Leistritz Twin Screw Extrusion Workshop to be held December 4-5, 2019
Dates: December 4-5, 2019
Place: Classroom sessions, Clinton, NJ. Demonstrations are at the Leistritz Process Laboratory.
Cost: $800 before Nov. 8th, $900 thereafter
Leistritz will host its' annual Twin Screw Extrusion Workshop on December 4-5, 2019 in NJ. Although focused on plastics, many representatives from Life Science have benefited by attending this program.
A partial list of topics includes:
- Co-rotating and counterrotating twin screw extrusion technology
- Techniques for dispersive and/or distributive mixing
- Sequencing of multi-stage process operations
- Devolatilization process techniques and practices
- Scale-up of the twin screw extrusion process
- Feeders and material handling for pellets, powders and liquids
- Downstream systems: tube, profile, film, sheet, laminate, fibers+
- Control and monitoring options
- Twin screw extruder maintenance tips and procedures
"Hands-on" demonstrations at Leistritz NJ process laboratory will include:
- Co-rotating and counterrotating twin screw extruders
- Devolatilization via extrusion: ambient, vacuum assist, and multi-stage
- Pelletizing: hot face cut, underwater and strand
- Direct sheet/film extrusion with gear pump front-end
- Foam extrusion via supercritical injection
- Screw assembly and disassembly
Installation of a twin screw extruder system…. it’s all about planning and preparation!
Preparation phase: Installing a twin screw extruder system is a big job. Site preparation and coordination of the many divergent tasks that are required to install and successfully commission equipment is best not left to chance. Even modest planning will yield benefits far beyond the installation and start-up phases of a new project.
Barrel alignment procedures for twin screw extruders
The alignment of the barrel to gearbox on an extruder is important to minimize screw and barrel wear, as well as avoid fatigue cracks in the shafts. Required tools include a precision millwright's level and wrenches (to adjust the barrel support nuts).
Managing Melt Temperature in a Twin Screw Extruder
The co-rotating, intermeshing twin screw extruder (TSE) is the most prevalent device for continuous mixing of polymers with additives and fillers. Exotic formulations that utilize atypical active ingredients are also processed. Materials exposed to high shear and temperatures will degrade. Most products benefit by strategically managing how shear (and energy) is imparted into the materials being processed and measured by the resulting melt temperature. Various factors are considered to manage and control the melt temperature, including operating conditions and screw design. In this paper, emphasis is focused on the melting zone in the screws.
A series of experiments were performed on a ZSE-27 MAXX (28.3 mm dia. screws and 1.66 OD/ID ratio) to compare the resulting melt temperature for different melting zone screw configurations for a 2 MFI PP. An "aggressive" melting zone with melting completed by barrel position 3 (12 L/D) was compared to an "extended" melting zone, where melting was completed by barrel position 4 (16 L/D). Only a single kneading block set was specified after melting to help isolate and compare the different melting zone configurations, and the resulting melt temperature. A low-pressure discharge die was used to minimize the effects of pressure on melt temperature. Both flush and immersion melt temperature probes were utilized in the experiments. Various rates and screw rpm tests were performed and compared.
TSE formula: Temperature rise caused by pressure
Pressure generation in the extruder front-end caused results in a temperature rise. The more restrictive the front-end, the higher the pressure and melt temperature rise, which may adversely effect product quality. A temperature rise formula is as follows:
∆ T (°C) = ∆ P (bar) / 2
∆ T = Change in temperature in °C
∆ P = Change in pressure (1 bar = 14.503 PSI)
For example: If a TSE is processing 500 kgs/hr and the die pressure is 40 bar (580 PSI) then the associated melt temperature rise can be 20°C (∆ T = 40/2).
This formula is meant to be insightful, not necessarily accurate. Of course, the TSE rpm, and the geometry of the discharge screw elements are significant factors in the actual melt temperature. The moral of the story, don't underestimate the role discharge pressure might be contributing to the melt temperature.
Gear pump attached to twin screw extruder for 3D filament production
Side view gear pump (courtesy Witte Pumps)
The use of a gear pump or single screw pump can be integrated into the TSE system to keep the discharge pressure low and decrease melt temperature as compared to directly pressuring the downstream die/filtration system. Oil temperature control of the gear pump or intensive cooling of screw pump can help minimize the temperature rise associated with either device.
Test, don’t guess! Leistritz USA process laboratory expanded and improved
The Leistritz USA process laboratory includes 5 twin screw extruders and can test a 50 gram batch or run a process @ 1000 kgs/hr. A wide array of upstream and downstream equipment is available to allow testing of cutting edge technologies. A partial list of capabilities follows:
- Co-rotating and counterrotating twin screw extruders
- Downstream sheet/film/lamination systems with die widths from 2 to 40 inches wide
- Co-extrusion, up to 5 layers
- Loss-in-weight feeder for pellets, powder and fibers
- Liquid injection, heated and ambient
- Supercritical CO2 injection for foaming or stripping
- Extended L/Ds for multi-stage devolatilization
Leistritz Extrusion Technology brochure
A 16 page brochure is available that describes the current range of twin screw technologies and services available from Leistritz.
To download the Leistritz Technology brochure click HERE.
Visit Leistritz at these upcoming industry events:
- Plastic Technology's Extrusion 2019, Sep 17-19, 2019 Rosemont, IL
- SPE CAD RETEC, Sep 23-25, 2019 Cleveland, OH
- K 2019,Oct 16-21, 2019, Hall 16/Stand F22, Dusseldorf, Germany
- PharmSci 360,Nov 3-6, 2019 San Antonio, TX
- MDM/Plastic West,Feb 11-13, 2020 Anaheim, CA
- SPE ANTEC, Mar 30-Apr 2, 2020, San Antonio, TX
- SPE Shape Extrusion Topcon, May 12-14, 2020, Nashville, TN
We are looking forward to meeting you there!
Your Leistritz team
175 Meister Ave.
Somerville, NJ, 08876, USA
ph: 908 685-2333