K '98: The future of injection molding, Part II

By: 
February 06, 1999


Representing the approach of many new control systems for injection molding machines, this MC4 from Krauss-Maffei is designed for ease of operator use with a graphical user interface and extensive use of symbols.

How a molding machine drives is just as important as the body construction and what's under the hood, and control technology showed a number of advancements in Dusseldorf. PC controllers, the replacement of alphanumerics with icons and symbols recognizable in any part of the world, shopfloor internet access for quicker service . . . these were among the latest trends in molding control systems. Here are a few specifics.

Digital Profile Trace Control

Fanuc, a specialist in NC controls, is about to do to injection molding machine control technology what it did to machine tool control technology. It has developed a system called Digital Profile Trace Control (DPTC) for its Roboshot all-electric molding machines. DPTC is a natural extension of the Roboshot's AI Pressure Profile Trace Control system; wherein, the machine follows an ideal pressure profile found to produce ideal parts, monitoring the run with its sensors, and making realtime, on-the-fly parameter corrections to trace the ideal profile. It is one of the keys to the Roboshot's repeatability.

Finding the ideal pressure profile has, until now, largely been a matter of trial and error. DPTC captures data directly from a 3-D CAD/ CAM/CAE file of the part, mold, and, most of all, from data in flow analysis process simulation to develop the pressure profile the machine will follow with digital precision to make ideal parts. In doing so, Fanuc may close the loop between injection molding design and manufacturing, making setting up a machine easier than developing machine tool cutting paths. A beta site is presently testing DPTC in Japan.

Neural Networks Close the Loop

Kistler Instruments used the occasion of K'98 to debut Autoflow, a closed-loop process control system based on cavity-pressure profiling that is designed to make even the best closed-loop molding machine perform even better. Autoflow controls process controllers. Using simultaneously operating neural nets run on advanced fuzzy logic algorithms, Autoflow automatically adapts the molding machine to any changes in variables that could even hint at adversely affecting repeatable part quality.

It has individual neural networks for injection speed, holding pressure, holding time, and mold temperature. Cavity pressure sensing is the key. In realtime, Autoflow monitors the parameter networks and evaluates their impact during fill on an ideal cavity pressure curve. It not only examines changes in the slope of the cavity pressure curve but in its integer, rather, how the area beneath the curve changes. Autoflow even automatically recognizes volumetric cavity filling, and it communicates all its findings to the molding machine's own control system for steady-state process modifications and shot-after-shot quality.

The compact Revolution hot runner controller sits on the stationary side or the center section of a stack and supplies 1100 watts/zone for nozzles and 3300 watts/zone for manifolds without all those mold interface cables for power and thermocouples and those press-side electronic cabinets.

Autoflow has already proven its worth to Philips in Drachten, Holland in production of the "Philishave Cool Skin" electric razor. Kistler worked in collaboration with Engel on the project. Philips was shooting for Cpk values of two, up from a basic product requirement of at least 1.33. Autoflow delivered Cpk values of more than five in seven weeks time. Engel demonstrated Autoflow patched into its own high-speed Engel Monitoring System interface at K'98 on an 800-kN (88-ton) tiebarless press with two L-configured shooters. The robotized molding system flawlessly produced complex 3-D molded interconnect devices.

Controllers Get Graphic and Smarter

You could call the trend to easier-to-operate, graphics-based controls a quiet revolution. Many injection machines on the display stands at K'98-very likely a majority-featured new or recently introduced graphic interface controls. These controller improvements were often not a featured item, but based on their sudden increase, they are certainly a trend. The following examples are only a few of the many new controls seen at K.

The first of the new controllers in Battenfeld's Unilog Series, the B2 and B4 (there is no B3), were mounted on the company's Micromolder and TM series toggle machines. The B2 and B4 are low-end and high-end, respectively, but the issue is not that simple. The design, according to Thomas Kosthorst, who is responsible for control systems at Battenfeld, is based on customer requirements.

A graphic interface with symbolic icons solves language problems and speeds up the work of an operator who can read this alphabet. Performance improvements include better movement control of machine axes by the faster processors, improved control algorithms, and "look-forward" capability. The controller looks ahead to what it must do, such as stop the platen at a very precise point, and adjusts ramp and acceleration accordingly. The action is similar to a driver looking ahead to a stop light at the next intersection and adjusting speed. By the time K'01 comes around, Kosthorst adds, machine controllers may well be connected to a global network like the Internet to meet the needs of global manufacturers.

Labotek's newest gravimetric blender is the Gravimix, available in four different sizes with capacities from 110 to 4400 lb/hr. It can be fitted directly on the feed throat, or separately on a mobile stand, and reportedly offers a dosing accuracy of ±.1 percent.

Controller architecture has moved another full step on Negri-Bossi's new Canbio Series (40 to 160 tons) of hydraulic injection machines. It may be more accurate to say controller architecture has stepped outside the controller and into the rest of the machine. N-B's Canbio machines are managed through the Controller Area Network system, or CANbus, developed by Bosch for automobile control systems and adapted by N-B and Bosch for these machines.

