In the fields of new materials, new energy, and fine electronic chemicals—such as high‑nickel cathode slurries, solid electrolytes, conductive silver pastes, and semiconductor encapsulation adhesives—the purity of the material directly determines the electrochemical or electrical performance of the final product. In the micron‑/nanoscale dispersion processes for these high‑value materials, the three‑roll mill has become a core piece of equipment because it delivers high shear forces.

However, many R&D and process engineers often face a thorny problem: after milling in a three‑roll mill, the slurry often shows excessive levels of metallic foreign matter (e.g., iron, chromium, nickel, etc.) in post‑process testing.

This metal contamination does not originate from the raw materials themselves, but rather from the minute wear of the rollers during high‑speed shearing and compression. This article provides an in‑depth analysis of the physical characteristics of three mainstream roller materials—high‑chromium alloy steel, silicon carbide, and zirconia ceramic—and discusses their decisive impact on metal contamination control in high‑purity slurries.

1. Mechanism of Metal Contamination Origin: Micro‑Wear under Compression and Shear

The operating principle of a three‑roll mill relies on the shear force, compressive force, and linear speed differences between adjacent rollers. When the material (especially a solid‑liquid mixed slurry containing particles of relatively high hardness) passes through the micron‑sized gap between the rollers, the roller surfaces are subjected to extreme friction and local high pressure.

Mechanical wear: The solid particles in the slurry (such as solid‑state electrolyte oxides, high‑nickel cathode particles, fillers, etc.) act as abrasives, causing micro‑cutting on the roller surface, which leads to roller material shedding and entering the slurry.

Chemical corrosion: Some electronic or battery slurries are mildly acidic or alkaline. Under the high temperatures generated during milling, electrochemical corrosion on the metal roller surface can accelerate, further exacerbating the release of metal ions.

2. Performance Comparison of Three Main Roller Materials and Their Impact on Contamination Control

To fundamentally block or reduce metal contamination at the source, the industry has developed rollers made of different materials. Below is a comparative analysis of high‑chromium alloy steel, silicon carbide, and zirconia ceramic in terms of metal contamination control and key performance characteristics.

2.1 High‑Chromium Alloy Steel Rollers (Chilled Cast Iron / Alloy Steel)
Contamination control performance: Poor (high risk)
Mechanism analysis: The core composition of alloy steel rollers is iron (Fe), with additional metallic elements such as chromium (Cr), nickel (Ni), and manganese (Mn). Although surface heat treatment provides considerable hardness, over prolonged milling of high‑hardness materials, micron‑level wear still occurs on the surface. The shed particles directly translate into magnetic foreign matter in the slurry.
Applicable scenarios: Conventional materials with no sensitivity to metal contamination, such as ordinary inks, paints, industrial adhesives, etc. Essentially banned in the lithium battery and semiconductor fields.

2.2 Silicon Carbide (SiC) Ceramic Rollers
Contamination control performance: Good (no magnetic metal contamination, but minor non‑metal particle shedding needs attention)
Mechanism analysis: Silicon carbide features extremely high hardness (second only to diamond) and excellent thermal conductivity. Since its chemical composition is silicon and carbon, it contains no metallic elements like iron or nickel, thereby fundamentally avoiding the risk of introducing magnetic metal contaminants.
Potential risk: Although it does not introduce metals, under extremely high shear forces, minute non‑metal wear may occur on the SiC surface. The shed silicon carbide particles could slightly affect the purity of semiconductor slurries that are critically sensitive to silicon content.
Applicable scenarios: Conductive pastes or new material milling that demand high heat dissipation, strictly prohibit magnetic metal contamination, but allow trace amounts of silicon.

2.3 Zirconia (ZrO₂) Ceramic Rollers
Contamination control performance: Excellent (the preferred choice for high‑purity slurries)
Mechanism analysis: Zirconia ceramic (typically yttria‑stabilized zirconia) possesses high hardness, high toughness, and extremely strong wear resistance due to its special crystal structure. Its surface roughness can be made extremely low, with a minimal microscopic friction coefficient.
Non‑metallic nature: Its composition is zirconium dioxide, containing no magnetic metal elements, so no Fe, Cr, Ni, etc. contamination is generated during milling.

High wear resistance reduces overall particle shedding: With fracture toughness far higher than that of silicon carbide, the microscopic shedding of the roller itself is extremely low when subjected to impact and shear from hard solid particles.
Applicable scenarios: Solid electrolytes, high‑nickel cathodes, semiconductor packaging pastes, high‑end cosmetics, and other extreme high‑purity applications where metallic foreign matter must be controlled at the ppb (parts per billion) level.

