Are injection/extrusion barrel linings a good idea?
The barrel used in an extrusion or injection molding machine will affect the final parts, the machine’s overall efficiency, and the project budget. Selecting the right barrel for the materials to be processed is essential. To further avoid production issues, manufacturers must also closely monitor their selected materials’ effects on their equipment. Processing abrasive, corrosive, and high-temperature resins, as well as engineering plastics, thermoplastics, specific other elastomers, and new biopolymers, plus a variety of material enhancements or additives such as glass fibers, can be trapped between the screw & the barrel wall & quickly degrade these parts.
Corrosive wear occurs when the barrel’s liner & backing material is attacked by acids or acidic gasses while processing materials. Acidic polymers (such as acetals, fluoropolymers, and PVC, among others) dissolve oxide coatings and can severely damage the screw and barrel. Abrasive wear occurs when glass fiber fillers and other hard particles grind against the barrel during processing. This is to be expected, they key is to manage wear by selecting a premium barrel liner such as carbide or high nickel content.
How can these issues be mitigated?
Of course, you know that it is crucial to stay on top of regular preventative maintenance to ensure that your production isn’t slowed or halted altogether due to a worn barrel. The best way to ensure extended barrel life and better resistance to your materials is to use a bimetallic lined barrel specifically designed to withstand the plastic resins being processed. Wear-resistant barrels that protect against abrasion, corrosion, and high temperatures may cost a bit more than the standard non-lined varieties; however, they provide better wear life and longer intervals between servicing needs.
Bimetallic barrels are manufactured as one-piece units. A lining alloy (typically 1mm-2mm in thickness) is centrifically casted to the inside of a seamless pre-machined steel tube. Since the lining of a bimetallic barrel is metalurgically bonded to the outer barrel, it will avoid some of the issues that may occur with multi-piece barrels.
Bimetallic barrels may also be a bit more costly to purchase; however, their extended life and better resistance to wear and corrosion mean you will save money in the long run. An investment in your machinery, ensuring the highest quality components and tools, is essential for manufacturing the best quality products.
Materials used for lining barrels
The outer shell for most barrels is made from 4140 OR micro alloy series carbon steel due to the strength the material offers. The linings are usually either nitride, cast bimetallic, or tool steel.
For example:
| Tan Star High-Performance Bimetallic Barrel linings offered | Other High-Performance Bimetallic Barrels linings offered |
| TP-F Nickel base for corrosive resistance F10 Iron/Boron for general purpose | R241 Nickel base with carbide for high wear and moderate corrosion resistance |
| T10 Nickel base with carbide for <15% glass fiber | R112 Iron base for general purpose |
| T25 Nickel base with carbide for <30% glass fiber | BO55 Nickel base and 0% iron content casted by HIP (Hot Isostatic Pressing) for severe corrosive resistance |
| T40 Nickel base with carbide for <50% glass fiber | |
| T60 Nickel base with carbide for Halogen free materials with high corrosion resistance |
As you can see, the best way to protect your equipment from corrosive or abrasive polymers and resins is to select a barrel that is constructed of the proper materials for your specific manufacturing needs.
How can we help you?
The doors have been open at Santa Fe Machine Works, Inc. since 1923, and for the past 45 years we have been dedicated solely to the manufacture and supply of new & rebuilt injection & extrusion screws, barrels & valves to the plastics industry. We also offer custom-tailored screw, barrel, and valve combinations, allowing our customer’s production goals to be met in the best, fastest, and most cost-effective ways possible. Our employees have over 200 years of combined experience in the plastics industry and are eager to support your specific extrusion or injection needs. Have a question, need assistance, or looking for a quote? Contact us today!
