Plastic Extrusion Machines
Suppliers of plastic extrusion machines. Extrusion machines for sale such as plastic extruders, plastic extruder machine, plastic extruders, extruder, pe foam sheet extruder,epe foam sheet extrusion line,ps foam sheet extrusion line,cable extrusion machine,pipe extrusion machine,plastic pipe extrusion machine,pvc pipe extrusion machine,blown film extrusion machine. Suppliers of plastic extrusion lines, extruders, plastic extruders,extruder, foam sheet extrusion lines, cable extrusion,pipe extrusion line, profile extrusionline, film extrusion line and pelletizers. Pipe extrusion line, Pipe Lines, Complete Pipe lines, Pipe extruders, Twin Screw Pipe Extruders , Single Screw Pipe Extruders, Polyolefin Pipe Heads, PVC Pipe Heads, Profile Extrusion, Sheet Extrusion, Cast Film extrusion , PVC Sheet extrusion , Thermoplastic Sheet extrusion, Thin sheet Extrusion , Thick Sheet Extrusion, Compounding Masterbatch compounding , High Filler Loading, Reaction compounding , Engineering Plastics compounding, Rubber Extrusion, Rubber Calendaring, Rubber Sheet Manufacture , Rubber Roller Covering, Rubber Profile Extrusion.
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Plastic Extrusion Machines
Plastic extrusion machines, extrusion lines, plastic extrusion machines, extruders, plastic extruders,profile extruder, foam sheet extrusion lines, cable extrusion,pipe extrusion line, profile extrusionline,film extrusion line pelletisers
Cable Extrusion Machines and Extrusion Equipment
Cabletech Marketing
KraussMaffei
Berstorff
Cutting Machines, Laser Cutting Machines
PE Foam Sheet Extruder,EPE Foam Sheet Extrusion Line,PS Foam Sheet Extrusion line
Technimac
(Pty)Ltd
Hestico
(Pty)Ltd
KraussMaffei
Berstorff
Plastic Extrusion Machines / Extrusion Systems / Pelletizer Extruders /
Plasquip(Pty)Ltd
Hestico
(Pty)Ltd
Technimac (Pty)Ltd
Cabletech Marketing
PBS Machine Tools (Pty)Ltd
KraussMaffei Berstorff
Maritime
Marketing
Hans
von der Heyde
Auschmidt cc
Blown Film Extrusion Machines
Plasquip(Pty)Ltd
Technimac (Pty)Ltd
KraussMaffei
Berstorff
Plastic Pipe Extrusion Machines and Profile Extrusion Lines
Plasquip(Pty)Ltd
Hume Machinery
Cabletech
Marketing
PBS
Machine Tools (Pty)Ltd
KraussMaffei
Berstorff
Hans
von der Heyde
Plastixportal Sponsors
In the extrusion of plastics, raw thermoplastic
material in the form of small beads (often called resin in the industry)
is gravity fed from a top mounted hopper into the barrel of the extruder.
Additives such as colorants and UV inhibitors (in either liquid or pellet
form) are often used and can be mixed into the resin prior to arriving
at the hopper.
The material enters through the feed throat (an opening near the rear of the barrel) and comes into contact with the screw. The rotating screw (normally turning at up to 120 rpm) forces the plastic beads forward into the barrel which is heated to the desired melt temperature of the molten plastic (which can range from 200 °C/400 °F to 275 °C/530 °F depending on the polymer). In most processes, a heating profile is set for the barrel in which three or more independent PID controlled heater zones gradually increase the temperature of the barrel from the rear (where the plastic enters) to the front. This allows the plastic beads to melt gradually as they are pushed through the barrel and lowers the risk of overheating which may cause degradation in the polymer.
Extra heat is contributed by the intense pressure and friction taking place inside the barrel. In fact, if an extrusion line is running a certain material fast enough, the heaters can be shut off and the melt temperature maintained by pressure and friction alone inside the barrel. In most extruders, cooling fans are present to keep the temperature below a set value if too much heat is generated. If forced air cooling proves insufficient then cast-in heater jackets are employed, and they generally use a closed loop of distilled water in heat exchange with tower or city water.
