Replacing slitting circular knives is a routine operation in industrial cutting (e.g., slitting corrugated cardboard, thin metal sheets, and plastic profiles). However, neglecting details during the process can easily lead to safety accidents (such as hand cuts or accidental equipment startup), knife installation deviations (resulting in reduced slitting accuracy and rapid blade wear), or equipment damage (e.g., spindle deformation). Most of these issues stem from "inadequate safety protection, poor installation accuracy control, and non-standard tools/processes". While the replacement step seems simple, it actually requires implementing preventive measures throughout the entire process: "pre-replacement preparation, old knife removal, new knife installation, and post-installation debugging". This article details 6 core preventive measures for replacing slitting circular knives, covering key dimensions such as safety, accuracy, and maintenance, helping you avoid risks and ensure stable operation of the knife after replacement.
1. Pre-Replacement Preparation: Implement "Safety + Tools + Inspection" Triple Prevention
Preparation before replacing slitting circular knives is the foundation for risk avoidance. Focus on safety protection, tool adaptation, and new knife inspection to avoid problems caused by "hasty operations".
1. Safety Protection: Eliminate "Unprotected Operations"
Slitting circular knives (especially cemented carbide ones) have sharp edges, and there is a risk of accidental equipment startup. Safety protection must be prioritized:
- Power Off and Lockout: Turn off the main power of the slitting machine, unplug the power cord, or lock the distribution box (hang a "Maintenance in Progress—Do Not Switch On" warning sign) to prevent others from accidentally starting the equipment (statistics show 30% of replacement accidents are caused by unexpected equipment startup).
- Wear Protective Gear: Wear cut-resistant gloves (Kevlar material recommended, cut resistance level ≥ Level 5), safety goggles (to prevent iron chips from splashing into eyes during removal), and non-slip work shoes. Do not wear loose clothing or jewelry (to avoid getting caught in equipment).
- Clear the Operation Area: Remove debris (e.g., tools, parts boxes) from the workbench and reserve an operation space of at least 1.5 meters to ensure no obstacles interfere with removal and installation.
2. Tool Preparation: Avoid Damage Caused by "Inappropriate Tools"
Using suitable tools reduces accidental damage to knives and equipment. Prepare the following tools in advance and check their condition:
| Tool Name | Purpose | Preventive Points |
|---|---|---|
| Torque Wrench | Tighten/remove knife fixing bolts | Confirm torque range (usually 8-15 N·m, refer to equipment manual). Avoid using ordinary wrenches by feel (prone to bolt stripping or insufficient torque). |
| Dial Gauge | Detect spindle runout and knife concentricity | Check dial gauge accuracy (error ≤ 0.001mm) to ensure measurement data is reliable. |
| Copper/Rubber Hammer | Tap the spindle lightly when removing old knives (avoid hard strikes) | Do not use a steel hammer (prone to damaging the spindle or knife edge). |
| Cleaning Cloth + Alcohol | Clean the spindle and knife locating surface | Use a lint-free cloth (avoid fiber residue from ordinary rags) and alcohol with concentration ≥ 95% (ensure thorough cleaning). |
3. New Knife Inspection: Eliminate "Knife Defects"
New slitting circular knives may have factory defects (e.g., edge chips, locating hole deviations). Installing them directly will cause slitting problems, so pre-inspection is necessary:
- Visual Inspection: Check for chips or scratches on the edge (run your hand lightly along the edge—any resistance indicates a defect). Inspect the knife’s locating hole (or locating step) for flatness, burrs, or deformation.
- Dimension Verification: Use calipers to measure the knife’s diameter and thickness (e.g., common diameters for corrugated cardboard slitting knives are φ200-300mm, thickness 3-5mm). Confirm dimensions match the old knife (a deviation exceeding 0.1mm will cause installation misalignment).
- Material Confirmation: If replacing a cemented carbide knife, ensure the material matches the slitting material (e.g., YT15 with TiC for stainless steel slitting, YG8 for cardboard slitting) to avoid "wrong knife use" and rapid wear.
