Canadian Plastics

A systems approach

If you're a processor considering the move to automated testing, you need more than incremental performance gains to justify the often substantial up-front costs of equipping a modern quality lab. Be ...

July 1, 1999   By Jim Anderton, associate editor

If you’re a processor considering the move to automated testing, you need more than incremental performance gains to justify the often substantial up-front costs of equipping a modern quality lab. Be assured, there are more than incremental gains to be had. With powerful processors appearing in even entry-level instrumentation, there’s a solution for almost everyone. Instron Corporation communications manager James Martin explains: “Eliminating the manual calculation and interpretation of results of materials tests significantly improves the laboratory’s productivity, often by a factor of 10 or more. At the same time, it reduces variability from shift to shift and operator to operator, solving an even more vexing problem.”

Martin’s comment addresses the two primary components of the automated equipment purchase decision. One is the need for enhanced productivity, both for the bottom line, and to satisfy increasingly stringent customer requirements. The other is the drive toward mistake-proofing as a means of attaining zero defects.

Software is as important as hardware

One approach to cost-effective automated testing uses modular software to allow users to buy just the amount of capability they need, while accomodating for future growth. An example is Instron’s Merlin II software for the firm’s 5500 Series Testing Systems (64). The system divides software into application packages, for specific tests such as compression, flexure and tension. Options for enhanced reporting and graphics allow users to tailor the sophistication of results presentation, while a “Test Director” option prompts the operator during each step of the testing procedure.

If the test sample requires special ambient conditions, universal testing machines (UTM) can often be equipped with environmental chambers to simulate the end-use environment or test “edge of the envelope” sample performance. An example is Tinius Olsen’s H10K-S (65), which is currently in use with Rohm & Haas Co. to test stress-strain and tensile elongation properties of elastomeric roof coating polymers. Olsen offers customized UTM for Windows software for special applications and processes.

When sourcing UTM’s, the extensometer should be carefully matched to the application. Mechanical attachments are a mass which may affect results, particularly where samples must be tested at low stress values. Thin films, such as the Rohm & Haas 20 to 30 mil membranes, are difficult to test using conventional extensometer attachments. A laser extensometer is essential for testing thin films which yield at low stress.

Know your flow

Rheology is the study of the deformation and flow of matter, and for many processors understanding the rheology of polymer melts was historically left to large molders, compounders, and academics. With the combination of the precision control afforded by modern processing equipment, and new, lower cost instrumentation, however, rheometry is becoming a common tool both for quality and process control applications. Measuring melt flow can involve a number of variables, but the exponential growth of computing power per dollar is making rheology widely accessible and affordable.

Paar Physica’s MCR300 instrument (66), for example, features both true controlled stress and controlled strain operating modes, allowing test protocols such as frequency, amplitude, temperature, time sweeps, flow curves, creep/recovery, step strain, and stress growth. Automatic gap setting, thermal gap compensation and normal force controlled gap setting and testing are standard on the MCR, which ships with computer and software for under US$50,000.

Modular hardware (as well as software) enhances productivity and lowers costs, especially where quality labs must monitor widely differing processes or materials. Haake’s PolyLab System (Folio Instruments, 67), for example, uses the firm’s Rheocord torque rheometer as a control center for other system components as well as a PC. Measuring extruders and mixers are configured for each application, and deliver data to the rheometer master by a data bus. This “plug and play” architecture means that once a measuring sensor has been docked to the base unit, the master automatically detects the new configuration and all unit-specific limits and characteristic values are set accordingly.

The Dynisco LCR 5000 (Cyronix Instrumentation & Controls, 68) capillary rheometer features an onboard 32-bit computer for recording polymer melt viscosity data. Raw data is obtained by connecting a printer directly to the unit. KARS for Windows software allows PET intrinsic viscosity measurement as well as shear rate versus viscosity data. The rheometer/software combination provides test capabilities more comprehensive than those of a conventional melt indexer. The LCR 5000 also allows the resonance time capabilities of materials to be studied at a wide range of processing temperatures and shear rates so optimal processing windows can be determined.

