Introduction Due to its excellent material characteristics and its outstanding price / performance ratio, until today PVC is the most used material worldwide for pipes or profiles made from plastics. As the market is very competitive manufacturers of RPVC/UPVC pipes or profiles have been exposed to increasing pressure on prices and costs for years. At the same time higher and higher demands are made on the product quality. So, lets have a look at HOW Neoplast’s Conical Twin Screw Extruders are helpful in producing better quality PVC Pipes or Profiles !!!

Design of Conical Twin Screws 1. Feed Zone 2. Plasticizing Zone 3. Compression Zone 4. Vent Zone 5. Metering Zone

Importance of Each Zone Feed Zone: Feeding and pre-heating of the material. Plasticizing zone: Heating and agglomeration. Compression Zone: Sealing-off of vent zone in support of the plasticizing process.

Importance of Each Zone Vent zone: Degassing & venting of the melt. Metering Zone Completion of melting, homogenizing & outputting of melt.

Advantages of Conical Screws Larger L/D Ratio: From the illustration, it is easily understood that the 45/97mm conical screw, for example, discharges like a parallel 45mm, feeds like a parallel 97mm & matches the gearing of a parallel 110. Dia 110 mm Dia 97 mm Dia 45 mm

In other words, A Conical 45mm extruder can match the output of a 65 mm parallel model, the intake section has the surface area and gentle plasticizing of a 100 mm parallel, while only the metering section has the excess friction and shear of a 45 mm parallel. The small screw front face results in a low axial force on the screws. The wide screw shaft center distance at the rear - allows space for large thrust bearings and a simple, sturdy, distribution gearbox.

Gentle & Efficient Plastification The screw surface area in the feed zone is considerably larger than that of the parallel screw offering a same output. As a result, transmission of heat energy and the plastification in the feed zone is much more efficient. Moreover due to larger feed zone, plastification work is spread out over a larger section of the screw. F=1250 cm2 F=490 cm2

Comparison of the meshing Surface Area Vent Zone Feed Zone Compression Zone Plastizing Zone Metering Zone Conical Parallel From above graph, if is evident that – the meshing surface area is higher for conical twin screws compare to the same diameter parallel twin screws hence homogeneous and better melt quality.

Optimized Screw Geometry Digressive Pitch in the feed & Compression Zone ensures the continuity of compression. Hence in Conical Twin Screw extruder, there is no pressure peaks, which is in favour of a prolong life of the Gear box. In the metering section, the meshing surface area of the conical screws is less than that of parallel screws, giving lower shear energy input, and in addition, the shear rate is further reduced because of the conical screw design.

Continuity of Compression From the graph, it can be derived that by using conical twin screws, compression continuity can be maintained throughout the length of the screw and hence better quality of the end product.

Life of Gears The pinion gears of conical twin screws last much longer than those of parallel twin screws. The reason is – the center distance is much larger, the gear pinions are much larger in diameter. The life of gear pinions increases with approximately the cube of the diameter ; which enhance reliability.

Exceptional Pressure Build-up & Thrust absorbing Capability The metering zone of NCMT series extruder is designed for the most efficient pressure build-up. In comparison with other designs, the energy input required for pressure build-up is lower by about one third so that the danger of overheating is reduced dramatically. The axial forces arising are easily absorbed by heavy-duty thrust bearings.

Higher Output with less stress on the material : The relative small diameter of the conical screw in the discharge zone keeps friction to a minimum and hence conical twin screw are claimed as the ideal choice for the sensitive materials like C-PVC. In India, the biggest & pioneer manufacturer of the C-PVC pipes, M/s. Astral Polytechnik, is using only Conical twin screw extruder and still adding on more machines of NCMT series conical twin screw extruders – An ample proof of absolute customer satisfaction.

Specific Throughput : A high specific output means a high material throughput at low screw RPM means low Power consumption. Moreover, low screw speeds required to achieve specific output results in low shear stresses, gentle plasticizing and low screw wear.

Ease of maintenance The conical twin screws are taken out from the backward direction. The barrel is simply moved to the side. When active screw core thermoregulation is used, the coupling elements for the heat transfer oil lines remain attached to the screw tappets & oil spillages cannot occur. Higher productivity – by time saving.

The Cincinnati Advantage The new NCMT series of Conical Twin Screw Extruders introduced by Neoplast is the FIFTH Conical machine generation developed under technical collaboration with M/s. Cincinnati Extrusion, who have an experience of designing more than 6000 PVC Processing Extruders. Our customers benefit from this experience by way of enormous processing latitude, extreme life & the most favourable price/performance ratio.

