Flashless Forging• "true" closed die forging in which metal deformed in a die cavity permits virtually no excess metal to escape.• Carried out in an elevated temperature which in between cold and hot forging.• Warmed work piece is compressed between a punch and a die having the shape of the compressor scroll or balance plate until deformation occurs.
flashless forging imposes requirements onprocess control that are more demandingthan impression die forging . most importantis that the work volume must equal the spacein the die cavity within. Very close toleranceif the starting blank is too large excessivepressures may cause damage to the die orpress. if the blank is too small, the cavity willnot be filled because of the special demandsby flashless forging . the process lends itselfbest to part geometrics that are usuallysimple and symmetrical and to work materialssuch as a precision forging process.
• . The process is used to produce a near-net or net shape forging. The dies make no provision for flash because the process does not depend on the formation of flash to achieve complete filling. Actually, a thin fin or ring of flash may form in the clearance between the upper punch and die, but it is easily removed by blasting or tumbling operations, and does not require a trim die. The process is therefore called "flashless forging", and is sometimes called "enclosed die forging".
figure 19.17flashless forging (1)just before initial contact with work piece, (2)partial compression, and (3)final punch and die closure. Symbols v and f indicate motion(v=velocity) and applied force respectively • coining is of course in the minting of coins shown in Figure 19.18. The process is also used to provide good surface finish and dimensional accuracy on workparts made by other operation.
FIGURE 19.18Coining operation (1) Start of cycle(2) Compression Stroke (3) Ejection of Finish part