Slotting Machine | Mechanism of Feeding in a Slotter

Slotter

        Slotter is a type of reciprocating machine. The tool is held in the ram reciprocates vertically and the work piece is held on the table. The slotter has a base upon which the column is being integrated. The column houses the driving mechanism for the ram. The top portion of the ram has the guide ways. With the help of this guide ways the ram reciprocates vertically. This reciprocation is achieved by the quick return mechanism. The base has horizontal guide ways which enables the saddle to move perpendicular to the column.

01 - SLOTTING MACHINE - SLOTTER

        The top face of the saddle has guide ways. These guide ways are perpendicular to the guide ways present in the base over which a cross slide moves. This movement is parallel to the column face.

        A circular shaped rotary table is mounted on top of the cross slide. This rotary table can be rotated about a vertical axis parallel to the column. This movement is the circular feed for the table. All the feeding systems are graduated.

       T- Slots are being provided on the table for holding the work piece. The longitudinal feed of the saddle, the cross feed of the cross slide and the rotary movement of the table in all these feeding mechanism the feed can either be given by hand or by power.

Quick return mechanism

          Metal from the work piece is removed only during the cutting stroke. During the return stroke no metal is being removed. To reduce the idle time of the return stroke quick return mechanisms are being used. The following are the generally used quick return mechanisms in a slotting machine.

· Whitworth quick return mechanism.

· Variable speed reversible electric motor drive.

· Hydraulic drive.

Feed mechanisms

The following are the feed mechanisms generally used in a slotter

· Longitudinal feed: This movement is achieved by moving the saddle either towards or away from the column.

· Cross feed: This is obtained by moving the cross slide parallel to the face of the column.

· Circular feed: This is obtained by rotating the table about a vertical axis.

Automatic feed

        A groove for the cam is cut on the face of the bull gear of the driving mechanism of the slotter. A roller follower slides in this groove. The roller is fixed at one end of the lever. The lever is pivoted in the middle and the other end of the lever has a slot. In this slot a feed adjustment pin is fitted.

01 - mechanism in slotting mechanism - cam and roller follower

This pin is connected by a connecting rod to the pawl and ratchet mechanism.

01 - mechanism in slotting mechanism - ratchet and pawl mechanism

        The bull gear starts to rotate, the follower follows the groove profile. When the lobe portion of the cam groove passes the follower, the slotted end of the lever moves up and down. This makes the pawl to rotate the ratchet wheel. The ratchet is keyed to the feed shaft. This feed shaft is engaged with the longitudinal, cross or rotary feed screws. This makes to achieve automatic feed.

      The amount of feed can adjusted by shifting the location of the feed adjustment pin in the lever slot.

Electrical Discharge Machining | Non-Conventional Machining Process

Non-conventional machining process

In recent years many new materials have been developed. These include titanium alloys, hast alloys, nimonic alloys etc. these materials cannot be machined accurately with the help of conventional machining process so a different method of machining has to adopted. These new method of machining is called as non-conventional type or unconventional machining process. This type of process generally uses ultrasonic, plasma arcs, laser beam, chemical and electro chemical for machining purposes.

01 - electric discharge machining - unconventional machining process

Electrical Discharge machining

In this process metal is removed from the surface of the work piece by erosion. The erosion is caused because of the electric spark produced between the work piece and the tool. This process consists of a tank in which a fixture is placed inside. The work piece is held in the tank with the help of fixture. The tank is filled di-electric fluid such as kerosene, white spirit, mineral oil, paraffin. These di-electric fluids do not conduct electricity.

The work piece is connected to the positive terminal of the battery (usually a D.C supply). The tool is held vertically over the work piece. Graphite, copper, brass or tungsten is generally used for making tools. The tool is hollow. It is connected to the negative terminal of the D.C supply. This makes the tool to act as cathode. A gap in the range of micron is generally kept between the work piece and the tool. In this gap the di-electric fluid is passed through in a very high pressure.

When the power supply is given an electric spark is produced in the gap between the tool and the work piece. Because of the spark heat is generated in the gap. The heat starts makes the surface of the work piece to melt. Thousands of sparks occur per second across the gap. The forces due to the spark tear thee particle of molten metal from the work piece. The tool is connected to the negative terminal to minimize wear on the tool.

Servo mechanism is used to feed the tool and maintain a constant gap between the tool and the work piece. The di-electric fluid also acts like coolant and carries away the eroded metal particle.

Advantages

· All types of material which can conduct electricity can be machined using this method.

· The mechanical properties of the work piece are not affected by this process.

· Surface finish in levels of micron is possible using this method.

· All types of complicated shape can be made on the tool which can again be obtained on the work piece.

· It is less time operation.

· The hardness of the work piece is not a factor as long as the material conducts current it can be machined.

· No stress is applied on the work piece so thin work pieces can also be machined.

Disadvantages

· Very high power consumption.

· Only electrically conductive metals can be machined.

· Perfect square corners cannot be manufactured.

· Redressing of tools is necessary for deep holes.

Application

· Used for die sinking.

· Used to cut off rods.

· Used for making intricate shapes.

· Used for polishing of tools, cutters and broaches.

· Used for accurate drilling of very small holes, slots, etc.

· Profiles and cavities can be formed on hard and brittle like Brittle materials tungsten carbide using this method.