The Cincinnati Advantage & Neoplast’s Promise NCMT series extruders are designed to ensure a higher return on your investment, i.e. Outstanding cost-effectiveness Higher output & Excellent product quality. Neoplast offers Conical Twin Screw Extruders for RPVC pipes, CPVC Pipes, SWR Pipes, Engineering Profiles, Furniture Profiles & Building sections…

Twin Screw Extruder with Conical Twin Screws The conical idea - Brilliant when it was born, and still brilliant today… So, Lets have a look at the key features of NCMT series Extruders…….

Material feed Hopper Feeding Metering Unit For easy flowing dry-blends with constant quality & apparent density, a sliding hopper is used which allows for three positions Production, Shut-off & Emptying Metering Unit Metering units enable accurate adjustment of the screw filling factor and plasticizing capacity. They are ideal for materials with the possibility of density variations & particularly suitable for the processing of regrind and pellets.

Threaded Barrel for easy mounting of tool The barrel is made from Imported Nitro Alloy steel with hardness of 50 HRc, which in turn undergo Two-Stage Gas Nitriding to achieve Final Hardness of 70 HRc.

Barrel Heating Cooling system The design of the barrel heating and cooling elements (air power cooling), and optimal locations for the barrel thermocouples, ensure accurate temperature control. The large surface area cooling elements combine the advantages of high efficiency and minimal maintenance.

Screw and Barrel Life With a novel surface coating technique, Neoplast is offering extruders with exceptional lifetimes. The wearing layer achieved with this technique is denser, more compact and less brittle than conventional coatings applied with customary methods. We guarantee for extreme abrasion resistance.

Venting Unit The venting port on the barrel is coupled to specially designed efficient venting pump for effective removal of air and gases generated during the plastification process

Internal Screw Core Thermoregulation – Cimitherm This system is based on the heat pipe principle. Heat is transferred back from the hot screw tip to the cold feed zone, resulting in considerable energy savings. Cimitherm is a self-regulating system which adjusts to changing heat transfer requirements & doesn’t require any kind of adjustment.

Top - Performance Control Panel It contains the complete sequencing logic, dual display PID temperature controllers for all extruder and die zones, and provides for interfaces with upstream and downstream equipments used in extrusion. To guarantee optimal ease of operating, all set-point and actual values along the extrusion line can be processed, visualized and evaluated at a central location.

Down Stream Equipments For Pipe / Profile Extrusion / Palletizing

Die Head Optimized for PVC formulations of tomorrow…. Production flexibility by a modular system of basic heads, adapters and die sets Large head volume for a smooth inner surface of the pipe / profile High compression ratio to prevent spider lines & streamlined spider legs Automatic thermal centering for very tight wall thickness tolerances Corrosion-resistant hard chrome plated surface

Vacuum Sizing Tank For Pipe Extrusion Various models to suit outputs from 50 to 500 kg/hr. Vacuum calibration chamber length 3 to 6 meter, fully or partially under vacuum as per requirement. Individual headers for water & vacuum connections Uniform water spray with specially designed nozzles and inline water filters. Single or dual strand. After spray cooling, back or front seal supporting disk, guide rollers can be provided.

Vacuum Calibration Table For Profile Extrusion Various models to suit various profile shapes or number of calibrators requirements or output from 50 to 500 kg/hr. External tank for water drainage Individual headers for water & vacuum connections All water wetted contact parts – SS 304 Single or dual strand. Vacuum pump with higher vacuum efficiency

Haul Off Various models to suit various pipe or profile size or shapes with different throughput capacity. Precision clamping for to avoid distortion of product, slip less pulling of extrudate, stronger driving mechanism, step less or synchronized adjustable speed Two belts, three belts or multi belts Depends on product size, shape or output; belts or chains with customized pad shape

Cutting Saw Various models to suit various pipe or profile size or shapes with different throughput capacity. Different cutting system available like chopping cutter, saw cutter, Planetary saw cutter with optional chamfering provision. Specially designed cutter for profile cutting All cutters are with safety guards Optional saw dust collection unit

For Pelletizing Applications Pelletizing Head Suitable for soft & rigid PVC formulations Die mountings available for single or twin screw extruders & suitable to output ranges from 40 kg/hr to 800 kg/hr. Auto adjustable Spring loaded cutter blade Adjustable air cooling through efficient blower Guaranteed uniform pellet size

Pellet Cooler Suitable to cool soft & Rigid PVC pellets Adjustable vibration, easy cleaning & low noise Dust separator for dust free pellets Completely cooled pellets with reverse air cooling Compact, space saving & versatile system

Applications

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