1. Planer Machines

2. Introduction A planer is a type of metalworking machine tool that is some what similar to a shaper, but larger, and with the entire workpiece moving beneath the cutter, instead of the cutter moving above a stationary workpiece. The work table is moved back and forth on the bed beneath the cutting head either by mechanical means, such as a rack and pinion gear, or by a hydraulic cylinder.

3. Planers and shapers are used generally for generating accurate flat surfaces (horizontal / vertical / inclined) and cutting slots on work pieces which are too large and heavy to be accommodated on shaper machine table.

4. Working Principle In a planer, the work which is supported on the table reciprocates past the stationary cutting tool and the feed is imparted by the lateral movement of the tool. The tool is clamped in the tool holder and work on the table.

5. The bigger job is fixed with help of the grooves on the base of the planer and is accurately guided as it travels back and forth. The different mechanisms used to give reciprocating motion to the table are Reversible motor drive, Open and Cross belt drive & Hydraulic drive.

6. Planers are generally divided into 5 types according to their construction. Double Housing Planer Open Side Planer Universal Planer Edge type / Plate type Planer Divide Table Planer Pit type Planer Classification of Planers

7. Double Housing Planer It is the most common type of planer. It consists of mainly a massive bed on which the worktable reciprocates, and two vertical columns or housing, one on each side of the bed. Each column carries a tool head that can be slide up and down on the column.

8. A cross rail fitted between the two columns may carry one or two tool heads that can slide horizontally on the cross rail. All the tool heads can be clamped in position, and can be used collectively or individually depending on the requirements.

9. Open Side Planer Open side planer consists of only one vertical column or housing on which the cross rail is mounted. The column and the cross rail carry single and double tool heads respectively. This type of machine permits machining of wide work pieces.

10. Universal Planer The main feature of this type of planer is that it can cut on both forward and reverse strokes. Different cutting edges operate for cutting in the two strokes.

11. Edge type / Plate type Planer This type of machine is used for machining the edges of heavy work pieces. The work piece is clamped on the bed and the side mounted carriage supporting the cutting tool is reciprocated along the edge of the work piece. Cutting can take place during both directions of carriage travel.

12. Divide Table Planer It is also called tandem planer and consists of two worktables, which may be reciprocated together or separately. When mounting and setting of workpieces on the worktable consumes more time thereby restricting the machine for continuous mass production applications, divided table planer can be used. In this, one worktable can be used for setting up a new workpiece, while the second worktable carrying workpiece is being machined. The two tables can be joined together to hold large workpieces.

13. Pit type Planer A pit type planer differs from other planer in the sense that, the table and the work piece resting on it remain stationary and the tool reciprocates across the work surface. This type of machine is preferred for very large work, where the weight of the work piece and the table would make reciprocating movement difficult. The job is either mounted on a stationary table, or on the floor inside a pit, and hence the name pit type planer. One or two tool heads can be mounted on the cross rail and two side tool posts on the housings, if required.

14. The entire unit travels along the horizontal ways to and fro, thus the tool moves past the work surface during operation.

15. Planer Machine Parts Bed & Table Housings Cross rail Tool head Column Driving & Feed mechanism

16. Bed & Table It is of long & heavy base made of cast iron. Its top surface is flat and machined accurately. The flat top surface has slots in which the work piece can be securely clamped thus avoiding shifting out of its position. The standard clamping devices used on planer machine are: Heavy duty vice, T-holders and clamps, angle plate, planer jack, step blocks and stop.

17. The table movement may be actuated by a variable speed drive through a rack and pinion arrangement, or a hydraulic system.

18. Table & Housing The table supports the work and reciprocates along the ways of the bed. Table is made from good quality cast iron. The top face of the table is accurately finished in order to locate the work correctly. T-slots are provided on the entire length of the table so that the work and work holding devices may be bolted upon it. The housings are the rigid and upright column like castings. These are located near the centre on each side of the base.

20. Column These are rigid box-like vertical structures placed on each side of the bed and are fastened to the sides of the bed. They are heavily ribbed to trace up severe forces due to cutting. The cross rail may be made to slide up and down for accommodating different heights of work.

22. Cross rail It is a rigid box-like casting connecting the two columns. It may be raised or lowered on the face of the housing and can be clamped at a desired position by manual or electrical clamping devices. It should remain absolutely parallel to the top surface of the table. It is necessary to generate a flat horizontal surface on a work piece because the tool follows the part on the cross rail during cross feed.

23. The vertical movement of the cross rail allows to accommodate work piece of different heights. Since the cross rail is supported at both the ends, this type of planer machine is rigid in construction.

24. Tool Head Tool heads are mounted on the cross rail by a saddle. The saddle may be made to move transversely on the cross rail to give cross feed.

25. The swivel base is pivoted on the saddle and is graduated on each side to 60 degrees. The clapper block is hinged at hinge pins to the clapper box and it holds the tool post in which the tool is clamped by straps.

26. Driving and Feed mechanism The tool heads may be fed either by hand or by power in crosswise or vertical direction. The motor drive is usually at one side of the planer near the centre and drive mechanism is located under the table

27. Cutting Speed,Feed and Depth Of Cut Cutting speed The cutting speed of a planner is the rate at the metal is removed during the forward cutting stroke. Feed The feed in planning machine is the distance the tool head travels at the beginning of each cutting stroke expressed in mm per double stroke. Depth of Cut It is the thickness of metal removed in one cut and is measured by the perpendicular distance between the machined and unmachined surface. It is expressed in mm.

28. Machining Time If the cutting speed, feed, length of cutting stroke, width of the job and number of double strokes per minute for a planer operation are known, the machining time required for one complete cut may be calculated by using the equation: t m = L * B (1 + m) 1000 * v * f Where, L = length of stroke (mm)B = Width of job (mm) m = ratio of return time to cutting time V = cutting speed (m/min)f = feed (mm/double stroke)

29. Difference between Shaper and Planer In a Shaper, the tool is held on a ram which reciprocates and the work which is mounted on the table remains stationary and provides the feed. while in a Planer, the work is mounted on a table which reciprocates while the tool is held rigid on the frame and fed into the work. Multiple tooling with double or four tool heads in a Planer is used to machine more than one surface at a time thus reducing cutting time. The Shaper is driven using quick return mechanism, while drive on Planer table is obtained by gears or hydraulic means.

30. Planers are heavier, larger and costlier than Shapers. In a Planer, work setting requires much skill and time consuming, while in a Shaper, clamping is easy. In a Planer, tool is rigidly supported when the work moves assuring maximum accuracy on the machined surface, while in Shaper, due to overhanging of the ram during the cutting stroke and not robust design, the accuracy is not up to the mark. Tools used in Planer are much more robust (tough) than used in Shaper.

31. Quick Return Mechanism of a Planer to Drive the table by open and cross belting Table Drive Mechanism