These are some of our success stories that illustrate the range of possible applications of our products.
The following is an example of the value to be gained by upgrading a production machine to use DIVA Automation servo controls in place of an on/off control.
A company in Huntington Beach, CA, is a trusted supplier of ancillary equipment to the printing industry. Among others, they supplied a machine that was used at the end of a line of specialized machinery to perform the operations required in the production of magazines. One of their customers operates a printing plant in the middle of a cornfield in Hartford, Wisconsin.
This one plant prints all of the National Geographic, U.S. News & World Report, Time, Newsweek, Playboy and others. The post office in this town of about 10,000 is said to have the highest mailing volume of any post office in the U.S. Freight train loads of magazines leave every day for delivery around the world.
To print this amazing flow of material, they use a bank of very high speed printing machines from Heidelberg and others. Printing is performed on wide rolls of glossy paper at speeds so fast that it is impossible to focus on the images as they fly past.
After printing, the sheets must be slit into individual page widths and cut to page lengths, then bound. Advertising coupons and inserts must be combined with the editorial content. Address labels must be applied after the mailing sleeve is stuffed and finally, the magazines must be bundled and tied. The bundles are sorted by ZIP code and the magazines stacked in alternate directions to prevent lopsided stacks.
In all, more than fifty machines of various types are used in a typical line. Each is designed to perform a limited set of tasks, but it must be performed at high speed, with extreme reliability. In fact, the printing machines are so fast that the production of the entire plant can depend on the maximum speed of a single machine, or the failure of a single machine can stop production. Nobody wants to get last week's copy of Newsweek next week, so it is necessary to use multiple production lines to insure on-time delivery. The flip side of this coin is that an increase in the speed of a single machine can in fact increase the productivity of the entire plant and perhaps delay or eliminate the very large investment required to install another line.
Our customer wanted to speed up the throughput of his machine which was the next to last in the long line. It stacked the magazines and prepared the stacks for the last machine, which wrapped them with twine for shipment. Our customer’s machine was already faster than the wrapping machine, so it was designed to push alternate stacks to the wrapper on the right or the one on the left.
To maximize throughput, they had increased the speed of the mechanism that pushed the stacks to the wrapper so much that the mechanical shock of the high speed stop at the end of the push was damaging the structure of the machine. A 1 HP motor was being controlled by a standard PLC (Programmable Logic Controller) using an on/off control.
Our customer hoped that a servo controller could be used in place of the on/off switch to provide controlled deceleration, to limit the mechanical shock at the end of stroke. We assured them that it was true and were able to demonstrate the advantages very quickly. We were able to operate at much higher velocity and still reduce the end of stroke shock simply by virtue of the ability to provide a controlled deceleration.
The only modification required to their machine was to replace the motor starter with our servo controller. For a very small investment, they were able to nearly double the value of their machine in terms of throughput. A side benefit was to increase the service life and reliability of their machine and to decrease the operating noise at the same time.
This is an excellent example of the benefits of servo control over on/off controls. Similar, and even greater benefits can apply when stepper motors are replaced by servo controls when operating speed and reliable motion are more important than the small price difference between stepper motors and DC motors.
Here is an example of the benefits of applying electronic motion controls in an industry that has historically used pneumatic or mechanical controls.
Northwest Georgia is one of the nation’s largest suppliers of carpeting products. Some of the largest carpet manufacturers are located in and around Dalton, GA. Not surprisingly, some of the nation's largest suppliers of machines to make carpet are located in the same area.
DIVA Automation was approached by one of the leading suppliers of machinery to this market for help in finding a way to get around the patented mechanism used by most machines of this type in feeding the yarn to the needles. This mechanism used pneumatic controls to provide a selectable yarn length, which resulted in the ability to produce sculptured patterns using single colors with various lengths per stitch or multicolored patterns. Each needle was controllable to supply one of four lengths for each stitch.
The mechanism used to do this required that each needle have an associated solenoid valve. With a typical machine using 10 needles per inch of width, a machine capable of producing carpet nine feet wide required 1000 needles, 1000 solenoid valves, 1000 solenoid drivers, 1000 lengths of air supply tubing, an air compressor capable of supplying 1000 mechanisms, an electronic cabinet large enough to house 1000 solenoid drivers and the associated PLC controls, together with power supplies large enough to power 1000 solenoid valves.
When asked the cost of implementing a machine of this type, the manufacturer was able to add up a cost in excess of $50 per needle off the top of his head. When we presented to him the possibility of replacing this expensive patented mechanism with electric motors and controls at lower cost, he was understandably skeptical. If it could be done without an expensive multi-year development program, then why hadn’t other manufacturers already done so? The answer to that question is the same as it has always been. Innovation involves risk and most manufacturers prefer to avoid risk in areas they do not understand. Most manufacturers of mechanical equipment are very cautious about accepting new electronic technology. Many have painful memories of previous attempts.
However, our customer was willing to give us a try and we designed a PC-based system that provided simultaneous control for 1024 stepper motors. Instead of offering a selection of four pile heights per needle, it was now possible to select any desired length in increments of one thousandth of an inch.
Instead of thousands of feet of tubing, thousands of fittings and months of assembly, 1024 stepper motors were mounted in four groups of 256. Each group of 16 motors was wired to a locally mounted circuit board and each bank of 256 motors was controlled through a cable to the PC. It was possible to download a complete rug pattern to the distributed drivers in less than a second. The position of each motor was updated one thousand times each second and advanced if directed by the stored pattern program to supply more yarn.
The nightmare of maintaining a hugely complex pneumatic system that was prone to leaks and rust was replaced by simple stepper motors with an expected service life of several years. The only parts subject to wear were the motor bearings.
The size of the power supply was reduced significantly, as was the amount of power consumption. Assembly time for this much more simple arrangement was reduced from months to days.
Overall, the design was upgraded from Early Machine Age to Jet Age.
Created on ... September 08, 2007