Mono Layer Blown Film Extrusion Lines, Extrusion Machine
What is Blown Film Extrusion?
- Blown Film Extrusion is one of the most common polymer conversion processes in the world
- Film is made by extruding molten plastic through a circular die, forming an inflated tubular bubble that moves through a cage as it cools, that is then collapsed and formed into rolls
- The typical film blowing process consists of a series of stages, including extrusion, blowing, collapsing, and winding
HIPF Course Description
At the end of the course, the trainees will be able to:
- Develop a working knowledge of and learn how to operate a Blown Film Extrusion machine
- Understand the basics of blown film technology, the common material used, and some common problem solving situations
- Analyze and solve practical blown film problems
- Develop a working knowledge on maintaining a blown film machine
- Principles of Blown Film Extrusion
- Definition and Principle; Product and Applications; Film Fabrication Process; Types of Blown Film Machines
- Resin Materials for Blown Film
- Raw Materials Use for Blown Film Extrusion; Three Common Polyethylene Grades Used for Blown Film; Suitable Grade index for Blown Film
- Safety Education for Blown Film Operation
- Safety Guideline and SOP; Personal Protective Equipment (PPE); Safety Devices; Warning Signs; Safety Rules for Operation; Safety Instructions on Operation
- The Main Components of Blown Film Machine
- The Extruder; The Die Head and Die; The Bubble Cooling System; Bubble Stabilizer; The Take-Off System/Pinch or Nip Rolls; The Wind-Up System; Corona Treatment
- Die and Air Ring as Major Components for Blown Film
- Kinds of Die for Blown Film; Details of Die and How It Works; Details of Air Ring and How It Works; Die and Air Ring Care and Maintenance
- Introduction to the Blown Film Extrusion Machine
- BFE Process Flow; Start-Up of Blown Film Line; Quality Control for Blown Film; Scheduled Shut-Down of Blown Film Line; Emergency Shut-Down of Blown Film Line; Switching On After Emergency Stop
- Operating Skills for Blown Film Extrusion Technology
- Checking of Machine Conditions Before Operation; Winder Preparations; Film Guide Set-Up and Importance; Blown Film Run Preparations; Die Checking and Adjustments; Parameter Setting-Up; Switching On After Emergency Stop; Changing Die; Changing Materials and Filling Procedures
- Die Dismantling, Cleaning and Mounting
- Die Dismantling Procedure; Die Cleaning and Care; Understand Die Assembly and Mounting
- Blown Film Extrusion Troubleshooting
- Types of Trouble of Blown Film Process; Unstable Bubble; Film Appearance; Machine Malfunction
- Common Secondary Film Processing Methods
- Printing; Bag Making Process; Scrap Recycling
- Quality Control of Blown Film
- Quality Check for Blown Film; Production Recording; How To Report the Result of Manufacturing
- Practice Plant Operations
|provides the blown film industry with the latest in high “value added” technologies. Since 1989, DRJ has established industry standards in internal bubble cooling (IBC) control, width control, and machine direction sealing technologies and continues to develop innovations that make our customers more competitive and more profitable.|
The quickest way to get to know about us is to view this 4 minute video. It describes our company, our industry and how our products ensure that you add value to your bottom line.
Next if you are interested in IBC technology, click on the Getting Started link below. You can also click on the blown film line picture to see specific details. Don’t forget our Products link to see everything we do to provide solutions not just answers for your blown film processing requirements.
- This processing guide focuses on how to produce films made from either high density polyethylene (HDPE) or linear low density polyethylene (LLDPE) resins.
The HDPE FILM Resins section covers key terms and experience specific to polyethylene resins in
general, and HDPE resins specifically. It is organized into five subsections:
B. C. D. E.
Blown Film Extrusion
Extruder And Die Temperature Settings
The LLDPE Film Resins section covers key terms and experience specific to LLDPE resins. It is organized
into two subsections:
A. Blown Film Extrusion
B. Extruder And Die Temperature Settings
In addition, Table 1 presents a very useful polyethylene film processing troubleshooting guide.
The information, terminology and experience provided in this guide compile many years of technical
and operational knowledge into one handy resource, useful in most situations most of the time. For
more in-depth processing and troubleshooting assistance,
Polyethylene Film Processing Guide
I. HDPE FILM RESINS
high density polyethylene (HDPE) resins for
mainly blown film applications. The workhorse of Formosa Plastic’s HDPE film resins is the Formolene®
High Molecular Weight High Density Polyethylene (HMW-HDPE) resin product line, which is produced
using a unique Nippon Petrochemical bimodal process. These HMW-HDPE film products are designed to
have a broad, bimodal Molecular Weight Distribution (MWD) that provides both excellent extrusion processing and physical film properties.
Formosa Plastics also produces a family of conventional HDPE film resins from
process. These HDPE film resins from this process are categorized into two types of resins: Medium Molecular Weight High Density Polyethylene (MMW-HDPE) film resins and MMW-HDPE Moisture Vapor Transmission Rate (MVTR) barrier film resins.
HMW HDPE film resins range in density from 0.949 to 0.953 with a melt
index ranging from 0.040 to 0.15. These resins are designed with different melt index, density and/or additive packages for a variety of applications. Technical Data Sheets for these products are available at www.fpcusa.com/pe/index.html.
Films produced with HMW and MMW HDPE resins exhibit high impact and film stiffness, as well as good
tear strength and excellent tensile strength. The combination of a broad, bimodal MWD, low melt index
and high density of the Formolene® brand HDPE film resins provide an excellent balance of film performance properties for a variety of film applications.
