Single Screw Extruder Common Faults & Solutions (For Dog Chews & Secondary Puffed Products)

1. Discharging Abnormalities (Most Common)

1.1 Intermittent Discharging & Unstable Output

• Material bridging and caking in the hopper; high-viscosity dog chew raw materials with glycerin and colloid easily stick to the wall
• Feeding auger slipping, loose transmission chain or unstable frequency speed
• Worn feeding section screw leads to insufficient conveying capacity
• Fluctuations in raw material moisture content
• Overhigh temperature in the feeding barrel causes premature material gelatinization and blockage

• Install a stirring rod for the hopper; sieve raw materials to break up agglomerates
• Tighten feeding transmission chains and belts; calibrate frequency converter parameters
• Repair or replace worn screw modules
• Control raw material moisture steadily within ±1% tolerance
• Reduce feeding section temperature and turn on cooling water to avoid pre-gelatinization

1.2 Bubbles & Porous Finished Dog Chews

• Excessive raw material moisture leads to excessive expansion during pressure relief
• Oversized secondary expansion cavity without flow-limiting bushing
• Low barrel pressure causes incomplete maturation and water vapor precipitation
• Excessive foaming additives such as baking soda and sugar
• Overhigh die head temperature triggers rapid water vapor expansion

• Reduce mixing moisture and strictly control drying parameters
• Install flow-limiting bushing to reduce expansion cavity volume and increase die back pressure
• Add shear blocks to stabilize working pressure at 28–38MPa
• Reduce foaming auxiliary dosage
• Lower die head temperature and increase cooling water circulation

1.5 Overhard, Cracking & Chipping Dog Chews

• Excessive compression ratio and shear blocks lead to over-extrusion and cross-linking
• Low raw material moisture causes poor material toughness
• Excessive die resistance and high back pressure
• Low maturation temperature leads to incomplete starch gelatinization

• Remove 1–2 sets of shear mixing blocks to reduce compression ratio
• Properly add water and glycerin to improve material flexibility
• Replace larger aperture dies and remove partial flow-limiting components
• Adjust maturation section temperature to 85–95℃

1.4 Low Expansion Rate of Secondary Puffed Products

• Flow-limiting bushing for dog chews occupies expansion cavity space
• Insufficient barrel pressure and heat accumulation
• Low raw material moisture without enough vapor for puffing
• Low processing temperature leads to incomplete starch gelatinization

• Remove the flow-limiting bushing to expand the secondary puffing cavity
• Increase shear blocks to raise working pressure
• Appropriately increase raw material moisture
• Adjust middle and rear barrel temperature to 100–130℃

1.5 Uneven Discharging & Irregular Strip Thickness

• Offset flow splitter and misaligned die installation
• Uneven wear of screw discharge end
• Partial die hole blockage and carbon accumulation
• Asymmetric locking of flange bolts

• Reinstall and calibrate die head and flow splitter concentricity
• Repair or replace worn screw head
• Stop the machine to clean die hole carbon deposits and residual materials
• Lock flange bolts diagonally and evenly

2. Current & Pressure Abnormalities

2.1 Overhigh Current & Overpressure Shutdown

• Sudden drop of raw material moisture increases material viscosity sharply
• Low barrel temperature reduces material fluidity
• Die hole blockage causes sharp rise of back pressure
• Foreign matter jams the screw and barrel gap
• Excessive shear blocks lead to high extrusion resistance

• Adjust raw material moisture steadily
• Increase sectional barrel temperature to improve fluidity
• Dismantle and clean die head and blocked materials
• Remove hard foreign matters inside the barrel
• Reduce the number of shear modules to lower extrusion resistance

2.2 Low Current & Unreachable Working Pressure

• Excessive raw material moisture leads to low extrusion resistance
• Severe screw wear causes pressure relief
• Insufficient feeding volume and low barrel filling rate
• Overhigh barrel temperature causes premature material liquefaction

• Reduce raw material moisture and extend drying time
• Inspect and replace severely worn screws
• Increase feeding speed to stabilize barrel filling rate
• Reduce middle and rear barrel temperature

3. Temperature Control System Failures

3.1 Slow Temperature Rise & Unreachable Set Temperature

• Damaged heating coils and poor wire contact
• Falling off or failure of thermocouples (inaccurate temperature detection)
• Cooling water valve is always open causing continuous heat loss
• Material heat loss exceeds heating power under high output

