Precise Metering From a Distance
Published on : Tuesday 02-05-2023
Metering systems for contactless application of lubricants for automated production processes and in difficult-to-access areas.
The contactless application of lubricants meets all conditions for complex, automated production processes and is now standard in many industries. We present the options available and what needs to be considered in the design of the metering system.
Today, the limitations of dot application or continuous application in bead form are quickly reached. Lubricants often have to be applied in hard-to-reach places. This is the case, for example, in the automotive industry, where grease has to be applied to components after they have been assembled, as well as in other industries such as the furniture and household appliance industries. Here, contactless greasing in the form of a shot or spray application is often the only option.
The contactless material application offers numerous benefits: precision, speed, reproducibility, reliability, and documentation. With the contactless material application, the lubricant is applied to the component from a set distance. Regardless of the positioning of the valve on the axis, for example, shots can be set with 100 per cent accuracy with a shot or high-speed valve, even from distances of up to 120 millimetres. The shot valve can perform up to 200 switching cycles in a second with minimal amounts of material. Both valves apply the material in dot form, with the application taking place in the longitudinal direction of the nozzle. With the shot valve, the shot direction can be varied depending on the extension. The dots can be set individually or overlapping in the form of a bead. The application remains contactless compared to a dot application using a needle metering valve, where lubricant temporarily bridges the gap between the metering valve and the component. Spray valves are ideal for contactless, full-surface applications of greases and oils. They are capable of both intermittent and continuous material application. Here, too, the shot direction can be varied depending on the extension.
Let’s learn some more about them:
1. Shot valves:
Up to 200 cycles per second – the shot valve from DOPAG is a top performer for the dispensing of lubricants in highly automated production processes. The shot valve could dispense the smallest quantities of material with shot sizes up to 0.02 ml. The application is contactless, clean, and without dripping. This is possible thanks to the integrated 5/2 way solenoid valve, which is also used for control.
Various adapters and extensions ensure high flexibility. This enables them to cover places that are difficult to reach or different shot angles. Nozzle sizes are available from Ø 0.2 - 1.0 mm. Depending on the size, media with different viscosities can be processed easily. Optionally, heating could be added in order to achieve the optimum processing temperature. It has an adjustable needle rise with raster regulation. Further, the shot valve could be completed by various components for monitoring and control. DOPAG, therefore, provides stroke detection, pressure sensors, or a light barrier for shot detection.
2. Spray valves
Special valve technology enables grease or oil to be applied cleanly and precisely over the entire surface of angled areas or components with a longer immersion path. The spray valve has a variety of nozzle extensions with different spray cones and directions, enabling the specific requirements of the application to be met.
The material can be applied intermittently or continuously. Short airways in the body and the directly flanged 5/2-way magnetic valve allow very fast, precise intermittent operation. Nozzle sizes with a diameter of 0.2 to 1.5 millimeters are available. A special feature here is the integrated spraying air valve, which enables the post-blowing time to be adjusted for nozzle cleaning. An optional stroke sensor or pressure sensor can be added for process control. A heater with a temperature sensor can also be installed. Drum and barrel pumps or pressure tanks in various sizes are available for material supply, while greases and oils can be delivered cleanly and directly from the original containers.
Advantages of using these valves:
Contactless greasing is always a solution when the point of use of the valve is not freely accessible. Thanks to a wide range of extensions, attachments, and nozzles, all valves offer a high degree of flexibility. Different distances shot angles, andspray patterns, as well as complex geometries, are possible without any difficulty. Contactless greasing is a good solution when the component in question cannot be greased before the assembly of other parts that subsequently prevent access to the application point or when a long immersion distance has to be bridged. With the shot valve, for example, grease can be applied on two sides simultaneously, while, with the spray valve, 360° application is possible.
Whether contactless greasing is suitable and offers advantages over the material application with a metering valve should always be checked for the particular application. Both contactless applications with dispensing valves and metering valves enable precise metering and clean material application. The nature of the material itself plays an important role in the choice. The optimum combination of material and valve should always be chosen. The main advantage of contactless greasing is the higher frequency and speed of metering. In series production, in particular, a few seconds can be critical and can lead to improved efficiency and greater cost-effectiveness. The valves can be optionally supplemented with various measuring devices for optimum quality assurance and documentation, such as a light barrier for shot detection, a gear flow meter, stroke detection, or a pressure sensor. This means that process reliability, high quality, and continuous monitoring and control are possible at all times, even with short cycles, high repetition rates, and stringently defined tolerances.
The challenges involved in contactless greasing should not be underestimated. The type and consistency of the grease and oil play an important role. Not all types of material are suitable for all valves, for example, thin wetting of surfaces with the spray valve. Depending on the nozzle size, materials with different viscosities can be processed with high-speed and shot valves. In any case, it is important to consider the main criteria involved in the decision process before selecting the metering system. In this way, there are many benefits in terms of speed, precision, and material cost savings.
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