3. Equipment Selection Recommendations for High‑Purity Slurry Processing
In actual process implementation, controlling metal contamination in slurries is a systematic engineering task that cannot focus solely on the roller itself. If you are selecting equipment for high‑purity slurries, we recommend following these principles:
Red‑line principle: As long as the product application involves internal lithium‑battery cell materials (cathode, anode, separator coating, electrolyte) or semiconductor chip packaging, zirconia ceramic rollers or silicon carbide ceramic rollers must be mandatorily selected, and alloy steel materials must be completely eliminated.
Auxiliary component synergy: It is not enough to use ceramic rollers alone. The end dams (retaining rings) and scraper systems of the mill also come into high‑intensity contact with the material. They must be upgraded simultaneously—the dams to PTFE (polytetrafluoroethylene) or engineering plastics, and the scrapers to zirconia ceramic or PEEK scrapers—to ensure a “metal‑free contact” along the entire flow path.
Temperature control coordination: Although zirconia ceramic offers the best metal contamination control, its thermal conductivity is relatively low. If the temperature rises too quickly when milling high‑viscosity materials, it may in turn affect slurry stability. Therefore, when selecting equipment, it is necessary to confirm whether the mill is equipped with an efficient core cooling system, and to precisely control the gap via hydraulic or electronic adjustment to reduce mechanical wear caused by excessive compressive heating.

4. Conclusion

As the fine chemical and new‑materials industries move toward higher value‑added products, the control of material purity has progressed from “macro‑level prevention” to “micro‑level quantitative management.” The choice of three‑roll mill roller material directly determines the quality baseline for high‑purity slurry production. Clearly identifying the material hardness, thermal sensitivity, and contamination tolerance, scientifically selecting ceramic materials (zirconia/silicon carbide), and implementing a full‑flow‑path metal‑free design are the key technological pathways for enterprises to enhance their core product competitiveness.

In the production of high-end materials such as conductive inks, adhesives, and coatings, dispersion uniformity directly determines product performance. As a key dispersion equipment, the effectiveness of a hydraulic three-roll mill depends not only on the machine itself but also on parameter settings. By reasonably adjusting process parameters, the dispersion quality can be significantly improved.

I. Properly Control Roller Gap (Core Parameter)
The roller gap is one of the most critical factors affecting dispersion performance.

The smaller the gap, the stronger the shear force on the material, and the finer the dispersion result.

In practice, it is recommended to tighten the gap step by step: first set a larger gap for smooth feeding, then gradually reduce the gap to enhance shearing, and improve fineness through multiple passes.

However, caution is needed: an excessively small gap can cause material sticking to the rollers and excessive temperature rise. Therefore, a balance must be struck between effect and stability.

II. Optimize Roller Speed and Speed Ratio
Hydraulic three-roll mills typically operate with three rollers running at different speeds (speed ratio), which is key to achieving shear dispersion.

Generally: the front roller runs at low speed (stable feeding), the middle roller at medium speed, and the rear roller at high speed (main shearing zone). A proper speed ratio enhances shear force between rollers, thereby improving dispersion. If the speed ratio is too low, shearing is insufficient; if too high, material splashing or structural damage may occur.

III. Control Feed Rate and Feeding Method
The feed rate directly affects the residence time of material between rollers.

• Excessive feed: leads to material accumulation and insufficient dispersion.
• Insufficient feed: lowers production efficiency and may cause unstable dispersion.

A uniform, continuous feeding method is recommended to maintain a stable film thickness, allowing the material to be fully sheared between rollers.

IV. Properly Adjust Scraper Pressure and Angle
The scraper not only affects discharge but also indirectly influences dispersion uniformity.

• Scraper too loose: material residue may be repeatedly ground, leading to local over-shearing.
• Scraper too tight: affects discharge stability and may cause material accumulation.

It is recommended to maintain moderate contact between the scraper and roller surface, with the angle kept within a reasonable range, so that material is uniformly scraped off and enters the next process.

V. Control Temperature Rise (Key Auxiliary Parameter)
Temperature significantly affects material viscosity and fluidity, thereby influencing dispersion. Excessive temperature can cause: material thinning, reduced shearing effect; solvent evaporation, formulation imbalance; and changes in material structure.

Recommendations:

• Use a cooling system to control roller temperature.
• Reasonably reduce running time or process in batches.
• Pay special attention to temperature control for heat‑sensitive materials.

VI. Optimize Number of Passes (Process Control)
One pass often fails to achieve ideal dispersion. Multiple passes are usually required:

• First pass: preliminary crushing and mixing.
• Second pass: fine dispersion.
• Third pass and beyond: fine homogenization.

By gradually reducing the gap over multiple passes, final uniformity can be significantly improved.

VII. Material Pre‑treatment is Also Important
Proper pre‑treatment of the material before entering the three‑roll mill can greatly improve dispersion efficiency, for example:

• Pre‑mixing (uniform stirring).
• Reducing the proportion of large particles.
• Controlling viscosity within a reasonable range.

This reduces the load on the three‑roll mill and makes dispersion more uniform and stable.

VIII. Impact of Equipment Precision on Dispersion Performance
In addition to parameter settings, the precision of the equipment itself is equally critical. Factors such as roller parallelism, gap control accuracy, and operational stability directly affect dispersion consistency.

Some high‑performance equipment features optimized structures. For example, the Zhongyi hydraulic three‑roll mill demonstrates stable performance in gap control and operational stability, helping to achieve higher dispersion consistency, especially suitable for demanding material applications.

Summary
Improving dispersion uniformity of a hydraulic three‑roll mill is essentially a process of “parameter synergy optimization.” By reasonably adjusting roller gap, speed ratio, feed rate, scraper condition, and temperature control, combined with multiple passes and material pre‑treatment, dispersion results can be significantly improved, thereby obtaining high‑quality materials with more stable performance.

