Advantages of Single Screw Extruder

     Advantages of Single Screw Extruder

The significant advantages the Single Screw Extruder with barrier according to the present invention has the advantage that the pressure build-up capability is improved. Compared to the known Twin Screw Extruder it is not necessary any more to build up a very high pressure in the so-called feed zone as to enable a predetermined lower pressure at the end of thegravimetric feeder With the according to the present invention it is possible to substantially reduce the pressure between the feed zone and the melting zone. This in turn results in a reduction of wear of the gear pump in the transition area between the feed zone and the melting zone since it is operated with lower pressures.

(1)In a preferred embodiment the barrel comprises several grooves being equally spaced apart in circumferential direction which grooves extend preferably parallel to the longitudinal axis of the barrel. This has the advantage that the process of matching the grooves is simplified compared with the groove helically arranged.

(2)Due to the pressure reduction in the area of the feed zone it does not have to be constructed any more as complicated as in prior solutions and does not have to be provided with cooling means and a “heat separation” towards the heated melting zone. Advantageously, the feed zone and the melting zone may therefore be formed individually.

(3)In a further preferred embodiment the width and/or the depth of the groove varies in a longitudinal direction, preferably the grooves depth decreases towards the downstream end of the melting zone section, preferably to zero.

This has the advantage sheet production extruderthat the groove extends continuously without Single Screw Extruderany break along the feed zone and melting zone thereby further improving the output and the pressure build-up. 

In a further preferred embodiment of the invention at least one groove is provided also in the barrel inner surface (innerwall) in the area of the feed zone section, the groove extending parallel or helically relative to the longitudinal axis. Preferably, the groove in the area of the feed zone section leads into the groove in the area of the melting zone without transition. Preferably both grooves have the same lead angle.

What are the key differences between PVC and PE pipes and fittings?

      What are differences between PVC and PE pipes ?

PE  benefits

• Chemically inert, no off gassing or leaching.
• Flexible, can be pulled to around corners to eliminate fittings.  This give a better water flow, and saves time and money.
• Can freeze without bursting
• Is rated to last at least 200 years
• No glue to add poisonous vapors or soldering to reduce risk of fire.

Negatives

• Pipe and fittings are reduced in diameter, may need to up size for good flow.
• Pipe has no rigidity.  Must be supported it's entire length.
• Need special tools to install.

PVC and CPVC "for hot" benefits

• Any can do it, all you need is a cutter to assemble.
• Very cheap and you can get it anywhere.
• PVC is full bore, but only for cold water.

Negatives

• All sorts of leaching flavors and chemicals into water.
• Rated for 20 years, this is an over statement.
• Glue needs to cure for 24 hours before charging with pressure.  Most do not do this, but that is what is instructed.
• Freezes and bursts quite quickly.
• Some plumbers will not attach to it for it has a high failure rate.

How to Make Plastic Pipes

             How to Make Plastic Pipes

Plastic has largely become the material of choice for pipes. Its flexibility, ease of bonding, lighter weight than iron and steel and lower cost than copper has made it a common choice. Pipe is generally produced by an extrusion process. Although this process may vary in actual operating conditions (temperatures, pressures, extrusion rate) based on the type of plastic used, diameter of pipe and wall thickness, the fundamental process of extrusion is reasonably consistent throughout the industry. 

• Add the thermoplastic resin to the feed hopper. Although this can be done manually, it is generally transferred to the hopper via a vacuum feeder due to the steady state nature of the process. This helps minimize the chance of running out of resin during the process.
• Turn on machine screw and barrel heaters per specific resin requirements. The heaters add heat to the plastic while it is in the barrel to melt the plastic. The rotating screw adds shear heat to the plastic for melting as well as building up the pressure to force the plastic through the die.
• Extrude plastic through the die. The die is designed and built based on the dimensions desired in the pipe and the shrink rate of the type of plastic being used.

• Cut the pipe at the desired length. The extruded pipe will exit the die onto a roller system to allow the pipe to cool without deforming under its own weight. Once it has passed a certain length, it will trip a sensor (electric eye) triggering a cutting operation on the pipe. The cut is made by a cutter that moves forward at the rate of pipe extrusion to offset the motion of the pipe moving forward so that the end of the pipe will remain perpendicular to the pipe wall after it is cut.
• Continue the process in a steady-state environment until the desired quantity of plastic is produced.

     Ingredients of PVC Pipe Manufacturing

Polyvinyl Chloride (PVC) is a thermoplastic material that is used in a myriad of products including water pipe and electrical conduit. It is a polymer whose long chain molecules are made from the building blocks of vinyl chloride. Additives are used to enhance the properties of PVC for specific applications. Finished products come in a number of colors, are tolerant to ultraviolet light, and have various degrees of flexibility.

Raw Materials

• The two raw materials used in the manufacture of PVC are sea water and oil. Salt derived from sea water is used to make chlorine gas and petroleum oil is the original source for ethylene gas. Chlorine and ethylene are the two main ingredients needed to make PVC.

Chlorine

• Chlorine is produced from a saline solution by the process of electrolysis. A solution of sodium chlorine, or common table salt, is placed in a container with electrodes. When electric current is applied, the positive electrode attracts chloride ions in the solution where they combine to form chlorine gas.

Ethylene

• Ethylene is a colorless and odorless gas with the chemical formula C2H4. It is highly flammable and can cause explosions if mishandled. It is produced commercially from the refining of petroleum.

