Canadian Plastics

Central Materials Planning

The day when injection molders and extruders could think of their raw materials handling system as an "add on" is long gone. Today a highly automated, efficient and flexible materials handling system is a key for helping most processors, bo...

September 1, 2004   By Michael Legault



The day when injection molders and extruders could think of their raw materials handling system as an “add on” is long gone. Today a highly automated, efficient and flexible materials handling system is a key for helping most processors, both large and small, remain competitive with on- and off-shore manufacturers. “It appears that investment in all types of auxiliary equipment is accelerating at a faster rate than the investment in molding machines as processors continue to invest in process improvements,” says Mark McKibbin, vice-president of Motan Inc. Still, at many companies, there is the inertia to keep doing things the way they’ve always been done. Also, unlike purchasing primary equipment, where the strategy of buying the best machine for the money and application will usually suffice, installing a raw materials handling system requires planning and analysis. At today’s lean-running companies, with staff focused on day-to-day production, the first wise thing to do is to seek help.

“Talk with your materials handling supplier,” says Rob Miller, president of Nucon Wittmann. “A lot of processors don’t have a clue what the capabilities of their current raw materials handling system are, because, over the course of years, the system has been changed and tweaked repeatedly.”

Miller says Nucon Wittmann can conduct a plant audit of a processor’s raw materials handling system to assess its present state. Once the evaluation is complete the client will be provided with a report, including a complete 3D drawing showing the location of “every pipe, loader, dryer, pump and silo in the plant.” As well, the company will get a written description of its system and spreadsheet outlining system design parameters, material selection options, system capacities and other details on specific equipment.

“We can tell a customer, for example, that his pumps are only at 40% capacity, so he doesn’t need to buy new pumps if he wants to put in more machines,” says Miller.

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Knowing where you are now makes it easier to plan and specify a system that will meet your future needs. The importance of properly analyzing your operations and production needs applies to new installations as well as retrofits. Miller has seen more than one start-up that has had to tweak or redesign its raw materials handling system almost immediately when it became apparent that the specified layout didn’t meet its needs. More often then not, such problems arise from a communication breakdown between production staff and an engineer assigned to do the layout.

NEW OPTIONS FOR SMALLER SHOPS

For smaller-size molders it is important not to jump to conclusions about what may or may not be practical when considering a materials handling upgrade.

“Some processors think that because they use so many different materials, they can’t use a centralized materials management system in their plants,” says Chuck Thiele, senior consultant with Conair. “Not so.”

Thiele says that while a typical custom molder may run hundreds of different types of material, a shop usually only uses 10 or 15 of those materials on a regular basis. He says there are key opportunities at such companies to streamline materials handling and save money.

Conair’s ResinWorks system is designed for processors who run engineering resins that require drying and who make several material changes a day. Core components include drying hoppers, desiccant dryers, blenders, vacuum pumps and loaders. The machinery is pre-assembled and delivered with material-handling controls, conveying pipes, valves and other components.

Thiele calls ResinWorks more of a philosophy than specific equipment. “The main thrust of the concept is to centralize all materials handling and distribution in a remote area, away from the machines. If you use nylon on three machines, you dry it once in a dryer sized for three machines and convey it with dry air to each specific machine.” He says one customer with nine injection molding machines gained 40 hours of uptime a week after installing a customized ResinWorks system at his plant. The increase in uptime was a result of time previously spent changing resin, cleaning hoppers and drying new materials.

Smaller-size molders can also capitalize on the modular design of modern raw materials handling equipment. Universal Dynamics’ GS Series Dryers are modular in design and user-friendly. With dual desiccant beds, the GS is an energy efficient low dewpoint dryer equipped to handle large jobs. The material saver function permits the user to set material temperature limits and automatically lowers the setpoint to a temperature maintenance level when the user stops processing material or the hopper temperature equilibrium is reached. Modular design and quick-release connectors make all components easily accessible.

Centralized materials systems heighten the concern over material contamination. Many processors eliminate this potential problem by running dedicated conveying lines for each material, which can be expensive. Novatec’s LineClear Lateral is a new product that can be installed in a new common material line or retro-fitted into an existing common line to ensure that resin intended for a given molding machine actually goes to that machine, preventing blow-by material from accumulating and clogging the conveying line. The LineClear Lateral is equipped with an air-operated “gate”, which is installed at each point where resin is normally diverted from the common line to a given molding machine. In addition to eliminating the need for costly dedicated lines, the LineClear Lateral is an economical alternative to expensive knife gate valves, which have been traditionally used in common line systems to divert material.

