In the actual use of a CNC oscillating knife cutting machine, there are two main consumables: blades and felt. During production, it is common for blades to chip frequently, become dull in just a few days, and felt to quickly develop deep grooves. This leads to unstable cutting quality and gradually increasing consumable costs.
Therefore, blades and air-permeable felt account for more than 75% of the total consumable expenses in the operating costs of a CNC oscillating knife cutter. Extending their service life is crucial — it can save a significant portion of consumable costs and indirectly increase product profits.
Why Do Blades and Felt Wear Out Quickly?
Three Reasons for Blade Wear
Abrasive Wear
Abrasive wear is the most common form of tool wear. When cutting materials containing glass fiber, asbestos, or mineral fillers, hard particles grind the blade edge continuously like sandpaper. This constant scraping quickly dulls the blade, leaving rough cut edges and increasing cutting resistance. According to research on tool wear in material processing, abrasive wear has a significant positive correlation with material hardness (refer to the study on tool wear mechanisms in the journal《Wear》, https://www.sciencedirect.com/journal/wear).
Solutions:
Use tungsten steel blades for high-hardness materials
Avoid excessively high vibration frequency
Vibration Fatigue Wear
The high-frequency reciprocating motion of an oscillating knife (up to 18,000 times per minute) generates enormous alternating stress. If the frequency is set too high, microcracks will form inside the metal, eventually causing the blade to break suddenly without warning. Material fatigue theory states that repeated alternating stress accelerates the propagation of metal microcracks, significantly reducing service life (refer to Stephenson & Agapiou’s 《Metal Cutting Theory and Practice》).
Symptoms:
Micro-chipping of the blade edge
Notches on the blade tip
Abnormal vibration noise
Solutions:
Reduce unnecessary high-frequency operation
Avoid long-term full-load work
Regularly check the blade edge condition
Lateral Friction Wear
When cutting rubber or thermoplastics, heat generated by friction softens the material and causes it to adhere to the blade, increasing resistance and accelerating chipping. Or, when cutting thick materials, the blade remains embedded in the material for a long time, and the side wall of the blade rubs continuously against the material.
Symptoms:
Felt is repeatedly impacted
The side wall of the blade heats up
Decreased straight-line precision
Solutions:
Set the cutting depth to “just cutting through”
Use an automatic tool setter to calibrate cutting depth
Reduce the number of cutting layers and cut in batches
Reasons for Felt Being Quickly Frayed or Cut Through
Excessively deep cutting depth: Never develop the habit of setting the depth to “1mm overcut”—this damages the fiber structure of the felt, creating deep grooves on its surface and leading to premature failure. Suggestion: The blade tip should just penetrate the material.
Long-term concentrated cutting paths: If small parts are repeatedly cut in the same area of the table (usually the bottom left corner), the felt in that area will quickly sink while the surrounding area remains intact. Or, cutting constantly in the center of the table causes the middle area of the felt to wear out prematurely, while the edges are barely used. Suggestion: Adjust the origin position weekly and rotate the cutting area.
Insufficient material fixation causing repeated friction: If the adsorption force is insufficient, the material will shift slightly during cutting, and the blade will “drag” the material on the felt. This repeated friction frays the felt surface and even breaks the felt fibers. Suggestion: Regularly check the vacuum system and clean the adsorption channels.
How Do Different Materials Affect the Service Life of Blades and Felt?
Impact of High-Density Materials on Blades
When cutting high-density materials such as hard rubber and asbestos-free boards, the impact force on the blade is more than 10 times that of cutting corrugated paper. If the feed rate is too fast, the instantaneous force on the blade will exceed its yield limit, leading to direct breakage. Research on composite material processing points out that carbon fiber causes extremely severe tool wear (related literature in the Springer database: https://link.springer.com).
Suggestions: Use cemented carbide blades, control the feed rate, and reduce the vibration frequency.
Adhesion of Sticky Materials to Blades
When cutting adhesive-backed materials (such as self-adhesive paper and double-sided tape), the blade generates heat due to friction during high-frequency vibration, causing the adhesive to stick to and wrap around the blade. This not only increases cutting resistance but also prevents the blade from dissipating heat properly, leading to lateral bending or even breakage.
Suggestions: Use coated blades or spray soapy water on the blade.
Why Thick Materials Wear Felt More Easily
When cutting thick materials (e.g., 50mm thick foam), the blade stays in contact with the felt for a longer time and delivers more impacts, increasing the frequency of felt wear.
