How to Choose the Right Cutting Method for Plastic Bag Making?

Choosing the right plastic bag cutting method is critical when investing in a plastic bag making machine. The method you choose, cold cutting or hot cutting, can affect your production efficiency, seal strength, and machine compatibility.
Let Parkins, the leading plastic bag-making machine supplier, explain the two major cutting technologies used in bag production: cold cutting and hot cutting, and when to use each method based on your bag type and application.

Cold Cutting vs Hot Cutting in Plastic Bag Making

Cold Cutting uses mechanical blades to cleanly cut the film without heat. It’s suitable for bags that don’t require a sealed edge.
Hot Cutting uses heated blades that cut and seal at the same time — ideal for leak-proof packaging.

Cold Cutting Methods: Clean & Precise

Cold cutting is the standard method for many bag making operations. It provides sharp edges and no heat damage.

1. Up & Down Knife (Mechanical Blade)

• Best for: Bottom-sealed bags, customized bag lengths
• Pros: Simple, durable, low maintenance
• Machines: Compatible with most entry-level and mid-range machines

2. Flying Knife (High-Speed Rotary Blade)

• Best for: Large-format bags (over 1 meter wide)
• Pros: Fast, ideal for high-volume production

❓Is flying knife cutting accurate?

✅Yes, when combined with servo control and tension sensors, flying knives deliver consistent results.

3. Perforation Knife (Tear Line Cutter)

• Best for: Roll bags (trash bags, produce bags)
• Pros: Leaves a micro-tear line for easy tearing without full separation, increasing convenience for end users

❓Can your machines make die-cut handle bags?

✅Yes. Our optional punching units allow custom handle shapes.

Hot Cutting Methods: Cut & Seal in One Step

Hot cutting is preferred when sealing strength and leak prevention are critical.

1. Center Line Hot Knife

• Best for: T-shirt bags (vest-style bags)
• Function: Cuts between two heat-sealed lines
• Pros: Ensures strength and reduces splitting at the bottom

❓Does hot cutting cause film discoloration?

⚠️Only if the temperature is too high. Our machines include precise heat control to prevent edge burning.

2. Side Seal Hot Knife

• Best for: Side seal bags used in food or medical packaging
• Function: Seals and cuts on the side edge
• Pros: Tight, secure seals minimize leakage risk

Which Cutting Method Is Right for My Products?

Start with your bag type, application, and required production volume:

Still unsure? Contact us to get a machine recommendation based on your bag specs.

Frequently Asked Questions (FAQ)

Q: Can I switch between hot and cold cutting on one machine?

Some machines support both methods with interchangeable modules.

Q: What materials are suitable for hot cutting in bag machines?

Materials like HDPE, LDPE, and LDPE are suitable for hot cutting, as they can melt and seal easily under heat. Biodegradable and compostable films may require testing for compatibility.

Q: Is hot cutting suitable for recyclable plastic films?

Yes, as long as the film can withstand heat without deformation. NuPlastiQ®, PE, PP films are commonly used.

Q: How can I reduce waste during the plastic bag cutting process?

Using accurate servo control, tension management, and optimized knife settings can significantly reduce cutting errors and material waste. Modern machines include automation for waste reduction

Choosing the Right Cutting Solution with Parkins

Whether you need cold cutting for high-precision roll bags or hot cutting for leak-proof T-shirt bags, Parkins Machinery offers proven, flexible solutions tailored to your specific production goals. With over 30 years of experience and customers in more than 60 countries, we help manufacturers worldwide improve efficiency, reduce waste, and meet evolving packaging demands.

Not sure which cutting method fits your bag type?
Contact Parkins today for expert advice, or explore our full range of bag-making machines with high-performance, precision, and flexibility.