Machining time in electrochemical machining vs. drilling

A round hole 12 mm in diameter is being produced in a titanium-alloy block by electrochemical machining. Using a current density of 5 A/ $mm^{2}$ , estimate the time required for machining a 15-mm-deep hole. Assume that the efficiency is 92%. Compare this time with that required for ordinary drilling.

Question

Machining time in electrochemical machining vs. drilling

A round hole 12 mm in diameter is being produced in a titanium-alloy block by electrochemical machining. Using a current density of 5 A/[latex] mm^{2}[/latex], estimate the time required for machining a 15-mm-deep hole. Assume that the efficiency is 92%.Compare this time with that required for ordinary drilling.

Accepted Answer

Note from Eqs. (9.13) and (9.14)

[latex]F_{ave}=\frac{2mv}{t_{\omicron }} .[/latex] (9.13)

[latex]MRR = CI\eta [/latex] (9.14)

that the feed rate can be expressed by the equation

[latex]f=\frac{CI\eta }{A_{\omicron }} .[/latex]

Letting C = [latex]1.5 mm^{3}/A-min[/latex] and the feed rate is f = (1.5)(5)(0.92) = 6.9 mm/min. Since the hole is 15 mm deep,

Machining time [latex]=\frac{15}{6.9}=2.17 [/latex] min .

To determine the drilling time, refer to Table 8.12

TABLE 8.12 Approximate Range of Recommended Cutting Speeds for Milling Operations

Workpiece material		Cutting speed (m/min)
Aluminum alloys		300–3000
Cast iron, gray		90–1300
Copper alloys		90–1000
High-temperature alloys		30–550
Steels		60–450
Stainless steels		90–500
Thermoplastics and thermosets		90–1400
Titanium alloys		40–150
Note: (a) These speeds are for carbides, ceramic, cermets, and diamond cutting tools. Speeds for high-speed-steel tools are lower than those indicated in this table. (b) Depths of cut, d, are generally in the range of 1–8 mm. (c) Feeds per tooth, f, are generally in the range of 0.08–0.46 mm/rev.

and note the data for titanium alloys. Selecting the following values for a 10-mm drill—rpm = 325 and feed = 0.15 mm/rev—it can be seen that the feed rate is (325 rev/min)(0.15 mm/rev) = 48.75 mm/min. Since the hole is 15 mm deep,

Drilling time [latex]=\frac{15}{48.75} =0.030[/latex] min.,

which is about 14% of the time required for ECM.

Question 9.5: Machining time in electrochemical machining vs. drilling A r...

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