Mixing Nozzle Benefits

 

The most common use of mixing nozzles is to improve the distribution of color concentrates, improving the appearance or reducing the scrap rate due to poor color distribution.  Mixing nozzles can provide benefits often overlooked that improve the quality of the molded part as well as improve the performance and output of the machine.

Improved Overall Cycle Time- Overcoming mixing problems by use of the machine's back pressure slows the screw recovery and in many cases increases the total cycle time.  Increased temperature settings often result in improved melt quality.  But it increases the required part cooling time.  The use of an effective mixing nozzle will allow for faster screw recovery and lower temperature settings that results in faster cycle times.

Part Surface Finish- Variations in the melt temperature of the plastic from the layered flow effect in both the barrel and nozzle can result in "Seams" or "Flow Lines" in the molded part.  Blending the molten polymer just prior to the mold improves thermo homogeneity and results in improved flow into and through the mold.

Increased Levels of Regrind- The uneven size of regrind or reprocessed materials often presents process issues, limiting the amounts or making any level of these materials unusable.  Mixing nozzles allow the use of, or increase the usable levels of, regrind.

 

 

How Mixing Nozzles Work

 

Disruption of the laminar flow through the nozzle creates turbulent flow changes forcing the layers of plastic to collide into one another.

There are two main designs that create this turbulent flow:

A) Designs that use increasing and decreasing pressure flow moving the polymer into areas of greater volume then forcing the flow through areas of lesser volume.  The MX units are examples of this type of flow action and are recommended for unfilled stable polymers for the distribution of non-fiber additives like color.

B) Designs that displace the laminar flow layers, moving the center flow to the outer edges and back to the center.  Generally not as effective as pressure designs in their blending action, these designs are much gentler allowing their use on shear sensitive or materials with fiber additives.  The MS units are examples of this type of action.

 

 

Proper Sizing - Injection Pressure

The effect of flow rate on injection pressure is based on the flow volume through the mixing elements.  The proper size unit will create little, if any, pressure drop through the mixing element.  Each element design offers recommendations as to the machine's shot size limitations for the element.

If pressure drop creates a molding problem, moving to a different design in the same size unit with a higher flow volume may solve the problem.  If not, a large size unit may be required.

 

Literature Library

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M Series Brochure

MX-1000

MS-2000

MS-4000

MC-4000

MX-4000

MG-4000

MX-5000

MX-6000 & MX-7000