Position: The article's Minors Carousel system helps the ingredient batching,The system ensures correct ingredient addition to batches, inventory management, tracking and configurations.
Minor ingredient batching can attain a level of semiautomatic operation with a minimum use of floor space with the installation of BTI's Minors Carousel System. The Minors Carousel (see drawings) has 45 total bins on two independently controlled levels. Removable bins are arranged on each of die two levels in a circle. The bottom row is 24 inches from the floor (to improve operator access) and has 18 bins, each bin holding 2.6 cubic feet of material. The top row has 27 bins, each bin holding 1.3 cubic feet of material. Overall dimensions of the carousel are 14' 5" in diameter, 5-1/2'high, including shroud. A safety shroud surrounds the bins so that no moving parts of the carousel are exposed to the operator. Bin access is provided at two locations (one for draw and one for fill) through electrically locked access doors on each of the two levels. For additional safety, the doors have switches which are electrically interlocked with the drives and brakes to prevent rotation when doors are opened.
When the batching station is in automatic mode, the ingredient order of each batch charge unit (BCU) or the recipe is optimized for most efficient use of the carousel. Since each of the two bin levels are independently controlled, while the operator is drawing material from one bin level, the carousel can be positioning the bins on a separate level for the next draw.
As the operator starts processing the recipe, the carousel presents the correct draw side bin to the operator, turns on a light on the control panel to indicate the appropriate bin door and unlocks the door. It then down-loads the correct weight for the scale display. The target weight is displayed as a negative value that will decrement to zero during the weighment process as visual feedback. The operator opens the access door and then scoops the ingredient onto the scale platform. When die weighment is within tolerance (recipe parameter), an "in tolerance" light comes on. If the operator weighs out too much or tool little, the "out of tolerance" light comes on. This deviation can be corrected or accepted by the operator if the "out of tolerance accept" aw. When the operator has acknowledged completion of the draw, that bin light goes out. The operator then closes the door and the door is locked automatically. The cycle resumes for the next ingredient to be processed.
An alternate means of operation would be to weigh across multiple batches of the same recipe. This would reduce wear and tear of the carousel and speed up the batching of multiple recipes. In order for the control system to maintain batch integrity, BTI recommends this mode of operation be used only if a minors tote indexing conveyor is placed on each side of the scale platform. This hardware is listed as the Minors Staging Conveyor option and would include all hardware, additional PLC inputs and outputs, and software necessary to control the conveyors as an integral part of the batching system, with PAWS Production Automation Workstation Software) acting as the operator interface. When the inventory station is in automatic batching mode it will track carousel inventory and automatically prompt the operator when filling or changing of bins is required. Each removable bin is tagged with a bar code along with the chemical name. Whenever the operator is prompted by the station to handle a bin, it asks the operator to wand the bar code to verify the correct bin number. If the shelf inventory is tagged with bar codes, it will prompt for that verification as well. All bin numbers, corresponding chemicals and shelf codes are stored at the workstation and may be called up on the screen at any time. A beacon signals the fill station operator that a a bin has insufficient quantity to complete a set of batch charge units. When the filling acknowledge is selected, the bin in need of filling will index to the fill door. The operator then removes the bin, places it on the scale and wands the bar code. This will allow the computer to verify its contents and weight. Next, the operator wands the bulk container of the chemical that he retrieved for storage. When verified, the operator may fill the bin and press "Enter." The current weight is then stored for the carousel inventory and the operator is prompted to return the bin to the carousel. The operator may browse the bin inventory on the screen at any time, and select bins to fill at random, including the bins which are on the shelf.
Staging of ingredients in the carousel (for the day's run of recipes, size permitting) is performed at the start of each shift. The operator is prompted by the workstation to transfer unneeded totes to the shelf area, and needed totes to the carousel. The control system automatically positions the carousel for correct bin removal and insertion.
The shroud is sealed and is equipped with a six-inch hub at the top for connection to the facility's dust collection system. The stationary scale and drum locations make it easy for placement of dust collection hoods.
System overview
This system will provide an IBM PC/AT-compatible EGA color graphic workstation and a control panel with a PLC located at the fill side access doors (loading area). This system will provide automatic and manual modes of control for the minor weighing system. In automatic mode the carousel will index to the next ingredient automatically. Manual mode will require the operator to index the carousel with the manual controls. Ingredient data will be collected and archived by the workstation. This data will be available for viewing at the workstation or for communications to other systems providing long term analysis and storage. A second industrial terminal is included, and is linked to the minors workstation via serial communication link. This station serves as the operator interface for the batching side of the carousel. There is an operator pedestal at this location which contains the scale display and all automatic and manual controls for the scale and carousel.
Carousel positioning and centering is accomplished by using low maintenance proximity switches arranged to pick up binary coded ID plates coinciding with each bin location. DC variable speed drives control the speed and the direction of each level independently. The programmable controller (PLC) will rotate the carousel the shortest possible direction and perform a smooth stop at the appropriate door.
A maintenance control panel is included, allowing manual control of the carousel rotation and door locks. This maintenance panel is not intended for production use and is equipped with a key lock to prevent unauthorized use.
