Process Description

Plastic pellets of various components are blended together in specific proportions prior to entering the melting and forming process.  The exact composition of this blend is critical in the final product composition and quality.

Plastic pellet blending is accomplished using two methods.  One method is to meter individual components into a receiving hopper known as batch blending.  The receiving hopper is often mounted on a load cell systems and each component is metered sequentially in to the hopper to a preset target weight to prepare the batch for processing.

Alternately volumetric devices can be used to feed all of the compounds at the same time.  The compounds are mixed as they enter the receiving hopper during the transport phase.  Volumetric feeding can be timed to estimate the weight of the batch or can be fed in to a receiving hopper on load cells.

Consistency in the composition of the batch is a key element in quality control of the final product.  The ideal solution to this process would be to use a continuous weight-based feeding device to precisely blend the mixture in to the melting and forming process. 

Comptrol’s 25F Momentum Feeder is capable of delivering a controlled flow of material from a bin or silo at an accuracy of-/+ 0.5% of full scale over a wide operating range.  When connected to Comptrol’s Blendview  system, a number of the 25F Momentum Feeders can blend to a specific recipe the final product straight to the forming process.  This will produce a consistent blend based on precise weights and improve the final product’s consistency and quality.

Advantages of Weight Based Blending with 25F Momentum Feeders

1. Weight-based blending significantly improves the quality of the final product composition.  It produces a blended product with the correct composition of raw material by weight.  This is a key driving quality issue for weight based blending.

2. Repeatability achieved using weight-based technology versus volumetric technology produces better final product consistency.

3. In applications were one of the components is significantly more expensive, weight based blending ensure that there is no excessive waste of expensive materials.

4. High throughput processes are requiring continuous inline blending to meet production rates that are not achievable economically using batch blending approach.

Features Critical to Application.

1.  25F Momentum Feeder can be installed beneath silo or bins with as little as 18 inches (460 mm) of head room.

2.  25F Momentum Feeders can directly feed a mixing or transport conveyor with the precise weight based blend.

3. 25F Momentum Feeders can be installed in unheated environments since they do not require compressed air for operation.

Competitive Advantages

1. Cost comparable to variable speed volumetric device but with strength of weight based feeding.

2. Less expensive than loss in weight feeding technology but with similar results.

3. Feeders have a 10:1 turn down ratio.

4. A number of models are available from 4 tones through to 80 tones allowing a wide range of feed rates from a minimum of 800 lb/hr to a maximum of 160,000 lb/hr.

5. The feeders can be interface to a PLC application for control of recipe blending directly through standard I/O or to a SCADA system using a DDE link.

6. Feeder can be installed with a BlendviewÔ  system as a stand-alone blending system.  BlendviewÔ is capable of storing, controlling, tracking and reporting blends produced.  In addition, it monitors the current operation providing the operator with live feedback on the blending operation.

Target Customer

1. Stretch Film/Thin Film Producers

2. Plastic Extrusion Companies

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Copyright © 2003 Comptrol Technologies Inc.
Last modified: May 19, 2004