1. Description Of The Extruder
Thomas I. Butler
Blown Film Technology, LLC
9/8/2018

2. Conventional Extruder Grooved Feed Extruders Twin Screw Extruders
Extruder Types
Conventional Extruder
Single screw with a smooth barrel
Grooved Feed Extruders
Single screw with a grooved feed zone
Twin Screw Extruders
Co-rotating
Counter-rotating
Gear Pumps
9/8/2018

3. Presentation Overview
Description of A Single Screw Extruder
Single Screw Extruders
Smooth Barrel
Grooved Barrel
Single Screw Mixing
9/8/2018

4. Requirements for an Extruder
Convey pellets into screw channel
Compress solid bed/vent gas
Melt solid bed
Mix/blend to produce homogeneous melt
Produce desired melt temperature
Produce the pressure required for flow
9/8/2018

5. Extruder System Drive Motor Reducer Gear T p Pressure Transducers
Temperature
Thermocouples
Heating/Cooling
Zones
Diameter
Length/Diameter
9/8/2018

6. Extruder Drive Motor Extruder Max. Speed Output Rate Motor
inch rpm lb/hr Hp*
* For running 1.0 MI LLDPE
9/8/2018

7. Drive Coupling Shows one belt Extruder normally have multiple belts
Belt Drive
Direct Drive
Direct Drive
9/8/2018

8. Gear Reducer
Converts motor drive speed of 1750 RPM to useable extruder screw speeds of 40 to RPM
Conveys sufficient torque (horsepower) to shear, melt and transport materials along screw length. ( > 80% of energy input comes from the motor)
Thrust bearing must withstand tremendous rearward forces generated by screw.
9/8/2018

9. Gear Box Gear reduction ratio range 8 to 25 : 1 100 - 200 rpm 1750 rpm
9/8/2018

10. Thrust Bearing Assembly connecting the screw to the gear box
Tapered roller or Ball Bearing
Key
Bearings
Bearing
Assembly connecting the screw to the gear box
9/8/2018

11. Thrust Bearings
9/8/2018

12. The Extruder Hopper
A hopper is the storage area for all material fed to the extruder.
A two hour supply of material is a minimum hopper size.
A hopper should be equipped with a gate to start and stop the flow of material.
A slight window to observe the level of material
A dump/discharge port are usually supplied for quick changes.
Gravimetric load cells measure the output rate. 12
9/8/2018

13. Hopper Loader
Frequently, extruder users equip their machines with automatic hopper loaders. These devices, using vacuum or compressed air, transport material from a storage area into the extruder hopper.
9/8/2018

14. Multi Component Gravimetric Hoppers
Loss Weight Feeders
Each hopper is mounted to an independent load cell.
The weighing system is programmed for simultaneous and proportional metering of each ingredient. 14
9/8/2018

15. Crammer Feed Throat
Crammers help run low bulk density feedstock to increase output and improve stability.
It can increase output by as much as 30%.
Typical materials
Powders
Thin, flake regrind 15
9/8/2018

16. Feed Section Pellet feed from hopper Barrel is flanged
Support for screw
Barrel is flanged
to feed section
Cooling channel
9/8/2018

17. Extruder Barrel with Screw
Barrel Diameter
Length/Diameter
Thermocouples T T T T T p p p p p
Pressure
Transducers
Heating/Cooling
Zones
9/8/2018

18. Screw Design / Barrel Zones
Zone Heat/Cool
Feed
Melt
Meter 18
9/8/2018

19. Thermocouple T ~ DV J type thermocouple
Junction
Wire
Sheath
J type thermocouple
Two wires (iron & constantan) joined together at end.
Temperature is measured as a function of voltage difference
Thermocouple must be in direct contact with metal
J type thermocouple
Two wires (iron & constantan) joined together at end.
Temperature is measured as a function of voltage difference
9/8/2018