Hydraulic three-roll mills are widely used for grinding inks, adhesives, resins, and polymer materials. The stability of the hydraulic system is directly tied to operational safety and production quality. However, during high-load operations, sudden hydraulic oil leaks can occur. If not handled properly, these leaks can lead to severe equipment damage or safety hazards. This article outlines the essential steps for emergency shutdown and troubleshooting.

I. Common Causes of Sudden Oil Leaks
Aging or ruptured hydraulic lines: Long-term use of high-pressure oil pipes can lead to wear, cracking, or loose connections.

Damaged hydraulic seals: Aging O-rings and oil seals, or improper installation, frequently cause oil leakage.

Improper operation or overloading: Excessive pressure or overloaded grinding can subject hydraulic valves or pipelines to excessive stress, resulting in leaks.

External impact or foreign object damage: Collisions between workpieces or tools and the hydraulic lines or components can trigger a leak.

II. Emergency Shutdown Steps
Press the Emergency Stop button immediately: Cut off the power supply and stop the rollers from rotating to prevent further hydraulic oil leakage.

Isolate the hydraulic oil source: Turn off the power to the hydraulic pump. If necessary, close the main or sectional valves to stop the flow of high-pressure oil.

Evacuate personnel: Ensure that all operators step away from the leak area to prevent slipping, burns, or fire hazards.

Take protective measures: Wear oil-resistant gloves, safety goggles, and non-slip shoes to avoid skin contact with hot hydraulic oil.

III. Troubleshooting and Handling Process
Initial Cleanup
Use oil absorbent pads, blankets, or oil-resistant cloths to soak up the spilled hydraulic oil.

Prevent the oil from flowing into floor drains or inside the equipment to avoid secondary damage and environmental contamination.

Locate the Leak Source
Inspect pipeline connections, hydraulic valves, seals, and cylinders to pinpoint the exact location of the leak.
Carefully tighten suspicious joints or prepare to replace damaged seals.

Repair or Replace Damaged Components
Strictly follow the equipment manual and use original equipment manufacturer (OEM) parts or standard-compliant seals.
Contact professional maintenance personnel if necessary to avoid secondary damage caused by improper handling.

Pre-operation Inspection Before Restart
Check if the hydraulic oil level and oil quality are within normal parameters.
Run the machine idle at a low speed for 1 to 2 minutes to confirm there are no leaks, oil pressure is stable, and roller movement is smooth.

IV. Important Safety Precautions
Never dismantle pressurized lines or valves: Always depressurize the system first to prevent high-pressure oil from spraying and causing serious injury.
Clean up oil spills promptly: Completely remove residual oil from the floor to eliminate slip, fall, and fire hazards.
Record and analyze: Document the incident and analyze the root causes to implement preventive measures and avoid recurrence.
Establish a regular inspection routine: Routinely check the hydraulic system to detect and replace aging pipes and seals before they fail.

Conclusion
A sudden oil leak during the operation of a hydraulic three-roll mill is a critical emergency safety event. Pressing the emergency stop, isolating the oil source, protecting operators, locating the leak, and repairing it immediately are key to ensuring personal safety and equipment stability. Furthermore, regular proactive inspection of the hydraulic system and its seals remains the most effective way to prevent oil leak accidents from happening in the first place.

During long-term operation of a hydraulic triple roll machine, seals and bearings are typical wear parts whose condition directly affects equipment stability and service life. If not replaced in time, minor issues may impair grinding performance, while severe cases can lead to equipment failure or even shutdown. Therefore, it is essential to understand their reasonable replacement cycles and judgment methods.

I. Replacement Cycle and Judgment Method for Seals

Seals are mainly used in the hydraulic system and at the roller shaft ends to prevent leakage of lubricating oil or hydraulic fluid, while also keeping external contaminants out.

Under normal operating conditions, the service life of seals is typically 6 to 12 months. However, this period is influenced by operating time, temperature, and working environment. For example, high temperature, high load, or dusty environments will accelerate seal aging.

In practice, the following signs can be used to determine whether replacement is needed:

First, observe whether the triple roll machine shows oil leakage or obvious dripping, which is a direct manifestation of seal failure. Second, if the hydraulic pressure becomes unstable or the hydraulic response slows down during operation, it may also be related to degraded seal performance. In addition, when seals become hard, cracked, or deformed, they should be replaced immediately.

II. Replacement Cycle and Judgment Method for Bearings

Bearings are key components supporting roller rotation, and their condition directly affects the smooth operation and precision of the triple roll machine.

Generally, the replacement cycle for bearings is 1 to 3 years, depending on equipment usage frequency and maintenance conditions. Under high-load or continuous production conditions, the cycle may be shortened accordingly.

To determine whether bearings need replacement, consider the following aspects:

First, pay attention to the operating sound of the equipment. Abnormal noise, unusual sounds, or increased vibration are often signals of bearing wear. Second, monitor temperature rise. If the bearing area becomes significantly hotter, there may be lubrication problems or wear.

Additionally, during a shutdown inspection, manually turn the rollers to feel for any sticking or rough movement. If there is noticeable resistance or abnormal clearance, bearing replacement should be considered.

