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√ As the plastic industry developed a second type plunger machine appeared. known as two stage plunger. √ This type of equipment involved two plunger units set on top of other the one to plasticize the material and feed it to another cylinder that consist of a chamber to heat the plastic material by conduction and plunger that operates as a shooting plunger and push the plasticize material into the mould. Advantages    • Faster than conventional machine (single plunger) .  • No Pressure loss encountered in compacting the granules.   • Allows larger parts with more projected area. Disadvantage :  • Extra construction for pre plasticizing so cost is more.

ADDlTlVE - A substance added to a plastic compound to alter its characteristics. Examples are plasticizers, and flame retardants. ALLOY - A combination of 2 or more plastics which form a new plastic.  AMORPHOUS - A plastic material in which the molecular structure is random and becomes mobile over a wide temperature range. ANNEAL ~ To heat a moulded part up to a temperature just below its melting point and slowly cooling it back; down to room temperature. This relieves moulded stresses. ANlSOTROPlC SHRlNKAGE - S hrinkage that occurs more in one direction (usually the direction of flow; reinforced materials shrink more across the direction of flow) than another. AUTOMATIC OPERATlON -The term used to define the mode in which a moulding machine is operating when there is no need for an operator to start each cycle. BARREL - A metallic cylinder in which the injection screw (or plunger) resides in the moulding machine . Also called CYLINDER. BLEND -...

1. Intense industry competition often results in low profit margins. 2. Mould costs are high. 3. Moulding machinery and auxiliary equipment costs are high. 4. Lack of knowledge about the fundamentals of the process causes problems. 5. Lack of knowledge about the long term properties of the materials may result in long-term failures.

1. The Screw type Injection Moulding Machine consists of a hopper, a reciprocating screw and barrel assembly, and an injection nozzle. 2. This system confines and transports the plastic as it progresses through the feeding, compressing, degassing, melting, injection and packing stages. 3. A single screw injection Moulding machine for themoplastic showing the plasticizing screw,al a barrel band heaters to heat the barrel, a stationary platen, and a movable platen.

1. The plunger type injection moulding machine is available horizontal or vertical type and operated pneumatically or hydraulically.The clamping and Injection may be Semi or automatic. 2. In a semi Automatic type the clamping cylinder & the Injection cylinders are operated by levers which is connected the pneumatic or hydraulic cylinders. In Automatic type, the cylinders are actuated automatically to a set timers.

1. The cost of the machines is increased depending on their functions and Size . 2. The simplest Injection Moulding machine is a hand injection moulding machine With a very low cost . 3. The simplest mode of injection moulding machine may be considered as hand operated mode, which is an apt equipment to underStand the interaction of major operating parameters . 4. The machine consists of Barrel, Plunger, Band Heaters along with energy regulator, Rack & Pinion system for injecting the material by the plunger, a torpedo and nozzle.  5. The clamping is done manually on a working table. The machine is fitted on the working table. Heating is set manually .  6. The capacity of . the machine is available from 0.5 Oz to 2 Oz. Once heating is achieved the production starts manually. 7. The quality of the product is completely depend upon the skill of the operaton .The heating set point is achieved by heat & trial method. 8. Although Temperat...

• A  toggle  is  mechanically  device  to  amplify  force. • In  a  moulding  machine,  which  consists  of  two  bars joined,  together  end  to  end  with  a  pivot  . • The  end  of one  bar  is  attached  to  a  stationary  platen, and  the  other  end  of  a  second  bar  is  attached  to  the movable  platen. • When the  mould  is open,  the  toggle  is  in  the  shape  of  a  V. • When pressure  is  applied  to  the  pivot,  the  two  bars  form a  straight  line.

PE is made up from Ethylene monomers. PE is divided into different class according to their density. Different types of PE are as below: ( Polymers )                   ( Density ) LDPE               0.910 -0.940 (g/cc) LLDPE             0.915 -0.925 (g/cc) MDPE              0.926 -0.940 (g/cc) HDPE               0.941 -0.959 (g/cc) VLDPE             0.880 -0.915 (g/cc) UHMWPE        0.930 -0.935 (g/cc) Properties of PE: √ Very low cost √  Excellent chemical resistance √  Very good processability. √  High impact s...

1. Hand Injection Moulding Machine  (Vertical) . (Click Here) 2. Plunger Type Injection Moulding Machine (vertical & Horizontal). (Click Here) 3. Screw Type Injection Moulding Machine. (Click Here) 4. Plunger - Plunger Injection Moulding Machine. 5. Screw - Plunger Injection Moulding Machine.

