Metering mixing and dispensing equipment

Highly reactive adhesives are more difficult to mix and apply because of their short working life, resulting in inaccuracies and material waste. Automated metering, mixing, and dispensing equipment may be required. 

Because many acrylic adhesives cure very rapidly with a significant exotherm, manufacturers generally recommend that quantities greater than a pint (ca. 0.47 L) should not be mixed at one time. As a consequence of the rapid exothermic cure of many acrylic adhesives, the use of dual component cartridges is often ideal. Most products can be purchased in ready-to-use cartridges. For large continuous operations, various automated types of meter-mix-and-dispense equipment are marketed by a number of engineering companies. 

Composite Integration, http //www.composite-integration.co.uk Magnum Venus Plastech Limited, http //www.plastech.co.uk Liquid Control Corp., 7576 Freedom Ave. N.W., P.O. Box 2747, North Canton, Ohio 44720. Web page www.liquidcontrol.com. Meter, Mix and Dispense Equipment Engineering Handbook, 1996. 

Suppliers of metering, mixing and dispensing equipment for the two-component adhesives ... 

Although the material cost is relatively low, some adhesive systems may require metering, mixing, and dispensing equipment as weU as curing fixtures, ovens, and presses. Capital equipment investment must be included in any economic evaluation. The following items contribute to a hidden cost of using adhesives, and they also could lead to serious production difficulties ... 

For a large-scale bonding operation, hand mixing is costly, messy, and slow, and repeatability is entirely dependent on the operator. Equipment is available that can meter, mix, and dispense multicomponent adhesives on a continuous or shot basis. 

Table 1 shows suppliers of equipment for metering, mixing and dispensing, as well as spray equipment. 

An acceptable static mixer should develop 30,000-40,000 laminar deviations with a pressure drop not to exceed 200 psi, should have low shear, and should be short in overall length. Static mixers are located on extruders, mix-meter-and- dispense equipment, adhesive applicators, and other equipment where two or more components must be quickly blended together. Many major equipment manufacturers supply static mixers with their Unes. 

The use of accelerator lacquers as a means to cure acrylics has been a very popular method since it allows the priming and storing of parts, the achievement of very rapid cures, and does not require expensive meter-mix-dispense equipment. It should be noted that this cure mechanism is not possible with condensation polymers, such as epoxies and urethanes, since they require full and intimate mixing of both components to achieve complete cures. 

Application. The adhesive should be capable of being applied readily to both concrete and treated steel surfaces in layers from 1 to 10 mm thick, to allow for concrete surface irregularities. Proprietory dispensing equipment is available to facilitate correct metering and mixing of the adhesive. 

The equipment required ranges from bottle-based, hand-held dispensers through simple pressure-operated applicators to complex mixing and metering equipment. The latter is used in mass production or where viscous/thixotropic, mixed formulations have to fill large gaps. 

Process and Equipment. The critical requirements for urethane foam dispensing equipment are accurate metering of the ingredients to the mixing chamber, adequate short-cycle mixing, and proper dispensing ability. The polyol,... 

Material supply pumps Control equipment IK-Metering systems 2K-Metering and mixing systems Mixing systems Dispensing and peripheral equipments... 

Figure 9.12 Structural bonding application for a reinforced plastic bumper assembly for a truck. The equipment dispenses a two-component structural adhesive onto the bumper assembly before it is integrated into the truck. In production, this is typically done robotically with a manual backup system (shown). The system being used is a See-Ro 488 meter/mix system the dispense gun in the picture is model 2200-250-000 dual-spool Snuf-Bak dispense valve that utilizes a No-Rush disposable static mixer nozzle. (Photo provided by Sealant Equipment and Engineering, Inc.)...

Dispensable using meter-mix equipment. 3382 is packaged in cartridges, pails and drums. The adhesive reportedly emits no caustic odor, will not corrode equipment, and is fully compatible with current wafer cleaning solutions and processes. 

Two-part mixed-type acrylic adhesives are applied like two-part mixed epoxy adhesives with meter or meter-and-mix equipment. The two parts may be metered into a container for immediate mixing and application, or metered into a static mixer and inunediately dispensed to the adherends to be joined. A simple illustration of meter-and-mix equipment is the double-barrel syringe, which delivers the two parts of the adhesive to a nozzle containing static mixing elements. These elements are alternating right and left hand helices connected off center to each other. At the other end of the complexity spectrum is the equipment for automated assembly lines. 

This chapter will discuss in further detail each item of the process chain the storage of adhesives, the transfer to the application area, the different metering and dispensing technologies, the used mixing equipments, the substrate preparation, and the quality control. Proposals are made regarding people education and how to create a safe working environment. 

The sticker liquid, which is in the tank shown below the forward edge of the wing, is metered into a mixing chamber located immediately below the funnel-like structure located behind the tank. A wind-driven propeller mixes the sticker and the flake, which originates in the funnel structure, and forces the mixture out of the chamber via a screw-type arrangement toward a terminus equipped with a blade-like arrangement that rotates rapidly in flight. With the aid of the slip stream, the blade dispenses the flakes as individual particles. 

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