Normalised heat power

Figure 5.4 Machining speed dz/dt as a function of the normalised heat power k.

For practical applications, one should be able to estimate the normalised heat power k as a function of the machining voltage. A qualitative estimation can be obtained if it is assumed that each discharge transfers a similar heat quantity qE to the workpiece. The heat power P0 can be related to the mean number of discharges using Equation (4.38) ... 

Figure 5.5 shows the expected material removal rate as a function of the normalised heat power k for various tool-electrode radii b. In order to determine the relation between k and the machining voltage U, one has to compare these results with experimental data. 

Figure 5.6a shows experimentally measured drilling speeds in glass with a 0.4 mm stainless steel tool-cathode. The electrolyte used was 30 wt% NaOH. By comparing the measured drilling speeds with that computed using Equation (5.20), it is possible to determine the dependence of the normalised heat power... 

Figure 5.6 (a) Experimental glass machining speed dz/dt for a 0.4 mm stainless steel tool-electrode as a function of the machining voltage U. (b) Normalised heat power k as a function of the machining voltage U [65],... 

According to criterion (5.6), glass micromachining requires only low heat power (below 1 W), and approximation (5.16) can be used to describe the machining speed. Written in the form of non-normalised variables ... 

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