Raw Materials Handling:CHANGING TIMES
M any Canadian plastic manufacturers find themselves processing multiple materials, additives and colourants. Raw materials handling equipment plays a significant role in reducing the time for materia...
Many Canadian plastic manufacturers find themselves processing multiple materials, additives and colourants. Raw materials handling equipment plays a significant role in reducing the time for material changeovers and eliminating changeovers altogether.
Here, Canadian Plastics provides a comprehensive run down of the equipment you may need to keep up with the times and to shorten your downtime.
Maguire’s LPD vacuum resin dryers dry resin in 40 minutes — one-sixth of the time needed for conventional desiccant dryers. In addition, the three-station indexing system supplies resin to the machine while another batch is being dried, making it easier to work with smaller batches. The vacuum dryers enable faster changeovers because there is less raw material in the system, and batch producers can add a new material in an indexing station while old material makes the rounds.
According to some equipment suppliers, processors looking to reduce changeover times should also consider central dryers in place of machine-side units.
“If you use a conventionally drying machine at a press, you changeover times may be several hours,” noted Bob Crawford, VP of engineering for Universal Dynamics Inc. “Central systems have hoppers for a number of resins to predry and have them ready for processing.”
Another benefit of central systems is the reduced manpower needed to manage and maintain them — you may only need one person in the central area to access and clean the hoppers.
“One of the primary ways Conair Resin Works helps you to reduce time during changeovers is by avoiding changeovers completely,” said Doug Scott, conveying product sales manager for Conair. “For instance, your drying hoppers would be populated with all your different materials, you wouldn’t have to take time to clean out the hopper.”
Conair’s ResinWorks centralized drying and distribution system allows for faster changeovers because resin can be predried and conveyed to machines. Also, drying hoppers don’t need to be emptied and cleaned, and line purging prevents any material contamination.
ResinWorks drying hoppers are equipped with full-length doors to make cleaning easy, and the hopper’s air spreader cone is removable.
Motan’s Metrolink automated manifold conveying system can supply up to 15 processing machines, with up to 16 different materials. The system minimizes the chance of contamination with fixed pipe connections throughout the production process until a material change.
The system is automatically purged before every conveying cycle. Processors also have the option of operating Metrolink manually, or running the system fully automatically with a METROnet PLC microprocessor control.
Wittmann’s Feedmax B series material loaders
Photo Credit: Wittmann Canada
In manifolds, Lorenz’s manifolds allow users to quickly change one or more lines with little effort by the operator. The modular components allow for easy expansions and a variety of configurations, and the company’s manifolds can be supplied with our without slide gate valves and diverters to provide full automation. This would allow for full PLC control, eliminating costly spills, incorrect connections and safety problems.
LOADERS & RECEIVERS
The Access hopper loaders from Conair feature an angled canister, making it easier to see and reach inside for cleaning. The company has also added hinges that hold the canister lid open. “The primary advantage is that it does help reduce changeover time, and also makes it safer,” noted Conair’s Scott.
The new Feedmax B series of material loaders from Wittmann Canada feature a completely redesigned loader construction, with a slanted opening to the centre section. The company notes that by slanting the cylindrical part of the center section, a greater cross sectional area of the loader is achieved and guarantees easier access for cleaning. The loaders also employ a pneumatically actuated material discharge bell, providing a positive shut off versus a flapper design. The screen filter is fixed to the hinged lid, and automatically positioned between the material inlet and vacuum outlet when the lid is opened and closed.
True to its name, Novatec’s GlassVu vacuum loading system, supplied through Maguire Canada, features glass-walled cylindrical loaders and receivers. According to Novatec, full view of resin loading and consumption allows for fast setups, streamlined material flow, and rapid cleanouts. The loaders or receivers are mounted atop a swing-out glass hopper, which pivots away from the machine’s throat to allow drainage directly through a hole in the base plate of the mounting structure.
FEEDING, BLENDING & DOSING
For processors who work with additives and colourants, equipment suppliers have developed a range of products that offer efficient material consumption, accurate blends and little to no downtime.
AEC, Inc.’s Precision Series Volumetric Additive Feeders feature a modular design that can expand from one to two materials. All units feature a 1/10 hp DC motor, closed-loop motor control maintaining auger speed, and fluctuating line voltage. The Precision Series models also conserve headroom with a six inch throat and inspection windows, and have a large material flood zone for steady material flow.
Motan Inc. has developed the Minicolor G, a compact gravimetric dosing and mixing unit for the addition of masterbatch/ additive in granular form. The dosing station sits on a precise load-cell, and operates using loss-in-weight metering. The unit has been specially designed for direct mounting on the feed throat of the machine, which can reduce masterbatch consumption.
Motan said the speed of the dosing screw is continuously monitored, and automatically adjusted to the dosing throughput. Additionally, masterbatch storage bins can be removed together with the associated dosing screw.
Colortronic’s Colorblend, a digital dosing system designed for pelletized or powder plastic additives, offers quick disconnects that reduce changeover down- time. Colorblend units use correctly sized dosing discs with a DC drive motor and easy-to-operate control. As well, controllers are connected to the process machine and monitor screw recovery time for injection molding and blow molding, and the screw speed of an extruder.
Wittmann’s Gravimax blenders offer extremely accurate measurement, offering significant savings in colour and resin consumption. The blenders employ a unique three-stage metering method — free-flow, coarse pulsing and fine pulsing — to reach the precise target batch weight without underdosing or overdosing. The Gravimax line ranges from the GMX 14R for 130 kg/hr throughput and four components, to the GMX 608 with 5,000 kg/hr throughput and eight components.
SITUATION UNDER CONTROL
“Just as important as the hardware are your control and monitoring software,” noted Universal Dynamics’ Bob Crawford. “Una-Dyn has a distributed control and monitoring system that has served many customers of ours well.”
UnaDyn’s Factory Acquisition Control System (F. A. C. S.) is designed for plant-wide control of material conveying systems, and auxiliary and handling equipment. The system features an easy to use Windows design that has a two-wire power network, while also employing a smart I/O with its own CPU and controls for each connected device that is more reliable than distributed I/O.
F. A. C. S. has full graphing capabilities and a built-in SQL database to generate reports, and the system’s performance can be monitored on the plant floor or from a remote office location.
Crawford also noted that the system is programmed to avoid costly and time-consuming mistakes. For instance, processors can encode all the supply and destination positions, which means that the machine will never try to pull resin from the incorrec
t source. CPL