III. Key Factors Affecting Replacement Cycles

The actual service life of seals and bearings is not fixed and is mainly influenced by the following factors:

• Working load and operating hours
• Material characteristics (whether containing corrosive or abrasive components)
• Temperature control conditions
• Lubrication and maintenance level

Therefore, in actual production, adjustments should be made dynamically based on specific operating conditions, rather than relying solely on fixed cycles.

IV. Maintenance and Replacement Recommendations

To extend the service life of wear parts, it is recommended to establish a regular inspection schedule for the triple roll machine. For example, perform a visual and operational check once a month, and carry out key component inspections once a quarter.

When replacing parts, choose high-quality components that match the equipment and strictly follow specifications to avoid improper installation that could affect performance.

At present, some equipment has been optimized in structural design for easier maintenance of wear parts. For example, ZYE's hydraulic triple roll machine features improvements in bearing structure and seal design, making replacement more convenient while enhancing overall durability.

Conclusion

In summary, although seals and bearings are common wear parts, they are critical to the stable operation of a hydraulic triple roll machine. By reasonably determining replacement cycles and making judgments based on operating conditions, unexpected failures can be effectively avoided, improving equipment efficiency and safety.

In the precision grinding of high‑viscosity electronic pastes, high‑performance ceramic materials, and ultra‑fine inks, the three‑roll mill is a key piece of equipment for achieving uniform dispersion, thanks to its micron‑level gap control and high local shear forces.

However, on the production floor, operators often encounter two troublesome issues that disrupt continuous operation:

• "Material breakage" : The material fails to form a uniform, continuous micron‑level monolayer film on the roll surface, resulting in blank spots, broken lines, or intermittent absence of material.
• "Material wandering" : The material is unevenly distributed along the roll axis, migrating heavily toward the left or right side and overflowing, while the opposite side gradually dries out.

These problems not only lead to uneven fineness and a broadened particle size distribution in the ground slurry, but more seriously, localized material breakage can cause direct dry friction on the roll surface. This can induce local overheating, stress concentration, and thermal shock (sudden heating/cooling) on expensive ceramic rolls (e.g., zirconia) or alloy steel rolls, leading to roll scrap or blade chipping.

This article provides an in‑depth root cause analysis of material breakage and wandering during three‑roll mill operation, with a focus on how to solve these process issues through roll pressure compensation and linear alignment.

I. Root Cause Analysis & Process Countermeasures for "Material Breakage"
The essence of breakage is the disruption of the fluid continuity balance created by the linear speed difference between adjacent rolls and the compressive shear force.

1. Mismatch Between Material Rheology and Critical Rotational Speed
Root Cause: High‑viscosity slurries are typically non‑Newtonian fluids (thixotropic or shear‑thinning). If the roll linear speed is set too high – exceeding the material’s relaxation time – the internal tensile stress within the fluid exceeds its cohesive limit the moment it passes through the roll gap, causing microscopic fractures that appear as breakage on the doctor blade side.

Solution: During initial commissioning, follow the principle of "ramping speed from low to high" to determine the upper linear speed limit for the material at a given temperature. Alternatively, adjust the ratio of solvent or lubricant additives in the formulation.

2. Insufficient Feed or Uneven Feeding
Root Cause: Too little material in the "feed bank" (the V‑shaped reservoir between the slow and middle rolls) leads to uneven gravitational hydrostatic pressure along the axial direction, failing to provide a constant pushing force into the roll gap.

Solution: Keep the material height in the feed bank above the roll centerline. Use an automatic feeding system to achieve continuous, axially distributed feeding.

3. Wear or Misalignment of End‑Dam Blocks (Side Dam Rings)
Root Cause: End‑dam blocks wear over time due to friction against the roll ends, or they are installed with uneven clamping force, causing edge material leakage or drying. Hardened lumps of dried material can become embedded in the roll gap and directly block the smooth passage of subsequent fluid.

Solution: Regularly inspect and re‑condition PTFE or PEEK end‑dam blocks to ensure precise conformity to the roll curvature.

II. Root Cause Analysis for "Material Wandering": Why Does the Material Migrate to One Side?
The underlying mechanical cause of wandering is non‑parallel gaps (pressure imbalance) along the roll axis. Fluid always tends to flow toward the path of least resistance. Once the pressure at the two ends of the rolls is inconsistent, material will rush to the side with the larger gap (lower pressure).

1. Inconsistent Gap Adjustment at Both Ends (Manual or System Error)
For manually operated or traditional mechanically‑adjusted three‑roll mills, it is very difficult for operators to achieve micron‑level consistency on both sides by turning handwheels.

For hydraulically‑adjusted three‑roll mills, air pockets in the hydraulic lines, valve wear, or asynchronous response of proportional valves can lead to differences in the actual bearing‑housing pressure applied to the two roll ends.

Solution: For manual adjustment, use a feeler gauge to symmetrically check both sides. For hydraulic systems, regularly bleed air and calibrate pressure transmitters.

2. Thermal Deformation of Rolls (Non‑Uniform Temperature Rise)
Grinding high‑viscosity materials generates significant shear heat. If the internal cooling water circuit is scaled or partially blocked, or if the inlet/outlet design creates an axial temperature gradient, the hotter side of the roll will expand slightly (thermal expansion), reducing the gap and increasing pressure on that side, thereby pushing the material toward the cooler side with better cooling.

