Troubleshooting common defects process simulator exercises include. Any gaps in film develops shear zones in metal which eventually develop into surface cracks. When pressure is applied at the closed end, complex shapes can be produced by complex openings fig. Plastemart provides technical information, literature and articles related to plastics industry, market reports, industry scenario, machinery, latest processing technology and recent developments in plastic raw materials and additives. Extrusion process, defects in plastic pipe, impact of defect, product quality. Gels are a common quality problem in extrusion of clear film and tubing less than 0. Surface defects of linear low density polyethylene annular. Modified extrusion and injection molding processes extrusion blow molding small tube is first extruded, usually vertically, then clamped and air blown inside to expand it to fit a much larger diameter mold air pressures 350700 kpa 50100 psi can be a continuous process corrugated pipe and tubing injection blow molding. Defects can also result from a lack of control, or contamination, of the solutions used in the various stages used to produce an anodized finish. We cant see what goes on inside an extruder, so we depend on instruments. Technical training on blown film extrusion 1617 november 2015 9. The defects considered include zigzag features that can form on the surface or interfaces in the extruded multilayer films, and parabolic and finger. The randomizer moves the film back and forth, as it is slit and wound.
Therefore, it is rather difficult to predict extrusion force in hot extrusion. Strain effects on flow stress and hence on extrusion pressure are predominant for hot extrusion due to strain rate sensitivity. Blown film extrusion is best done with polyolefin type screws, described in section 5. Faulty thermocouple, or other fault in heating or cooling. Film defects troubleshooting guide 167 roll defects troubleshooting guide 184 glossary of terminology 191. The blown film extrusion process can produce magnificent arrays of products however.
Effective troubleshooting of extrusion problems aip publishing. Gels causess possible solutions dirty air ring cont. Some defects may originate in the substrate metal as a result of the thermomechanical fabrication process used to produce the sheet or extrusion or during handling and storage of. Blown film troubleshooting guide westlake chemical. Blown film processes and troubleshootingand troubleshooting the ultimate quality control tool presented by.
The most common defects may be described as pitting, streaking or general nonuniform appearance. Fundamentals of cast film extrusion technologymacro. The defects, or rejects, from an extrusion run may be named by such terms as. Inline extrusion monitoring and product quality tspace. Blown film extrusion is a technology that is the most common method to make plastic w films, especially for the packaging industry. The darker patches carry oxides and other inclusions into the extruded section, leading to extrusion defects. In order to evenly distribute defects on the extruded film thickness variations a randomizer is used. Online quality control of polymers and extruded films.
Polyethylene film processing guide quality, value and performance our guiding principles everything we do at formosa is measured against the following guiding principles. The lubricant film must be complete and continuous to be successful. Pdf extrusion defects and flow instabilities of molten polymers. This new edition has allowed updating and expanding on defects commonly found in paper and paperboard products and in the production and converting of nonwovens, films and laminations. Paul waller president plastics touchpoint group, inc. Detect a wide variety of defects in coating and metallizing, such as voids, streaks, chatter, fibers, gels, spots, dimples, contaminants in substrate and coated film. Pvc extrusion is a continuous processing method that offers high speed and high volume production with the ability to create products of varying shapes, thickness, hardness, additives and colors. Alter formulation or equipment to achieve suitable extruder speeds. A methodology to link process parameters and fluid rheology to onset of certain types of defects is developed. This paper deals with defects in multilayer plastic films in the extrusion process. Center burst defect is an internal crack that develops as a result of tensile stresses along the center line of the workpart during the extrusion process. Coextrusion of blown film coextrusion is the extrusion of multiple layers of material simultaneously.
Extruder speed too slow or too fast for optimum extrusion. The identification and prevention of defects on finished. Pdf product defects in aluminum extrusion and their. Extrusion is the method that produces the largest volume of plastic products extruded products are generally long uniform and solid or hollow complex crosssections 2 sheet and film extrusion other types tubing, electrical wire coating, pipes to extrude thin film, air is forced into an. In addition, we would like to thank john herrmann, jim reilly, and joan decoste of the dynisco companies and christine ronaghan and. The extrusion of plastic film containing defects 5. Integrity because no successful bond can be formed without trust, we are fair and honest in all our relation. First of all, we would like to thank john goff and tony whelan who have contributed new material that has been included in this new addition of their original book. A study of plastic extrusion process and its defects ijltemas. This bubble is then collapsed and used as a layflat film or can be made into bags. Gels are primarily visual defects caused by small bits of highermolecularweight material or contamination that reflect and transmit light differently from the rest of the material.