√ The function of the torpedo is to help the material for proper melting and crate back pressure for help in mixing. Torpedo used Vartical Hand Injection Machine .

1. A devices made of two dissimilar metals which are used to measure the temperature of a heated area such as the barrel or nozzle. 2. It sends a signal to controller which then turns off or  on to control the temperature of that area.

1. Parts can be produced at high production rates.  2.Large volume production is possible. 3.Relatively low labour cost per unit is obtainable.  4. Part require little or no finishing.  5. Many different surface, colours, and finishes are available.  6. Good decorations is possible.  7. For many shapes this process is the most economical way to fabricate.  8. Process permits the manufacture of very small parts which are almost impossible to fabricate in quantities by other methods. 9. Close dimensional tolerances can be maintained.  10. Parts can be moulded with metallic and non-metallic inserts.

√ Advantages - { injection Blow Moulding } 1. Accurate shaping of the neck. 2. A High level of dimensional accuracy. 3. Mini weight tolerance. 4. The highest quality surface finish. 5. Production absolutely free from waste. 6. Crystal clear containers for pharmaceutical  application. 7. Finished bottle without weld line and scrap. 8. Secondary /finishing operation can be avoided. 9. Multi-cavities can be operated. √ Disadvantages -{ injection Blow Moulding } 1. The preform design generally establish the core rod length & diameter. 2. The process is more expensive than extrusion blow moulding. 3. Compromise between preform wall thickness and blow up ratio. 4. The ratio of the maximum wall thickness to minimum wall thickness across a preform cross-section should be less than 1.5 to prevent weld lines. 5. Preform thickness greater than 6 mm is unstable during blowing since the thick section cannot be properly conditioned. 6. The technique is not suit...

√ General Rules for Safety&Precaution  ,Fitter tools,  Introduction of polymers & Fundamental Termininology of polymers PDF files- (Download)

Solid Cross - 1. A Typical Die Design for extruding a solid rod is show in figure. 2. In the figure, DD is the diameter of die orifice,  DB is the diameter of bore of extruder barrel, α is the lead -in angle ,  and  P is the die land. 3. Because of the screen pack and breaker plate assembly,   the pressure in the extruder (PE)  is reduced by the pressure loss across the assembly (PL). 4. Since the die outlet is at atmospheric pressure,  the working pressure is the die pressure (PD)   given by the difference : PD = PE -- PL

Straight - Through Dies : √ Those die whose axes are arranged to be in line with the direction of supply of melt. √ Spider,  mandrel is needed for tubes . √ Used for the extrusion of pipe ,  rod ,  profiles and sheet . Crosshead  Dies - • Arranged with their axes at an angle of 908 (458 and 308 are also used)  to the melt feed.  •No need to for Spider assembly . Used for the production of insulated wires,  cables.  Offset Dies - • Combination of both straight - through die and off-set dies.  • Used for the production of pipe. 

Die Design - 1. The role of a die is to from the melt into a desired linear product : fibres, films, sheets, profiles, rods , etc . 2. The die is a channel, whose profile changes from that of the extruder bore to an orifice, which produces the required form. 3. The dies can be classified using different criteria.     Example - Considering cross section of the extrudate one may recognize dies to produce -     • Solid Cross - Sections (Click Here)     • Hollow Cross - Sections 4. Another classification scheme is based on the die attachment to the  extruder barrel -     • Straight - throught Dies - (Click Here)      • Cross - heat dies-  (Click Here)     • Offset dies - (Click Here)

Breaker Plate - 1. This is performed metal disk,  with a multitude of small diameter holes. 2. The breaker plate is placed in between the screw and the die assembly. 3. It's principal function is to provide support for the screen pack . 4. The breaker plate helps also to convert the spiral flow of the polymer melts leaving the screw into a linear, axial one. Screen Pack - 1. Screen Pack is usually a multilayered,  nearly symmetrical sandwich of metallic wire screens.  2. It is placed between the screw and the breaker plate,  using the latter for physical support. It's  role is to eliminate the particulate contaminants.  3. The screen pack composition is always based on trade-offs, there is need to eliminate particulates using screens with high mesh,  but at the same time this create flow restriction,  it reduced the throughput, thus low mesh would be preferred.  4. Decision should be made as for as the maximum tolerabl...

