The success story of gravimetric batch blenders in the plastics processing industry began more than 10 years ago.
The success story of gravimetric batch blenders in the plastics processing industry began more than 10 years ago. Motan contributed significantly to its success, and with "IntelliBlend" technology, the specialist for material handling reveals an inside look to its workings. Scott Harris, Vice President of Sales for Motan Inc., shares the details. Mr. Harris, what was the trigger for the development of gravimetric batch blenders within the plastics industry? Scott Harris: The basic process to blend ingredients in a container placed on a scale in accordance with a predefined recipe was not just common practice to the plastics industry. Mainly, this procedure served to provide centrally a large quantity of blended material, to transport it to the production hall and to feed the processing machine. Especially for the injection molding industry, this process was cheaper than continuous operation of a gravimetric system at each machine. The real innovation of the first batch dosing and blending units was the compact design as well as the favorable price. Gravimetric blending on the machine became more and more popular with injection molding, and they frequently replaced volumetric units. How can you explain the success of gravimetric systems? Scott Harris: The definition of the problem clearly came from the market. Due to economic constraints, our customers were forced to bring more and more regrind into the production process. Nevertheless, emphasis was put on a consistent product quality. Further development of our units as well as a high degree of recipe accuracy, repeatability and detailed report functions for data collection were indispensible for meeting the ever-increasing quality requirements processors were facing. Today, our units are self-calibrating, easy to operate and maintain. What has improved since Motan introduced their gravimetric blender into the market? Scott Harris: On one hand we simplified operation and handling. On the other hand we improved accuracy and reliability of the units expanding at the same time their field of applications. A very important point was the smooth integration into the Ethernet network technology which contributed considerably to today's success on the market. An improved performance adaptation through self-optimization and intelligent process adjustment together with stainless steel parts in contact with the material, complete the picture. One simply can't imagine the production processes of injection/blow molding and certain extrusion applications without gravimetric batch dosing and blending equipment. What are the bestselling features in this field? Scott Harris: First of all, our GRAVICOLOR Blenders are capable of processing throughputs of up to 2000 lb/h without any problem. To achieve the most precise blending accuracy and to avoid bridging, cone dosing technology is used - except for very small quantities. With very small quantities the Motan patented micro dosing technology is used. If material separation is not a problem when conveying materials with different densities, central mixing stations for feeding several machines is the most economical solution. Thanks to the innovative vibration management of the GRAVInet control, the units can be operated directly on fast cycling injection molding machines. Quick material changes and easy cleaning are achieved through removable bins and sight glasses. All controls are easy to operate via the WEBpanel, a color graphic display with touch screen. Nominal and actual process parameters with current throughput values are displayed. Stored recipes can be retrieved directly via touchscreens and for unlimited use. When does Motan's IntelliBlend technology come ?into play? during the process? Scott Harris: The new generation of the GRAVInet control is an intelligent, self-optimizing system targeting to reach the highest possible blend accuracy in the running batch. Even before the batch is created, IntelliBlend applies the best start up conditions. This sounds like high-precision. How does IntelliBlend reach this accuracy? Scott Harris: The GRAVInet control automatically determines the best order for all components of the set recipe. During metering of the individual components, the metering rates are permanently updated and bulk weight variations as well as material-dependent flow properties are taken into consideration. IntelliBlend immediately compensates for unavoidable dosing tolerances by exact adjustment of the following component blends. After completion of each batch, IntelliBlend corrects the remaining deviation in the following batch. This means that IntelliBlend controls regrind dosing automatically as well? Scott Harris: Right, by adjusting the regrind, IntelliBlend meets the most demanding requirements in injection molding and extrusion. In a typical injection molding application with regrind transported from the granulator, a shortage of regrind in the batch is automatically replaced by virgin material and the corresponding quantity of masterbatch. In extrusion, the regrind material which is always available and may not be lacking as an important component is automatically added to the masterbatch and the virgin material with high accuracy. Can the controls be networked or can the customer log important process data? Scott Harris: GRAVInet controls having an Ethernet interface can be networked with other dosing and blending units as well as controls for drying and conveying. The controls can either be operated with a local operating unit, a WEBpanel or a central PC. For example, via Motan LINKnet all important process parameters of Motan units can be queried centrally and exported into other programs with the corresponding interfaces. In order to master comprehensively the issue of data logging we developed the GRAVIreport software: a program which is used on the Microsoft® Windows platform ? in particular under Windows XP, 2000 or NT. It is a message, acquisition and report program for up to 252 GRAVICOLOR units. Report functions concerning production and material data ? either on a local or superior level, for example, to data administration systems - can be expanded without problem. Can the GRAVInet control be integrated into the conveying process? Scott Harris: Yes, absolutely, because all GRAVICOLOR units can be equipped with an integrated convey control which controls up to seven hopper loaders, a blower station as well as a standby blower - if required. What is the advantage to this? It allows for our customers to operate all connected hopper loaders directly from the blending unit. Does Motan's IntelliBlend technology offer your customers a measureable savings in their annual expenditures? Scott Harris: Yes, it does indeed, because the necessity of overdosing for a better color consistency is omitted. Therefore, especially when masterbatch is expensive, the amortization period can be within three to four months due to savings in color, working hours and shorter production downtimes at color change. In addition, when developing the units we emphasized the importance concerning its easy operation, simple service, cost effectiveness, reliability and durability.