Apply Adhesives According To The Component

2023 Author : Hannah Pearcy | [email protected] . Last modified: 2023-05-24 11:12

There is a wide range of applications between simple processing using a cartridge gun and the application robot. There are a wide variety of processing devices for these today.

Apply one-component adhesives

In the area of single-component products alone, there are hand-operated, compressed-air and battery-operated pistols with different pressure ratios. The devices can be divided not only by the drive types, but also by the packaging type of the adhesive or sealant.

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With the handguns , the possible pressure force ratio ranges from 7: 1 to 35: 1, the feed rates that can be achieved with this from 12.5 mm to 28 mm and the maximum pressure force from 1.0 kN to 5 kN, but always only in the pressure peak. This aspect alone makes it clear that there can be no standard or unit pistol. In order to choose the right pistol, you have to take into account not only the material characteristics but also the special features of the respective application, such as the discharge quantity.

There are also different designs for the compressed air pistols, also adapted to the material to be discharged and the task to be carried out. Selection criteria here are the fineness of the pressure control, the maximum pressure force when the pressure regulator is fully open and the repeatability or reproducibility.

But that's not all: different controllers and maximum pressure can be combined, which leads to hundreds of new variants. The material to be processed and the desired discharge quantity per given time unit are the most important selection criteria.

If you work with an air-operated gun in an industrial environment, the in-house air line is usually used, which has to supply a wide variety of devices and consequently has pressure fluctuations. In order to guarantee a reliable application of adhesive / sealant, it is advisable to measure and regulate the inlet pressure already. The necessary displays and controllers can be retrofitted to most devices and have a great impact with little effort. A more recent development is an Innotech / Festo system in which the same amount of adhesive is always dispensed per shot, regardless of how long the processor triggers the material flow. This is the ideal solutionwhen automation cannot or cannot yet be used and a defined quantity should nevertheless be carried out for each order. This system is also available as a retrofit kit for existing compressed air guns.

Like compressed air pistols, battery -operated pistols do not require any effort from the processor, but they reduce the risk of accidents because they can be used without cables. For the same reason, these pistols enable processing in areas that are difficult to access or on large objects such as a truck body or a bus.

The current progress in battery technology has opened up new possibilities with regard to the duration of use and the achievable feed forces. This means that battery-operated pistols can also be used today where a lot of mass has to be continuously discharged or a lot of power is required, for example when processing products with a so-called "High Position Tack" (highly viscous adhesives, which, due to their internal strength, bond the parts into Hold position). Especially for these and also for so-called warm melts, the battery drive can be combined with a heated cylinder, so that the contents of the cartridge are heated and their viscosity is reduced for processing. When the applied adhesive cools down, it reaches its previous, high viscosity and thus results in very high initial adhesion. This lends itselfif, for example, large-format windows are glued into vehicles or ships.

In addition to the high-speed version, which enables fast working with standard viscosities, Innotech has developed a high-force variant of the battery pistol specifically for the high-position tack products that are increasingly used in vehicle glazing, with the speed being in favor of Pressure was reduced. The discharge quantity can also be precisely regulated here.

Supplementary information on discharge quantity precisely regulated

The following example shows what is possible today:

For a specific application in aircraft construction, Innotech has developed a discharge-controlled battery pistol for 2K 50 ml mixing cartridges. With a 3 g shot, a deviation of +/- 0.25 g is permanently achieved. This ensures that the optimally required amount of adhesive is always applied. This prevents underdosing (which can lead to adhesive failure) as well as overdosing, ie waste of material.

Apply two-component adhesives

In large-volume, industrial processing, two-component adhesives are the domain of the mixing and dosing systems. But what about repair applications or applications in places that are difficult to access? Or for series start-ups where the quantity to be produced makes the use of the system uneconomical?

Here, the same materials are used, but packaged in multi-chamber cartridges, mostly twin cartridges. These are available in a wide variety of sizes and are also adapted to the different mixing ratios of the materials. Cartridges with 23 different mixing ratios are currently on the market. With the same feed rate, one component, for example, has to convey up to 25 times the quantity. Please note the following when selecting the device:

• the mixing ratio,
• the material viscosity, which also has a high influence on the miscibility,
• the cartridge mass / cartridge geometry
• the desired or required discharge quantity per given unit of time or per “shot” and
• the intended application taking into account the spatial conditions (eg internal sealing in narrow housings).

Hand, compressed air and battery operated devices are also available here. Especially when processing 2-component material, it is important to take into account the back pressure built up in the mixer when selecting the gun. Especially when the components to be mixed have very different viscosities and the quantities differ greatly, the even feed of the pistons must contribute to the homogeneous mixing of the two components. At the same time, the gun has to overcome the pressure building up in the mixer in order to ensure fatigue-free and even application. (qui)

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* Joachim Rapp Managing Director, Innotech Marketing and Confection Red, Rettigheim

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