- Slotting machine is a reciprocating type of machine tool which operates on the same principle as that of shaper, except that the ram of the slotter reciprocates in vertical direction.
- In a slotter, the ram holding the tool reciprocates in a vertical direction; the work mounted on the table remains stationary and provides the feed.
- It is very useful for cutting grooves, key ways, straight and curved slots, for machining regular and irregular surfaces (both internal and external), machining of dies, cutting of external and internal teeth of large gears.
- The slotters may be puncher slotter and precision slotter.
- The slotting machine consists of a base, which acts as a support for column, driving mechanism, ram, table and all other parts. Refer Fig
|Block diagram of slotting machine|
- The column is an integral part with the base.
- It is a vertical member. At its front, it carries vertical guide ways along which the ram reciprocates. It houses the driving mechanism.
- Saddle is mounted on the bed ways and provides a longitudinal feed on the saddle cross slide is mounted in the guide ways Cross slide can be moved in a direction perpendicular to the movement of the saddle.
- A rotor table is mounted on the top of the cross slide and can be rotated by hand or power by means of worm and worm gear mechanism situated underside the table.
- The table is graduated in degrees, which enables it to be rotated for indexing’ T-slots are also provided on the top of the table.
- Ram is reciprocating member which moves vertically up and down. The cutting takes place during the downward stroke of the ram.
- A special type of tool box is provided to relieve the tool during its return stroke.
Types of Drives
There are mainly four types of mechanisms used in slotters for driving the ram:
- Slotted disc mechanism
- Variable speed reversible motor drive
- Hydraulic drive
- slotted link mechanism
Slotted disc mechanism
- It is the simplest of all the ram drive mechanisms and is very commonly used in size slotting machines.
- In this mechanism, the driving pinion gets drive from a pulley which runs through belt by motor.
- The pinion rotates the gear which in turn rotates the slotted driving disc.
- The rotation of the slotted disc is converted into the vertical reciprocating motion ram with the help of connecting rod.
- The length of stroke of ram can be changed by shifting the crank pin towards or from the center of the slotted driving disc.
- Position of the stroke is adjusted with the help of hand lever provided for adjustment.
Variable speed reversible motor drive
- Such a drive is used in large modem slotting machines.
- Slotting machines have an attached or enclosed motor drive with a multi speed gear box to give a range of speeds to the ram.
- A typical range would be 40 to 150 strokes or cycles per minute.
- Hydraulic drive is used in large-modem slotted machines.
- The drive is similar to that employed for the shapers.
- In this drive, the hydraulic cylinder is in vertical direction.
- Both constant pressure and constant volume type drives are used.
Work Holding Devices
- In slotting machines, it is necessary that the work piece should be held rigidly in a suitable device or clamped to the machine table, to withstand cutting forces. For this purpose following devices are used :
- Parallel strips
- Special fixtures
- These devices components are placed as in case of shaper machines.
The operations performed on a slotter are:
- Machining flat surfaces
- Machining cylindrical surfaces
- Machining irregular surfaces and cam machining
- Machining slots, keyways and grooves.