Plastic extruder cut in half to show the componentsAt the front of the barrel, the molten plastic leaves the screw and travels through a screen pack to remove any contaminants in the melt. The screens are reinforced by a breaker plate (a thick metal puck with many holes drilled through it) since the pressure at this point can exceed 5000 psi (34 MPa). The screen pack/breaker plate assembly also serves to create back pressure in the barrel. Back pressure is required for uniform melting and proper mixing of the polymer, and how much pressure is generated can be 'tweaked' by varying screen pack composition (the number of screens, their wire weave size, and other parameters). This breaker plate and screen pack combination also does the function of converting "rotational memory" of the molten plastic into "longitudinal memory".
After passing through the breaker plate molten plastic enters the die. The die is what gives the final product its profile and must be designed so that the molten plastic evenly flows from a cylindrical profile, to the product's profile shape. Uneven flow at this stage would produce a product with unwanted stresses at certain points in the profile. These stresses can cause warping upon cooling. Almost any shape imaginable can be created so long as it is a continuous profile.
The product must now be cooled and this is usually achieved by pulling the extrudate through a water bath. Plastics are very good thermal insulators and are therefore difficult to cool quickly. Compared with steel, plastic conducts its heat away 2000 times more slowly. In a tube or pipe extrusion line, a sealed water bath is acted upon by a carefully controlled vacuum to keep the newly formed and still molten tube or pipe from collapsing. For products such as plastic sheeting, the cooling is achieved by pulling through a set of cooling rolls.
Sheet / film extrusion
For products such as plastic sheet or film, the cooling is achieved by pulling through a set of cooling rolls (calender or "chill" rolls), usually 3 or 4 in number. Running too fast creates an undesirable condition called "nerve"- basically, inadequate contact time is allowed to dissipate the heat present in the extruded plastic. In sheet extrusion, these rolls not only deliver the necessary cooling but also determine sheet thickness and surface texture (in case of structured rolls; i.e. smooth, levant, haircell, etc.).
Often co-extrusion is used to apply one or more layers to obtain specific properties such as UV-absorption, soft touch or "grip", matte surface, or energy reflection.
A common post-extrusion process for plastic sheet stock is thermoforming, where the sheet is heated until soft (plastic), and formed via a mold into a new shape. When vacuum is used, this is often described as vacuum forming. Orientation (i.e. ability/ available density of the sheet to be drawn to the mold which can vary in depths from 1 to 36 inches typically) is highly important and greatly affects forming cycle times.
Thermoforming can go from line bended pieces (e.g. displays) to complex shapes (computer housings), which often look like being injection moulded, thanks to the various possibilities in thermoforming, such as inserts, undercuts, divided moulds.
Plastic extrusion onto paper is the basis of the liquid packaging industry (juice cartons, wine boxes...); usually an aluminum layer is present as well. In food packaging plastic film is sometimes metallised, see metallised film.
Blown film extrusion
The manufacture of plastic film for products such as shopping bags is achieved using a blown film line.
This process is the same as a regular extrusion process up until the die. The die is an upright cylinder with a circular opening similar to a pipe die. The diameter can be a few centimetres to more than three metres across. The molten plastic is pulled upwards from the die by a pair of nip rolls high above the die (4 metres to 20 metres or more depending on the amount of cooling required). Changing the speed of these nip rollers will change the gauge (wall thickness) of the film. Around the die sits an air-ring. The air-ring cools the film as it travels upwards. In the centre of the die is an air outlet from which compressed air can be forced into the centre of the extruded circular profile, creating a bubble.This expands the extruded circular cross section by some ratio (a multiple of the die diameter). This ratio, called the “blow-up ratio” can be just a few percent to more than 200 percent of the original diameter. The nip rolls flatten the bubble into a double layer of film whose width (called the “layflat”) is equal to ½ the circumference of the bubble. This film can then be spooled or printed on, cut into shapes, and heat sealed into bags or other items.
Tubing extrusion
Plastic tubing, such as drinking straws and medical tubing, is manufactured by extruding molten polymer through a die of the desired profile shape (square, round, triangular). Hollow sections are usually extruded by placing a pin or mandrel inside of the die, and in most cases positive pressure is applied to the internal cavities through the pin.
Sometimes tubing with multiple lumens (holes) must be made for specialty applications. For these applications, the tooling is made by placing more than one pin in the center of the die, to produce the number of lumens necessary. In most cases, these pins are supplied with air pressure from different sources. In this way, the individual lumen sizes can be adjusted by adjusting the pressure to the individual pins.
