The HOFFMANN plate-type edge filter is a filter for micro-filtering of grinding oils, in particular for tool grinding, that does not require the use of consumables

Modern machining methods, such as high-speed cutting (HSC) and high-speed milling (HSM) place ever-increasing demands on the properties of tool materials and promote the increasing use of carbide tools. The machining required during manufacturing and sharpening of these high-strength tools also places high demands of the grinding oils in the process, as these oils must not only withstand high hydraulic stresses but are also subjected to ingress of very fine particles of impurities. As grinding dust from carbide metals is very fine-grained however, filtration using conventional filter facilities, such as belt filters and centrifuges, does not meet the requirements imposed for these applications. HOFFMANN Maschinen- und Apparatebau GmbH, based in Lengede, Germany, has therefore developed a highly effective filtering system to perform these demanding filtering tasks.

Method of operation:

Filter cartridges are arranged vertically in a pressure vessel, the filter vessel. Soiled oil flows through the filter cartridges from the outside toward the inside, where impurities are deposited around the cylindrical circumference of the cartridges. The machining oil is routed via the clean tank section to nozzles of the grinding machine after being finely filtered. The differential pressure in the filter vessel rises as the degree of fouling of the filter cartridges increases, resulting in a decrease in the throughput rate. Cleaning can be performed quickly by blowing out the dirt and rinsing the filter cartridges. Continuous supply of oil to the grinding machine is ensured at all times by the rapid, automatic cleaning process.

Advantages:

• filtration down to 1 µm
• automatic operation without the use of consumables
• low maintenance functioning
• reduction of grinding oil losses
• minimum follow-up costs
• for use also with materials that are difficult to filter