How to Avoid Material Wall Sticking in Screw Feeders

How to Avoid Material Wall Sticking in Screw Feeders

1. Equipment Design Optimization

1.1 Barrel Inner Wall Treatment

• Adopt mirror polishing or hard anodizing for the barrel inner wall to reduce surface roughness (Ra ≤ 0.8μm is preferred) and minimize material adsorption points; for viscous materials, line the barrel with polytetrafluoroethylene (PTFE) or ultra-high molecular weight polyethylene (UHMWPE) to leverage their low-friction and non-stick properties for reducing wall sticking.
• Optimize the gap between the barrel and screw blades: Excessively large gaps cause material retention and wall sticking, while overly small gaps lead to wear. Generally, the gap between the blade outer diameter and barrel inner wall is set to 2–5mm (adjust based on material particle size; use smaller values for fine powders).

1.2 Screw Blade Structure Design

• Select ribbon blades (instead of solid blades) or blades with scraping edges; attach wear-resistant polyurethane scraping strips to the blade edges to directly scrape the barrel inner wall during rotation and remove adhered materials. For easily agglomerated materials, add crushing teeth or stirring rods on the blades to break up lumps and avoid wall accumulation.
• Adopt variable pitch design: Smaller pitch at the feeding end (to enhance pushing force) and larger pitch at the discharge end (to accelerate material discharge) reduce material residence time in the barrel and lower the risk of wall sticking.

1.3 Auxiliary Structure Configuration

• Install vibrators (e.g., electromagnetic or pneumatic vibrators) on the barrel outer wall; high-frequency micro-vibrations cause adhered materials on the inner wall to fall off, suitable for granular materials or slightly viscous materials. Adjust vibration frequency to match material characteristics to avoid material agglomeration from excessive vibration.
• For high-temperature fusible materials (e.g., plastic pellets), design the barrel with a jacketed temperature control structure; circulate cooling water or heat transfer oil to maintain the barrel temperature below the material softening point and prevent material melting and wall sticking.

2. Material Pretreatment and Adaptation

2.1 Control of Material Characteristics

• Drying treatment: For hygroscopic materials (e.g., flour, plastic pellets), dry them in advance to a moisture content ≤ 0.5% (adjust based on material requirements) to avoid agglomeration and wall sticking caused by moisture; use a hopper dryer if needed.
• Sieving treatment: Remove large particles, lumps, or impurities from materials to prevent foreign objects from getting stuck in the gap between blades and the barrel, which causes material accumulation and wall sticking.

2.2 Additives (for Viscous Materials)

• For highly viscous materials (e.g., starch, pasty materials), add appropriate release agents (e.g., food-grade talcum powder, silica) or anti-adhesive agents to reduce adhesion between materials and metal surfaces. In the food industry, use additives that comply with food safety standards.

3. Operation and Maintenance Specifications

3.1 Rational Control of Operating Parameters

• Adjust screw speed: Excessively low speed leads to slow material advancement, long residence time, and wall sticking; excessively high speed may cause excessive centrifugal force, making materials adhere to the inner wall (especially fine powders). Debug the optimal speed (usually 30–100r/min) based on material characteristics.
• Avoid long-term idle operation: Friction between blades and the barrel during idling generates heat, which may cause residual materials to melt and stick to the wall; empty the barrel of materials before shutdown.

3.2 Regular Cleaning and Maintenance

• Establish a cleaning cycle: Purge the barrel inner wall with compressed air after each shift; disassemble the barrel for manual cleaning weekly (use scrapers and brushes to remove stubborn adhered materials; use food-grade cleaners in the food industry). For corrosive materials, dry the inner wall after cleaning to prevent rusting.
• Inspect blade wear: Increased gaps between worn blades and the barrel cause material retention and wall sticking; replace worn blades or scraping strips in a timely manner. Lubricate bearings regularly to ensure stable screw operation and avoid local material accumulation from shaking.

4. Targeted Measures for Special Materials

• Powdery materials: Install a hopper arch-breaking device (e.g., pneumatic arch breaker) to prevent hopper bridging, which leads to uneven material feeding and local wall sticking in the barrel. Add a dust removal port at the top of the barrel to reduce dust adhesion to the inner wall.
• High-temperature materials: Use high-temperature resistant materials (e.g., 316L stainless steel) for the barrel and add thermal insulation layers to reduce heat dissipation from the outer wall, avoiding material agglomeration and wall sticking due to sudden temperature drops.