A heat/shrink tunnel, is an enclosed and heated area that is used to not just apply heat to an object, but create a heated local environment around said object. Heat tunnels are generally found above or enveloping a section of conveyor belt to allow for automated travel through the tunnel. The most common use for a heat tunnel is the activation of heat shrink labels, packaging, and tamper bands on a container; however, they are also used to cure paints and heat parts. This article series will cover the most common types of heat tunnels available, their advantages and disadvantages, and the technical complications of heat shrinking.
Types of Heat Tunnels
The type of heat tunnel is determined by the heat source used. Common heat sources include infrared, steam, and hot air. Regardless of the type, all heat tunnels work by transferring energy from a heat source to an object within an enclosed area. The goal may be to a shrink film/label, cure a coating of paint, remove excess water/moisture, or any other application requiring immersion in heat but the principals remain the same. The amount of energy transferred depends on the output capacity of the heat source, the material being heated, and the residence time of the object in the tunnel.
A welding rod, as recommended by the manufacturer, must be used when installing linoleum, rubber, PVC, or TPU surfaces. Welding rods are generally available with 3 to 5 mm diameters. Speak with your material manufacturer or supplier to find out more.
Before welding, the seam edges must be milled or grooved to approx. 2/3 of the thickness of the material. The welding rod is then welded into the groove to create a strong bond. It is important that the welding rod fully penetrates the milled groove otherwise the seam may fail prematurely.
The welding rod is then trimmed in two stages: The first pass is done with a trimming guide immediately after welding. This removes the bulk of the excess rod. The second pass is done once the material has cooled completely. This helps prevents concave seams, producing an even, flush seam with a long service life.
A properly prepared substrate should be solid, evenly laid, and free from debris such as loose screws or stones.
If it is raining, welding must not be carried out without special protective equipment.
Welding must be suspended at temperatures below +5°C in order to prevent the material from being exposed to an excessively high thermal load (in accordance with DVS 2225-4).
In some cases, excessively high humidity can cause condensation to form on the welding surface, which has a negative effect on seam strength.
If there is strong wind, the tool may not reach the required welding temperature. This can be counteracted by raising the welding temperature by 20 to 30°C or reducing the speed by 20 to 40 cm/min. If the wind is excessively strong, the welding area should be shielded against wind or welding should be suspended.
Prolonged exposure to the sun can cause the material to heat up significantly causing thermal expansion. This causes wrinkles which makes the welding process more difficult and leads to an unacceptably high level of tension in the seam area when the material cools.
Maintaining the Tools
The air inlet and filter should be cleaned frequently and the heating element removed and cleaned periodically. This ensures the tool is able to produce the correct air volume and temperature output.
Using Generator Power
The generator must have the correct specifications in order to ensure safe operation:
Manual Welding Process
The distance between the pressure roller and the nozzle opening should be between 20 and 30 mm to ensure that the weld seam is joined as efficiently as possible. The pressure roller must be guided so that it is parallel to the nozzle. This will ensure that the welding process yields the best possible results (see images above).
The hot-air nozzle should be cleaned periodically to keep the contaminants out of the welding seam. A blocked nozzle will restrict the tool’s air output which may cause fluctuations in the output temperature.
Large format printing of banners can produce a stunning final product. Very large banners require the joining of two or more pieces of material by welding, stitching, or gluing. When welding two banner pieces together the type of ink used becomes an important consideration.
Solvent-based inks cannot be welded. The ink interrupts the bonding process. Instead, leave a margin unprinted on the banner the width of the required weld. Be sure to carefully align the pieces of material to make sure the final product is perfect.
Water-based inks can be welded without issue, no margin need be left when printing.
Have questions about your material? Give us a call.
The new HEMTEK stationary welder from Leister is easy to use, see how in this video:
We’ve written a lot of articles about air heaters and heat systems over the years. Here’s a roundup to help you navigate the content we have available.
If your business uses compressed air to clean, dry, or cool, your air system may not be as efficient as you think – in fact, the worst offenders are less than 10% efficient. For many applications, it is advantageous to convert to a blower based air system which leads to long term cost savings.
Blow-off of water, dust, coolant and other contaminants, drying, cooling, and heating may all be achieved using either compressed air or blower operated systems; there are several factors to consider when choosing the best system for any application utilizing air. Each factor carries varying weight depending on the application specifics and the existing infrastructure.
1. Energy cost
2. System cost
3. Maintenance and operating cost
4. Application particulars
5. Availability of electricity
6. Space and weight
7. Noise considerations
1. ENERGY COST
Blower operated systems, particularly for continuous flow applications, are almost always the more energy efficient choice. Some blower installations can reduce energy costs up to 80% over previous compressed air systems. When used for the right application, blower bases systems often have an ROI of less than one year due to significant energy savings.
In applications where the need for air is sporadic or in short bursts, the amount of energy consumed by a compressed air system decreases. In these applications compressed air may be the energy efficient solution.
For both system types, implementing a proper control system can further minimize the air and power consumption. TIP: If you're looking to change from compressed air to a blower system or vice-versa, ask your supplier to provide an ROI to see how quickly the change will pay for itself.
We’ve written a lot of articles about blowers over the years. Here’s a roundup to help you navigate the content we have available.
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