Press ram

A die stamping was produced in just one action. Stock (2) was fed into die (1) and the deformation to obtain a cup was performed by a stamp (3) which moved in a sleeve (4) driven by a piston of a hydraulic cylinder. The strain obtained was measured with strain gauge (5). The temperature of the deformed alloy was maintained by heating device (7) and controlled with sensor (8). After the deformation was completed shedder (9) driven by a piston (10) of hydraulic cylinder (11) ejected the cup. The whole press ram rested upon base (12). 

PTFE sintering, pressing, ram or paste extrusion, compression moulding or isostatic moulding, machining, hot stamping, extrusion of pre-sintered powders on special machines. 

Before the actual sintering, the powder was pelleted in a small die. The pellets varied from 7/16 to 3/16 inch in diameter and were about 0.006 inch thick. After pelletization, the sample was placed between the faces of the anvils. A ferric oxide-coated pyrophylite ring was used to contain the sample. Pressure was increased in 10,000-atm. increments. About 2 minutes were allowed for the dissipation of the heat generated by each compression. The sample was maintained at the maximum pressure for about 10 minutes, after which pressure was reduced continuously until the press rams opened, permitting withdrawal of anvils. 

The press ram is fitted to the front end of the piston rod and can be rotated around the centre line or arranged in a fixed position. The press ram must be easily replaceable, as it is subject to wear and tear. It is made either of metal or plastic and may be of a convex or concave shape as the case may be. The position of the press ram is always displayed at the control panel. 

In order to reduce charging times, a second receiver is freshly loaded with material and placed in position ready to be swung in and located beneath the lifted press ram. In this way the extrusion process can be continued within a short period of time. In the meantime the first emptied receiver can be refilled, etc. (Fig. 15). This idea has been pursued in several ways, such as that of filling the receiver by means of continuous feed screws. 

Figure 2 Press ram travel as a function of speed and time.

Stroke strok [ME akin to OE strican to stroke] (13c) n. (1) The movement of a hydraulic piston, press ram, or other reciprocating machine member. (2) The distance between the extremes of movement of such a member in normal operation. 

Good press ram alignment due to the small punch-to-die clearance of metal dies. Three types of dies are used—progressive, compound, and steel rule. An accurate press feed is necessary with progressive dies. Feeding is not as critical... 

When the press reaches bdc, the clutch must disengage the flywheel to remove the source of power. The brake then engages, holding the press ram stationary in the bdc position. Since the material shrinks in the thickness direction upon cooling, the pressure is reduced thus permitting the press ram to restock readily without excessive clutch wear on the flywheel face. Brake wear is also minimized since the plastic material acts as a shock absorber as it is contacted by the plunger. 

Flash-free, molded holes can be produced during stamping. When the hole is vertical or parallel with the press ram motion, fixed pierce punches are used. The punches must be located on the side from which the part is to be stripped. As a rule, the part will bind on the protruding punches, eliminating the need for additional undercuts. The part will nearly always stay on the mold half with the punches. 

The material, under heat and pressure in the transfer pot, softens and flows into the mould. Thus pins and inserts are not subjected to direct pressure from the press ram. 

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