Maguire: New blender-based yield control

Gravimetric blenders powered by new LineMaster (TM) software from Maguire Products, Inc. raise extrusion yield control to a new level of simplicity and accuracy and enable processors to enhance product consistency, save on raw material, shorten setup times, and reduce scrap, the company announced at NPE 2003 (Booth 9101). The yield control system has already been used commercially-see accompanying news release on blown film producer Coextruded Film Technologies for an example.

The new technology makes advanced yield control available without need for large, complex, and costly hardware systems such as loss-in-weight blenders, according to B. Patrick Smith, vice president of marketing and sales. ‘It is now possible to achieve consistent accuracy in material consumption and product quality using nothing more elaborate than the Maguire (R) Weigh Scale Blender,’ Smith said. ‘The simplicity, ease of use, and low cost of this system have made it by far the most widely used blender in the world, yet its precision and reliability also make it eminently suitable for governing the entire extrusion process with unvarying accuracy.’

The LineMaster system combines advanced blender controller software with Maguire’s Gravimetric Gateway (TM), or ‘G2,’ software for integrating blenders in a computer controlled network. This integrated system makes it possible for the blender controller to adjust two critical process parameters simultaneously.

In standard extrusion control, the blender controller automatically adjusts only one parameter-extruder speed-to achieve a manually set target throughput (weight of raw material processed per unit of time). Somewhat more advanced is a basic type of yield control, in which the controller once again automatically adjusts only extruder speed, but does so by first calculating target throughput on the basis of two manually set parameters: target line speed (length of product per unit of time) and target yield (weight per length of extruded product). In contrast with these systems, the LineMaster system simultaneously adjusts both throughput and line speed to achieve target yield, providing complete control of the process.

‘Until the advent of our LineMaster technology, the vast middle ground of extrusion processors have had to choose between cumbersome and costly loss-in-weight yield control systems or very basic forms of extrusion control,’ said Smith. ‘Now any extrusion processor armed with our software can lock in desired product yields via simple connections between a standard Maguire blender and the extruder-screw and hauloff-speed controls. Once set up, this system quickly establishes control over the amount of material per length of product, without need for prolonged setups in which operators must optimize speed settings.’

Three yield-control configurations are possible with the LineMaster system, in each of which 1) the blender is connected to the downstream speed control and automatically adjusts it to maintain line speed; and 2) the desired yield is entered by the operator. The three configurations vary according to which other parameter is to be set as a target by the operator:

▪ Line speed. Blender calculates required extruder throughput based on pre-set line speed and yield and automatically adjusts the extruder speed control.

▪ Extruder throughput. Blender calculates required line speed based on pre-set throughput rate and yield and automatically adjusts the extruder speed control.

▪ Extruder speed. Blender calculates required line speed based on pre-set extruder speed and yield and automatically adjusts downstream speed control.

Gain-in-Weight Blending and Advanced Software Are Keys to Precision Yield Control

Mounted directly over the throat of an extruder, a Maguire (R) Weigh Scale Blender controls raw-material metering by weighing each recipe batch. Recipe ratios can be varied from 0.01 to 100% with simple thumb-wheel settings. In operation, the blender sequentially dispenses all ingredients, in their targeted recipe proportions, from separate hopper bins into a weigh chamber (hence the term ‘gain-in-weight’). From the weigh chamber the batch falls into a mixing chamber, then is fed directly into the extruder. In subsequent batches, small corrections are made automatically. Added to this precise information about the weight of each batch (in grams) is information about the exact time (in tenths of a second) required for each batch to be consumed by the process.

These data enable the blender to adjust the speed of the extruder screw to maintain a targeted throughput rate. To carry out coordinated, simultaneous adjustments of both line speed and throughput to ensure maintenance of targeted product yield, the blender must be used in combination with G2 software.

Leave a Reply

You must be logged in to post a comment.