Solution: Periodically descale the roll cooling channels using acid‑based cleaning agents. Ensure sufficient cooling water flow rate and control the axial temperature difference within ±1°C.

3. Roll Bearing Wear and Runout
Under long‑term heavy‑duty operation, minor wear or cage loosening in the spherical roller bearings on one side can cause radial runout or axis misalignment during high‑speed rotation.

Solution: Use a dial indicator to measure radial runout at both ends of the rolls. If runout exceeds the process requirement (typically <2 µm for precision grades), replace with high‑precision dedicated bearings.

III. Core Solutions: Roll Pressure Compensation & Linear Alignment Standard Procedure
To fundamentally eliminate breakage and wandering, relying solely on the operator’s visual judgment is insufficient. A standardized linear pressure compensation and parallelism alignment procedure must be established.

Step 1: Zero‑Point Calibration
With no material loaded, start the fluid cooling system (to bring the equipment to standard operating temperature). Fix the middle roll. Slowly bring the slow roll and the fast roll toward the middle roll until a sudden change in hydraulic/mechanical resistance is observed on both sides. At this point, use the electrical system or mechanical scale to define this position as the "absolute parallel zero point" .

Step 2: Implement Axial Linear Pressure Compensation
For advanced precision hydraulic three‑roll mills, activate the automatic pressure compensation algorithm. Using differential pressure closed‑loop control (with high‑precision pressure sensors mounted on the bearing housings at both ends of the slow and fast rolls), when the system detects that the actual pressure on the left side is higher than on the right side (meaning material is migrating to the right), the hydraulic proportional valve automatically increases thrust on the right‑side hydraulic cylinder to provide real‑time online linear compensation.

For rolls with a large length‑to‑diameter ratio, also verify whether a crowned roll design or pre‑stressed spindle compensation is incorporated to eliminate deflection deformation.

Step 3: Dynamic Balancing of Doctor Blade Pressure
If the doctor blade system has uneven counterweight or hydraulic clamping force at its ends, it will create an uneven discharge resistance on the fast roll surface, indirectly pushing fluid to wander between the rolls.

Solution: During alignment, use pressure‑sensitive paper to confirm that the contact pattern of the blade along the entire fast roll length is completely uniform in width.

IV. Summary & Daily Inspection Redlines
The three‑roll mill is a highly precise industrial fluid processing machine. Material breakage is mostly related to macroscopic fluid behavior (material properties, speed, feed bank). Material wandering is a mirror that directly reflects the microscopic state of roll parallelism and axial pressure distribution.

• Never run dry: Whenever large‑area breakage is observed, reduce speed or replenish slurry within 30 seconds. Ceramic rolls are especially sensitive – dry friction is strictly prohibited.
• Keep both pressure ends in sync: Before each batch, the difference in set parameters between the two sides (hydraulic or mechanical display) must not exceed 3% of the system scale.
• Temperature interlock: Link infrared roll surface temperature monitoring to an equipment alarm. Once the axial temperature difference exceeds a preset red line, trigger an automatic shutdown to prevent thermal deformation from causing severe wandering.

By establishing a systematic pressure compensation mechanism and scientific on‑site maintenance inspection routines, companies can significantly extend the service life of their core rolls and ensure that every batch of high‑value slurry leaving the factory achieves ultimate fineness and stability.

Note: This article discusses emergency measures for three‑roll mills, but the most important thing is prevention – never allow tools near rotating rollers!

Despite strict safety regulations, accidents can still happen. If a tool (such as a scraper, wrench, or cleaning cloth) gets caught in the roll nip, it can not only damage the equipment but also cause serious injury to the operator. Today, we will explain the emergency procedure for when a tool is pulled into a three‑roll mill. We hope you never need it, but you must know it.

I. Two Dangers of a Tool Being Caught
1. Danger to the operator
During operation of a three‑roll mill, if a hand‑held tool is accidentally drawn into the nip and the operator is still holding it, the hand can be instantly pulled toward the gap. The rotational force of the rollers is enormous – once a hand is drawn in, the consequences are catastrophic: crushing, tearing, even amputation.

Even more dangerous: The tool may break and fly out, striking the operator or others nearby.

2. Danger to the equipment
Roller damage – The rollers are the most critical precision components of a three‑roll mill. If a metal tool (especially one harder than the roller material) enters the nip, it can directly create dents or scratches on the roller surface. Ceramic rollers may crack.

Gear lock‑up – If a tool jams in the nip, it may overload the drive system, damaging the gears or motor.

II. Emergency “Four‑Step Procedure”
Step 1: Immediately press the emergency stop
Action: No matter what you are doing, press the emergency stop button immediately.

Why?

• The emergency stop cuts power instantly, stopping the equipment.
• It prevents the tool from being drawn further into the nip, reducing damage.
• It creates safe conditions for subsequent steps.

Note: Do not try to observe first, and do not try to pull the tool out with your hands – every millisecond of delay can cause greater harm.

Step 2: Warn nearby personnel
Action: Shout loudly “Machine stopped! Don’t touch it!” or place warning signs.

Why?

• To prevent others from mistakenly restarting the machine.
• To alert people to stay away from the danger zone.

