Barrels for Injection Molding and Extrusion

The barrel is the pressure carrying vessel with heat transfer demands for assisting in the plasticization of the material being processed. In an extruder, it is the hollow chamber in which the screw(s) operates. If one screw is used, the barrel has a cylindrical cross-section. If two screws are used, the barrel has a figure eight cross-section.

The screw and the barrel interact to melt, convey, and generate pressure on a polymeric material within an extruder. It is crucial that this is done under monitored and controlled conditions since the extruder's job is to produce uniformly plasticized material, having consistent composition, at the required rate.

To attain this, the barrel must be made very accurately. The total out-of-alignment error (or Total Indicated Runout), after machining, needs to be less than one-half of the screw/barrel clearance. A barrel is typically rated in terms of its diameter (D) in inches or millimeters. Though more straightforward in design than complex screw and tip geometries, the function is just as important. Quality is of utmost importance to us at TIR and our standards meet or exceed the SPI Guidelines.

Information on our varied range of premier designs and material options may be found on this page.

Barrel Capabilities

New Barrel Design

Key characteristics we consider when designing, manufacturing, and selecting materials for barrels, include:

• Dimensional stability of the lining alloy and backing steel

• Straightness is crucial to ensure that the screw and tip are centered throughout the entire length.
• Materials are chosen to withstand the immense pressures and changes in temperature from shut down to processing, based on application.
• TIR's barrels exceed the SPI standards, ensuring the straightest barrels available.
• Feed throat design, to promote free flow of feed material. 

Materials and Capabilities:

• Construction Method and Alloy Type: Tool Steel-lined and Bimetallic Barrels: Whether dedicated or custom molding, once your process requirements are outlined, we will recommend either a tool-steel-lined barrel or bimetallic barrel and apply the correct lining alloy to maximize the wear life of the barrel.
• Primary Materials: Bimetallic - tungsten carbide or standard liners, Nitrided and tool steel barrels
• Make/Model: Any
• Segmented Barrels: single and twin, vented and non-vented
• Hardware: diverters, vent plugs and stacks

Barrel Relining

Barrels relining is a standard  process in our manufacturing facility so we do not recommend that you throw out a worn barrel until you talk to us. Relined barrels perform equal to or better than the original barrel lining and are dimensionally straight and on size. Relined barrels often present an immediate cost saving over replacing with new.

Materials and Capabilities:

• Tungsten carbide
• Standard bimetallic
• Short relines on feed and/or discharge end can be most economical
• Segmented single and twin barrels

Other Services

• Emergency services such as pressing a screw out of the barrel
• Honing service