Dri-Air Industries’ PDII dual hopper dryer is designed to address the molder’s need for fast material changeovers. While running material in one hopper, the second hopper dries the material for the next run, eliminating the time to dry the new material. Material changeover times are now determined by the short time to change tools, rather than the hours required to dry the next resin. For two-shot molding, the PDII includes a dual closed-loop loading system to feed the receivers on each injection unit.

“One customer making many material changes on his machines increased uptime by 30% with the PDII,” says Charlie Sears, Dri-Air president. Sears observes that an increase in machine run time and capacity also translates to a tangible cost avoidance for the purchase of new machines.

The handling of multiple materials is made easier with K-Tron Feeder Group’s new Gain-In-Weight batching system. The KGIW is designed for use in batch applications involving up to eight materials and 100 recipes. The system can produce batch sizes from five to 800 kg. Each material is sequentially and independently metered to the weighted collection hopper from which the completed batch is discharged.

CONTROLS IN DEMAND

“We’re never going to be able to beam pellets across the plant,” says Nucon Wittmann’s Miller. “Where we see customers improving the efficiency of their materials handling systems is in the controls.”

Miller says his company has installed several systems recently in which customers asked for a basic materials loading system with state-of-the-art controls. Such a control system, which Miller says can be configured with off-the-shelf computer and control hardware and an Ethernet card, allows managers and operators to monitor everything from blender settings to dryer dewpoints from a remote PC.

On-the-floor programming and control systems that simplify materials handling commands and protocols are also an increasingly critical component of a modern materials handling system, says Miller. Wittmann’s new M7 TouchScreen network control system incorporates the same high-resolution 8.5 in. VGA TFT color TouchScreen used for its proven CNC7 robot control system. The M7 TouchScreen control is designed to simplify the management and control of medium to complex network systems with up to 240 network nodes.

Universal Dynamics’ PC Windows-based
Echo Millenium System permits the user to exercise plant-wide control of a material conveying system as well as monitoring of most SPI compatible equipment such as mold temperature control units, chillers, dryers and blenders. Through a PC, the user can control or monitor system performance from the plant floor or from remote locations. Echo Millenium requires no programming. The user may use plant nomenclature to define his process and equipment, import drawings and pictures to show system configurations or location of equipment.

Process Control Corporation’s Material Manager is a versatile data collection tool that enables the user to analyze the material usage of a blender system over time, providing tighter control of a processor’s inventory. Using a Windows-based PC, Material Manager can accurately track the material usage of all components used on a production line. Communication is established with the mini-op controller using a serial or Ethernet port connection with the aid of an OPC/DDE server package residing in the PC. The data collection tool automatically collects usage data and stores the information on the hard drive of the PC. Material throughput reports can be broken down by job, recipe, blender, shift and total resin usage over any time period.

M-tek (a division of Mould-tek) has introduced a new remote PC blender control, T-COM3. The T-COM3 continuously monitors and controls each blender and central loading system during operation from remote PCs in real time. Using RS485 and Ethernet technology, the T-COM3 allows monitoring of materials dispensing to target weights, blending rate, accumulative total of processed batches and alarm status. Reports consisting of formulas, cycles, batches, blenders, inventory and materials usage can all be viewed and printed.

As you can see, processors have plenty of bells and whistles to choose from, but once again, the first step is to analyze and plan before buying.

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PROCESSORS SEEK WORK-CELL EFFICIENCY

“We’re seeing more of a tendency to set-up self-contained, highly automated work cells,” says Charlie Sears, president of Dri-Air Industries. “Regrind material never leaves the cell but is metered right into the virgin resin at the press.”

Some loading/blending systems are better than others for running regrind. Sears says some proportional vacuum loaders can result in layering of material. He recommends using a volume-based blending system, such as Dri-Air’s twin-auger, dual hopper PDII system to achieve more consistent, on-demand delivery of virgin-regrind materials.

The Cyclomax series of filterless loaders are ideally suited for conveying regrind and dusty pellets. The loader incorporates two cyclones and a secondary self-purging discharge system to completely separate product from transfer air. The design removes the filter, the most problematic element of any loader, saving time, maintenance and money. By adding a high-quality cartridge filter, fine powders and other difficult products can be conveyed. The double cyclone removes up to 99% of powder from the air stream with any remaining fine particles being removed as the air passes through the cartridge filter.


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