Optimisation of Fluid Application in Grinding M.N. Morgan 1 , A.R. Jackson 1 , H. Wu 1 , V. Baines-Jones 2 , A. Batako 1 , W.B. Rowe 1 (1) 1 AMTReL, Liverpool John Moores University, Byrom Street, Liverpool, UK 2 Cinetic, Landis Grinding Ltd, Keighley, West Yorkshire, UK Abstract This paper addresses the quantity of fluid required for grinding and the method of application. Results from this research suggest that supply flowrate needs to be 4 times the achievable ‘useful’ flowrate. Extra flowrate is wasted. It is shown that jet velocity and jet flowrate can be separately specified. Improved system design allows ‘actual’ useful flowrate to approach ‘achievable’ useful flowrate. Achievable useful flowrate depends on wheel porosity and wheel speed whereas actual useful flowrate depends on nozzle position, design, flowrate and velocity. Experimental methods are complemented by computational fluid dynamics simulations. Keywords: Grinding, Coolant, Fluid delivery 1 INTRODUCTION Waste occurs because supply flow fails to become useful flow that reaches inside the grinding contact. Only useful flow can lubricate the grinding action, prevent wheel wear and clogging, maintain low surface roughness and prevent excessive grinding temperatures. At very high wheel speeds, fluid delivery requirements increase machine costs and power demands [1]. Information from the UK government suggests that purchase, management and disposal of metal working fluids can in some cases approach 15% of manufacturing costs [2]. There is also an environmental impact of grinding fluid. Various researchers found that useful flow rate depends on nozzle position, jet speed and wheel porosity [3-5]. Engineer at al, [5] found that percent useful flowrate was 5- 20% of jet flow. Akiyama et al [6] found 20-40%. Chang [7] analysed depth of fluid penetration into a porous wheel and predicted smaller depth at higher wheel speeds. Gviniashvili et al [8] found that useful flowrate was maximised with the nozzle as close as possible to the contact zone. Ebbrell et al [9] demonstrated deflection of the grinding fluid by the air boundary layer at high wheel speeds, also the benefit of using an air scraper in front of a nozzle. A nozzle tangential to the wheel and positioned 10˚ - 25˚ before the contact zone was seen as optimal for jet delivery [10-12]. If jet speed equals wheel speed, a tangentially directed jet can easily displace air because the liquid momentum is greater than the air momentum. However, at lower jet speed the jet may be required to point more directly towards the wheel to avoid being deflected. Optimum angle may therefore depend on jet speed/wheel speed ratio. Webster et al [13] showed the need for jet coherency. The present paper aims to find practical ways to estimate fluid delivery requirements. 2 USEFUL FLOW PROGRAMME A flow separator was developed, Figure 1, allowing useful flow to be collected over a timed period while actually grinding. The system captures fluid passing through the contact region but excludes other flow. Sensors monitored temperature, acoustic emission, power and force [14]. The capacity of the wheels to transport fluid through the grinding contact was determined by measuring the surface topography of the wheels. Figure 1: Useful flow separator Wheel porosity after dressing and also after wear was investigated. Replication techniques were employed and evaluated by optical scanning systems. A typical image obtained from optical interferometry is shown in Figure 2, with porosity shown in blue. Achievable useful flowrate was estimated based on surface porosity. Figure 2: Optical image of a wheel surface nozzle wheel flow separator mm 0.87 0.50 0.00 -0.50 -1.28