This system is based on BTI's PAWS. This software functions as tool set and provides the user with the ability to configure and expand the system. A local area network (LAN) may be added to provide communications to other workstations, manufacturing cells or systems in the facility.
Drum stations
Drum access control stations (QTY 4) are included with the carousel to provided a means of handling large volume materials with the required access control. Drum dollies (QTY 15) are also provided to transport drums to and from age. Proximity switches mounted at each drum station will read binary ID tags mounted to each drum dolly (QTY 15).
When an ingredient in a drum is required, the control system searches the four drum stations for the correct drum dolly. If it is present at one of the locations, it lights a light above the correct drum. If it is not present the screen will prompt the operator to get the right chemical/drum from storage and place it in any one of the drum stations with a flashing light (a flashing light above any drum location indicates the chemical is not required for the current recipe/compound).
PAWS
BTI became involved in the rubber mixing industry in 1987 with the installation of a complete computer integrated manufacturing system for a large rubber manufacturer. Rubber manufacturers striving to improve the consistency and quality of their products are turning to an enhanced process control and data acquisition system.
This system, which also provides for the accurate traceability of raw materials, is based on BTI's software package, which is known as PAWS (Production Automation Workstation Software). Because is is so configurable and easy to expand, each customer acquires a system adapted to meet its needs now and in the future.
This innovative system provides all of the data that are needed to control production while ensuring that the much broader informational needs of the factory are met. This approach makes the system easy for the manufacturer to use and applicable to any process in the facility, thus eliminating the need for a variety of different systems on the factory floor. In addition, it has been designed to be developed and maintained by the customer's own production department.
The system improves consistency and quality of the product by ensuring that there is no unplanned variation in the way in which rubber products are made.
Equally important it provides 100% traceability of ingredients in each batch. Because the process is so highly controlled and well documented, ingredients can be traced in terms of batch, quantity, vendor and lot number, among others, while repeatability of the process can be assured.
In case of a problem, it is far better to have detailed, objective information at hand than to have to attempt to reconstruct what might have gone wrong. Many of the end users of rubber products, in fact, have begun demanding that production procedures not only guarantee control but be verifiable as well.
Process equipment such as mixers, mills and ingredient batching systems, along with laboratory/quality control equipment, can be controlled and supervised, as well as linked with one another and with the manufacturer's business system (MIS), through use of the PAWS software.
In materials handling areas, for example, BTI has combined the PAWS software with its Minors Carousel System to prevent errors in ingredient selection.
This semi-automatic materials handling system provides the controlled access to ingredients that is needed to ensure traceability and the prevention of errors.
In addition, the system tracks the inventory, prompting the operator as the bins need firing and keeping factory records up to date.
Software can be designed to perform at all levels of the factory. One of its major applications is as an operator interface. By simply looking at a computer terminal, the operator can see exactly what is happening in the manufacturing process. Furthermore, the operator's work station can be linked to those of other operators and they, in turn, can all be linked to the company's business system computer (MIS). Stations, for example, that handle scheduling, weighing of ingredients and the creation and maintenance of recipes can all communicate with one another and with operators in charge of each function.
The PAWS software is designed to be easy for the operator to use. By its use of a menu system, the operator can pick a selection which will then give him a choice of actions to take. If the operator is unsure which course of action to pursue, he can push a "help" key to obtain more information about the various choices.
Simple, animated graphics also assist the operator by changing size, shape and color depending on die status of a process. For example, a bar chart might vary depending on how much of a particular ingredient is left in a tank. These charts and graphs change immediately as the information is sent from the "real time" computer on the factory floor.
Because of die flexibility of the system, even the computerized drawings, which usually are mechanical or electrical diagrams, can be taken from the customer's own computer-aided design (CAD) system without any need to redraw them. These drawings become graphic depictions of the process being controlled and might show whether a particular valve is on or off, as well as which chemicals have been fed into the tank and in what quantity. They then tell the operator what should be done during each step of the process, with the instruction currently underway taking on a different color of highlighting.
Just as the operators' computers can communicate with one another, they also can communicate with the manufacturer's business system. Because of this, a corporation's MIS people can have the information they need as soon as a procedure is performed. Information such as inventory transactions and schedule status/performance becomes immediately available to MIS.
This exchange of information also works the other way. For example, as soon as schedules are set, the information can be sent to all work stations. In addition, communications between shifts is improved because operators find it easy to see exactly what was done previously and even to leave messages for one another.
The software makes it easy to do more than just control the individual process. With the help of actual drawings, for example, it can tell the operators what maintenance work needs to be preformed. It also can alert the operators to scheduling plans, along with inventory management monitoring procedures.
In addition, the system extends readily to the control and data acquisition involved with support procedures, such as inventory control, tool management, lot tracking and even accounting functions such as time and attendance and inventory usage and tracking.
BTI has found that its customers significantly increase efficiency when they begin using PAWS software to control a variety of scheduling procedures. As the firms start acquiring up-to-the-minute information on inventory quantities and aging along with production requirements, the scheduling becomes so accurate that it increases productivity in addition to improving quality and consistency.
