Process control and simulation lead news at SPE ANTEC.
ON-LINE VISCOSITY DATA
A prototype system that will provide molders with a simple, low-cost handle on material rheology was previewed by Dynisco Instruments, Sharon, Mass. The Intelligent Process Analyzer (IPA) links Dynisco's MTX infrared temperature sensor and ordinary position and pressure sensors with PC analysis software.
Using real-time data on nozzle melt temperature, the IPA calculates and displays a "viscosity index." Not a viscosity measurement in an absolute sense, this index instead provides warning of material variations in real time. "It's really a measurement of relative viscosity," explains product manager John Czazasty.
An ANTEC paper by Dynisco marketing v.p. Gene Yazbak describes how this relative-viscosity reading - which he calls the "pressure/temperature interactive viscosity index" - can ultimately be used as a closed-loop control parameter. For instance, the index could serve as the basis for adjusting injection pressure.
Data captured by the IPA can be downloaded into Windows-based analysis software. This menu-driven package features graphical displays of pressure and temperature profiles, along with the new viscosity index.
Commercial release of the new system has been slated for October. Dynisco is currently lining up beta sites. Molders wishing to get an early look at the analyzer can call John Czazasty at (617) 784-8400.
New simulation software for injection-compression molding is nearing completion by Moldflow Inc. of Shelton, Conn. Developed in collaboration with GE Plastics of Pittsfield, Mass., and Ford Motor Co., Dearborn, Mich., the new software has undergone initial testing and should be ready by year's end.
In a separate development, Mold-flow announced support for Microsoft's Windows NT and forthcoming Windows '95 operating systems. By adapting its Dynamic Series software for these 32-bit operating systems, Mold-flow hopes to make analyses run faster, though it's too soon to say how much, according marketing manager Mark Toussaint. Moldflow Dynamic Series users will also benefit from the new operating systems' improved interfaces and multi-tasking capabilities, Toussaint adds.
In other simulation news, AC Technology of Ithaca, N.Y., announced a $4 million program to develop a true 3-D flow-simulation package. Working with Los Alamos National Laboratory and General Motors over the next two years, AC Technology will develop a 3-D filling simulation package that takes a polymer's viscoelastic behavior into account. Phase one of the project, discussed in an ANTEC paper by Los Alamos researcher David Guell, tells sophisticated users how to evaluate common sources of error in current mold-filling software - errors from the underlying model, from materials property values, and from numerical methods of finite-element calculations. AC Technology North America president Peter Medina says this sort of critique of current methods is the first step toward developing true 3-D mold-analysis. (AC Technology also announced that it has completed its injection-compression simulation software. See story on p. 31.)
A new "Control Limit Simulator" has been added to the Expert Manager CIM software from Hunkar Laboratories, Cincinnati. According to marketing director Robert Fariss, the simulator lets users experiment with different SPC control limits - without interrupting production - as they try to optimize their process. The simulator's graphical display reveals which machines in a plant would be able to remain within statistical control under different sets of control limits.
Hunkar also showed two enhancements to its SmartBox Parison Programmer for blow molding, which was first introduced at NPE '94 (see PT, May '94, p. 68). New features include SPC tracking of hydraulic servo-valve performance and position-based parison programming for wheel-type machines. Before, the SmartBox supported only time-based programming, says product manager Andrew Fricke. The new system can program up to 300 points based on the position of the programming mandrel.
SHAKE UP YOUR MELT
"Rheomolding," an injection molding method designed to improve physical properties and eliminate weld lines by oscillating the melt inside the mold, has become commercial in two configurations (see PT, March '94, p. 21). Rheojector I consists of auxiliary injection cylinders that mount at an angle between the nozzle and main barrel to oscillate the polymer through the entire mold. Rheojector II, which attaches to the tooling, oscillates the polymer at specific points in the mold - at the gates, for example. Both systems can be retrofitted to existing molding machines or tools. Licenses for either system are available from TherMold Corp. (formerly Solomat Partners), Stamford, Conn.
Another process targets weld lines and other processing problems by shaking up the molten polymer a bit. The SCORIM process uses a special retrofittable processing head mounted between the screw and mold (see PT, Oct. '92, p. 17). The head divides the melt into two streams, which then pass through separate hydraulic piston chambers. Working both in and out of phase, these pistons establish a rapid cadence of flow compression and decompression at the beginning of the hold cycle. Later on, the pistons simultaneously apply high compression force to finish off the holding cycle.
Now commercially available from Scortec Inc. of Gulph Mills, Pa. (which has sold eight systems in the U.S.), SCORIM has been used to address several real-world processing problems. Applications include an ABS radio cover that was plagued by weld lines, sinks, and blush marks. By solving these problems, SCORIM saved $1/part in painting costs. SCORIM also eliminated weld lines from a VCR remote-control cover and reduced the cover's cycle time by 17%. Faster cycles are reportedly a common effect of the SCORIM process because it packs more material into the mold, which promotes better heat transfer and faster cooling.
NEW STABILITY TEST DEBUTS
A new way of testing oxidative stability of polymers was introduced by Custom Scientific Instruments (CSI) of Cedar Knolls, N.J. The new CL400 ChemiLume system measures "chemiluminescence" - the faint light emission caused by thermal oxidation. This alternative to other test methods is said to be faster than oven aging and runs at lower temperatures than oxygen-uptake measurements or differential scanning calorimetry (DSC). According to Dr. Norma Searle, consultant to CSI, the method has been around for decades, though not commercially. The CL400 can handle up to four specimens at once, running either dynamically with heating rates from 1 to 15 [degrees] C/min or isothermally with an upper temperature limit of 350 C. Price is roughly $40,000.
In other testing equipment news, Kayeness Corp. of Morgantown, Pa., came out with a new high-speed, high-force capillary rheometer. The Galaxy V Model 8052M has a max. force of 9 kN at a maximum speed of 600 mm/min; previous models could reach that force or speed, but not both at once.
Kayeness also came out with a new version of its KARS software, which handles rheometer data acquisition and analysis. New version 6.0 lets users input all experimental parameters from a personal computer and monitor data collection in real time. According to marketing coordinator Stephen Wagner, the computer automatically determines the steady state and records up to 45 data points from one sample charge.
New flexible PVC injection molding compounds from Teknor Apex Co. of Pawtucket, R.I., reportedly offer matte finishes without requiring any changes in processing or tooling. Philip Morin, industry manger for engineered vinyl, says the matte finish provides a "dryer, more rubber-like feel" than glossier vinyl compounds, making the new compounds a good alternative to molded rubber. Applications include automotive ann rests, where a matte finish is perceived as more luxurious than a glossy look. The Apex 1700 series consists of nine compounds ranging in Shore A hardness from 50 to 90. Tensile strengths are from 1000 to 3040 psi, elongations from 340-29096, and brittle points from -47 to -24 C.