Products / Sheet Lines
Sheet Lines(199) items
|Complete Sheet Lines (74) items|
|Extruders And Coextruders (9) items|
|Dies & Coex Blocks, Melt Devices (74) items|
|Cooling Stacks & Haul Offs (5) items|
|Pump Groups (2) items|
|Scanners/Treaters (1) items|
|Slitters/Guillotines (11) items|
|Winders/Stackers (12) items|
|Printers (2) items|
|Feed Equipment Vol/Grav Hoppers (2) items|
|Ancillaries (7) items|
Sheet extrusion is in its simplest form the process of converting a thermoplastic pellet or chip into a flat sheet, foil or film. The sheet extrusion process usually covers thickness ranges of 200micron to 20mm. Thinner films tend to be made on cast film lines. Greater thickness sheets are rare, but sometimes manufactured. The basic process is well established and has existed, largely unchanged for over 40 years. Control systems have become far more sophisticated, but the core mechanical components are largely unchanged in general principle.
Sheet extrusion lines usually comprise a feed system, one or more extruders, cooling rolls, haul-off rolls and handling equipment for the finished sheet.
The feed system can be a simple hopper or multi component blender, with either volumetric or gravimetric control .
A single screw extruder generally comprises an electrically driven screw turning in a barrel with controlled heating which melts and pumps the plastic feedstock to the die. The drive is most commonly a variable speed dc drive and motor coupled to the screw through a speed reducing gearbox. Barrel temperature is normally controlled by electrical resistance heaters and air or water cooling. Some material processes benefit from having volatile gasses vented from a special vent part way along the barrel. To avoid damage from contaminated material, extruders usually have screen changers, which act as filters to protect the downstream equipment. Multiple extruders are used for the manufacture of multi layer coextruded sheet or to increase output. Melt, or gear pumps are often found on the main extruder (and less often on coextruders), to regulate the pressure and flow of the material. Combining the melt flow from main extruder and coextruder is done within a coextrusion feedblock. This part can take many forms, from the simple to the very sophisticated. Where the combining materials are of similar rheology, a simple block usually suffices.
The die head can be bolted directly to the feedblock. Sheet dies distribute the material across the width of the die and at the thickness required. This is achieved using a specially designed internal flow profile to equalise the the flow rate across the width so the material flows evenly out of the die lip. Some dies are fitted with an adjustable internal restrictor bar to give more control of the flow profile. There are many designs of die constuction but most dies in current use are flex lip. This means that the top lip of the die is a flexible part of the upper half of the die. Adjustment is done by pushing, or pulling on bolts so that the lip is flexed against the main body of the die. This adjustment is usually restricted to 2 -3 mm per lip but can be varied across the width of the die . The rigid bottom lip can be fixed, adjustable or replaceable , dependent on the amount of thickness adjustment the die is designed for.
From the extruders , the molten homogenised material is delivered through the die head to the polishing or cooling rolls . These chrome plated rolls, either polished or embossed with a pattern, are held within a very rigid framework known as the roll stack in either vertical, horizontal or inclined configuration. The roll stack is designed to take the melted thermoplastic material, fine control the thickness and surface finish, and cool the material so the sheet is solid enough to haul or draw along a cooling conveyor through a nipped pair of rollers and send to a guillotine, winder, or cross cut saw. Generally each roll of a roll stack has an individual oil or water cooling circuit so its temperature can be closely monitored and adjusted. Depending upon the final use of the sheet, the speed control of the chrome rolls can be very critical. The rolls can be individually driven with ac, or dc motors, or can be driven together using a chain, with torque limited slip of the last roll to accomodate sheet shrinkage.
In general sheet extrusion lines for commercial applications are between 500mm wide and 2500mm wide. Most packaging applications are for producing sheet for thermoforming machines, In general these machines require sheet of between 400mm and 900mm wide. The sheet thickness in these cases is generally between 200 micron and 2mm. Although other materials may be used, the majority of rigid packaging sheet is made from PS, PP, APET, CPET, ABS, PVC or PLA.
Industrial sheet for sheet fed thermoforming applications in the construction, or automotive fields are generally wider, operating at between 1500mm and 3000mm. The sheet thickness is generally between 1mm and 15mm. These sheets can be made from a wide variety of materials depending upon their application but the most common are PS, HIPS, ABS, SAN, PC, PMMA, HDPE, PP, or PVC.
TransXL buy and sell sheet extrusion machinery from well established manufacturers from around the world .
Examples of of USA manufacturers - Welex, Davis Standard, Brown, Egan, Gloenco, NRM, Cincinatti
Examples of of European manufacturers - Reifenhauser, Kuhne, Diamat, Breyer, Amut, Omipa, Kaufman, OMV, Krauss Maffei, Covema, Henschel, Erwepa, Battenfeld, Union, Brabender, SML