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Shrink Tunnel 101

Shrink Tunnel 101

Shrink wrapping is an effective way to protect perishable or delicate products from environmental conditions and the rigors of transport, as well as tightly binding products, making them easier to ship and store.

Heat shrink tunnels are an efficient way to package hundreds or thousands of products – available in various models and sizes to suit any packaging project.

This article explains what a heat shrink tunnel is, its purpose, and its potential advantages and disadvantages.

Types of Plastic Packaging

What is a Heat Shrink Tunnel?

Before discussing the purposes and benefits of heat shrink tunnels, it’s first essential to understand what they are. A heat shrink tunnel is a machine that is used to apply heat to shrink film. Most have two distinctive features – a heating tunnel and a conveyor belt.

Items are guided along the conveyor belt and heated as they pass through the tunnel. This causes the loose-fitting film covering an item to shrink and tighten firmly around it.

Heat shrink tunnels are used for automatic and semi-auto shrink wrapping – saving time and effort compared with manual methods such as heat guns – which can take minutes per product depending on size and the film being used.

There are different types of heat shrink tunnels and the best machine for each project will change depending on the type of packaging project as well as the shrink material being used:

Types of Plastic Packaging

Steam Tunnels: a heating tunnel that uses hot steam to tighten shrink wrap. Steam tunnels are often used for shrink sleeves and branding. PETG labels often require steam to shrink evenly. Tunnels will need or include a steam generator that can cost as much as the tunnel itself. Steam tunnels must be made from stainless steel due to the moisture from the steam.

Types of Plastic Packaging

Infrared Tunnels: Use infrared light to generate radial heat for shrink-wrapped products. Commonly used to wrap products that are vulnerable to heat exposure. Infrared heating is used for neck banding safety seals. For some materials, the lights can cause hot spots and limited shrinking. Be sure the material being used will work appropriately with an infrared tunnel before making a purchase.

Types of Plastic Packaging

Recirculating Tunnels: Arguably the most popular shrink tunnel, these use a heater coil and blowers to circulate dry, hot air for even shrink rates. Used for centerfold shrink rolls, bags, and tubing, the suitable machine will shrink products evenly over and over throughout the day.

Read our helpful guide for more information on the differences between shrink tunnels!

What Is the Purpose of a Shrink Tunnel?

The purpose of any shrink tunnel machine is to harness heat to shrink plastic until it conforms to the item being wrapped. Many shrink tunnels provide additional measures to help achieve this, such as temperature control and conveyor belt speed adjustments. Another common purpose for many tunnels is curing. Products requiring a curing or drying process often go through a tunnel slowly at low temperatures.

Additional features help users adjust the settings of the heat tunnel to suit the different applications. For example, a lighter material may require a faster conveyor speed and a lower temperature to avoid damage. However, thicker materials often require longer in the tunnel and are heated at higher temperatures to shrink correctly.

To understand the exact settings needed to shrink-wrap a particular product – and how to adjust these settings – a user must first understand how shrink tunnels work. It is essential only to adjust one setting when attempting to find the proper shrink rate. Changing more than one variable can hamper setup and overall production.

Types of Plastic Packaging

How Much Does a Shrink Tunnel Weigh?

The weight of a shrink tunnel depends on the materials themachine is made from
and the size of the tunnel chamber.

Shrink tunnels can be made from stainless steel, aluminum, and regular steel. Generally, shrink tunnels weigh between 250 and 1000 lbs if not over or undersized. Large shrink tunnels for shrink bundling or pallet shrink wrapping can weigh more than 1,000 pounds.

How Fast Can a Shrink Tunnel Go?

A shrink tunnel can go as fast as the conveyor motor and controls allow. It all depends on the machine's gearing. Faster tunnels with larger conveyor motors are longer to allow enough time for heat to shrink the product correctly.

US Packaging & Wrapping has geared tunnels that can go as slow as 6 inches per minute and as fast as 100 feet per minute. The maximum speed is not as important as many other factors. Running products at 100 feet per minute while the final wrap is loose, inconsistent, and unpresentable is not ideal.

View our range of shrink tunnels today and enjoy high-volume, high-quality protective wrapping projects!

Types of Barrier Packaging

What Can Heat Shrink Tubing Be Used For?

Heat shrink tubing is a type of tubular plastic that contracts when exposed to heat. Tubing can be a type of heat shrink packaging used for elongated products. Heat shrink tubing for wires is made differently and is often thicker than shrink tubing for packaging.

Heat shrink tubing has many uses beyond electrical wiring.
Below are materials heat shrink tubing can be made from:

  • PVC – Popular for packaging many products and as neck banding safety seals for bottles.
  • Polyethylene – Used for heavier products, often special order, ordered in a two mil thickness and higher
  • Polyolefin – Thick, colored tubing is found on electrical wires. For packaging applications, thinner polyolefin tubing can be difficult to source.
  • PETG – Polyethylene-based tubing is commonly used for shrink sleeves and can require steam to shrink without wrinkles.

What Are the Benefits of a Heat Shrink Tunnel?

