The feed screw is the heart of any extrusion process. In the Technically Speaking section of this issue of Akcelerator, we explore, in-depth, the technical and financial benefits of optimizing your machine’s performance with barrier screw technology. In Product News you’ll learn about our new AKcess Limited touch screen system. It is priced well below our fully customized AKcess system, yet provides all of the functionality required by the medical and automotive industries. Worth Noting recognizes our own Ed Steward as the 2004 recipient of ANTEC’s prestigious Bruce Maddock award. And you'll want to check our new operator/maintenance tool kit in AKt NOW.

TECHNICALLY SPEAKING...

All feed screws are NOT created equal!
How an optimized screw design can boost profits and reduce headaches

Many processors believe that they (a) already have the best screw for their process and/or (b) are convinced that their process is “downstream limited”… and not “extruder limited”. However, almost all extrusion processes can benefit from improvements in screw performance. We’ve delivered well over 1,500 Steward Barrier screws for all extrusion processes, proving day-in and day-out that a properly designed and customized screw can improve even the most well refined extrusion lines.

Here’s a brief synopsis of the AK step-by-step methodology leading to the proper barrier screw recommendation. (For our longer technical article on this subject, please visit Technically Speaking at www.americankuhne.com.)

Start by benchmarking
To properly benchmark existing data, the first step is to collect detailed information on seven kinds of baseline data:

1. Resin type and consistency — A screw designer needs to know detailed specifications for the resins to be run on any individual screw. For common resins, we have a large data base and previous design/performance experience. For unique formulations, we have an extensive data acquisition system in our fully instrumented extrusion lab and will run your resin at no charge.

Typically, a screw that will run one or two resins can be optimized for maximum performance. Conversely, a screw that must run many different types of resins (wide viscosity range) must be designed for versatility and will, as a result, sacrifice some performance.

2. Levels of regrind and other additives — Lower than normal bulk density and/or unique additives (either already compounded in the base resin, or additives introduced by blending with the base resin at the extruder feed throat) often affect the feeding characteristic of the resin and can result in reduced output and/or pressure fluctuations (surging).

3. Existing screw design/screw speed — It is vital to understand the maximum screw speeds required to produce the product at the required output rate. Metering screws can typically provide acceptable performance on most resins when operating below approximately 30 to 50 rpm. Above 50 rpm, their simple design can often lead to poor melt quality and/or surging. The core benefit of the barrier/mixing screw design is that the barrier flight enables greater screw depths, thus pumping more lbs./rpm at lower melt temperatures.

4. Screw, barrel, and feed section wear levels — For more information regarding the impact of “excessive” wear, please review our Technically Speaking article, “Effects of Screw and Barrel Wear on Extruder Performance.”

5. Head pressures — Optimal screw performance is more easily achieved when head pressures are relatively low. Higher head pressures result in higher melt temperatures and reduced output (lbs/rpm) for most resins.

6. Available HP and torque — When retrofitting a higher performing barrier screw, it is critical to know the extruder drive size and maximum screw speed to properly calculate the available torque.

7. Downstream cooling performance — Downstream cooling can often limit the overall performance of an extrusion system. One of the fundamental benefits of an improved barrier screw design is to deliver higher output at the same or lower melt temperature as the existing screw design – potentially resulting in little, if any, increased demand on the downstream cooling system.

-- PRODUCT NEWS --

New, mid-level AKcess Limited debuts on turn-key tubing system
All new hardware and software brings unprecedented value and control feedback

The new AKcess Limited system combines a high quality 12” color screen with Windows technology, running a premiere off-the-shelf software package worthy of medical and automotive industry requirements.

For coordinated control of complete extrusion lines, operators have easy to use graphical screens for recipe upload and download as well as alarm logging and process trending. The central computer communicates with auxiliary line equipment via industrial busses such as ProfiBus, Device Net and ModBus. The AKcess Limited may also be linked to a plant-wide network via Ethernet connection to export CSV files.

WORTH NOTING

Congratulations, Ed!
Ed Steward receives outstanding achievement honor at ANTEC in Chicago!

During the ANTEC technical conference in Chicago last month, Ed Steward was honored with the Bruce Maddock award for “contributing significantly to the advancement of single screw technology – by providing experimental achievements and understanding to the fundamentals of solids conveying, melting, mixing and pumping functions of single screw extruders”. This is the industry’s highest honor for a screw designer, and is given in memory of Bruce Maddock, a pioneer in screw design and lab experimentation. Ed is in good company, as only a few other very notable specialists have received this same honor, including Robert Barr, Norton Wheeler, George Kruder, Chan Chung, Zehev Tadmor and Kun Hyun.

AKt NOW!

New Operator/Maintenance Tool Kit Available!
All the tools and supplies you need in one very affordable kit.

Our new operator/maintenance kit has all the essentials needed to operate and maintain your extruder. Included in the storage toolbox with tote tray are a brass scraper, two wire brushes (small and large fine filament), copper gauze, Kevlar gloves, anti-seize compound, brass needle-nose pliers, straight and bent brass picks, screen packages (20, 40, 60, 80 and 100 mesh) and an aluminum alloy hammer.
Special introductory sale price: $250.00