Step 3: Assess the situation
After ensuring the machine has come to a complete stop and power is disconnected, observe:

Tool status:

• Where is the tool stuck?
• Is any part still exposed, or is it fully drawn in?
• Is the tool broken? Where are the fragments?

Roller status:

• Are there visible marks on the roller surface (dents, scratches, cracks)?
• Can the rollers still rotate?

Personnel status:

• Is the operator injured?
• If injured, administer first aid immediately and seek medical attention.

Step 4: Remove the tool
Principle: Reverse rotation – never force it out!

Correct method:

• Confirm that power is disconnected.
• If part of the tool is still exposed, try to manually reverse the rollers (using a handwheel or by carefully turning the rolls) so that the tool backs out with the reverse rotation.
• If the tool is completely jammed and cannot be reversed, do not force it – this could break the tool or further damage the rollers.
• Contact the equipment manufacturer or a professional maintenance technician.

Absolutely forbidden:

• Restarting the machine forward with greater force to try to “blast through” the jam.
• Hitting the tool with a hammer to shake it loose.
• Trying to pick it out directly with your fingers (the tool may suddenly loosen, and your hand could strike the rollers).

III. Inspection After Removal
1. Inspect the tool
Is the tool deformed or broken? If there are fragments, have all been recovered? (Prevent any fragments from remaining inside the three‑roll mill.)

2. Inspect the rollers

• Visual inspection: Use a strong light to carefully check the roller surface for dents, scratches, or cracks.
• Touch inspection (only after confirming the machine is stopped): Wear clean gloves and gently feel for any irregularities.

If damage is found:

• Minor scratches – may still be usable, but monitor the fineness closely.
• Obvious dents or cracks – must contact the manufacturer for evaluation; roller replacement may be required.

3. Check the nip gap
Re‑check the roll gap and confirm it has not changed. If necessary, recalibrate parallelism.

4. Check the doctor blade
Inspect the doctor blade for damage (tool entanglement may also damage the blade).

IV. Preventive Measures: How to Avoid Tool Entanglement (The best response is to prevent it from happening at all.)
1. Tool management

• Designated tools: Use only tools specifically designed for the three‑roll mill (scrapers, wrenches, etc.).
• Tool placement: Return tools to their designated storage location immediately after use – never leave them on top of the machine.
• Tool inspection: Regularly check tool condition; replace damaged tools promptly.

2. Operating procedures

• Guard closed: The machine guard must be closed during operation – this is the most effective barrier against tool entanglement.
• Hand on tool: When feeding material, always keep your hand on the tool; never leave it suspended above the rollers.
• Jog mode: If adjustments are needed while the machine is running, use jog mode and keep your hand near the emergency stop.

3. Training and awareness

• New operators must receive tool safety training before working on the machine.
• Conduct regular safety drills to reinforce emergency response.
• Share accident case studies so everyone understands the severe consequences of tool entanglement.

Tool entanglement in a three‑roll mill is a completely avoidable accident. It arises from a moment of carelessness but can lead to lifelong regret.

Remember the four steps of emergency response: Emergency Stop → Warn → Assess → Reverse Removal. But even more important is making “keep tools away from rotating rollers” a muscle memory. Safety starts with placing each tool correctly – every single time.

Many vacuum mixer failures occur due to neglected daily inspections, where minor issues gradually escalate. In fact, just 5 minutes of daily inspection can help identify 80% of potential faults in advance, ensuring stable equipment operation. Today, we’ll share a practical daily inspection checklist—from simple to more detailed, from exterior to interior—to guide you through the process.

I. Pre-Start Inspection (3 minutes)

• Visual Check: Observe whether the vacuum degassing mixer has any deformation or damage. Ensure that the frame and housing screws are tight, with no looseness or displacement. Check that the material barrel and fixtures are intact, free from cracks or deformation, and fit snugly against the carrier.
• Fluid Check: Verify that the vacuum pump oil level is between the upper and lower scale marks and that the oil is clear, not cloudy. Ensure sufficient lubricating grease at gears and bearings, with no leaks or dryness.
• Electrical Check: Inspect power cords, plugs, and terminals for any damage or looseness. Confirm that the driver and control panel display are normal, with no error messages or black screen.
• Seal Check: Examine the vacuum chamber sealing ring and pipeline interface gasket for damage or aging. Ensure surfaces are free from oil residue or leftover material.

II. In-Operation Inspection (1 minute)

• Sound Check: Listen for any abnormal noises during operation. The vacuum pump, motor, and transmission components should run smoothly, with no friction, jamming, or vibrating sounds.
• Pressure Check: Verify that the vacuum pressure gauge reading is stable and can quickly reach the standard value (≤ -90 kPa), with no abnormal fluctuations or pressure rise.
• Temperature Check: Touch the motor, driver, and vacuum pump housing to ensure they are warm but not hot (normal temperature should not exceed 60°C).

III. Post-Shutdown Inspection (1 minute)

• Cleaning Check: Clean any material residue from the material barrel and vacuum chamber. Wipe away oil and dust from the equipment surface to ensure no residue buildup.
• Status Reset: Turn off the main power, return the material barrel and fixtures to their original positions, and check that all switches and knobs are in the off position to prevent accidental startup next time.
• Defect Logging: If any minor abnormalities (e.g., loose screws, slightly cloudy oil) are found during inspection, address them promptly and record the issue. If the problem cannot be resolved immediately, suspend equipment use and contact maintenance personnel for repairs. Never operate the equipment with existing issues.

