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In a 1mm tungsten sheet a 150 micro m wide slot is to be cut using an electron beam of 5 KW. Find the cutting speed.

for tungsten,

		W
	Cp = 2.71-------------
		cm3C
		W
	k =	-----------	(thermal conductivity from lookup tables)
		2.15cmC
	θ m = 3400C
	Z =	0.1cm (plate thickness)
	d =	0.015cm (beam and slot width)
	P = 5× 103W
	0.1 =		5× 103
			2.15( 0.015) v( 2.71)
		3400

cm v = 24.7----------

sec

•Other effects of EBM

-process done in vacuum, so it is best suited to small parts, but vacuum also reduces contamination

-very high heat concentration reduces peripheral heating of surface less that 50 micro m from the cut the part is at room temperature.

•Summary of EBM characteristics,

-mechanics of material removal - melting, vaporization

-medium - vacuum

-tool - beam of electrons moving at very high velocity

-maximum mrr = 10 mm3/min

-specific power consumption = 450W/mm3/min

-critical parameters - accelerating voltage, beam current, beam diameter, work speed, melting temperature

-materials application - all materials

-shape application - drilling fine holes, cutting contours in sheets, cutting narrow slots

-limitations - very high specific energy consumption, necessity of vacuum, expensive machine.

60.1 REFERENCES