Instead of a wiring grid connecting the controller to the various control points of the system, there is a communication bus, and the peripheral devices, for example, proportional distributors, transducers, and pumps, have on-board intelligence. Thus, the controller is not responsible for each signal communication. Instead, it transmits a signal to the pump, for example, that triggers a sequence of events controlled by the pump. In the Canbio Series, there is direct transfer of the hold-pressure switching signal from the position sensor to the pump, and position transducers supply measurements in physical dimensions (mm or m/sec) that need no conversion.

Negri-Bossi had three Canbio models running at K'98, and the series is on the market now. Modular design allows affordable application-specific configurations and supports high reliability and low maintenance. Other robotics and machinery companies use CANbus, but Negri-Bossi says this is the first all-CANbus injection machine control system.

The Procan control system of Dr. Boy has gone to a new level with the introduction of Procan CT at K'98. Though it retains the basic concept and ergonomic terminal operations as before, it now incorporates touch-screen technology to eliminate the time spent on a keyboard. Functions are selected intuitively by pointing at the screen, and the Windows-oriented interface reduces the time required to become familiar with the system.

At the system's core is a 32-bit microprocessor with additional programmable hardware logic. The Procan CT uses hardware comparators, like its predecessor, permitting real-time operating characteristics that increase reproducibility and precision in the control system. An industrial PC is included to handle all communications and visualization functions. A 1.4 GB hard disk and floppy drive are standard to provide storage capacity for setup data, including peripherals, process data, alarm messages, and setpoint changes. Standard features include offline editing of setup records, SPC/SQC, fuzzy logic temperature control, graphic setpoint input, configurable interface, and remote diagnostics.

Adding to the line of small dosing units introduced at the show was Motan, debuting the Minicolor, which is small enough to be mounted between the feed throat and the hopper on top of an injection molding machine. It comes with the option of two dosing stations, each with a maximum capacity of 44 lb/hr. Optionally, a small, encased, compressed air loader can be added, making it the Minicolor VL. The loader is attached by changing the hopper lid.

The need for simplified user interface and more advanced and powerful controls extends to every size of machine. Butler Designs (England) has just extended its 12/90 range of nine-ton injection machines, adding the 12/90H fully-automatic horizontal machine and two machines for LSR molding, one vertical and one horizontal. At the same time, said Managing Director Nigel Rust, it was necessary to upgrade the Omron PLC controls to give users the information they required. The control now has a touch screen MMI and important communication links. The machines can be networked using Windows-based technology in groups as large as 32 machines to allow control from a central point. It is also possible to set up a modem link from Butler's Technical Support Office direct to a machine anywhere in the world. Software upgrades can be installed and fault diagnosis can be on-line.

But one of the most important new developments in injection molding controls technology at K'98 had nothing to do with injection molding machine control. Rather, it had to do with controlling molds-hot runner molds to be precise. It's aptly trademarked "The Revolution" by its developer, American MSI, who started the revolution in computerized hot runner controllers a decade ago. The Revolution is a mold-mounted hot runner controller, the world's first, and patents are pending, worldwide.

The compact Revolution-9 1/2 inches long by 4 1/2 inches deep by 8 inches high, including the junction box-sits on the stationary side or the center section of a stack and supplies 1100 watts/zone for nozzles and 3300 watts/zone for manifolds without all those mold interface cables for power and thermocouples and those obstructive electronic cabinets cluttering up beside-press floorspace.

You no longer have to stress over hassles like which connector or which wiring pattern to use, cable length, or wiring amperage ratings. Short cables, broken insulation, and connection points that are poorly crimped and intermittently working all are things of the past. And your molding machines, robots, and auxiliaries will no longer be constricted by a tangle of cables.

Conair is replacing its successful Thermolator range of water and oil temperature controllers with the TC-150, which combines both water and oil circulating functions, depending on the temperature range of the application. With switchable 3-, 6-, or 9-kW heating, the unit provides temperature control to 194F for water and to 302F for oil. The control is designed to sense shifts in temperature caused by changing load conditions and automatically react to maintain temperatures.

It has a built-in supplemental cooling system and an easy-to-use mold interface system, and it links to any of MSI's standard user interfaces, which can be machine mounted or built right into the machine itself. The Revolution also can have a direct communication interface with the molding machine's controller. It comes in six-zone increments, with 12 zones as a minimum, up to 48 zones as standard. Custom versions can be built for molds requiring higher amperages or more control zones. A complete 12-zoner, ready to bolt-on and run, sells for just $4700, some 30 percent less than conventional systems.

Auxiliaries

The popularity and pervasiveness of the Internet in general, and the PC in particular, is generating a mini-wave in machine control innovation for auxiliary equipment, too. Material handling equipment manufacturer Maguire introduced at K its Gravimetric Gateway Materials Management System, a PC-based hardware/software system that communicates with controllers on Maguire's weight scale blenders on multiple processing machines-across the plant or across the world. From one central location, the system allows users to document material usage, check alarm conditions, download recipes, and generate material usage reports. It runs on a Unix-based Windows platform and uses a Java-based architecture to allow data sharing with production monitoring systems. The network capability means molders can link multiple machines from multiple locations anywhere.

