Screws

At Reiloy Westland Corporation, we manufacture all kinds of screws ... custom screws for extrusion, blow and/or injection molding screws, mixing screws, even rebuilt screws. If you need a screw for your project, we can help.

Overview:

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Injection Molding Screws

General Purpose . . . Specifically Tailored

The selection of the proper injection molding screw design for a given processing environment should be based on the resin or resins to be processed. There are no standards in the plastics industry for a general purpose injection molding screw design.

The OEM general purpose injection molding screw designs are each different. A processor must be diligent in understanding an OEM GP design and how it will affect the way the resin melts. Each design will process differently.

In an injection molding plant utilizing machines manufactured by different OEMs, more than likely there will be jobs that run better on some than others. Due to the different OEM GP designs, obtaining the proper residence times and shear rates to achieve an homogenous isothermal melt quality on each machine may be difficult to do. Some resins cannot tolerate high shear rates, higher temperatures and/or longer residence times.

The injection molding screw geometry needs to match the resin. The more the melt and shear curve of a material(s) is accommodated, the greater the opportunity to achieve a high quality, homogenous isothermal melt quality.

Reiloy Westland Corporation has a strong reputation for developing custom – general purpose – injection molding screw designs tailored to making the same job run similarly on all machines in a particular plant.

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Custom Screws

Designed for your needs . . . By our standards

The selection of the proper screw for a given plastics processing application (be it an injection molding screw, extrusion or blow molding screw) is critical to its success.

Reiloy Westland Corporation has documented cases where customers have improved production rates (cycle times) by more than 25% by simply changing to an improved screw design. In other cases, part reject rates have been reduced from more than 5% to less than 1/2 of 1% by utilizing a custom designed mixing screw. These facts alone illustrate the importance of the screw and its design to efficient processing performance.

The Eagle can be designed to process most resins manufactured for your application and is a proven winner in extrusion, blow molding and injection molding environments. If a number of different resins are being processed with the same screw, that screw should be designed to optimize its performance, allowing for all the materials to be processed with reasonable success.

Reiloy Westland Corporation’s engineers work hard to gather the information needed to design the screw most suited for your particular processing situation. All the variables of screw design are discussed on the custom designed screw page under services and in the screw design processing tips section. When we manufacturer a new injection molding screw, extrusion or blow-molding screw for you, our design engineering capabilities are provided to you at no additional cost.

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Eagle® Mixing Screw

Faster . . . More precise

The Eagle® Mixing Screw is a low shear plastics mixing screw that provides the processor with outstanding color mixing. In addition, many of the processors using the Eagle® have experienced improved production rates, both in recovery rate and throughput (pounds per hour).

Although the design of the screw and mixer are modified somewhat for different resins, the Eagle® has successfully processed commodity resins as well as engineering grade resins.

The Eagle® Mixing Screw has:

  • Improved production rates by more than 25%
  • Reduced part reject rates from more than 5% to less than 1%
  • Reduced the amount of color concentrate required to achieve optimum color mix from 4% to 3%

Whether you need an injection molding screw, or an extrusion or blow-molding screw, the Reiloy Westland Corporation Eagle® Mixing Screw is a proven winner.

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Eagle® Barrier Screw

The Ultimate Processing Solution . . . 

The Eagle® Barrier Screw combines the advantages of the Eagle® mixer with the plastic melting efficiency of the barrier screw design. Its “solids and melt” channels provide the effective melting of all resins, especially the “hard-to-melt” crystalline resins.

The material is then conveyed through the mixer to produce a high quality, isothermal melt. The Eagle® Barrier may be the answer for processing difficult materials, whether using an injection molding screw or blow molding screw, or extrusion screw.

The design of the barrier portion of the screw and the mixer itself is dependent upon the type of material being processed and whether the application is injection molding, blow molding or extrusion. The Eagle® Barrier has been Reiloy Westland Corporation’s most effective design for all types of extrusion applications and has worked effectively in injection molding high melt index materials.

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Extrusion Screw

Get With the Flow . . . 

Practically all thermoplastics can be processed by extrusion, but in order for the extrudate to maintain its shape until solidification, extrusion grades require a higher molecular weight associated with higher viscosity and melt strength. Melt Index, which relates to strength and flow behavior, is lower for extrusion materials than for injection materials where the easier flowing material is necessary to fill cold molds.

A major difference between injection molding and extrusion relates to the time that the material has to melt. In injection processing, a pellet typically has 2 to 5 minutes from the time it enters the barrel from the hopper until it exits the nozzle end of the screw. This residence time allows the resin to heat, soak and absorb conductive heat energy (in addition to shear heat) as it works its way up the screw.

In extrusion, a pellet is typically allowed less than 2 minutes (and in some cases, less than one minute) to travel from the feed pocket of the screw to the screen pack.

The most obvious difference between injection and extrusion screw designs is the length of the flighted surface, or the L/D ratio. Where a 20:1 ratio is common for injection molding screws, 24:1 is considered a standard L/D ratio for extruder screws- and many have ratios of 30:1 or more. Lacking residence time, extruder screws must compensate by keeping the material on the screw for a greater length.

Extrusion screws tend to have greater shear capability, resulting from the increased use of barrier designs and the utilization of a grooved feed zone in the barrel. A shallow feed zone channel in the screw in combination with a grooved feed section in the barrel also creates shear and a more aggressive feeding of the material.

Reiloy Westland Corporation has been successful in using the Eagle™ mixer in its extruder screw designs.

 

→Download Reiloy Westland Product Handbook

 

 


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