New System for Machine Tool Cooling Lubricant Supply

Continuously increasing the cutting speeds in modern machining requires the use of through-the-tool coolant delivery at higher pressures than ever before. Using the new KST booster from Bosch Rexroth, the high-pressure coolant supply is generated using a cost effective, hydraulically controlled solution with pressure and flow to spare.

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The KST system completely eliminates the motor-pump supply line on the cooling lubricant circuit and uses existing hydraulics on the machine to pump the coolant. It both reduces upfront costs and lowers energy consumption by up to 88 percent.

"Conventional systems for supplying coolant to machine tools use a filter, pump and a pressure relief bypass to provide coolant for the spindle," says Tom Peric, a senior application engineer with Bosch Rexroth. "With the new KST booster solution, customers use the existing hydraulic power unit to control a three-chamber cylinder. One chamber is directly coupled to the hydraulics and the other two chambers, being mechanically linked to the first, are used to pump the coolant."

Since the hydraulic system is typically idle while the high pressure coolant is active, the hydraulics can now perform both duties with little additional cost. The system not only eliminates the pump, valve and filtration system but also saves money because the filter and pump are maintenance items that typically need to be replaced every two years.

Reduced cost and complexity are not the only benefits to using the hydraulic booster. Using hydraulic technology, the system is able to provide a consistent flow of coolant at precise flow and pressure settings. Pressures up to 120 bars and 50 l/min are achievable. The controls are all electronic and can be directly linked to the CNC control though an integrated bus system. The service life of the supply unit is extended by moving the control functions into a particle-free hydraulic circuit. Fine filtration is no longer required to protect the delicate pumps of the past. Peric says that about 90 percent of applications can be accomplished without the cooling lubricant fine filter that has been necessary up until now. The KST booster can be retrofitted into existing machines and reduces the average noise emission considerably.

In addition to the coolant booster, Bosch Rexroth is offering a complete coolant solution including chip conveyers and coolant filtration with integral containment. The KST Booster is supplied as an integrated product that is fully tested at the factory and conveniently eliminates expensive, unreliable high pressure coolant systems. Often the hydraulic unit in a machine tool is used only for clamping or moving parts, but now it can also be used to control the coolant supply and provides a simple, effective way to reduce energy costs.