2. Old Knife Removal: Prevent Equipment Damage from "Violent Removal"
Old knives may stick to the spindle after long-term use (e.g., rust or residual impurities). Avoid violent operations during removal to prevent spindle deformation or knife chipping.
1. Clean Before Removal: Reduce "Impurity Jamming"
- Use compressed air (pressure ≤ 0.6MPa) to blow away iron chips and dust between the spindle and old knife. For oil stains or rust, soak the locating surface in alcohol for 5-10 minutes, then clean gently with a copper brush (do not scrape hard to avoid damaging the spindle’s locating surface).
- If the old knife is tightly stuck to the spindle, apply a small amount of rust remover (e.g., WD-40) to the locating surface. Wait 10 minutes before attempting removal. Do not strike hard (prone to spindle bending, which causes concentricity deviations when installing the new knife).
2. Symmetric Bolt Removal: Avoid "Uneven Force"
- If the knife is fixed by multiple bolts (usually 2-4), remove them gradually in a "diagonal symmetric" order (e.g., remove the top-left bolt first, then the bottom-right, and so on). Loosen each bolt by no more than 2 turns at a time (to prevent the knife from tilting suddenly and injuring hands or equipment).
- When removing the last bolt, hold the old knife with your other hand (or place a soft cloth underneath) to prevent it from dropping suddenly (cemented carbide knives are heavy—dropping can chip the edge or damage the workbench).
3. Old Knife Disposal: Avoid "Safety Hazards" and "Resource Waste"
- Immediately place removed old knives (especially those with sharp edges) in a dedicated knife box (with foam slots), with the edge facing away from the operation direction. Do not place them randomly on the workbench (prone to cutting others).
- If the old knife is repairable (e.g., flank wear ≤ 0.2mm), mark it as "To Be Re-Sharpened" and store it separately. If irreparable, dispose of it in accordance with hazardous waste regulations (do not mix with ordinary garbage).
3. New Knife Installation: Focus on "Accuracy Control" to Avoid "Installation Deviations"
New knife installation is a critical step—deviations exceeding 0.01mm can reduce slitting accuracy or accelerate knife wear. Focus on locating surface cleaning, concentricity adjustment, and torque control.
1. Locating Surface Cleaning: Eliminate Deviations Caused by "Impurities"
- Clean the spindle’s locating surface and the new knife’s locating hole (or locating step) with alcohol, wiping 2-3 times repeatedly to ensure no iron chips, oil stains, or fiber residues remain (even 0.005mm of impurities can tilt the knife and cause uneven wear during slitting).
- After cleaning, use a dial gauge to check the flatness of the spindle’s locating surface (error ≤ 0.002mm). If there are scratches or deformation (e.g., spindle wear), repair the spindle before installing the new knife (otherwise, the knife will run with excessive runout).
2. Concentricity Adjustment: Ensure "Synchronized Rotation of Knife and Spindle"
- Gently slide the new knife onto the spindle and rotate it by hand to check for resistance (if there is resistance, impurities may be on the locating surface or the knife’s locating hole is deviated—reclean or inspect the knife).
- Fix the dial gauge on the workbench, touch the gauge head lightly to the knife’s outer circle (5-10mm from the edge), and rotate the spindle manually. Record the dial gauge reading (runout must be ≤ 0.005mm). If the runout exceeds the limit, fine-tune the knife’s position (or check for spindle bending) until it meets requirements.
3. Bolt Tightening: Control "Precise Torque" to Avoid "Over-Tightening or Under-Tightening"
- Install bolts in a "diagonal symmetric" order. First, tighten all bolts until they "fit the locating surface" (hand-tightened). Then use a torque wrench to gradually tighten them to the torque specified in the equipment manual (e.g., 10-12 N·m for cemented carbide knives), tightening each bolt to the target torque in 2-3 steps (avoid one-time tightening, which may tilt the knife).
- After tightening, recheck the knife’s runout with the dial gauge (ensure it remains ≤ 0.005mm). If runout increases, bolt torque is uneven—re-adjust.
