Food and beverage professionals understand the problem, but bringing precision and repeatability to machine changeover is a challenge that increases exponentially as more lines and facilities are added to the mix. For the last 16 years, Dragan Filipovic’s work in US industry-first on the machine-control side and then in manufacturing-opened his eyes to the need for, and challenges in, delivering precise changeovers. Working independently for the last year, Filipovic developed an advanced sensing device he calls COT, shorthand for changeover tool. Consisting of a sensor and a controller plus customized software, COT guides mechanics in replicating the ideal settings in a machine changeover. Commercial deployment began in July.
An electrical engineer and native of what is now Serbia, Filipovic has conducted research in electro-optics, laser tomography, RFID and other technologies. MSEE and BSEE degrees preceded a Ph.D. in physics in a collaborative program between University of Belgrade, Yugoslavia, and Uppsala University in Sweden. He served as principal control engineer at an Elk Grove Village, IL, packaging machine manufacturer in the 1990s before joining Kraft Foods Inc. as associate principal scientist. His duties included systems development to support lean manufacturing with technological tools to improve overall equipment effectiveness. He left Kraft in June 2008 to form MID-Manufacturing Improvement Devices. COT is the firm’s first product.
FE: How does the changeover tool (COT) work?
Filipovic: There are two elements: the sensor and the base, and they work independently of each other. The sensor has two microprocessors and a multi-turn potentiometer with a spiral-spring wire. One microprocessor calculates distance to sub-millimeter accuracy and communicates wirelessly with the base. The second sensor manages the battery. Nonmagnetic brackets and pegs are affixed to the packaging machine at each point where a position setting needs to be made. The mechanic or operator places the sensor on a position bracket and pulls the retractable wire to the related peg. LED lights on the sensor’s case guide the mechanic in adjusting the machine to the precise set point. The setting then is relayed via ZigBee wireless protocol and recorded by the controller. It’s like GPS: the transmission can’t be disrupted or altered by another device, the unit only transmits. The mechanic then moves the sensor to the next bracket and repeats the process.
The base station houses the controller and can be up to 100 meters away. It consists of a hard case containing a solid-state netbook with an eight-hour battery and a bracket and post to calibrate the sensor at the start of each changeover.
I looked at laser, ultrasonic and Parallax for position sensing, but laser would consume 20 times more power, and there were repeatability and accuracy issues with the other technologies. A multi-turn potentiometer can experience small changes in length and is not ideal, but the issue is addressed by recalibrating, a process that takes five seconds.
Up to 250 machine set points are stored on the laptop in a recipe program for each product that will run on the packaging machine. As the mechanic dials in the settings from point to point, the laptop records them on an SD card for time-and-date stamping on an Excel spreadsheet. If a location is skipped or is not properly set, the program will not confirm that the machine is ready to run. However, COT is strictly diagnostic. It is there to inform the operator without disrupting machine controls. I will never connect a wire or touch machine code; this is completely separate and supplemental.
FE: Why didn’t you bundle everything into a device the mechanic could carry to the machine?
Filipovic: Originally I was going to put all the electronics at the point of use, but in numerous in-depth interviews, mechanics all said they needed to have their hands free. Everything they needed had to be in the sensor box, with the controller in a passive role. They also told me, “Give me green/red lights to guide me.”
FE: How did you settle on 250 set points?
Filipovic: It has to do with using the first eight bits of the digital signal from the sensor. On big packaging machines, 30-40 changeover locations are not uncommon, and it’s easy to miss one. The netbook screen displays green and red squares to guide the user to the locations where adjustments remain to be made. Multiple machines can be set up with one COT.
FE: Did you collaborate with other firms on development?
Filipovic: I systematically tested all the options for distance sensors, and the best I could get was a unit from Micro-Epsilon, a German technology company. They supply pentiometers that help position X-ray imaging tables. COT is recoiled much more frequently, and they are supplying me with a modified return-tension mechanism hardened for industrial use. I’m using off-the-shelf components wherever possible so that replacement parts will never go dry. The netbook’s board and other components are solid state. You can drop them, no problem.
I delegated development of the battery management system to Revtel, an electronics firm in Lake Zurich, IL. Battery management is critical. The battery automatically shuts down after two minutes if no adjustments are made. Everything is in the computer, so you resume where you left off. I backed their system with a redundant power shut-off in the controller. The lithium battery in the sensor should last 1-2 years.
Another collaborator is my 15-year-old son, Julian. He set up my Web site at www.oeeincrease.com. He did the design in his room, while I focused on the software in another room. Programming is tedious, with trial and error and tweaking to resolve minor glitches, but that is what I do. The idea is to spare the end-user by keeping the complexity deeply hidden in electronics. Complexity is not the goal; all the operator needs to see is red or green, good or not good.
FE: Contrast development working independently with development in a corporate environment.
Filipovic: Project prioritization rules the corporate environment, and engineering development is a stepchild. If you are planting in infertile soil, your project is doomed.
My colleagues at Kraft could see the conceptual potential of a changeover tool, but the execution process is so long, with many managerial levels to satisfy. The original idea gets diluted, and being stopped and reviewed many times undercuts personal drive.
Working independently, I’m motivated to use resources effectively to get a final product as quickly as possible. Innovation is knowledge and execution.
FE: Do you anticipate resistance to COT on the shop floor?
Filipovic: Mechanics introduce variance by insisting they know how to set a machine better than anyone else. That creates changeover problems. COT has a learning mode where the OEM’s best mechanic sets the machine perfectly, and all the settings are stored automatically. If a mechanic believes he can set the machine better, his settings can be tried and date-stamped in the system. If throughput or some other metric shows improvement, the learning mode is used again to set the new standard.