Making PVC

• The chlorine and ethylene gases are combined to produce ethylene dichloride which is converted at high temperatures to vinyl chloride (CH2=CHCl). The vinyl chloride molecules are then polymerized to form the PVC resin. Other compounds are added to improve its appearance and physical and chemical properties. The finished product is formed into pipe or other products where it hardens as it cools.

Additives

• A number of compounds can be added to raw PVC. The most common additives are pigments to add color, UV inhibitors to protect the material from being degraded by prolonged exposure to sunlight, and plasticizers to adjust the degree of flexibility of the specific product. Most plasticizers come from a chemical group called phthalates.

Toxicity of Materials

• Chlorine in the gaseous form is dangerous because it is a severe irritant to the skin, eyes, and respiratory system. Ethylene chloride compounds that are made in the manufacturing process and not converted into polymers are known to be carcinogenic. There are remnants of these compounds that are not combined in the finished PVC which makes water pipe and other products potentially hazardous as well. The phthalates that are used as to increase plasticity are also very toxic.

           The Plastic Manufacturing Process

Plastic Extrusion Molding Process

• Extrusion molding is another method of manufacturing plastic components. Extrusion molding is very similar to injection molding and is used to make pipes, tubes, straws, hoses and other hollow pieces. Plastic resin is fed into a barrel where it is liquefied. A rotating screw propels the liquefied plastic into a mold, which contains a tube-shaped orifice. The size and shape of the tube determines the size and shape of the plastic piece. The liquefied plastic then cools and is fed through an extruder, which flattens the plastic and forms the piece into its final shape.

Plastic Injection Molding Process

• Injection molding is one of the main methods by which parts are manufactured from plastic. The first step in the injection molding process is to feed plastic pellets into the hopper, which then feeds the pellets into the barrel. The barrel is heated and contains a reciprocating screw or a ram injector. A reciprocating screw is typically found in machines that produce smaller parts. The reciprocating screw crushes the pellets, making it easier for the plastic to be liquefied. Toward the front of the barrel, the reciprocating screw propels the liquefied plastic forward, thereby injecting the plastic through a nozzle and into the empty mold. Unlike the barrel, the mold is kept cool to harden the plastic into the correct shape. The mold plates are held closed by a large plate (referred to as a movable platen). The movable platen is attached to a hydraulic piston, which puts pressure on the mold. Clamping the mold shut prevents plastic from leaking out, which would create deformities in the finished pieces. 

The advantages of twin screw extrusion

      The advantages of twin screw extrusion

Twin screw extrusion has become the standard over time in several industries because it offers numerous advantages over single screw extrusion:

1.More consistency in production and control of product quality

2.Increased productivity due to continuous processing, faster start up and shut down between product changes, quick changeover and advanced automation

3.Greater flexibility, with the capability to process a wide range of raw materials

4.Optimized footprint thanks to energy and water savings

5.Simple and easy to maintain and clean

Twin Screw 

Maintenance Method Of Plastic Extruder in Daily

Today we know the plastic extrusion machine maintenance method!

Ventilation points • plastic extrusion equipment should be placed to ensure motor heat and prolong its life; maintain good grounding of the machine.

• Regularly check tool screws, new machine using 1 hours Hou, with tool tight solid moving knife, set knife of screws, strengthening blade and turret between of fixed sex; should regularly on bearing raises lubricants, guarantee bearing between of lubrication sex; for guarantee tool incision of sharp degrees, should often check tool, guarantee its sharp degrees, reduced due to blade blunt deficiency and caused other parts of not necessary damaged; regularly check belt whether relaxation, timely adjustable tight.

• Restart-the second start, should clear the remaining scrap, reduce the starting resistance. should periodically turn inertia cover and belt pulley cover, remove flange bottom ash, Crusher discharge powder into the axle bearing.

• Replacement parts-when replacing the cutters, knives and the gap between the fixed knife: 20HP Crusher 0.8MM, 20HP Crusher 0.5MM. recycled material is thinner, the clearance can be adjusted.

Extrusion System For Plastics Extrusion Machine

Extrusion system consists of screw and barrel, Hopper, die, and die, plastics by squeezing the system plastics melt evenly, and, in the process of establishing, under pressure from continuous by screw extruder.

1, screw: is the most important parts of extruder, it is directly related to applications and productivity of extruders, made from high-strength corrosion-resistant alloy steel.

2, barrel: is a metal cylinder, generally with higher heat resistance, compressive strength, strong wear-resistant, corrosion-resistant alloy steel composite pipe made of or lined with alloy steel. Barrel and screw fit, realize the plastic pieces, softening, melting and plasticizing, vent and compaction, and uniform conveyor rubber molding system. Barrel length is 15~30 times the diameter, so that the plastic is fully heated and fully plastic into principles.

3, Hopper: hopper with cut-off device at the bottom, so you can adjust and cut off the flow, side of the hopper with sight and calibration of metering devices.

4, die and mold: head made of alloy steel and carbon steel coat, and head is equipped with mold, heads are used to rotate the plastic melts into parallel straight line movement, steady import model Kit, and endows plastics with the necessary pressure. Plastic plastic in the barrel of the compaction, porous plate along a certain flow through head neck into head mold, die mandrel set appropriate, formation cross section decreases of the annular space, plastic melt around the wire to form a continuous solid tube coating. In the guarantees head plastic reasonable channel, elimination of accumulated plastic corner, often placed with split sleeves, for elimination of plastic extrusion pressure fluctuations, there is set of grading rings. Head is also equipped with mould correction and adjustment device, easy to adjust and align core and mould sleeve of concentricity.