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July 1, 1999

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Product News - Blender Is Designed Exclusively For Extruders

Blender Is Designed Exclusively For Extruders

pn4-799.jpgExtruders looking for accuracy in blending materials now have a blender that has been designed specifically for them. The new XB extrusion batch blender is suitable for use on mono- and co-extrusion lines producing film, sheet, pipe, tubing, profile, wire and cable.

The unit is claimed to provide accurate gravimetric blending and tight control over blend consistency and weight per length of extruded product. In fact, the manufacturer says the blender provides continuous mixing of blended material to the extruder with 0.1% accuracy.

The XB can be supplied with yield-control functions that provide adaptive control of extruder take-off speeds, reducing start-up scrap, eliminating over-feeding of expensive ingredients, saving material and increasing yield by up to 4%.

The yield-control functions start with target values entered as weight per hour, weight per length or thickness. In mono-extrusion, the control monitors haul-off speed, comparing the rate at which product is coming off the line against the weight of material being fed by the blender to the extruder.

If the extruder throughput changes, due to screen build-up or a change in material bulk density, the control automatically adjusts screw speed to compensate.

While conventional open-loop controls can allow for swings in extruder throughput of 4% or more, the XB blender's yield control keeps fluctuations to within ±0.5%. This allows extruders to 'dial down' weight per length with confidence, knowing they'll still be making on-spec product even if material or processing conditions change.

By cutting waste and eliminating overweight product, extruders can increase yield by 3 or 4%, according to the company. At this rate, a typical processor, with an extruder running 600 lb of LDPE/hr at 6000 hr/yr, could recover the cost of the blender (starting price is $25,000) with yield control in less than seven months.

In co-extrusion, the manufacturer's LRC-8000 layer ratio control system, working in conjunction with XB blenders, can monitor haul-off rates and adjust the speed of up to five extruders to ensure that the relative amount of material in each coextruded layer remains constant.

The standard XB system blends up to eight primary and secondary ingredients at maximum throughputs ranging from 600 to 4400 lb/hr. Ingredients are metered into a weigh hopper that uses gravimetric technology to ensure that recipe percentages are accurate to within 0.1%. When the batch is complete, it drops into a reverse-auger continuous mixing chamber that is said to ensure a uniform blend and to prevent separation.

The control panel has a large, high-visibility display. On-screen menus lead operators through keypad entry, storage and recall of up to 60 recipes. The XB control also provides real-time production status reports, roll, order and shift summaries. Reports include total weight per component, total length, average throughput, customer and  material codes and time and date.

Pittsburgh, PA

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