HDPE film resins are easily processed into very thin gauge films as low as 6 microns
(0.25 mils), as well as into heavy gauge films on the order of 96 microns (4.0 mils) or greater. The
broad MWD of Formolene® brand HDPE film resins enables them to be processed at lower melt
temperatures than competitive HMW HDPE blown film resins. This provides for better bubble stability and gauge control, as well as improved energy savings.
HDPE film resins are designed with excellent stabilization packages to protect the
integrity of the polymer from degradation, especially for applications requiring a high level of trim
recycle such as grocery bags commonly referred to as “T-Shirt” bags due to their resemblance to the undergarment.
Polyethylene Film Processing Troubleshooting Guide
Common film processing problems and possible corrective actions
1. Low Dart Impact 5. Gels, Holes, Bubble Breaks 9. Low Extruder Output
2. Low MD Tear; Split Film 6. High Gauge Variation 10. High Extruder Pressure
3. Melt Fracture 7. Die Line 11. Poor Roll Geometry
4. Poor Bubble Stability 8. Port Line
Abbreviations: BUR = Blow-Up Ratio MD = Machine Direction MI = Melt Index
Problem Observed Possible Causes Possible Corrective Actions
1. Low Dart Impact 1. High melt temperature
2. Inadequate cooling
1. Reduce melt temperature
2. Increase cooling, neck height, BUR
2. Low MD Tear / Split Film 1. Too much film orientation
2. Resin density too high
3. Thermal degradation of the
polymer during extrusion
1a. Increase BUR
1b. Decrease die gap
1c. Increase frost line height
2. Use a lower density resin
3a. Decrease melt temperature
3b. Add an antioxidant masterbatch
3. Melt Fracture 1. Low extrusion temperature
2. Inadequate die gap
3. Excessive friction at die lip
4. Resin MI too low for extrusion
conditions or equipment
1. Increase melt temperature
2. Increase die gap
3a. Lower processing rate
3b. Add processing aid to reduce COF
4. Use a higher melt flow resin
4. Poor Bubble Stability 1. Melt temperature to high
2. Too much or too little cooling air
3. MI too high for process
4. Output rate too high
5. Misalignment of nip rolls
1. Reduce melt temperature
2. Adjust cooling air
3. Lower processing rate
4. Reduce output rate
5. Realign nip rolls
5. Gels, Holes, Bubble Breaks 1. Contamination
2. Excessive regrind or reprocessed
3. Dirty screw, die or screen pack
4. Poor mixing
1. Check for contamination in silos, transfer
systems, colors and other masterbatches
2. Stop or reduce the ratio of regrind and
reprocessed material until problem improves
3. Clean screw and die plus change screen pack
4a. Check screw
4b. Check heater bands and thermocouples
6. High Gauge Variation 1. Dirty screw, die or screen pack
2. Uneven cooling
1a. Clean screw and die plus change screen pack
1b. Clean die
2. Check temperature settings & recalibrate
7. Die LIne 1. Dirty or damaged die lip
2. Insufficient purging
1. Clean or repair die
2. Increase purge time between transitions
8. Port lines 1. Resin viscosity too high for die
2. Die and melt temperature off
3. Melt temperature too low
1a. Use a resin with a higher MI
1b. Consider using a processing aid
2. Narrow the temperature differences between
the die and polymer melt temperature
3. Increase the melt temperature
9. Low Extruder Output 1. Melt temperature too high
1a. Reduce melt temperature.
1b. Check external cooling.
1c. Check extruder screw wear.
10. High Extruder Pressure 1. Contamination 1a. Check extruder heaters, screen pack.
1b. Check for contamination.
11. Poor Roll Geometry 1. Poor bubble stability 1a. Reduce melt temperature.
1b. Increase cooling, die temperature.
1c. Clean die.
B. BLOW-UP-RATIO (BUR) AND POLYMER ORIENTATION
To produce the best physical properties in an extruded film, the proper balance of film orientation in
the machine and transverse direction of a film must be achieved. This relationship is achieved by
adjusting the blow up ratio of the film. The blow up ratio (BUR) is the ratio of bubble diameter to the
die diameter; it indicates the amount of stretching the polymer is undergoing during the shaping of the
Blow Up Ratio (BUR) = (0.637 x Lay-Flat Width) / Die Diameter
Lay-Flat is the width of the collapsed film
Die Diameter is the fixed diameter of a given die
The HMW-HDPE blown film lines typically have small diameter dies to achieve the relatively high BUR
ratios required to obtain optimum film properties. Other polyethylene resins, such as low density
polyethylene (LDPE) and linear low density (LLDPE) resins, normally operate at much lower BURs of 2 to
3. The typical die gaps for HDPE blown film lines are 1.0 to 1.5 mm (40 to 60 mils), which are narrower
than die gaps used for conventional LDPE and LLDPE blown film lines.
As shown in Figure 1 below, HDPE blown films lines have a very unique “High Stalk” bubble shape. The
stalk height recommended for HMW HDPE blown film lines is 7 times to 9 times the die diameter. The
characteristic high stalk bubble shape used for HMW-HDPE Blown film production results in a very high
frost line, which is the transitional phase from molten polymer to solid film. A high frost line enables
the polymer to achieve a balance of film properties by imparting more bi-axial molecular orientation in
the film in the transverse direction (TD) to match the machine direction (MD) orientation.
HMW HDPE AND LLDPE BLOWN FILM
Bi-axial orientation of the polymer molecules in a blown film is important to achieve a balance of the
film’s physical properties. Bi-axial orientation of HDPE blown film is much more difficult than with
either LDPE or LLDPE blown film due to the inherent differences of the polymer structures. Long side
chain molecular branching is prevalent in LDPE and to a lesser degree in LLDPE, but HDPE has very few