The first step in most rubber manufacturing processes is compounding. This requires the mixing / blending together of various raw materials in a specific proportion in order to produce a rubber a compound. Most often to produce a rubber compound a combination of plastic resin (pellets, flakes, powders, or liquid) is combined with other materials, including liquids and bulk solid materials. Sterling Systems & Controls, Inc. has designed and supplied a customized batching system for a rubber compounding application. This system includes a variety of mechanical equipment, such as a bulk bag unloading system, electrical controls and automation of the batching and mixing processes. In this application the automation control system includes a PanelView+ touchscreen HMI with a customized RSView ME software application.
As a part of the compounding process the batched ingredients must be mixed. Because there are both liquid and solid ingredients a specialty mixer is used. The workhorse mixer of the rubber manufacturing industry is the internal mixer, or Banbury (named for its principle inventor) in which heat and pressure are applied simultaneously. The internal mixer uses two interrupted spiral rotors moving in opposite directions at a set RPM, as required by the compounding process for the specific rubber compound being produced. The shearing action in the internal mixer is intense, and the power required for the mixing/blending operation can be quite high.
Mixer process control is required to produce the end product and is automated for optimal efficiency. This is a part of the overall automation and process control system provided by Sterling Systems & Controls, which includes:
Main batching process
Drop mill process
The HMI Mixing screen is an extension of the Main Batching screen (shown here) showing all of the equipment associated with the Mixer. From the Mixing screen, the user has the capability to control the mixer’s RPM on the formula being run, like on the Main Batching Process screen, but with the additional capability to view the status of and control the related equipment shown on the left side of the Mixing screen. This screen also offers a data trending screen that allows the user to view the Batch Temp, Mixer Torque, Mixer Power, and Mixer Speed for the last twenty hours.
Added to this Rubber Compounding automation process control system is Sterling Systems & Controls WebCentral supervisory control application. WebCentral™ is a software package that allows corporate users to access the database of a Sterling Systems & Controls, Inc. process control system, such as the mixer process control mentioned above. This can be used to enter and manage all configurable items remotely. Sample WebCentral pages for the mixing process are shown here.