Coextrusion
Coextrusion refers to the extrusion of multiple layers of material simultaneously. This type of extrusion utilizes two or more extruders to melt and deliver a steady volumetric throughput of different viscous plastics to a single extrusion head (die) which will extrude the materials in the desired form. This technology is used on any of the processes described above (Blown Film, Overjacketing, Tubing, Sheet). The layer thicknesses are controlled by the relative speeds and sizes of the individual extruders delivering the materials.
There are a variety of reasons a manufacturer may choose coextrusion over single layer extrusion. One example is in the vinyl fencing industry, where coextrusion is used to tailor the layers based on whether they are exposed to the weather or not. Usually a thin layer of compound that contains expensive weather resistant additives are extruded on the outside while the inside has an additive package that is more suited for impact resistance and structural performance.
Extrusion coating
Extrusion coating is using a blown or cast film process to coat an additional layer onto an existing rollstock of paper, foil or film. For example, this process can be used to improve the characteristics of paper by coating it with polyethylene to make it more resistant to water. The extruded layer can also be used as an adhesive to bring two other materials together. Click on the company listing - to open the listing in a new window please close the window to return to this page.
Contact the companies above for your plastic machine requirements including:
plastic injection moulding machines, blow moulding machines, film blowing machines, bag making machines, cable extrusion machines, pipe extrusion machines, slitting and rewinding machines, printing machines, labelling machines, plastic recycling machines, twine and rope making machines, vacuum forming machines, extrusion machines.
The material enters through the feed throat (an opening near the rear of the barrel) and comes into contact with the screw. The rotating screw (normally turning at up to 120 rpm) forces the plastic beads forward into the barrel which is heated to the desired melt temperature of the molten plastic (which can range from 200 °C/400 °F to 275 °C/530 °F depending on the polymer). In most processes, a heating profile is set for the barrel in which three or more independent PID controlled heater zones gradually increase the temperature of the barrel from the rear (where the plastic enters) to the front. This allows the plastic beads to melt gradually as they are pushed through the barrel and lowers the risk of overheating which may cause degradation in the polymer.
Extra heat is contributed by the intense pressure and friction taking place inside the barrel. In fact, if an extrusion line is running a certain material fast enough, the heaters can be shut off and the melt temperature maintained by pressure and friction alone inside the barrel. In most extruders, cooling fans are present to keep the temperature below a set value if too much heat is generated. If forced air cooling proves insufficient then cast-in heater jackets are employed, and they generally use a closed loop of distilled water in heat exchange with tower or city water.
Plastic extruder cut in half to show the componentsAt the front of the barrel, the molten plastic leaves the screw and travels through a screen pack to remove any contaminants in the melt. The screens are reinforced by a breaker plate (a thick metal puck with many holes drilled through it) since the pressure at this point can exceed 5000 psi (34 MPa). The screen pack/breaker plate assembly also serves to create back pressure in the barrel. Back pressure is required for uniform melting and proper mixing of the polymer, and how much pressure is generated can be 'tweaked' by varying screen pack composition (the number of screens, their wire weave size, and other parameters). This breaker plate and screen pack combination also does the function of converting "rotational memory" of the molten plastic into "longitudinal memory".
After passing through the breaker plate molten plastic enters the die. The die is what gives the final product its profile and must be designed so that the molten plastic evenly flows from a cylindrical profile, to the product's profile shape. Uneven flow at this stage would produce a product with unwanted stresses at certain points in the profile. These stresses can cause warping upon cooling. Almost any shape imaginable can be created so long as it is a continuous profile.
The product must now be cooled and this is usually achieved by pulling the extrudate through a water bath. Plastics are very good thermal insulators and are therefore difficult to cool quickly. Compared with steel, plastic conducts its heat away 2000 times more slowly. In a tube or pipe extrusion line, a sealed water bath is acted upon by a carefully controlled vacuum to keep the newly formed and still molten tube or pipe from collapsing. For products such as plastic sheeting, the cooling is achieved by pulling through a set of cooling rolls.
Sheet / film extrusion
For products such as plastic sheet or film, the cooling is achieved by pulling through a set of cooling rolls (calender or "chill" rolls), usually 3 or 4 in number. Running too fast creates an undesirable condition called "nerve"- basically, inadequate contact time is allowed to dissipate the heat present in the extruded plastic. In sheet extrusion, these rolls not only deliver the necessary cooling but also determine sheet thickness and surface texture (in case of structured rolls; i.e. smooth, levant, haircell, etc.).