4. Post-Installation Debugging: Conduct "Test Operation" to Avoid "Direct Mass Production"
Do not put the new knife into mass production directly after installation. Verify its condition through test operations to prevent "hidden issues" from causing batch defects.
1. Manual Test Rotation: Check for "Mechanical Jamming"
- In the power-off state, rotate the spindle manually 3-5 times to feel for uneven resistance (e.g., jamming or abnormal noise). If present, check if the knife collides with other components (e.g., pressure rollers, workbench) or if bolts are over-tightened, causing bearing jamming.
2. No-Load Operation Test: Verify "Stable Equipment Operation"
- Turn on the power (assign someone to monitor the distribution box, ready to cut power at any time), start the slitting machine for no-load operation (no materials), and run it for 5-10 minutes. Observe if the knife rotates stably (no vibration or abnormal noise).
- Use an infrared thermometer to measure the spindle bearing temperature (≤ 40℃). If the temperature is too high, the bearing may be worn or bolts over-tightened—stop the machine for inspection.
3. Test Cutting Verification: Confirm "Qualified Slitting Quality"
- Take 3-5 pieces of the material to be slit (e.g., corrugated cardboard, thin metal sheets) and perform test cuts using normal parameters. Check the edge quality of the slit material (no burrs, fraying, or dimensional deviation ≤ 0.05mm).
- If there are burrs, the knife edge may be misaligned or pressure insufficient—fine-tune the knife position or slitting parameters. If dimensional deviation is large, check the workbench’s positioning accuracy. Only start mass production after test cuts are qualified.
5. Clarifying Common Misconceptions: Avoid "Hidden Risks During Replacement"
Many replacement accidents or installation issues result from "taken-for-granted" operations. The following 3 common misconceptions require key correction:
Misconception 1: "Ordinary Gloves Are Sufficient—Cut-Resistant Gloves Are Unnecessary"
Fact: Ordinary cotton gloves cannot resist the sharp edge of cemented carbide knives. An operator once cut their hand (requiring 5 stitches) when removing an old knife with cotton gloves, as the edge sliced through the fabric. Cut-resistant gloves with level ≥ 5 are a must to effectively prevent cuts.
Misconception 2: "The Tighter the Bolts, the Better—To Avoid Loosening"
Fact: Over-tightening bolts can deform the spindle or damage the knife’s locating surface (e.g., chipping the locating step of a cemented carbide knife), which actually increases knife runout. A factory once tightened bolts to over 20 N·m (required 10 N·m), causing spindle bending. Subsequent slitting led to rapid knife wear (life shortened from 80 hours to 30 hours), and spindle repair cost over 10,000 yuan.
Misconception 3: "Test Cutting Is Troublesome—Direct Mass Production Saves Time"
Fact: Skipping test cuts may cause batch defects. A packaging factory skipped test cuts after replacing corrugated cardboard slitting knives and started mass production directly. Due to excessive knife runout, over 1,000 cardboard sheets had frayed edges, requiring rework. The loss exceeded 2,000 yuan, and the process was more time-consuming than test cutting.
Conclusion: The Core of Replacing Slitting Circular Knives Lies in "Safety First, Accuracy Priority, and Process Discipline"
Preventive measures for replacing slitting circular knives are not "redundant steps"—they are key to reducing accidents, ensuring accuracy, and extending knife life. From pre-replacement safety protection and tool preparation, to mid-process precise installation, and post-installation test verification, every link requires attention to detail. For professionals in the tungsten carbide industry, it is not enough to provide customers with suitable slitting circular knives—guiding them in correct replacement (e.g., providing replacement process manuals) to help avoid risks is also a crucial part of improving customer satisfaction.
If your enterprise still faces safety hazards or installation deviations when replacing slitting circular knives, or needs customized cemented carbide circular knives (with replacement guidance) for specific slitting equipment, feel free to communicate. We can provide on-site replacement guidance or customized knife installation solutions to help you standardize operating procedures.