Process for economical manufacture of brushes of predetermined anisotropy

A method of manufacturing a brush having a head portion and a foot portion, comprising the steps of:

• a) providing a female die with two sheaths intersecting 90.degree. from each another, one said sheath vertical and the other said sheath horizontal, each said sheath provided with at least one male die, said sheaths forming a compression cavity of useful volume (V.sub.o);
• b) with the compression means spaced-apart, introducing a batch of volume (V.sub.o), of at least one conductive powder into said cavity;
• c) performing a first compression under displacement control using compression means of one of the two sheaths, so as to obtain an intermediate tubular cavity of volume (V.sub.i), having the cross section of the other sheath, and to keep this cross section constant during a second compression of the brush, in such a way as to obtain an crude brush having a cross section properly calibrated after a second compression;
• d) performing a second compression under pressure control using the compression means of the other sheath so as to obtain a crude brush of final volume (V.sub.f) with the desired final compression rate;
• e) moving the compression means of each of the sheaths apart from one another, first those under pressure control and then those under displacement control, and ejecting the crude brush,
• thereby forming a crude brush of predetermined dimensions and favorably oriented anisotropy,
• wherein the compression under displacement control initially has a mean rate T.sub.i =V.sub.o /V.sub.i between 1.5 and 3.5, and wherein the compression under pressure control has a rate T.sub.o =V.sub.i /V.sub.f between 1.1 and 1.2, and
• wherein there is a total compression rate T.sub.t =T.sub.i .times.T.sub.T.sub.c between 2.5 and 4, depending on the nature of the at least one conductive powder.