Often co-extrusion is used to apply one or more layers to obtain specific properties such as UV-absorption, soft touch or "grip", matte surface, or energy reflection.
A common post-extrusion process for plastic sheet stock is thermoforming, where the sheet is heated until soft (plastic), and formed via a mold into a new shape. When vacuum is used, this is often described as vacuum forming. Orientation (i.e. ability/ available density of the sheet to be drawn to the mold which can vary in depths from 1 to 36 inches typically) is highly important and greatly affects forming cycle times.
Thermoforming can go from line bended pieces (e.g. displays) to complex shapes (computer housings), which often look like being injection moulded, thanks to the various possibilities in thermoforming, such as inserts, undercuts, divided moulds.
Plastic extrusion onto paper is the basis of the liquid packaging industry (juice cartons, wine boxes...); usually an aluminum layer is present as well. In food packaging plastic film is sometimes metallised, see metallised film.
Blown film extrusion
The manufacture of plastic film for products such as shopping bags is achieved using a blown film line.
This process is the same as a regular extrusion process up until the die. The die is an upright cylinder with a circular opening similar to a pipe die. The diameter can be a few centimetres to more than three metres across. The molten plastic is pulled upwards from the die by a pair of nip rolls high above the die (4 metres to 20 metres or more depending on the amount of cooling required). Changing the speed of these nip rollers will change the gauge (wall thickness) of the film. Around the die sits an air-ring. The air-ring cools the film as it travels upwards. In the centre of the die is an air outlet from which compressed air can be forced into the centre of the extruded circular profile, creating a bubble.This expands the extruded circular cross section by some ratio (a multiple of the die diameter). This ratio, called the “blow-up ratio” can be just a few percent to more than 200 percent of the original diameter. The nip rolls flatten the bubble into a double layer of film whose width (called the “layflat”) is equal to ½ the circumference of the bubble. This film can then be spooled or printed on, cut into shapes, and heat sealed into bags or other items.
Tubing extrusion
Plastic tubing, such as drinking straws and medical tubing, is manufactured by extruding molten polymer through a die of the desired profile shape (square, round, triangular). Hollow sections are usually extruded by placing a pin or mandrel inside of the die, and in most cases positive pressure is applied to the internal cavities through the pin.
Sometimes tubing with multiple lumens (holes) must be made for specialty applications. For these applications, the tooling is made by placing more than one pin in the center of the die, to produce the number of lumens necessary. In most cases, these pins are supplied with air pressure from different sources. In this way, the individual lumen sizes can be adjusted by adjusting the pressure to the individual pins.
Coextrusion
Coextrusion refers to the extrusion of multiple layers of material simultaneously. This type of extrusion utilizes two or more extruders to melt and deliver a steady volumetric throughput of different viscous plastics to a single extrusion head (die) which will extrude the materials in the desired form. This technology is used on any of the processes described above (Blown Film, Overjacketing, Tubing, Sheet). The layer thicknesses are controlled by the relative speeds and sizes of the individual extruders delivering the materials.
There are a variety of reasons a manufacturer may choose coextrusion over single layer extrusion. One example is in the vinyl fencing industry, where coextrusion is used to tailor the layers based on whether they are exposed to the weather or not. Usually a thin layer of compound that contains expensive weather resistant additives are extruded on the outside while the inside has an additive package that is more suited for impact resistance and structural performance.
Extrusion coating
Extrusion coating is using a blown or cast film process to coat an additional layer onto an existing rollstock of paper, foil or film. For example, this process can be used to improve the characteristics of paper by coating it with polyethylene to make it more resistant to water. The extruded layer can also be used as an adhesive to bring two other materials together. Click on the company listing - to open the listing in a new window please close the window to return to this page.
Contact the companies above for your plastic machine requirements including:
plastic injection moulding machines, blow moulding machines, film blowing machines, bag making machines, cable extrusion machines, pipe extrusion machines, slitting and rewinding machines, printing machines, labelling machines, plastic recycling machines, twine and rope making machines, vacuum forming machines, extrusion machines.
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Disclaimer: Any information gained from the plastixportal.co.za website is used at your own risk, we do not take responsibility for any loss whatsoever as a result of information taken from our website.