• Test and replace damaged heating coils, fasten wiring
• Reinstall and fix thermocouples closely to the barrel surface
• Close redundant cooling water valves and enable automatic temperature linkage
• Properly increase heating power or reduce instantaneous feeding volume

3.2 Overheating & Overtemperature Alarm

• Faulty temperature controller and short-circuited thermocouple
• Stuck AC contactor causes continuous heating
• Blocked cooling water pipeline and insufficient flow
• Internal barrel blockage leads to sharp friction heat rise

• Replace temperature meter and repair thermocouple lines
• Replace sticky contactors
• Clean water filter and increase cooling water flow
• Stop the machine to clean blocked materials and reset process parameters

4. Mechanical Vibration & Transmission Faults

4.1 Abnormal Noise & Severe Vibration

• Screw bending causes friction between screw and barrel
• Insufficient gear oil or worn gearbox parts
• Loose anchor bolts cause equipment resonance
• Hard foreign matters rub against the barrel inner wall

• Detect screw straightness, correct or replace deformed screws
• Replace gear oil and inspect gearbox bearings and gears
• Fasten all anchor bolts and add shock-absorbing pads
• Install magnetic separators to remove metal foreign matters from raw materials

4.2 Gearbox Overheating & Oil Leakage

• Insufficient or deteriorated lubricating oil
• Damaged cooling fan leads to poor heat dissipation
• Aging oil seal and worn output shaft
• Long-term high-load operation for high-viscosity dog chew production

• Fill and replace special gear oil regularly
• Repair cooling fans and clean dust on heat dissipation parts
• Replace skeleton oil seals and repair worn shafts
• Avoid long-term extreme high-pressure operation

4.3 Rapid Wear of Screw & Barrel

• Raw materials contain sediment and hard impurities
• Long-term high-pressure and high-shear working conditions
• Failed nitride wear-resistant layer on screw surface
• Acidic formula causes metal corrosion

• Screen raw materials and equip magnetic iron removal devices
• Optimize shear block configuration to avoid long-term limit pressure
• Repair screws by surfacing wear-resistant materials
• Adjust formula pH value to reduce corrosive additives

5. Feeding System Failures

5.1 Feeding Motor Overload & Auger Blockage

• Material caking jams the feeding auger
• High-viscosity dog chew materials stick to auger blades
• Unmatched high frequency speed setting

• Stop the machine to clean caked materials
• Clean sticky materials regularly and control raw material moisture
• Reduce feeding speed to match host extrusion speed

5.2 No Feeding & Idling Auger

• Powder bridging and arching in the hopper
• Severe wear of auger blades reduces conveying capacity
• Overhigh hopper temperature causes material pre-gelatinization and adhesion

• Install vibration feeding devices to eliminate material bridging
• Repair worn auger blades
• Reduce ambient temperature around the hopper

6. Cutting System Failures

6.1 Uncut Materials & Sticky Strips

• Worn and blunt cutting blades
• Mismatch between cutting speed and extrusion speed
• High material viscosity caused by excessive discharging temperature
• Excessive distance between cutter and die head

• Polish or replace cutting blades
• Adjust cutter frequency to synchronize with host discharging speed
• Reduce die head temperature and install air cooling device
• Shorten the distance between cutter and die face

6.2 Uneven Cutting Length

• Unstable extrusion discharging speed
• Faulty cutter frequency converter with unstable speed output
• Slipping traction conveyor belt causes speed fluctuation

• Stabilize feeding volume and host pressure to ensure uniform discharging
• Inspect and calibrate cutter frequency converter parameters
• Adjust conveyor belt tension to eliminate slipping

7. Daily Maintenance Tips for Dog Chew & Puff Production

• Regular Cleaning: Clean hopper, feeding auger and die carbon deposits per shift to avoid material carbonization and blockage (critical for high-viscosity colloid raw materials).
• Parameter Switching: Adjust shear blocks and flow-limiting bushings timely when switching between dog chew (low expansion, high density) and secondary puff products (high expansion, porous structure).
• Data Recording: Record real-time current, pressure and sectional temperature data to predict potential faults in advance.
• Impurity Removal: Equip raw material screening and magnetic separation devices to protect screw and barrel from wear and damage.
• Mechanical Maintenance: Check gearbox oil level and thrust bearing temperature weekly for long-term high-load dog chew extrusion production.