Screw Cooling - 1. Larger screws are bored though for passage of heat transfer medium. However, care must be used not to over-cool the screw. 2. The cooling may be freeze a layer of plastic on the screw root, reducing the channel depth thus producing more shear at a cost throughput. 3. This may  also reverse the required relationships between the friction coefficient (low friction coefficient on the screw, high on the barrel),  further reducing the drag flow. 4. Furthermore,  there is a danger that the material staying a long time near the screw root will degrade,  contaminating the product. 5. It is important to remember that the conveying ability of the screw is controlled by the friction coefficient ratio : f(barrel)/ f(screw) it is important to maximize this ratio. 6. Under normal circumstances the minimum value of the ratio that guarantees conveying is 1.4 7. Screw cooling may be recommended to prevent decomposition of heat sensitive materials. 8. H...

                    : Barrel Cooling : 1. Barrel cooling is needed to prevent overheating that may cause degradation. 2. For small extruders fans that blow air over or around the barrel are used. 3. Other cooling system used include . 4. Cooling channel inside the barrel wall. 5. Find on the barrel or on the heaters to speedup that transfer. 6. A watet-fog spray over barrel. 7. Continuous, controlled vaporization of liquid (water) 8. Copper tubing carrying cold water is sometimes used.               *Hopper Cooling Systems* • Water-cooling is used to cool the hopper throat to prevent bridging and to protect the rubber parts present in the screw support  assembly.

Steam heating : 1 . The high specific heat and latent heat of vaporisation of water makes steam an excellent heat transfer medium. 2 . Howevery, this system is not frequently used because of low maximum temperature that can be achieved,  a need of working with high pressure piping,  frequent leaks of steam that require shutting down of heating for repairs,  and corrosion effect.

Fluid Heating System : 1. The Heating fluid, that is most commonly used for extruders is oil. It may be heated by any suitable means (mainly electrical). 2. The heating system consists of a heater a circulating pump,  a surge tank, and a heat transfer channel in the extruder barrel.

Band Heaters : • They consist of Ni-chrome or other resistance wires mica or ceramic insulated,  then encased in steel cover.             *Mica insulated * 1. Flexible , supplied as a single piece . 2. Can withstand a load of 23-31 KW/m2 3. Shorter service life 4. Less expensive            *Ceramic insulated * 1. Rigid,  supplied in 2 halves. 2. Can withstand higher heating load 3. Better services life 4. More costly

√ The insulated heating elements are cast into semi-circular or flat aluminum blocks,  which are machined to match the surface to be heated.

Heating Systems ( Element ) - There are three methods of heating extruders : 1. Electric. ( Three Type heating ) 2. Fluid . (click here) 3. Steam Heating. (click here) Electric Heating : (a) . Induction Heaters. (click here) (b) . Cast-in Heaters. (click here) (c) . Band Heaters (Two Type Heaters). (click here)          (i).  Mica Insulated          (ii). Ceramic Insulated √ The electric heating is most commonly used due to : • Accuracy • Reliability • Easy to hook up.                  *Cooling Systems*     1 . Barrel Cooling. (click here)   2. Hopper Cooling. (click here)   3. Screw Cooling. (click here)

1 . AC Current passed through coil thus setting up a magnetic flex. Heat is generated from the resistance offered to the eddy current set up by the flux. 2 . The barrel is heated directly by its resistance to the induced current.                   * Advantages *    √ Accurate  Control of Temperature.    √  Good provision for cooling the barrel.     √   No possibility for hot or cool spots.                      * Disadvantages *     √ Relatively  high cost.        

Thrust Bearing - The screw fits into a thrust bearing located behind the feed hopper. The function of the thrust bearing is to absorb the thrust force acting on the screw inside the extruder barrel. 1. The bearing prevents  the screw from moving  backward . 2. Bearing life-time depends on the pressure and screw speed. For high speeds, oversized being is needed. 3. For twin screw extruders several smaller bearings joined in one shaft is used. (Thrust Force = Extrusion Pressure X Cross Sectional Area of the screw )

Drive Moter : 1. Drive moter provides the torque that turns the screw, and thus provides power to push out the material. 2. DC-Motor are widely used. 3. AC-Motor is used fluctuations in output (surging)  may occur.   <Gear Reduction And Torque Transmission> 1. The role of gear reduction and transmission is to reduce the motor speed (1750-2000 rpm) to workable screw speed (15-200 rpm) and transfer the motor torque to the screw. 2. For the variation of screw speed over a wide range without reducing it's  torque,  strapless speed changers are used. 3. In the older and smaller extruders,  V belts offered direct coupling,  to transmit the motor torque to the reduction gearbox. In modern machine the transmission is achieved by direct coupling.

