Design And Fabrication Of Automatic Pvc Pipe Cutting Machine 111463

Design And Fabrication of Automatic PVC Pipe Cutting Machine How is PVC made The chemical process for making PVC involves taking the simplest unit, called the monomer, and linking these monomer molecules together in the polymerisation process. Long molecular chains are formed called polymers (which are also called macromolecules). This is the case for PVC, which is made from vinyl chloride monomer known usually by its initials VCM through polymerisation. Some monomers exist in the form of reactive gaseous chemical substances, and some of these may cause health hazards when in direct with humans. In these cases they are manufactured and processed under strict control for health, safety and environmental protection. On the other hand, polymers such as PVC, which are manufactured from monomers through polymerisation, are solid and chemically stable substances, therefore do not affect human health. VCM, which is the raw material for PVC, is a gas at ambient temperature but is usually stored in liquid form under pressure. Ethylene and chlorine are raw materials for PVC. Upstream industries are those that provide these materials and include producers of basic petrochemicals (sometimes known as feedstocks’), which supply ethylene, and the chlor-alkali (caustic soda) industry, which supplies chlorine.

By thermal cracking of naphtha or natural gas, the basic petrochemical industry manufactures ethylene and propylene, etc. Naphtha is mainly supplied from the petroleum refinery industry, which uses crude oil as raw material. At a first stage in the PVC production process ethylene and chlorine are combined to produce an intermediate product called ethylene dichloride; this is then transformed into vinyl chloride, the basic building block of polyvinyl chloride or PVC. The process of `polymerisation' links together the vinyl chloride molecules to form chains of PVC. The PVC produced in this way is in the form of a white powder. This is not used alone, but blended with other ingredients to give formulations for a wide range of products. Most commodity plastics have carbon and hydrogen as their main component elements. PVC differs by containing chlorine (around 57 per cent by weight) as well as carbon and hydrogen. The presence of chlorine in the molecule makes PVC particularly versatile because it makes it compatible with a wide range of other materials. The chlorine content also helps to make PVC flame retardant. It can also be used as a `marker' to distinguish PVC in automatic sorting systems for plastics recycling. PVC formulations can be shaped by a variety of techniques and, using very little energy, made into the final product form. PVC polymer is chemically stable, neutral and non-toxic. PVC formulations have a wide range of applications including the most sensitive, such as medical equipment, plus construction, automotive and electrical cabling.

Additives used in pvc pipes    

Calcium carbonate Sms 305 stablizer Titanium dioxid colourant Lubricant wax

Working Typical Pipe Extrusion Line Raw Material Weighing Mixing Batching Extruder Head & Die Sizing Bath Basically, PVC products are formed from raw PVC powder by a process of heat and pressure. The two major processes used in manufacture are extrusion for pipe and injection

moulding for fittings. Modern PVC processing involves highly developed scientific methods requiring precise control over process variables. The polymer material is a free flowing powder, which requires the addition of stabilisers and processing aids. Formulation and blending are critical stages of the process and tight specifications are maintained for incoming raw materials, batching and mixing. Feed to the extrusion or moulding machines may be direct, in the form of “dry blend”, or pre-processed into a granular “compound”. Polymer and additives (1) are accurately weighed (2) and processed through the high speed mixing (3) to blend the raw materials into a uniformly distributed dry blend mixture. A mixing temperature of around 120°C is achieved by frictional heat. At various stages of the mixing process, the additives melt and progressively coat the PVC polymer granules. After reaching the required temperature, the blend is automatically discharged into a cooling chamber which rapidly reduces the temperature to around 50°C, thereby allowing the blend to be conveyed to intermediate storage (4) where even temperature and density consistency are achieved. The heart of the process, the extruder (5), has a temperature-controlled, zoned barrel in which rotate precision “screws”. Modern extruder screws are complex devices, carefully designed with varying flights to control the compression and shear, developed in the material, during all stages of the process. The twin counter-rotating screw configuration used by all major manufacturers offers improved processing. The PVC dryblend is metered into the barrel and screws, which then convert the dry blend into the required “melt” state, by heat, pressure and shear. During its age along the screws, the PVC es through a number of zones that compress, homogenise and vent the melt stream. The final zone increases the pressure to extrude the melt through the head and die set (6) which is shaped according to the size of the pipe required and flow characteristics of the melt stream. Once the pipe leaves the extrusion die, it is sized by ing through a precision sizing sleeve with external vacuum. This is sufficient to harden the exterior layer of PVC and hold the pipe diameter during final cooling in a controlled water cooling chambers (8). The pipe is pulled through the sizing and cooling operations by the puller or haul-off (9) at a constant speed. Speed control is very important when this equipment is used because the speed at which the pipe is pulled will affect the wall thickness of the finished product. In the case of rubber ring ted pipe the haul-off is slowed down at appropriate intervals to thicken the pipe in the area of