An alternative approach is to move the slitter and winder back and forth relative to. Troubleshooting the extrusion process hanser publications. The aluminium extrusion process begins with heating. Trouble shooting and solving extrusion problems is one of the most critical.
Troubleshooting melt fracture in profile, tubing extrusion. Be patientsome changes take longer than others wrinkle. The information is offered solely for your information and is not allinclusive other variables or constraints may impact the ability of the user to apply them. Table of contents chapter 1 polymer properties and terminology 1. This technical paper was written and developed in may 1994. Effects of antiblockprocessing aid combinations on llpde blown film extrusion intro. If the plastic bag will have gussets, special frames called gusset. The term gel is commonly used to refer to any small defect that distorts a film product. The extrusion process converts a solid plastic feedstock material into a molten viscous fluid, and then to a finished solid or flexible film product for practical use. Blown film extrusion is one of the most commonly used thin gauge fabrication processes for manufacturing plastic films in the world.
Some of the common extrusion defects are improper operation, resin defects, trapped air, overheating, melt fracture, moisture absorption, poor mixing, surging. Troubleshooting the extrusion process a systematic approach to solving plastic extrusion problems 2nd edition maria del pilar noriega e. The analysis system can provide a list of defects and the amount lost to each, so that the most onerous defects can be eradicated. Product defects in aluminum extrusion and their impact on operational cost vol. Troubleshooting and mitigating gels in polyolefin film.
Troubleshooting guide for cast film and sheet extrusion problem possible causes possible solutions 1. Dimple on film the system specifications are developed by identifying defects that need to be detected and their size using laboratory systems. As the film reaches the top of the cooling tower, the guides gradually flatten it into a layflat form. Eliminating gel defects from extruded polyolefin film products can be difficult, time consuming, and expensive due to the complexity of the problem and the high levels of offspecification product produced. Blown film properties purchasing production maintenance raw material properties mw mwd density. Extrusion coating troubleshooting guide edge t ear excessive odor gauge bands poor adhesion poor heat sealability causess possible solutions insufficient oxidation decrease the line speed increase the air gap chill roll tack lower the temperature of the chill roll substrate is too rough treat the substrate surface prior to use. We need to be sure that all sensors are working and readouts are calibrated correctly. The information contained in these guidelines is provided in good faith and may assist with problem solving and troubleshooting. The ultimate roll and web defect troubleshooting guide is an updated and expanded version of the roll and web defect terminology 2nd edition. Tapered tension reduces end crowning, buckling, starring and dishing roll defects in rolls of flexible packaging film material. Online quality control of polymers and extruded films oliver hissmann.
Although tensile stresses may not usually be seen in a compression process such. Due to the complexity of the extrusion processing method, problems can and will. Pdf when certain critical conditions are exceeded, the flow of a. Locate defects, identify, and mark location on web and log defect information into an electronic file and data base. To ensure quality extrusion pipe manufacturing, it is essential to identify. In india, extrusion based methods account for 75 % of the total plastic processed. Chris rauwendaal isbns 9781569904701 1569904707 hanser hanser publishers, munich hanser publications, cincinnati sample chapter 1. Zone 1 shows the flowing metal through the rigid conical zone 2, which is defined to be a deadmetal zone. Dyneon llc was formerly a whollyowned subsidiary of 3m company and was fully integrated into 3m company on january 1, 2011.
Check for control valve problems if using an internal bubble cooling ibc system. This technical paper was written and developed in may 1994 when the authors was an employee of dyneon llc. Troubleshooting guide for cast film and sheet extrusion. Irregularities during the process of extrusion these are mainly due to non uniform flow and stress distribution number of defects depends upon. Ppt extrusion powerpoint presentation free to download. Classification of main faults in the production process of. Jiri george drobny, in handbook of thermoplastic elastomers second edition, 2014. Applesauce, gels, poor clarity melt temperature too high, or excessive residence time reduce melt temperature correct malfunctioning thermocouple and controllers install a lower shear screw. The ultimate roll and web defect troubleshooting guide.1404 596 1462 827 1417 356 100 602 1346 231 1277 1395 201 1423 960 1071 978 1394 1468 203 1058 1172 634 629 443 661 623 487 1019 768 495 1171 1166 519 898 1450 354 667