Conical twin screws extrude difficult materials

Conical twin screw extruder is offered to process high-volume, low-shear, homogenous melts - especially with problem materials - and handles high fiber loading and natural fiber blends.

Proven solution to difficult materials and blends, the Cincinnati Milacron TC86 uses world-leading large conical twin-screw technology to bring unique compression and low-shear mixing capability to an unmatched material processing range.

Particularly effective at woodfiber/plastic composites (WPC) with up to 70% fiber loading, the TC86 delivers high-output homogenous melt from blends of natural and synthetic fibers, heat- and shear-sensitive thermoplastics, recycled plastics, coupling and nucleating agents, pigment and other additives.

At NPE show, Milacron Extrusion Systems showed a Cincinnati Milacron TC86 conical twin and Akron Milacron PAK200 single-screw extruder configured in a cell for co-extrusion of wood composite handrail using Strandex tooling.

The TC86 extrudes the fiber composite handrail core, which is then encapsulated in a weatherable, pigmented polymer matrix delivered by the PAK200 to produce a UV stabilized capstock layer with colors designed to complement the deck board.

Milacron's Extrusion Systems Business exhibit featured a 12ft x 12ft deck manufactured with Cincinnati Milacron twin-screw extrusion technology by a licensee of the leading-edge Strandex WPC process.

Deck components include wood-look, pre-colored deck boards and vertical posts, and color-matched co-extruded post caps and railing.

Smooth to the touch, the co-extruded parts look and feel expertly finished, but will not flake or peel over time like stain or paint.

Milacron originated large conical twin-screw extruders and is the leading global supplier with a complete conical product line.

Created using proprietary engineering and machining technologies, the TC86's large diameter screws - 176mm tapering to 86mm (6.9in to 3.4in) with 27:1 LD ratio - optimize feed zone surface area for faster, more uniform heat transmission from screws to material.

Tapered screw design allows a larger feed zone for 'fluffy' light bulk density material and applies a natural compression (large volume to small volume) during processing.

Materials are subjected to both dispersive and distributive mixing to achieve a fully homogenous extrudate prior to devolatilization.

Deep flight channels and tight intermesh clearances between the conical screws optimize material pumping characteristics while reducing shear forces.

High torque at low screw speed (33 rev/min) enables gentle low-shear melting and mixing, yet gives efficient plasticizing in Vinyl extrusion.

The gentle, thorough mixing minimizes undesirable fiber breakdown and achieves excellent fiber distribution when processing wood and natural fiber composites.

Small exit diameter reduces rotational shear and screw thrust, while increasing pumping efficiency into the die area.

The conical twin-screw action generates positive pumping pressure for quality extrusion of viscous rigid PVC and WPC material, particularly the higher head pressures needed for engineered profiles with thin walls and small die openings.

Consistent, controllable process heating and cooling, critical to the extrusion process, are accomplished by supplying the proper balance of mechanical induced heating by the screws and externally applied energy.

The TC86 maintains consistent, controllable process heating and cooling with four barrel zones with a total barrel heating capability of 54kW.

Three of the barrel zones are provided with cooling, using a water-cooled system to dissipate heat.

An individual temperature control zone for screws provides a heat capacity of 9kW to 18kW, depending on the application.

Eight die zones (including entry adapter) are provided with maximum heating capacity of 51kW.

Unitized construction mounts all components on a single base for fast, easy installation with space-saving compactness - 196in L x 55in W x 104in H (5000 x 1400 x 2650mm).

The design simplifies maintenance with easy access to all sub-components.

Screws can be removed from the rear of the machine without disturbing downstream equipment, and all base sub-systems are accessible via easy slide-out trays released via a simple trigger mechanism.

The compact TC86 delivers outputs comparable to a 110-115mm parallel twin screw extruder, while providing space savings of 15% and more.

The conical twin gives these maximum output rates for various materials as follows.

* Rigid PCV pipe or sheet - 2000 lb/910kg/h.

* Rigid PVC profile - 1200 lb/550kg/h.

* Rigid PVC siding - 1700 lb/770kg/h.

* Rigid PCV pelletizing - 2000 lb/910kg/h.

* Flexible PCV pelletizing - 2200 lb/1000kg/h.

* Wood/plastic composite - 1600 lb/725kg/h.

The TC86 extruder comes standard with the Cincinnati Milacron/Mosaic touch-screen control with 15in (381mm) LCD screen, self-diagnostics, and Ethernet TCP/IP connectivity.

Proven Milacron software provides full production control, including SPC monitoring and analysis, process alarms, slaved co-extruder speed control, and process 'recipe' storage and call-up.

Operators are provided with on-screen control panels, instant-access information screens with full-color graphics, and multi-language capability.

* About Milacron Extrusion Systems - Milacron Extrusion Systems offers a comprehensive range of conical twin-screw extruders meeting every requirement from lab/development work to precision profiles and high-output shape production.

Models are available with 35mm, 50mm, 55mm, 65mm, 80mm, 86mm, 92mm and 96mm conical screws.

Proven champs at quality production of WPC shapes for decking and rails, Cincinnati Milacron conical twins bring superior versatility, melt homogeneity and process control to emerging applications for WPC profiles and structural components.

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