the socket. An in-line printer (10) marks the pipes at regular intervals, with identification according to size, class, type, date, Standard number, and extruder number. An automatic cut-off saw (11) cuts the pipe to the required length. A belling machine forms a socket on the end of each length of pipe (12). There are two general forms of socket. For rubber-ring ted pipe, a collapsible mandrel is used, whereas a plain mandrel is used for solvent ted sockets. Rubber ring pipe requires a chamfer on the spigot, which is executed either at the saw station or belling unit. The finished product is stored in holding areas for inspection and final laboratory testing and quality acceptance (13). All production is tested and inspected in accordance with the appropriate Australian Standard and/or to specifications of the purchaser. After inspection and acceptance, the pipe is stored to await final dispatch (14). MANUFACTURE Extrusion (Figure 1.1) 5 PVC Pressure Pipe Systems PVC Pressure Pipe Systems PVC Pressure Pipe Systems PVC Pressure Pipe Systems PVC Pressure Pipe Systems PVC Pressure Pipe Systems Introduction The pipe is pulled through the sizing and cooling operations by the puller or haul-off (9) at a constant speed. Speed control is very important when this equipment is used because the speed at which the pipe is pulled will affect the wall thickness of the finished product. In the case of rubber ring ted pipe the haul-off is slowed down at appropriate intervals to thicken the pipe in the area of the socket. An in-line printer (10) marks the pipes at regular intervals, with identification according to size, class, type, date, Standard number, and extruder number. An automatic cut-off saw (11) cuts the pipe to the required length. A belling machine forms a socket on the end of each length of pipe (12). There are two general forms of socket. For rubber-ring ted pipe, a collapsible mandrel is used, whereas a plain mandrel is used for solvent ted sockets. Rubber ring pipe requires a chamfer on the spigot, which is executed either at the saw station or belling unit. The finished product is stored in holding areas for inspection and final laboratory testing and quality acceptance (13). All production is tested and inspected in accordance with the appropriate Australian Standard and/or to specifications of the purchaser. After inspection and acceptance, the pipe is stored to await final dispatch (14).

Limit Switch

In electrical engineering a limit switch is a switch operated by the motion of a machine part or presence of an object. They are used for controlling machinery as part of a control system, as a safety interlocks, or to count objects ing a point.[1] A limit switch is an electromechanical device that consists of an actuator mechanically linked to a set of s. When an object comes into with the actuator, the device operates the s to make or break an electrical connection. Limit switches are used in a variety of applications and environments because of their ruggedness, ease of installation, and reliability of operation. They can determine the presence or absence, ing, positioning, and end of travel of an object. They were first used to define the limit of travel of an object; hence the name "Limit Switch". A limit switch with a roller-lever operator; this is installed on a gate on acanal lock, and indicates the position of a gate to a control system. Standardized limit switches are industrial control components manufactured with a variety of operator types, including lever, roller plunger, and whisker type. Limit switches may be directly mechanically operated by the motion of the operating lever. A reed switch may be used to indicate proximity of a magnet mounted on some moving part. Proximity switches operate by the disturbance of an electromagnetic field, by capacitance, or by sensing a magnetic field. Rarely, a final operating device such as a lamp or solenoid valve will be directly controlled by the s of an industrial limit switch, but more typically the limit switch will be wired through a control relay, a motor or control circuit, or as an input to a programmable logic controller. Miniature snap-action switch may be used for example as components of such devices as photocopiers, computer printers, convertible tops or microwave ovens to ensure internal components are in the correct position for operation and to prevent operation when access doors are opened. A set of adjustable limit switches are installed on a garage door opener to shut off the motor when the door has reached the fully raised or fully lowered position. A numerical control machine such as a lathe will have limit switches to identify maximum limits for machine parts or to provide a known reference point for incremental motions.