Impact of Improper Parameter Settings on Blades and Felt
Chain Reaction of Excessively High Vibration Frequency
An excessively high vibration frequency increases the number of impacts on the blade edge, accelerating tool wear. It also increases the vibration amplitude of the felt and may transfer generated heat to the felt, causing the felt fibers to melt and harden (glazing) and lose air permeability. According to Taylor’s tool life formula, cutting parameters have an exponential impact on service life.
Impact of Excessively Fast Feed Rate
A fast feed rate means the blade must displace more material in a shorter time. This sharply increases lateral force and friction frequency, making blade breakage more likely and indirectly damaging the felt.
To learn how to set the cutting speed of a CNC oscillating knife cutting machine, also read: How to Set Cutting Speed for CNC Oscillating Knife Cutter
Excessively High Blade Pressure Damages Both Blades and Felt
Excessively high blade pressure causes the blade to bend, cuts deep into the felt, and crushes the felt’s elastic layer, making it lose rebound ability.
To learn how to set the cutting depth of a CNC oscillating knife cutting machine, also read: How to Set Cutting Depth for CNC Oscillating Knife Cutter
How to Scientifically Set Parameters to Extend Consumable Life?
Principle of Minimum Effective Vibration Frequency
On the premise of ensuring complete cutting, select the lowest possible frequency. For example, cutting corrugated paper usually only requires 12,000 RPM, not 18,000 RPM. It is best to start testing from a low frequency and gradually increase it until no sawtooth marks are visible on the cut edges. Practical experience shows that reducing the frequency by 10%-20% can significantly extend blade life.
Material-Graded Parameter Management Method
Establish a 《Material-Parameter Comparison Table》:
Soft materials (EPE): High frequency, medium speed, zero overcut.
Hard materials (rubber): Medium frequency, low speed, minimal overcut (0.1mm).
Sticky materials (self-adhesive): Low frequency (to reduce heat generation), high speed, negative overcut (kiss cut).
Importance of Automatic Depth Calibration
Avoid manual tool setting as much as possible; use an automatic tool setter instead. It can control the Z-axis zero error within 0.05mm. Strictly limit the overcut amount to 0.1mm 0.2mm. This ensures complete cutting while only slightly scratching the surface of the felt.
Correct Usage and Management Methods for Felt
Strategy of Rotating Felt Use
Purchase two pieces of felt and rotate them. The replaced felt can recover its elastic fibers to a certain extent after cleaning and “resting.” Or change the cutting area weekly to avoid repeated cutting in the same fixed position.
Zoned Cutting Method
Divide the table into 4 – 6 areas and rotate their use. For example, start from the bottom left corner today and the top right corner tomorrow. This ensures uniform wear of the felt across the entire table, avoiding local failure and increasing felt utilization by more than 30%.
Regularly Flip the Felt
Air-permeable felt: Usually has the same material on both sides and can be flipped. When the front side is severely worn, flip it over to extend the replacement cycle.
Conveyor belt felt: Usually has a specific reinforcement layer and cannot be flipped.
When Must Felt Be Replaced?
Replace the felt immediately if the following signs appear:
1. Significantly reduced adsorption force: The material still cannot be held firmly even when the fan is at maximum power.
2. Severely uneven surface: The surface is rough and uneven with deep grooves exceeding 3mm.
3. Hardening and glazing: The felt becomes hard due to glue or hot melting, making it easy to chip the blade tip.
Blade Selection and Matching Strategy
HSS vs Tungsten Steel
HSS (High-Speed Steel): Good toughness, not easy to break, suitable for cutting soft and thin materials. Low price.
Tungsten Steel: Extremely high hardness, wear-resistant but brittle. Suitable for cutting hard materials containing glass fiber or carbon fiber. Never use tungsten steel blades on uneven tables—they will break with a single vibration.
Matching Specialized Blades for Different Materials
Examples:
Cutting thick foam: Choose double-edged long blades to reduce resistance.
Cutting rubber: Choose coated blades (e.g., TiN, DLC) to reduce the friction coefficient and prevent adhesion.
Cutting leather: Choose single-edged eccentric blades for more flexible cornering.
To learn more about matching tools with materials, also read: Best Blades for CNC Oscillating Knife Cutters: Full Guide
Establish a Consumable Data Management System
Record Life Data for Each Material
Hang a notebook next to the machine to record: date, material type, cutting length, and reason for blade replacement. Identify which materials consume blades and felt the most, then calculate the cutting cost per meter to adjust the cutting process accordingly.
Predict Replacement Cycles
Use historical data to predict the optimal replacement time. Do not wait for blade breakage to shut down the machine, as this avoids unplanned downtime. Based on the data, set a preventive replacement cycle (e.g., mandatory blade replacement every 2000 meters cut). This prevents injuries from flying broken blades or workpiece damage, and avoids both “premature replacement” and “overuse.”
