SEPTEMBER 2003   
 

The feed section is one of the most commonly overlooked components on an extruder. In the Technically Speaking section of this issue of Akcelerator, we explore its design and role in the overall performance and longevity of an extruder. In Product News we introduce our new “modular” M-Series extruder that enables you to change extruder sizes in minutes. We also show our new, cost-effective adjustable height extruder design. Worth Noting invites a look at AK’s new, improved web site and AKt Now offers special low pricing on breaker plates.

TECHNICALLY SPEAKING...

Feed Section Choking Your Profits?

A crash course on feed section design and rehabilitation.

The extruder feed section performs a number of important functions. It isolates the gearbox and thrust bearing from excessive heat. It optimizes material flow with an adequately sized feed opening and geometry. And, via the water jacket, it prevents incoming pellets, regrind or fluff from melting prematurely, causing bridging on the in-feed.

A poorly designed or improperly functioning feed section can cost you in three ways: decreased throughput; process instability; and shorter gearbox life. Here’s a fast run-through of what you need to know. (For our full-length technical article on the subject, please visit “Technically Speaking” at www.americankuhne.com.)

Common problems and possible solutions

Years of use can cause existing equipment in the field to develop some common problems. Often these problems are fixable in the field.

Problem – A partially or completely clogged water-cooling jacket can prevent water flow and, therefore, accurate temperature control.
Solution – Try flushing out corrosion and other debris with an appropriate cleaning treatment. If you can regain cooling flow so that the casting stays between 100°F and 140°F you’re in good shape.

Problem – Wear in the rear bushing area can allow material (regrind, fluff and fines) to escape and build up in the feed section’s air-spacer area.
Solution – New bushings can be installed at the back to prevent material from escaping.

Problem – Increased clearance around the screw flights due to wear can impede material movement.
Solution – To fix a casting with a worn bore around the screw, the feed section must be removed, machined and a new liner pressed in.

Problem – Older extruders often have much smaller feed openings (as little as one diameter round). This may significantly restrict material flow and throughput when compared to today’s large rectangular feed openings.
Solution – Perhaps it’s time to purchase a new, modern extruder!

What to Look for in a New Extruder

Replaceable feed liner

If you anticipate high wear levels in the feed section, consider having a wear-resistant (nitride-hardened or bi-metallic) liner installed in the machine during manufacture. (AK offers an option that allows the liner to be replaced with the feed section installed on the machine, using standard tools).

Full-surround water cooling
  

Look at a drawing of the water jacket design. Most are designed in a “U” shape, cooling only the bottom and sides of the casting. (AK’s “full-surround” water flow cools the critical area above the screw and downstream of the hopper opening. This unique design can significantly help reduce premature melting and/or bridging of many pelletized and regrind materials.)

Optimized feed geometry
Choose the right feed section geometry for your application. North American manufacturers have historically used “smooth-feed” while Europeans have favored “grooved feed” designs. Grooved designs can be more efficient for some materials, but require longer feed length, more water-cooling, shallower screws and increase the overall machine cost. However, significant gains can be achieved by adapting the “conventional” smooth feed design with specially designed liners. (AK has developed field replaceable liners with grooves, tangential undercuts and other design changes to specifically solve feed problems related to a resin’s frictional characteristics.)

For a detailed review of your specific application(s), please contact your local American Kuhne Sales Representative, email Ed Steward or call him at (860) 886-7745, ext. 114.

 

-- PRODUCT NEWS --


New Modular Extruder for Fast Screw and Barrel Size Changes
Change from a 2.0-inch to a 3.0-inch machine in minutes!

For processors requiring a wide range of outputs from a limited number of production lines, or for lab/development applications, American Kuhne has developed a unique “modular” extruder allowing fast changes in extruder sizes. For example, the module pictured above allows you to convert from a 2.0 -inch to 2.25, 2.5, 2.75, or 3.0-inch machine in a matter of minutes.

New Cost Effective Approach to Adjustable Centerline Height
Available on 2.5-inch extruders and larger!

American Kuhne has developed a new system using multiple interconnected precision screw jacks to provide +/- 6” or more of height adjustability. Movement can be powered by hand, electric motor or pneumatics. An optional closed-loop height position control is also available.

WORTH NOTING

AK Web Site New and Improved!
We've updated our web site (www.americankuhne.com) with a number of important and useful new features.

  • Expanded content on AK's capabilities.
  • Direct links to the web sites of our sales reps.
  • Full-length technical articles in "Technically Speaking".
  • Access to archived editions of our newsletter "Akcelerator".
  • A password-protected, detailed technical review of our extruder design features and benefits plus access to an extensive photo library of our extruders (coming soon).
  • On-line commerce allowing credit card purchases of parts for American Kuhne and competitive extruders (coming soon).


AKt Now!

Get a Break on Breaker Plates
Special low pricing through October 31, 2003 on AK and competitive breaker plates.

Sample prices for conventional (round hole) stainless steel breaker plates:

2.5-inch
3.5-inch
4.5-inch
6.0-inch

$100.00*
$200.00*
$300.00*
$400.00*

*Note: Please email Stew Pollin or call him at (860) 886-7745, ext. 128 for confirmed prices on your specific design.

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