20. Zone Temperature Control
Heater
Blower on
Cooling Fins
Thermocouple to PID controller
400
9/8/2018

21. Heater Elements Inside Band21
9/8/2018

22. Barrel Heater / Air Cooling
9/8/2018

23. Liquid-Cooled Band 23
9/8/2018

24. Variable Depth Thermocouple
Located in the adapter pipe
9/8/2018

25. Pressure Transducer Pressure Transducer Rupture Disk Push rod
Capillary
Rupture Disk
9/8/2018

26. Rupture Disk Must be operational at all times. Common Ratings:
5,500 psi
6,500 psi
7,500 psi
10,000 psi
9/8/2018

27. Screw Design / Barrel Zones
Feed
Melt
Meter
Zone Heat/Cool
The barrel is divided into multiple temperature zones to insure proper extruder operation.
Stability of the temperature controllers is of prime importance in maintaining the final product quality. 27
9/8/2018

28. Screw Nomenclature Feeding Section (S) Compression Section (C)
9/8/2018 28
Feeding
Section (S)
Compression
Section (C)
Metering
Section (M) q P
Shank D F H L
D Screw Diameter L Length
q Helix Angle (17.65) P Pitch or Lead
F Depth of Feed H Depth of Metering
S Length of Feed/D C Length of Compression/D
M Length of Metering /D N Screw Speed rpm
W Flight Width
9/8/2018

29. Extruder Barrel Standard Sizes
English units (inch of inside diameter)
0.5, 0.75, 1.0, 1.25, 2, 2.5, 3.5, 4.5, 6, 8, 10, 12
Metric units (mm of inside diameter)
20, 30, 40, 50, 60, 70, 90, 120, 150, 200
Common L/D’s
18, 24, 28, 30 , 32, 40
Lab scale Extruders Commercial Extruders
9/8/2018

30. Screw Types Metering Screws Barrier Screws Grooved Barrel Screws
Vented Screws
9/8/2018

31. Metering Screw
9/8/2018

32. Barrier Screw
DSB-II
9/8/2018

33. Grooved Feed Housing Feed Section One-piece feed section housing
Single-piece feed section
High Flow Cooling Channel
One-piece Grooved
Liner Insert
Feed Section
One-piece feed section housing
One-piece groove liner
Intensively water-cooling over grooves (highly turbulent flow)
9/8/2018

34. Groove-Feed Barrel
9/8/2018

35. Vented Barrel Extruder
A vented barrel provides for the removal of volatiles (moisture, gases, air).
The volatiles are remove through an opening in the barrel cylinder.
A 2-stage screw is used in vented extruders
Vent
For Hygroscopic
Thermoplastics
Vent, dryer, or both
May be used.
9/8/2018

36. Filtering 36
9/8/2018

37. Breaker Plate/Screen Pack
9/8/2018

38. Screen Pack Typical Screen Pack:
Breaker Plate: 20 /40 / 80 / 40 / Screw
9/8/2018

39. Screen Pack Opening Sizes
Mesh Micron Wire Diameter Inch 39
9/8/2018

40. Automatic Screen Changers40
9/8/2018

41. Adapter Pipe 41
9/8/2018

42. Static Mixers Corrugated type – better mixing/more pressure drop
Helical twist type – less mixing/less pressure drop 42
9/8/2018

43. Mixing Sections DISTRIBUTIVE Pineapple Mixer Saxton Mixer
Dulmage Mixer
Pin Mixer
DISPERSIVE
Union Carbide Mixer
Helical UCC
Cavity Transfer Mixer
9/8/2018

44. Uses for Static Mixers Viscosity decreases at higher temperature
Hard to improve mixing at low viscosity
Use Static mixers
Improve pigment dispersion
Improve additive dispersion
Improve melt temperature uniformity
Problems of static mixers (gels)
Increased residence time distribution
Stagnant flow channels 44
9/8/2018

45. Coextrusion Piping Minimize residence time Watch pressure
Safety concerns during heat-up 45
9/8/2018

46. Twin Screw Extruder
WP (Werner & Pfleiderer)
9/8/2018

47. Gear Pump
9/8/2018