Common Wrong Operations
Using one blade for all materials: Using a dull blade designed for paper to cut leather will only pull the material, forcing you to increase the cutting depth and ultimately damaging the felt.
Continuing production with dull blades: A dull blade requires 3 times the cutting force of a new blade. This extra force acts entirely on the motor and felt, accelerating their wear and increasing unnecessary power consumption.
Continuing to use worn-through felt: Air leakage will cause local loss of vacuum suction, leading to material shaking and a high risk of blade breakage. It may also cause the blade tip to scratch the aluminum table, reducing the service life of the aviation-grade aluminum table.
Not cleaning dust in a timely manner: Dust accumulated in the felt pores will cause secondary abrasive wear to the blade, accelerating its damage. Be sure to clean debris on the felt with a vacuum cleaner before the end of each workday.
For more maintenance knowledge about CNC oscillating knife cutting machines, also read: CNC Oscillating Knife Machine Maintenance Checklist
FAQs
How to Remove a Broken Blade Embedded in Felt?
Never pick it out with your hands!
Methods: First, try to extract it with a magnet. If that doesn’t work, carefully pull it out with needle-nose pliers. If the broken piece is deeply embedded and does not affect flatness, some operators choose to press it deeper into the felt (not recommended, as it carries a risk of re-breakage). The safest option is to partially repair or replace the felt.
What Are the Characteristics of High-Quality Felt?
High-quality felt performs well in uniform air permeability and rebound. For example, felt produced in Germany or Italy has a denser fiber structure, uniform air permeability, good rebound after long-term compression, and is not easy to harden. Its service life is usually 30%-50% longer.
How to Judge When a Blade Needs to Be Replaced?
Do not wait for it to break. Replace it immediately if the following signs appear:
Listen to the sound: The cutting sound becomes louder, with a tearing sound instead of a crisp cutting sound.
Check the edges: Burrs or pilling appear on the material’s cut edges.
Check for uncut areas: The bottom is often not fully cut, requiring manual tearing.
If the blade life suddenly shortens, what should be checked first?
It is recommended to check in the following order:
- Has a new batch of materials been replaced (has the material hardness changed)?
- Was the frequency adjusted by mistake?
- Has the vacuum adsorption weakened?
- Has the felt hardened?
- Is the blade holder loose?
Can Felt Be Washed with Water When Dirty?
Generally, it cannot be washed directly with water.
Air-permeable felt swells and deforms when absorbing water, and it is difficult to dry completely. Moisture can damage the vacuum pump.
Cleaning suggestions: Use a high-pressure air gun to blow out dust, or wipe off glue stains with industrial alcohol. For local oil stains, use a dedicated dry cleaner.
Can Lubricating Oil Be Sprayed on Felt to Protect Blades?
Absolutely not.
Oil will block the air-permeable pores of the felt, causing vacuum adsorption failure. Additionally, oil stains will contaminate your cutting materials (such as fabric and leather). Lubrication should target the blade itself (e.g., atomized oil injection), not the table.
How Many Times Can Felt Be Refurbished (Milled Flat)?
Generally 1-2 times.
Felt is usually 3-4mm thick. Each milling removes 0.5-1mm. If milled too thin, the air permeability resistance becomes too low, making it difficult to hold small parts and easy to cut through to the hard base plate below.
What Causes Frequent Blade Breakage?
Blade breakage is usually related to the following factors:
- Frequently cutting thick materials
- Continuing to use a blade that has already bent sideways
- An uneven table
- Local collapse of the felt
- Excessively fast speed at corners
What Impact Does Felt Glazing Have on Blades?
After felt glazes, the following occurs:
- Decreased air permeability
- Unstable adsorption
- Increased material micro-displacement
- Greater lateral force on the blade
Consequences:
- The blade is more likely to chip
- Decreased cutting straightness
If the felt surface is shiny and hard, it means the fibers have lost their elasticity.
Why Does New Felt Wear Blades More Easily Immediately After Replacement?
The reasons are usually:
- New felt has high elasticity, and the blade pressure has not been recalibrated
- The depth is still set according to the old felt
- Excessive overcut amount
Suggestions after replacing felt each time:
- Perform automatic tool setting again
- Retest the cutting depth to ensure complete cutting
References and Information Sources
Stephenson, D. A., & Agapiou, J. S. (2016). Metal Cutting Theory and Practice. CRC Press.
Elsevier. (n.d.). Wear Journal – Tool wear mechanisms. Retrieved from https://www.sciencedirect.com/journal/wear
Springer Link. (n.d.). Composite material machining research articles. Retrieved from https://link.springer.com
