Free plastic forming of a slender part means that an initially straight bar, clamped at its both ends, is bent and twisted by an appropriate motion of the end supports only. Emphasis is attached on the computer controlled, precise forming of workpieces with prescribed shape. In this paper the design of an appropriate forming machine at the laboratory scale will be presented. Moreover, the forming limits due to replastification of already completed sections of the part will be illustrated geometrically using one or two “cylinders of admissibility.” Finally, the method will be demonstrated by means of actually formed parts.

1.
Lippmann
,
H.
,
1990
, “
Free rigid/plastic plane bending of a slender beam
,”
Ing.-Arch.
,
60
, pp.
293
302
.
2.
Reigl
,
M.
,
Lippmann
,
H.
, and
Mannl
,
V.
,
1994
, “
Querschnittsa¨nderung von schlanken Profilsta¨ben beim freien Biegen
,”
Z. Angew. Math. Mech.
,
74
, pp.
157
159
.
3.
Reigl
,
M.
,
Lippmann
,
H.
, and
Mannl
,
V.
,
1994
, “
Air bending as a numerically controlled forming process to produce S-shaped bars
,”
J. Mater. Process. Technol.
,
45
, pp.
389
394
.
4.
Reigl
,
M.
,
Lippmann
,
H.
, and
Mannl
,
V.
,
1994
, “
Pliage libre de fils, tubes et barres par les extre´mite´s: Un nouveau proce´de´ de formage
,”
Me´tal Industries
, Nov., pp.
17
21
.
5.
Reigl, M., Lippmann, H., and Mannl, V., 1995, “Erzeugung vielfa¨ltiger Werkstu¨ckformen durch kaltes und warmes endgesteuertes freies Biegen,” Flexible Umformtechnik, DFG (Deutsche Forschungsgemeinschaft), eds., Mainz Scientific Publ., Aachen, pp. 2.2-1 to 2.2-15.
6.
Thalmair
,
M.
, and
Lippmann
,
H.
,
2000
, “
Spatial free plastic forming of slender parts—Fundamental relations and first example
,”
Int. J. Mech. Sci.
,
42
, pp.
1851
1865
.
7.
Thalmair, M., and Lippmann, H., 1999, “Spatial free plastic forming of slender parts,” Microstructures and Mechanical Properties of New Engineering Materials, B. Xu et al., eds., International Acad. Publ., Beijing, pp. 161–166.
8.
Lippmann, H., Mannl, V., and Reigl, M., 1993, “Freies Plastisches Biegen,” German patent appl., file no. DE 43 10 773.7, Deutsches Patentamt, Munich, submitted 06, Oct.
9.
Lippmann, H., Mannl, V., Reigl, M., and Thalmair, M., 1999, “Maschinensteuerung und Maschine zum endgesteuerten Umformen,” German patent appl., file no. 199 60 819.9, Deutsches Patentamt, Munich, submitted 16 Dec.
10.
Hill, R., 1956, The Mathematical Theory of Plasticity, corrected ed., Clarendon Press, Oxford.
11.
Lippmann, H., 1981, Mechanik des plastischen Fließens, Springer, Berlin.
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