Testing the limits
F or most people, the word "test" probably conjures up a slew of bad memories from their school days. For plastics processors, however, testing is a good thing -- the last line of defense against the ...
For most people, the word “test” probably conjures up a slew of bad memories from their school days. For plastics processors, however, testing is a good thing — the last line of defense against the disaster of shipping defective or “out of spec” parts to a customer.
For these, the testing process is more attractive still when it can be carried out right on the factory floor; and testing equipment manufacturers and suppliers note growing demand among processors for equipment that does just that. “Our customers have continuously expressed interest in having testing equipment on the floor,” said Richard Goshgarian, applications laboratory manager at Instron. “And even if a company has a quality control lab, being able to verify products on the line or floor reduces cost and time.”
For other processors, testing parts on the floor is their only option. “There are many cases where companies don’t have a lab available but still want to do analysis because the results can be used to benefit the bottom line,” said Jeff Ho, international sales representative with Arizona Instrument LLC.
Unfortunately, operating sensitive testing equipment in the middle of a busy manufacturing space is not done without risk. “When you place a testing instrument on a production line it must be highly reliable in order to avoid line stoppage interruptions,” said Richard Grady, vice president of marketing with Cincinnati Test Systems Inc. “This is especially true of lines operating 24/7/365.”
Manufacturers and suppliers of testing equipment highlight several important factors necessary in making machines suitable for this task.
As strange as it may seem, the equipment has to begin by having the right look. “In order for processors and their customers to have faith in what the equipment is telling them, the instrument itself has to be believable,” said Jeff Ho. “The equipment has to be built like a tank in order to withstand the rigors and bumps of the production floor environment.”
It’s important, then, for processors to rely on equipment crafted for use on the floor. “The instruments that we offer, like the Sentinel leak test instrument family, are normally designed for use in production on the shop floor,” said Cincinnati’s Richard Grady. “They are built for that environment using hardened electronics and communication protocols commonly used in production environments.”
Merely looking the part is not enough, however. The equipment also has to be able to test according to established standards. “One of the challenges has been the lack of a standardized test method for moisture analysis that could
be used with equipment that is production floor-friendly,” Jeff Ho explained. According to Ho, the Computrac Vapor Pro line of moisture analyzers from Arizona Instruments are useable under newer ASTM test methods, such as D7191-05, which is used to determine the level of moisture in plastics by relative humidity sensor.
And Dynisco’s series of on-line Rheometers can measure according to the standards of ASTM D1238 Melt Flow Rate (MFR), as well as high and low load MFR and Apparent Viscosity, according to David Azevedo, regional sales manager with Dynisco Polymer Test. “Our ViscoSensor attaches to the process through a single M18 transducer port, making it easy to install and maintain,” he explained. “All of our on-line Rheometers can be outfitted for use in explosive and hazardous environments.”
Another hurdle to overcome involves communicating test results accurately and quickly. “Our equipment allows the line supervisor to be notified in real-time by field bus Ethernet connection, or by email to their Blackberry, when something goes wrong,” said Cincinnati’s Richard Grady. “The supervisor himself sets this option; they can choose to be alerted when they have three bad parts in a row or in a shift, for example, and set the criteria for intervening in the production process.”
One possible factor keeping some plastics processors from incorporating testing equipment directly in-line is a belief that their workers will find the technology difficult. Manufacturers and suppliers respond by stressing that their products are increasingly operator-friendly. “Our Melt Flow Indexers and Lab Rheometers are designed for ease of use to enable the end user to adapt quickly to the test procedures,” said Dynisco’s David Azevedo. “Basic training is also available, which may help management feel better about the competence of their employees.”
According to Cincinnati Test Systems, its equipment is designed with the realities of multi-tasking on a shop floor firmly in mind. “Because line operators often change and can be required to do several different tasks on the production line, we strive to make our instruments and systems operatorfriendly by designing them to take the measurements, analyze the data and determine if a part is good or bad,” said Richard Grady.
Nor should plastics processors be reluctant to use shop floor testing equipment for high volume production, manufacturers say. “In high volume production facilities, quality control efforts typically require a high volume of verification testing,” said Instron’s Richard Goshgarian. “Robotized specimen handling systems are commonly used to increase output and efficiency, with little if any operator intervention.”
This is not to say that quality control labs have been made irrelevant. “We do feel that the lab equipment ultimately provides more control in polymer testing,” said Dynisco’s David Azevedo. “One of the risks [in testing on the shop floor] is that operators might manipulate the variables like drying times and historical data, to name just a few.”
Other manufacturers and suppliers admit this is a potential problem that new technology is hard-pressed to solve. “Unfortunately, there will always be some bad parts getting passed simply because the operator is inattentive or bored,” said Cincinnati’s Richard Grady.
There are also problems inherent in bringing quality testing out of the controlled confines of the audit lab. “When a specimen is being tested, there may be issues if the environment is not controlled,” said Instron’s Richard Goshgarian. “In the case of non-contact extensometry, proper lighting conditions are vital for maintaining the contrast of a specimen to the targets that a noncontact extensometer would normally follow.” To counter this, Goshgarian said, Instron’s latest line of video extensometers utilizes a lighting system that ensures optimum lighting is maintained under all ambient lighting conditions.
Moisture is another difficulty for any hygroscopic polymer and it will have a significant impact on results if not managed properly, manufacturers and suppliers say. Here, too, progress is being made. The Aquatrac moisture meter from C.W. Brabender, for example, detects water content down to 0.0005 per cent for solid parts in granular form. The unit does not require calibration for each individual substance tested and is designed to withstand the variables of harsh shop floor environments.
A final challenge is reconciling results obtained through tests carried out on the shop floor with those obtained from the quality control lab. “The need for shop floor testing is driven by the customers requirements to provide traceabilty to quality assurance in production,” said Dynisco’s David Azevedo. “At present, this cannot always be correlated to lab testing or lot-to-lot sampling of incoming materials.”
Arizona Instrument LLC (Tempe, Az.); www.azic.com; 800-528-7411 Tracelogix Inc. (Richmond Hill, Ont.); www.tracelogix.com; 905-882-8000 C.W. Brabender Instruments Inc. (South Hackensack, N.J.); www.cwbrabender.com; 201-343-8425 Cincinnati Test Systems Inc. (Cleves, Ohio); www.cincin
nati-test.com; 513-367-6699 Dynisco Polymer Test (Franklin, Mass.); www.dynisco.com; 800-396-4726 Folio Instruments Inc. (Kitchener, Ont.); www.folioinstruments.com; 800-683-6546 (Pointe Claire, Que.); 800-767-9695 Process Heaters Inc. (Toronto, Ont.); www.processheaters.ca; 877-747-8250 Instron Canada Inc. (Burlington, Ont.); www.instron.com; 800-461-9123