IV. Inspection Tips
Create an inspection sheet and mark off each daily inspection to help track equipment status and identify recurring issues over time.
During inspections, pay special attention to easily worn components (sealing rings, lubricating grease, filters). Keep spare parts on hand to avoid downtime when failures occur.
Daily inspections may seem simple, but they are highly effective in reducing equipment failure rates. Develop good inspection habits to keep your equipment running smoothly and productively!

The vacuum chamber and the carrier are core components of the vacuum degassing machine. In daily operation, foreign matter left in the vacuum chamber or carrier failures can lead to a series of problems such as abnormal noise, uneven mixing, and equipment damage. Many operators tend to neglect the maintenance of these two parts, causing minor issues to escalate. This article shares common symptoms, handling methods, and preventive measures for such problems.

I. Problems Caused by Foreign Matter in the Vacuum Chamber and Their Handling
1. Common Symptoms
During operation of the vacuum degassing machine, collision or friction noises may be heard inside the vacuum chamber; mixing may be uneven; the inner wall of the vacuum chamber may be scratched by foreign matter; in severe cases, the vacuum pump may seize (if foreign matter enters the piping or pump body).

2. Handling Methods

• Emergency procedure:Immediately stop the machine, cut off the power, and release the pressure to atmospheric pressure. It is strictly forbidden to open the vacuum chamber under pressure.
• Foreign matter removal:Open the vacuum chamber door. Use a lint-free cloth and dedicated tools to thoroughly clean the interior of the chamber, including material residues, detached part fragments, dust, etc. Pay special attention to corners inside the chamber and gaps between stirring components to ensure no residue remains, keeping the degassing mixer cavity clean.
• Follow-up inspection:After cleaning, check the inner wall of the vacuum chamber for scratches or damage, and check the stirring components for wear. Inspect the interface between the vacuum chamber and the piping to ensure no foreign matter remains, preventing debris from entering the pump body.

II. Problems Caused by Carrier Failures and Their Handling
1. Common Fault Types and Symptoms
(1) Carrier damage:
The carrier is deformed or cracked, resulting in the material bucket not being properly fixed. During mixing, the material bucket shakes, producing abnormal noise, and may even damage the bucket or stirring components.

(2) Loose fit between carrier and material bucket (fixture):
The material bucket is not secured firmly, causing it to collide with the carrier during mixing, generating abnormal noise and leading to uneven mixing.

2. Handling Methods
(1) Carrier damage:
If the carrier is deformed or cracked and cannot be repaired, replace it directly with a new carrier. Ensure that the new carrier model is compatible with the degassing mixer and the material bucket. After installation, check that it is firmly fixed.

(2) Loose fit between carrier and material bucket:
Replace the material bucket and fixture with compatible ones. Adjust the fastening devices (e.g., clamps, bolts) to ensure the material bucket fits tightly against the carrier without shaking. If the fastening devices are worn, replace them at the same time.

III. Preventive Measures

• Material pretreatment: Before putting material into the bucket, thoroughly remove impurities and hard lumps to prevent foreign matter from entering the vacuum chamber, thereby reducing potential failure risks of the degassing mixer at the source.
• Regular inspection: Inspect the inside of the vacuum chamber once a week, and check the condition of the carrier once a month. Timely remove foreign matter, tighten loose parts, and replace damaged carriers promptly.
• Proper operation: When loading materials, avoid bumping the material bucket against the inner wall of the vacuum chamber or the carrier. Handle with care to reduce component damage.

In practical applications, the term "three-roll machine" can easily cause confusion, especially between the hydraulic three-roll mill and the hydraulic three-roll plate bending machine. Although their names are similar, there are fundamental differences in functionality, application industries, and working principles. Quickly distinguishing between these two types of equipment is very important for equipment selection or information retrieval.

I. Differences in Equipment Essence and Function
The hydraulic three-roll mill is a device used for dispersing and grinding high-viscosity materials. It primarily uses the speed difference and gap control between three rollers to apply shear and compressive forces to the material, achieving particle refinement and uniform dispersion. Its core goal is to improve the fineness and stability of the material.

In contrast, the hydraulic three-roll plate bending machine belongs to the category of metal forming equipment. It is mainly used to roll steel plates, stainless steel plates, and other materials into cylindrical or curved shapes through roller pressure. Its core goal is to achieve shape change of the plate, not particle processing.

II. Completely Different Application Industries
From the perspective of application fields, the hydraulic three-roll mill primarily serves the fine chemical and new material industries, such as conductive inks, electronic pastes, adhesives, and coatings, where dispersion precision and uniformity are highly required.

In contrast, the hydraulic three-roll plate bending machine is widely used in machinery manufacturing and heavy industries, including pressure vessels, storage tanks, pipelines, and steel structure processing. It focuses more on forming accuracy and processing capacity of the plate.

III. Working Principles and Processing Objects
The working principle of the hydraulic three-roll mill is to finely process slurries or pastes through the shearing and squeezing action between the rollers. It is a typical material dispersion device.

The hydraulic three-roll plate bending machine, on the other hand, relies on the compressive force between the three rollers to cause plastic deformation of the metal plate, thereby completing the bending and rolling process. It is a mechanical forming device.

