Shearing mandrel

The tube is separated from the discard by means of a shearing mandrel. This tool consists of a longitudinally slit sleeve, as shown in Fig. 102, which is swung about an axle at the frame into the center of the press and embraces the mandrel. The swivel arm of the sleeve is axially movable on its axle and follows the ram motion. The shearing mandrel, whose diameter is only slightly smaller than the outside diameter of the tube and which is centered in the inside diameter of the tube by a cone, having pierced through the discard, the tube drops off. 

When the crosshead is lifted, the discard is caught on the shearing mandrel which for this purpose is provided with a small eccentric relief. It is removed from the shearing mandrel by blows with a hammer after the sleeve has been swung out of the press. 

There are a number of ways to reduce this nonuniformity. The mandrel can be placed eccentrically in the die, allowing for a wider gap at the remote end from the lead port. Such a design can, in principle, provide uniform flow rate, but shear rate and temperature histories will remain nonuniform. In another solution [Fig. 12.42(b)], an insert directs the flow at the far end upward, reducing the flow length around the mandrel and eliminating slow flow (stagnant) regions. In addition, the mandrel is also eccentric. 

Conventional shear forming is not flexible, since a specific mandrel is required for each product. To overcome this limitation, four different... 

Kawai K, Yang L-N, Kudo H (2(X)1) A flexible shear spinning of truncated conical shells with a general-purpose mandrel. J Mater Process Technol 113(l-3) 28-33... 

LLDPE can be drawn or stretched in the melt with low induced orientation (see Chapter 1), so a wide die gap does not add undesirable film stresses for LLDPE as with LDPE. The optimum die gap for each application will vary according to resin grade, melt heat, and output rates. Only the die mandrel requires modification for conversion to LLDPE. If only LLDPE is to be run, then the existing mandrel can be machined down. If both resins are to be run, two separate mandrels are required. As cast film is processed at considerably higher heats than blowm film, shear stresses are minimized, and no die modifications are required. 

Components of stress tensor in cylindrical coordinates Components of stress tensor in rectangular Cartesian coordinates Shear stress acting on mandrel surface [Eq. (46b)]... 

The two variable-delivery axial piston pumps k and I for the motions of the ram and the piercing mandrel are driven by a common motor and arranged on the top of the frame directly above the main cylinder. The oil collector tank and two geared pumps for the auxiliary drives are arranged in a pit below floor level. The auxiliary drive units operate the container and die-carrier shifting devices, the shear, the locking mechanism of the die-carrier and the control gears of the two axial piston pumps. 

Draw die, squeeze roll, breakdown roll, idler roll, guide roll, and so on Bending die, pressure die, mandrel, expand punch, swaging die, shear blade, feed guide, and so on... 

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