Type of Frames in Press Working Tools

The presses are categorized according to the category of frames such as gap frame and straight side frame.

Presses with Gap Frame

Presses with gap frame are generates with solid frames in a vertical or inclined position. They are cut back in the form of letter "C" below the ram so which strip is fed from the side. A few presses have open-back so that strip is fed from front to back. A press is inclined so that the elements may fall through the open-back by gravity. Now-a-days, open-back inclination (OBI) is hugely used for blanking and piercing operations on little workpieces.

Presses with Straight Side Frame

Presses with straight side frame consist of a slide or ram that travels up and down among two straight slides or housings. They are extensively used for large and heavy work. The size of a press is limited because of the presence of housings. It has longer strokes because of the frame construction. These presses are additionally classified as single point, two point and four point suspensions, depending upon the number of connections among the slide and the main drive shaft.

According to the Number of Slides

There are three presses according to the number of slides, viz. single-action presses, double-action presses and triple-action presses. A single-action press has one slide, while a double-action press has two slides, viz. one inner and the other outer slide. It is commonly used for drawing operation in that outer slide carries the blank holder & inner slide carries the punch. Outer slide has shorter stroke than inner. Two slides move in the same direction and against the fixed bed of the press. The working of a triple-action press is same as the double-action press along with the addition of third ram. Three rams are situated in the press bed. It moves upwards immediately after other two ram moves down. All three actions are properly synchronized for drawing, forming and redrawing.

According to the Method of Actuation (Slide)

These presses consist of flywheel attached to the main shaft. The rotary motion of flywheel is converted within the linear motion of the slide or ram. This is achieved by using crankpins or eccentrics into the main drive shaft. The number of points of suspension of the slide determines the number of throws or eccentric on the main shaft. The points of suspensions are places where pressure is transmitted by connection to the slide. The shut height of the press can be varied with the help of adjustable connecting rods or pitmans. The main benefit of eccentric is that it offers more surface area for bearing the support for pitman. The limitation of eccentric is in that the length of stroke is limited. A crankshaft driven device provides longer strokes. The slides are also actuated thorough cams, rack, toggle, and pinions, screws and knuckles.