Planers are usually classified according to their main structures and accordingly they can be of the following types:
i. One side,
ii. Double housing,
iii. Pit edge (plate),
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iv. Profile type.
The open side planer is made with only one supporting column. Its main advantage is that work may be extended out over the bed. It is less rigid. Three tool heads, two on cross-rail and one on column can be provided.
The double-housing is of extremely robust construction and most commonly used. The support is furnished to the tool by two columns and heavy cross-rail thus allowing heavy cuts to be taken even far above the table.
1. Double Column Planing Machine (Refer Fig. 15.1A):
These are high speed, heavy duty and rigid machines. Their rigid design ensures a high degree of surface finish either with high speed steel or with tungsten carbide tools. These incorporate two vertical upright columns that support a cross-rail. Tool slides are mounted on the cross-rail and also on columns for side cutting.
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Their capacity is however, limited to the width of the table. These machines are employed for machining of heavy castings such as large bed and table ways, dovetails, slide and other guiding surfaces. The longer planing lengths allow machining of several objects simultaneously when clamped on the table in succession thereby considerably reducing the machining time.
Two rail heads provided on the cross-rail and two side heads, one on the left hand and other on the right hand side can be operated either independently or simultaneously, thereby reducing the machining time. All operating movements of the machines can be controlled both from the pendent and as well as from the control desk.
Fig. 15.1A shows a double-housing planer and open- side planer. Fig. 15.2 (a) shows a double-housing planer of Fig. 15.2 (b) shows as open-side planer.
Some of outstanding features of planer machines are:
i. The infinitely variable table speed enabled by DC regulation motor with Ward-Leonard control;
ii. Extremely high resistance of the table against deflection, torsion, vibration and wear;
iii. Highly rigid cross-rail with automatic hydraulic clamping and unclamping devices;
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iv. Infinitely variable hydraulic feed motion of the rail and side heads and tool slides; and
v. Centralisation of all controls in one place on the pendent and on the control desk.
The typical specifications of the machine are given below:
i. Planing width 1600 mm,
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ii. Planing length 4000 to 12,000 mm
iii. Planing height 1600 mm
iv. Clamping surface of table (width x length) 1400 x 4000 to 12000 mm
v. Vertical movement of tool head slide 350 mm.
2. Edge Planing Machine:
These machines are used with advantage whenever the edges of plates have to be machined, particularly in structural and boiler shops in the shipyards. They are capable of machining edges of plates upto maximum lengths of 6, 9 and 12 metres according to the model chosen. Maximum thickness of plates machined is 80 mm for all models and the maximum cross-section of chip is 33 sq. mm.
Broad specification are:
i. Maximum planing length 600 mm
ii. Maximum thickness of plate 80 mm
iii. Range of working speeds 14—18—22.4—28 m/min
iv. Main Drive motor: output 22 kW, speed 1450 r.p.m.
3. Pit-Type Planer:
The pit-type planer is more massive in construction than the double housing planer. In it the tool moves over the work by means of gantry type super structure which travels over the ways on either side of the table. The clapper boxes, which are of the double block type, allow planing operation in both the directions.
4. Plate Type Planer:
It is used for squaring or levelling the edges of very thick steel plates of sufficient width. This machine looks more or less like a plate shearing press.
5. Profile Type Planer:
In profile type planer, the hydraulic tracing attachment allows three dimensional work. A model made of wood or plaster may be used where the profile of the part changes in both directions and not in right angle relationship.
6. Duplex Table Type Planer:
This has two split cross-wise sections of table. It increases the productivity because one section of table can be used for loading and setting up and other section can be used for planing. It is also possible to fasten together both the sections and use it as single log table.
Accessories and Attachments:
Versatility of planer can be increased by using accessories such as copying attachment which permits contour planing of complicated parts like large propeller blades. Other useful attachments available for use on planer are milling heads, grinding heads etc.