The processing objects are also completely different: the former targets liquid or high-viscosity materials, while the latter processes solid metal plates.

IV. How to Quickly Distinguish?
In practical judgment, you can quickly distinguish them through the following simple methods:

First, look at the processing object. If it involves fluids or semi-solid materials such as inks, pastes, or adhesives, it is typically a three-roll mill. If it involves steel plates or metal sheets, it is a three-roll plate bending machine.

Second, look at the processing result. The goal of a mill is to make the material "finer and more uniform," while the goal of a bending machine is to "bend or form" the plate.

Additionally, equipment structure can also be used to distinguish them. A mill has a smaller roller gap, a precise structure, and is usually equipped with a scraper system. In contrast, a plate bending machine has a larger body, thicker roller diameters, and larger spacing to allow plates to be inserted for processing.

V. Selection Suggestions
In the equipment selection process, you should first clarify your own process requirements. If it involves dispersion and refinement of high-viscosity materials, you should choose a hydraulic three-roll mill. If it involves bending and forming of metal plates, you should choose a hydraulic three-roll plate bending machine. The two types of equipment are not interchangeable, and incorrect selection will directly affect production results.

Conclusion
Overall, although the hydraulic three-roll mill and the hydraulic three-roll plate bending machine have similar names, they are completely different types of equipment serving different industrial systems. By clarifying the processing object, process purpose, and equipment structural characteristics, you can quickly and accurately distinguish them, thus avoiding selection errors.

In the practical use of three-roll mills, material sticking to rollers and overflow are common operational issues, particularly noticeable with high-viscosity slurries or in fine dispersion processes. These problems not only affect grinding efficiency but can also lead to material waste and increased equipment cleaning burdens. To address these phenomena, a comprehensive analysis and adjustment must be made from multiple aspects, including material properties, equipment parameters, and operating methods.

I. Causes and Solutions for Material Sticking to Rollers
Material sticking to rollers typically manifests as material adhering to the roller surface and failing to be properly removed by the scraper, disrupting continuous production.

• Excessively high material viscosity is a primary cause. When the system has a high solid content or insufficient solvent ratio, fluidity decreases, making it easier for the material to adhere to the roller surface. To address this, adjust the formulation by increasing the solvent ratio or adopt multi-pass processing and staged grinding to improve dispersion.
• Improper roller gap settings can also lead to sticking. If the gap is too small, the material experiences increased resistance when passing between rollers, causing it to accumulate on the roller surface. It is recommended to gradually tighten the roller gap during operation rather than adjusting it too drastically at once.
• The condition of the roller surface is equally critical. Residual debris, wear, or changes in surface roughness significantly increase the likelihood of material adhesion. Therefore, clean the rollers regularly, inspect their surface condition, and perform maintenance or repair as needed.
• Improper scraper angle and pressure can hinder effective material removal. By reasonably adjusting the scraper angle (typically between 30° and 45°) and ensuring uniform contact, sticking can be effectively reduced.

II. Causes and Optimization Measures for Material Overflow
Overflow generally appears as material spilling from the sides of the rollers or the feed area, often due to an imbalance between feed and discharge.

Excessive feed rate or too rapid feeding is the most common cause. When the material supply exceeds the roller gap's processing capacity, it tends to accumulate on the roller surface and spill over the sides. To address this, control the feeding rhythm and maintain stable supply by using small, repeated additions.

• Poor discharge can also trigger overflow. For example, if the rear roller gap is too small or the scraper is improperly adjusted, the material cannot be discharged in time and builds up on the roller surface. Slightly enlarging the discharge-side roller gap and optimizing the scraper position can help resolve this.
• Fluctuations in material viscosity due to temperature changes can disrupt the feed–discharge balance. Controlling material temperature or installing a cooling system improves process stability.
• Equipment operating parameters also matter. Excessively high roller speeds or improper speed ratios may cause material to be flung off the roller surface, resulting in overflow. In such cases, reduce the operating speed appropriately and check the equipment status.

III. On-Site Troubleshooting and Operational Recommendations
In actual production, it is advisable to troubleshoot in the order of: feed → roller gap → viscosity → equipment condition. In most cases, adjusting the feed amount and roller gap can resolve the problem.

At the same time, establish stable operating procedures, such as controlling the viscosity range of the material, avoiding large one-time feed additions, keeping equipment clean, and regularly inspecting key components. These measures can significantly reduce the occurrence of sticking and overflow at the source.

IV. Equipment Factors and Selection Tips
Apart from process factors, the equipment's own performance affects operational stability. For instance, roller machining precision, hydraulic system stability, and repeatability of gap adjustment all influence material flow behavior.

In recent years, some domestically manufactured equipment has made notable progress in these areas. For example, the Zhongyi hydraulic three-roll mill demonstrates reliable performance in gap control stability and operational consistency, helping to reduce the likelihood of sticking and overflow.

Conclusion
Overall, sticking and overflow in hydraulic three-roll mills are mostly caused by mismatches between process parameters and operating methods. By reasonably adjusting material formulations, optimizing equipment parameters, and standardizing operating procedures, grinding efficiency and product stability can be effectively improved, leading to a more stable and efficient production process.