How to Maintain your Tray Knives

 

How to Maintain your Tray Knives when sealing your Packaged Meats.

 

 

Tray knives (also known as tray sealer knives, tray forming knives, or form-seal blades) are specialized cutting tools used to trim, cut, and seal packaging films, foils, and plastics in automated packaging machines.

Key Applications of Tray Knives:

Tray knives are used in Modified Atmosphere Packaging (MAP) and tray sealing machines. They are generally used to cut lid films for containers for Ready-meals, meat, poultry, seafood, Fresh produce, fruits, and vegetables, although they also have many other applications.

They are specifically used for trimming excess plastic or foil packaging film after the sealing process, as well as for perforating plastic to create easy-open features, such as tear strips, in flexible packaging, or for creating specific shapes for unique packaging, such as holiday-themed containers or custom tray contours. 

Key Features and Benefits of Renlaw Tray sealer blades:

• Precision and Quality: Engineered for clean, accurate cuts, reducing waste and ensuring product integrity. Hardened to ensure maximum cut-life while remaining tough enough to resist tooth breakage.
• Durability: Made from high-quality materials like hardenable stainless steels to withstand high temperatures and pressures while offering good excellent resistance.
• Customization: Available in various shapes (straight, rotary, serrated) and, in some cases, custom shapes.
• Efficiency: Designed to work in automated high-speed, high-volume production lines. 

When buying tray knives it’s critical to prioritize precision, material durability, and compatibility with your machinery to ensure efficient, high-quality production. 

Here is what is important when buying tray knives:

1. Machine Compatibility and Customization

• Exact Fit: Ensure the knife fits your machinery (e.g., Multivac, Mondini, Sealpack, Proseal).  <<can we use these names in an article?>>
• Customization: Tray knives are often customized in shape to meet specific packaging requirements, with or without mounting holes, tabs or bases.

 Blade Material and Durability

• Material Choice: High-quality, hardened stainless steel (like 1.4021 or 1.4112) is essential for durability, corrosion resistance, and food safety.
• Hardness (Rockwell Scale): Look for blades with proper Rockwell C (HRC) ratings (generally over 40 HRc ) to ensure the blade is hard enough to resist wear but not so brittle that it chips.

3. Type of Cut and Edge Configuration

• Serrated edges are best for tough stretchy films, fibrous materials, or for creating a “saw” action to avoid tearing. Larger tooth pitches cut more easily, but also have poorer cut finishes.
• High-quality CNC grinding ensures consistent tooth profiles with no thermal shock, resulting in accurate cuts and airtight seals, which are critical for Modified Atmosphere Packaging (MAP). 
• Tray blades range in thickness, from 0.5 – 2mm thick, the thickness needs to increase relative to the toughness of the cut product and the blade height. Higher blades need to be thicker to avoid distortion of the blade during cutting.

4. Performance and Maintenance

• Long-Term Sharpness: The knives must remain sharp over thousands of cycles to avoid downtime, product spoilage, and high maintenance costs.
• Regrinding/Resharpening Due to their complex geometries, it is not recommended to resharpen tray knives.

Common Issues and Causes:

• Dullness and Reduced Performance: Blades become blunt, requiring more pressure to cut, which leads to slower operations and higher risk of injury.
• Chipping and Physical Damage: The edge develops small flats on the teeth tips, often caused by cutting on hard surfaces or applying excessive force.
• Corrosion and Rust: Exposure to moisture, food acids, and cleaning agents causes rust to form.
• Improper Alignment/Blade Play: The blade does not sit properly in the handle (off-center), caused by loose pivot screws, worn-out washers, or warped frames from impact.
• Jammed Mechanism: Dirt, debris, and dried lubricant can accumulate in the pivot, causing the knife to stick or resist opening.
• Weakened Springs: In automatic or OTF (out-the-front) knives, the springs can lose tension over time, leading to failed deployment.
• Inconsistent Cuts: Improperly adjusted anvils or blunt knives can result in jagged or incomplete cuts, causing packaging failures. 

Common Maintenance/Handling Mistakes:

• Washing: High heat and harsh detergents degrade the metal and damage the handles.
• Improper Storage: Poor storage of blades can cause them to collide with other tools, damaging the cutting edges.
• Incorrect Sharpening: Hand sharpening usually results in incorrect cutting angles and ruin the blade’s edge geometry.

Solutions and Prevention:

• Regular Cleaning and Drying: Wipe knives immediately after use to prevent moisture buildup.
• Lubrication: Apply a drop of oil to the pivot area to maintain smooth operation.
• Proper Storage: Store blades away from corrosives, individually, or with a protective layer fixed over the cutting edges.
• Regular Inspection: Check for loose screws, misalignment, and signs of wear to prevent sudden failure.

• Temperature Resistance: If used in thermoforming (heat sealing), the knife must withstand high heat without warping, ensure that your blade steel is correct for your application.

 

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