HMI monitors Injection Molding Machines

  • May 02, 2014
  • Case Study

By Denny Redwine, Kemper Controls  Machine operators don’t want to see faulty parts produced as a result of a machine error that wasn’t corrected in time, not does a plant manager want to deal with unhappy customers and money lost from problems that go undetected. The ability to monitor a process in real-time can address these types of issues, as well as providing other benefits. Production issues recently arose at TGKY, a plastic injection molding facility in Lebanon, KY.  The plant decided they needed to develop an application that would help plant operators monitor the injection molding processes in real time. The TGKY plant makes molded plastic parts for prominent Japanese automotive companies. Producing a high quality product is critical to fulfilling business contracts, and the ability to better monitor the part production processes is also crucial for the overall efficiency of the plant. Like many plants, each plant operator at TGKY is responsible for 50 – 100 machines per shift. Effectively monitoring all of these machines was going to take a level of automation over and above that which existed at the plant. When defective parts are made they have to be reworked or scrapped. In addition to extra labor and material costs, shipments may be missed while the correct parts are being made. The plant was having a particular problem with one of its injection molding machines that was causing non-conforming parts to be produced. Knowing the problem needed to be identified and fixed, the machine manufacturer called Schlemmer Associates, a distributor and solutions provider that specializes in process measurement, control and instrumentation. Schlemmer Associates in turn contacted our company, Kemper Controls, to work with them to address the issue. Our solution was labeled the Validator, an alarm and monitoring system which would alert machine operators to problems with the injection process in real-time. In addition to monitoring the problematic machine, the Validator was developed with the capability to monitor any number of machines and associate production processes, both at this facility and others. Monitoring Multiple Processes The plant’s machines could only monitor part production under their direct control, but many of the machines needed to interact with other items of equipment as part of the production process. The Validator would therefore have to monitor not only the machines in questions but all associated auxiliary equipment. For example, the Validator needed to monitor not only the problematic machine itself, but also the equipment that delivered water flow through the molds. Water is circulated through the molds to ensure the correct amount of heat is dissipated while the plastic is curing in the mold. Too much or too little water flow can produce a defective part, as can variations in water temperature.  (figure 1) For various reasons, water flow can be interrupted, which can cause major quality issues if the problem is not detected and alarmed immediately. Equally important are monitoring and alarming mold heater temperatures, as well as the overall machine status. Finding the Right HMI We wanted the Validator to be an HMI solution running on a Windows CE-based platform, as opposed to a full blown Windows system with its corresponding high hardware and software cost. The main challenge we faced was finding the best HMI for the job, one designed to work with Windows CE that would be also easy for operators to use. We found that InduSoft Web Studio provided the best solution because of its ability to work easily with Windows CE, and with other embedded Windows operating systems. Web Studio lets users develop the HMI application once, and then deploy the application it on any Microsoft-supported platform including Windows CE, Mobile, XP Embedded, and Server editions. This “develop once-deploy anywhere” capability dramatically cut development time. The over 240 native drivers included with Web Studio was also a major plus because the Validator would have to integrate seamlessly with a variety of components including PLCs, machine controllers and embedded controllers. In addition, its recipe capabilities enabled the creation of flexible, user-defined recipe groups within the SCADA software, as well the ability to import and export data recipes, reports and real-time data in XML format. Immediate Alarm Notification Ensures Quality Products The Validator system communicates with the machine PLC over a digital network in order to make decisions about alarming and recipe download verification. Operators view the process data, alarms and input data on the HMI via an easy-to-understand graphical interface. InduSoft Web Studio’s extensive graphics library decreased development time, enabling us to get the system to the customer faster. In addition to water flow, the Validator includes alarm monitoring capabilities for the hot runner system and the injection machine control. The machine’s limits are loaded into a recipe file for each mold the customer may run on that machine. The Validator then checks the machine status to ensure that criteria for production are met. This includes verifying a proper connection for each of three hoses, as well as making sure the thermalator, which regulates the mold’s temperature, is turned on.  (Image 2) To verify that the Validator is monitoring the correct parameters, the machine control sends a binary code that designates the correct production parameters. As the machine runs, the Validator constantly monitors the flow rate and alarm inputs from the machine alarms, and sends an output that activates an Andon light board if something goes outside the designated parameters. When plant workers see that the Andon light is on, they are immediately alerted to the problem. Production Problems Solved The results of the Validator’s implementation have been impressive for TGKY. The system has saved time and money that otherwise would have been spent on the material waste from defective parts, and on producing new parts to meet deadlines. In one instance the Validator received an input from the machine monitor that a screw was bottoming out. The Validator processed the error and activated the Andon alarm board mounted in the aisle of the plant. A plant engineer was notified and was able to quickly remedy the problem, preventing the production of defective parts. In addition to the screw bottoming out, the plant engineer also discovered a faulty valve. If not for the alarm, hours’ worth of defective parts would have been produced because the machine is typically only checked every two to four hours. The HMI is also able to help users see trends that indicate possible future problems by providing historical data side by side with the current data that displays immediate operating conditions. Comparison and analysis of historical data can often reveal potential problems before they occur, enabling proactive maintenance and decreasing or eliminating downtime. Schlemmer Associates has been so pleased with the functioning of the Validator system at TGKY that it’s expanding to markets beyond injection molding, and hopes to expand our solution to a wide range of machines. Schlemmer Associates, our company and our customers are also impressed with the economy and performance of InduSoft Web Studio, and we’ll keep relying on it to give our customers the best quality HMI with the shortest development time. Benefits of the Validator:

  • Designed for Window CE and other embedded platforms
  • Alerts machine operators immediately to problems with the injection process
  • Can monitor multiple machines and processes simultaneously
  • Provides intuitive graphical user interface for fast identification of problem areas
  • Offers both current and historical data displays

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