Model 16: Stepdwell motion of a strip for punching and extrusion

Kinematic scheme:

Dimensions:

 Dimensions [m] a 0.0240 b 0.0480 d 0.0635 k 1.016823 rad r 0.4074 e 0.0306 f 0.0125 g 0.045 h 0.063 m 0.374 n 0.063 u 0.138 v 0.329 p 0.198 q 0.008 a2 0.007 a3 0.018 c2 0.158 c3 0.160 a0 -0.1 rad b0 0.5 rad

Explanation:

The four-bar linkage performs a symmetrical coupler curve with equal curve radius r at the symmetry points K1 and K2. A connection bar with lengt r provides a double dwell for the rocker e. Via bars f, g and h the pulleys of the metal strip are driven. Because of the one-direction clutch this is a step-dwell motion: the start and the stop of the metal strip begins with velocity and acceleration both zero (see picture with transfer functions of g and d). The motion behaviour is appropriate for high-speed punching.

During dwell the punching of the metal strip can take place. A disk is punched out and in the same motion cycle it is deformed by the second punch until a cup-like product. Both punches are withdrawn sufficiently when the transport of the metal strip starts, see the picture with the transfer functions.

Literature: VDI-Richtlinie 2728-I. Loesung von Bewegungsaufgaben mit symmetrischen Koppelkurven – Uebertragungsaufgaben.

Remarks:

The motion analysis has been performed with the program Runmec. The values of angle k and radius r have been precalculated acc. (lit) for given (measured) values of a, b and d. The values of m, n and f are calculated also based on them. All other values are as measured from the model.

The start positions of both cranks are such that their phase angle differs from the one appearing in the model. The toothed belt at the backside of the model, connecting both cranks, is mounted such that the phase angle is apparently not correct.

In the real machine one of the pulleys has a permanent brake to guarantee the required decelleration of the strip.