Spraying Systems. - World's leading designer and manufacturer of industrial spray nozzles

MODULAR AUTOMATION

A new modular automated spray system brings an unprecedented degree of precision and control to reel or conveyor linked spraying operations in many sectors of industry.

An early user in the UK is the high-volume bakery industry, which has processes requiring finely atomised liquids to be applied to product in a mass-production environment, with minimum material wastage and overspray and maximum control of factors such as droplet size, liquid flow rate and fan width. The system is equally relevant to other industries and processes such as parts coating, mould lubrication and selective product marking. Proven or projected UK applications include (in paper converting) the application of liquid balm to tissue paper, and (for bakeries) the spraying of pre-bake egg glazes and post-bake sugar coatings.

In the bakery environment, the system has been shown in practice to deliver an even, repeatable and consistent performance and hold it through an extended period of 3-shift working. Perceived benefits include material savings, improved product quality, lower maintenance requirements and less downtime to fix problems.

Supplied by spray technology specialists Spraying Systems Limited, who are responsible for marketing and product support in the UK and Republic of Ireland, the control elements of the new system have been developed by AutoJet Technologies, a division of parent company Spraying Systems Co.

Essential elements are a programmable spray controller and a pneumatic control panel. They can be wall-mounted or incorporated in a mobile cart that can be withdrawn when not in use. The cart will also hold the detachable stainless steel pressure tank containing the liquid to be sprayed. A spray header, incorporating one or more drip-free automatic spray guns, normally remains fixed in working position (for example, over a conveyor).

Compressed air, at pressure levels set at the control module, performs on/off switching, fan width control and atomising functions and applies the pressure that delivers liquid to the guns.

Unlike a standard plc, the programmable AutoJet controller, Model 2250, has been specifically designed for spray installations. It is an exceptionally powerful tool, able to monitor and control every aspect of the system itself as well as taking account (if desired) of external factors, and it offers multiple choices to the programmer.

For example the timing cycle (spray on/off) can be arranged in many ways to suit different operating requirements - such as spraying at timed intervals or spraying on signals independent of time - with numerous refinements in each category.

A feature of the control system is that its sophisticated resources are pre-programmed at the factory to customer specification - so that they can be fine-tuned by designated non-specialised members of the customer's own staff, without calling on the services of a specialist programmer. This is not generally possible with a standard plc controller and it is a big factor in optimising spray performance and eliminating unnecessary waste.

Software in the 2250 controller makes it easy to programme setpoint parameters, allows fault diagnosis and troubleshooting. It affords continuous monitoring of system performance and indicates reservoir liquid level and/or unexpired spraying time. Information is shown on a clear digital display alongside a 15-key tactile keypad with 'smart' keys for data entry and function selection. All the pneumatic valves and pressure regulators that physically control liquid pressure (via air pressure to the tank) and pressures in the air lines feeding the spray header are housed in a second cabinet.

Spraying Systems manufactures a wide range of automatic spray guns compatible with the new control system. Of these, the VAU (variable automatic) spray gun offers special advantages because of its total flexibility. Separate air streams control atomisation, fan width and on/off cycling. Atomising air pressure can be adjusted with no effect on liquid flow or the width and distribution of the spray pattern, so all the variables can be fine-tuned for optimum droplet size and coverage. Accurate targeting with minimal overspray is easy to achieve. VAU guns are drip-free on closure, can be run at frequencies up to 180 on/off cycles/minute and give repeatable, uniform spraying even with viscous liquids.