechanical systems. "We effectively have a software calibrator that enables us to put a variable offset into the system. So instead of using precision mechanical gears and cams that are expensive and time-consuming to configure, we can now calibrate our machines digitally, which is easily done using Baldor's Mint programming language. This all-electronic approach has enabled us to create a physically compact machine with a small footprint, and helps to reduce machine build time and cost significantly,” he explains.
For more information, visit Baldor Electric Co.