The mold making process involves placing a first material (e.g. copper) with a certain melting point and a second powder-form material (e.g. chromium) with a higher melting point into a flat crucible. The crucible is heated to a temperature above the melting point of the first material but below that of the second. After cooling, the sheet mold thus produced is bent into a cylinder (20) and its two ends (21, 22) are welded to each other at the contact point.