Shrink tunnels offer several more benefits to the heat-shrinking process than heat guns can provide. Below are some of the key benefits and uses of heat shrink tunnels:

  • Consistency: One of the primary drawbacks of heat guns is product-to-product consistency. Because the user constantly moves the gun, one product can be fine while the next may have burn holes or spots that have not shrunk down.
  • Speed: Hands down, shrink tunnels are much faster than heat guns or chambers with lids. The tunnel maintains a consistent temperature with a conveyor transporting products through the heated tunnel. With the right tunnel, thousands of products hourly can be packaged.
  • Inline Flow: Shrink tunnels almost always have other machinery or conveyors for the infeed or outfeed. For more extensive production lines, an infeed conveyor transports products through the tunnel with an exit conveyor transporting out; after leaving the tunnel products can continue to another part of the production line without waiting for the shrinking process.
  • Increased Worker Satisfaction: Operating a heat gun during production or slowing down to heat and shrink products can be discouraging. With a heat tunnel, products are inserted into the tunnel with a shrink material and come out the other side conformed to the product and ready to be boxed.
  • Fewer Burn holes: Once a tunnel is set to the correct temperatures, products consistently exit with the correct amount of shrink. Heat guns can quickly cause hot spots. The need to redo the packaging increases time and labor costs.

What Are the Disadvantages of a Heat Shrink?

Despite its many benefits, there are also situations in which heat shrink tunnels may not be the most effective option for product packaging.
Some of the potential disadvantages of heat shrink tunnels are listed below:

  • Initial Capital Costs: Moving to even a smaller shrink tunnel can be costly from the cost of a heat gun. Without paying more than two thousand dollars for a smaller tunnel, you should question the quality especially if running the machine all day.
  • Smell: Due to the heat and products within some tunnels, an odor may be emitted from the machine initially until everything is broken in. Additionally, some shrink materials may also have a smell and proper ventilation is highly recommended.
  • Power Consumption: The larger the tunnel, the more power it requires. Some more giant tunnels operate on 220v, three-phase, or 480v because of the power draw.
  • Size: Shrink tunnels are larger and heavier than heat guns and all-in-one chambers. Be sure to have enough space for the tunnel, entry, and exit.

Faqs

Frequently Asked Questions (FAQs)

  • Q: What Are the Power Requirements for a Heat Shrink Tunnel?
    A: Power requirements are among the most critical aspects of purchasing heat tunnel machinery. Some tunnels come in a lower power supply variety (110v) but are lower volume machines. For higher-quantity production or more oversized individual products, 220v to 480v is the optimal choice. Before purchasing any heat tunnel, ensure that the power requirements at the production facility can support the machine. Most machines will come bare wire and require a male plugin or hard wiring.
  • ‌Q: What If I Do Not Have Money for a Shrink Tunnel?
    A: Heat shrink tunnels are not the only way to shrink-wrap products. More affordable alternatives include heat guns, which can heat shrink packages at a lower production speed. Shrink chamber machines come at a lower price point for medium production speeds. The budget buster route is shrink-wrapping with a blow dryer, but that takes a long time, does not look professional, and will not shrink all films.
  • ‌Q: What Is the Maximum Heat Setting for a Heat Shrink Tunnel?
    A: The temperature in most heat tunnels doesn’t rise above 400 degrees Fahrenheit; however, larger machines and custom options can exceed this standard temperature limit. Curing tunnels and specially-made machines can reach temperatures up to 500 degrees Fahrenheit.
  • ‌Q: What is the Maximum Product Weight for a Standard Shrink Tunnel?
    A: Manufacturers use various conveyor belts to make heat tunnels, so there is no single universal weight limit for all machines. There is also often more than one product on the conveyor at a time, and the machine must account for all products. If any items on the conveyer weigh 20-30 lbs or above, they must first be cleared with the machine manufacturer to determine whether the conveyer can handle the load. Electrical motors and other adjustments are required for heavier loads.
  • ‌Q: How do you replace the rollers for a shrink tunnel conveyor?
    A: Lift one side of the chain and carefully remove the old roller rod. With the chain still lifted, insert the new roller rod and then lower the chain to tighten around the roller rod. The process is better shown in his videot.
  • ‌Q: How do heat and airflow work in a shrink tunnel?
    A: Heat can come from multiple sources depending on the shrink tunnel. Recirculating tunnels use a heat bank and fans to move through the tunnel. Infrared tunnels use bulbs to heat the interior of the chamber.
  • ‌Q: How do you get the best results with a heat shrink tunnel?
    A: Begin with the recommended setting for the shrink film being used. If excess shrink and burn holes are experienced, incrementally speed up the conveyor without adjusting the heat. To obtain optimal results with a heat shrink tunnel, only change one variable at a time until the ideal settings are obtained.
  • ‌Q: What do shrink tunnels do?
    A: Shrink tunnels apply heat to a material while transporting it through the tunnel. They do not automatically apply materials over a product. They are often used with a sealer for shrink wrapping but can serve many other purposes.
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