Motan, on the other hand, has developed a new graphical user interface (GUI) called Linknet for its centralized material handling control system. The Windows-based system checks the input from each shift's database, which logs setpoints, feedback, alarms, and other event data.

Attracting attention from showgoers was Hettinga Technologies, which introduced the Hettinga Advanced-Level Control (HALC), an all-PC control system for plastics processing machinery, including injection molding machines and auxiliaries. Bypassing the traditional PLC-based control systems, HALC is designed to monitor and control up to 160 temperatures (including hot runner, mold, and barrel), injection rate, injection pressure, back pressure, and other setpoints. It features closed-loop injection velocity and can be expanded with the addition of input and output (I/O) cards that can be installed on the system.

Colortronic added to its established Ultrablend line with the Ultrablend II, a gravimetric blender that reportedly guarantees homogenous blending of powders, regrinds, and granules. It features a new hopper design; longitudinal, transverse, and vertical material mixing; self-calibration; and all-stainless steel construction. The Ultrablend line is available with weighing capacities of 2.2, 4.4, 11, or 22 lb.

In a mini-trend of sorts was the presence at the show of two material dryers that use compressed air instead of traditional desiccant technology. Una-Dyn, with its parent company Mann+Hummel, introduced a small compressed air dryer that mounts directly on top of the press. Una-Dyn's contention is that most drying applications require dewpoints of only -10F or +10F, which is easily attainable with basic compressed shop air. The unit consists of a cylindrical main chamber; attached to the side is a venturi for heating the compressed air, which enters at the top. The air circulates through the venturi before entering the chamber. Some air is recirculated through the system, but a pressure relief valve at the top of the unit vents off air periodically. It can process resin at rates up to 120 lb/hr. After startup, the venturi, says Una-Dyn, receives air at 5 cu ft/min, but the system reportedly recalculates at 20 to 25 cu ft/min. An optional miniature desiccant tower can be used to lower the dewpoint to -60F, with attenuation on recirculation to -10F to -120F.

Fasti's ERD compressed air dryer has been on the market for eight years but takes a slightly different tack. The air in the ERD system is not recirculated but instead expelled through the hopper. William O'Day, vice president of marketing & sales, says the ERD system routinely holds dewpoints of -20F and saves energy by not cyclically heating and cooling desiccant. As with Una-Dyn's system, a desiccant is optional, for dewpoints down to -40F.

In addition to releasing MF/Flow3D for thick parts, Moldflow also announced a new version for its Part Adviser (3.0), which now contains enhanced design advice, further CAD integration and emulation, as well as the ability to export files for secondary analysis and production. In addition, the software can now be shared over networks through floating licenses.

Moldfilling on Solid Ground

For filling simulation, the news centers on solid models. Moldfilling analysis vendors have listened and responded to a segment of the design community that prefers the ease and accuracy of analyzing solids rather than using a midplane mesh.

Moldflow announced a new product, MF/Flow3D, calling it the first true 3-D flow analysis product the company has offered. In the past, designers were always limited to a planar approach, according to Ken Welch, marketing vice president. "Designers working with thick-walled parts such as electrical connectors and gears had no tools available for filling analysis because no midplane model could accurately represent plastic flow through the part," he adds. Now, solid models read directly into MF/Flow3D are transformed into a tetrahedral-based finite element model with true volume elements, modeling the fountain flow of the melt. Adaptive mesh generation ensures that critical areas are refined with smaller elements in a reasonable amount of time. Moldflow also offers the newest release of Part Adviser (3.0), its CAD solids-based module, which is now network enabled and contains online help.

Moldfilling packages are taking a different approach to analysis, bypassing the midplane mesh for direct simulation on solids. Here, faSolid from Plastics & Computer uses a solid brick-element (hexahedral) mesh to simulate moldfilling on a solid model of the bezel for an automotive GPS navigation system.

Plastics & Computer came to K with two new products: faSolid and Kamms. The first, faSolid, works with any STL file generated by a solid modeling system and also analyzes the solid model rather than a midplane. Users can create an automatic structured mesh of solid-element hexahedrons to duplicate complex geometry, then optimize the mesh to reach the required precision level. These solid "brick" elements are compressed when necessary, depending on part geometry, but all data is retained with no interpolation or smoothing techniques. After creating the optimized mesh, users start the analysis by indicating gate positions. The model can also be transferred to Ansys or Abaqus for structural analysis.

Kamms, short for knowledge-aided molding machine, is an intelligent, closed-loop feedback system for optimizing machine settings. Using results of moldfilling analysis, users can set initial machine profiles. Kamms then lets users calculate and optimize processing parameters. During actual molding, data for all settings are sent to the machine, and actual molding condition data comes back, alerting operators if they are out of range. Kamms also offers diagnostics using a design of experiments method.



K '98: The future of injection molding, Part I

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