Ex truder Screw : 1. Due to screw rotation the frictional heat is produced . 2. The material flow in the screw channel in a spiral pattern, with the mixing. 3. However, by contrast with the ram extrusion, here the thermal and frictional heat affects continuously  renew the material surface,  thus the thermal degradation is not as severe. 4. The softened material is forced out by the screw.                * Functions of Single Screw Extruders (SSE) * 1. Plasticating the material (softening,  melting and mixing the melt). 2. Conveying 3. Pressurizing and pumping .            * Advantages of Single Screw Extruders (SSE)* 1. Uniform heating 2. Continuous process 3. Better mixing than in ram extruder 4. All types of resins can be processed. Extruder Barrel : 1. Barrel is the cylindrical chamber in which the screw rotates. 2. Hop...

1. The hopper purpose is to transfer a polymer into the extruder barrel, where it is compressed. This compressed forces the air out from between interstices of resin pellets or rubber chunks (air is expelled back through the hopper) . 2. Flow in the hoppers depends on their type (gravitational or forced), bulk density of the material, the shape and location of the feed inlet (direct or tangential feed, straight or with the chamfer on the down going side), as well on the type of screw and the barrel. 3. The solid conveying in the feed hopper usually depends on the gravity flow of particulate polymeric material moves down the hopper by its own weight. 4. Some materials have poor flow characteristics and may block the flow (know as arching or bridging). 5. This is more likely to occur when the particle shape is irregylar, the particles are small, and the internal friction on the bulk material is high. 6. Highly compressible bulk material are also susceptible to solids conv...

√ The Single Screw Extruders is a relatively inexpensive machine for small or medium size production lines. √ For line with the throughput exceeding 10 tons per hour (10/h), the capital costs of SSE and TSE are comparable. SSE that can produce 40 Tons/hour can be custom-built only few manufacturers. √ The Single-Screw Extruders consist of screw rotating in heated barrel or cylinder to which the material is fed.   1 . Feed hopper.  (click here)   2. Extruder Screw and Barrel . (click here)   3 . Drive system (motor,  gear box,  transmission). (click here)   4. Thrust Bearing. (click here)   5. Heating and Cooling Elements. (click here)   6. Screen pack and Breaker plate. (click here)   7. Die . (click here)   8. Temperature and pressure  controls. •Single Screw Extruders parts and function-(in short notes) 1. Screw Pump :    Combination of screw &Barrel 2. Hopper :   Funn...

√ Ram Extruder is discontinuous Process √ It uses a ram or piston operating in a cylinder √ The material is a softened by thermal energy from the outside heaters √ After softening the material is forced out by the ram movement.  After that ram retracted,  the cycle is repeated.               < ADVANTAGES > √ There are no violent agitation of the material. √ Simple process control. √ Material that can not under go shearing can be processed. √ Material having high viscosity ( PTFE, UHMHDPE ) can be processed. √ Power consumption is low.               < DISADVANTAGES   > √ Large temperature gradient between the ram cylinder wall and the interior of the plastic bed. The gradient may lead to degradation of the surface layer to the resin. √ Low throughput ...

√ Orientation of the barrel (vertical & horizontal) . Mechanism of the flow generatio n ( screw, disk, drum, barrel, two-stage disk Extruders, etc . ) √ The other type of extruders are being rarely used, mostly for specific reasons ( the multi-screw machines have been popular for the large volume compounding  of PVC . ) Two Type Extruders : 1. Batch Type : (a).Ram Extruders. (click here) (b).Reciprocating Screw Extruders. 2. Continuous Type: (a).Screws less extruders =              √ Disk   Extruders             √ Drum Extruders             √ Other Extruders (b). Screw Extruders =         √  Single screw Extruders (SSE)          √  Twin  screw  Extruders  (TSE)     ...

1 . Continuous process 2 . In principle, the plastic raw material is plasticated by means of a screw plastications unit and the molten material is continuously pumped out of through a standard orifice (die) in order to take the shape and then the shape is set by cooling/sizing system. 3 .The required materials (Polymers,  Additives, Re-inforcements, etc.) are fed through a feed hopper into a barrel.  4. The polymeric material soften by the heat from the external heaters and generated by frictional  force.  5 .The energy needed to convert the cold particle into a hot viscous melt depends on the specific heat, heat of melting (crystalline polymers), the maximum temperature of the extrusion.  6 .The transfer of heat into individual pellets by thermal conductivity.  Thermal conductions is important in removing the heat from the melt in order to solidify it.  7 .The pressure required for the continuous extrusion can be generated by t...