Even simple viscometers benefit from PC control and data acquisition. The Benz MV 2100 Mooney viscometer (Benz Material Testing Instruments, 69) uses digital temperature controls, real time display of torque versus time and data storage for statistical evaluation and manipulation, running on Windows 95. Measurements are recorded using their proprietary Benzwin 2000 software, which is included with the MV 2100. The Benz unit offers TPE users the ability to perform scorch and stress relaxation tests.

More options for color matching

The evolution of spectrophotometry from research lab curiosity to production line tool has driven instrument manufacturers to deliver both hand-held and bench-top instruments with steadily increasing performance/price ratios. The rise in performance in hand-held units can present the processor with a dilemma: upgrade to a new generation of portables or move to an integrated turn-key system? For smaller shops, the portability of hand-helds has an obvious advantage, and with current microprocessor technology, portables will continue to be a viable option as a business expands. Added onboard computing power enhances portables both by adding features and by simplifying operation, allowing consistent measurement with less operator training.

The method the instrument uses to view the sample is an important consideration in the purchase decision. Philip Lysack of Lysack Associates (Canadian distributor for HunterLab products, 74) describes the primary hand-held viewing geometries: “There are two schools of thought, 45/0 and sphere geometry. Both are right and both are wrong. If you want to have color reported, ignoring the effect of gloss, then the sphere instrument would be the correct instrument to use when you want to recipe-match a color chip. Incoming QC and color formulation might be better served with the sphere instrument, whereas outgoing QC would probably be better served with a 45/0 instrument which perceives color the same way the human eye does.” Lysack notes, however, that many processors use one geometry for both QC tasks. Many manufacturers supply units with either geometry running common software for easy interchangeability.

BYK-Gardner, for example, offers its color-guide (Folio Instruments, 70) portable instrument in both sphere and 45/0 versions, both with all commonly used color scales, illuminants and indices. Two hundred color standards with tolerances, and 999 readings can be stored. An RS 232 port allows data transfer to a PC for analysis by applications programs such as Excel or Lotus.

Another example of an advanced technology portable is GretagMacbeth’s ColorEye XTH (Prism Instruments, 72). The XTH features an easy-to-use intuitive interface with menu-driven operation to reduce start-up training time. A simplified keypad has only six keys, and the high-speed processor allows one color measurement per second for increased throughput. The unit uses a two-dimensional CCD for simultaneous measurement of SCE (specular component excluded) and SCI (specular component included). Prism Instruments’ president, Dan Williams, stresse
s the importance of the unit aperture in choosing a hand-held spectrophotometer: “It’s about accuracy. With the XTH you can have a large or a smaller view. They can buy the instrument with a small area view, and then add the large area view (capability) later on.” The XTH is easily mounted on robotic equipment for automated operation.

HunterLab’s MiniScan XE Plus (Lysack Sales Associates Ltd., 73) is yet another versatile portable, with a wide range of capabilities to store and output sample measurements. Readings may be stored in the instrument’s internal memory, printed as hard copy through a standard printer interface, or output to a PC.

Turnkey systems minimize risk

Another upgrade approach is to purchase a complete turnkey color quality package. Whether timed to coincide with the replacement of an existing PC or a new installation, this approach greatly reduces the risks of software incompatibility.

The QA 2000 from X-Rite, Inc. (75) consists of a spectrophotometer, PC and software (including Windows 98), as well as an installed modem and printer. The software utilizes client/server database technology for data storage and is 32-bit Windows NT and SQL compliant. The system has the ability to analyze density data, CMC and CIE94 color difference, and DIN metamerism as well as CIE L*a*b* or LCH. QA 2000 is available in single-user and multi-user network configurations, and with X-Rite’s ColorMail 2.0 software, color data can be transferred anywhere by e-mail and the Internet.

Another onscreen color specification and management system running on a Windows platform is Datacolor International’s Colorite ImageMaster (76). Digital sampling eliminates the possibility of sample degradation, and the color produced onscreen can originate from a spectrophotometer measurement or be created synthetically by the system and then applied to its own color images. The Windows-based ImageMaster features enhanced networking capabilities with built-in e-mail.

If you can’t afford a turn-key system, don’t forget about the future. Hal Good, director of marketing services for HunterLab, has definite recommendations for newcomers to quality color instrumentation: “If someone is starting off new, then go to the portable system along with PC software. I do suggest that they get a system with the capability to do that (interface with a PC) in the future, because nine times out of ten, they’ll want to in the future.”CPL

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