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Planing

Planing is a manufacturing process of material removal in which the workpiece

reciprocates against a stationary cutting tool producing a plane or sculpted surface.

Planing is analogous to shaping. The main difference between these two processes is

that in shaping the tool reciprocates across the stationary workpiece. Planing motion

is the opposite of shaping. Both planing and shaping are rapidly being replaced by

milling.

 Process Characteristics :

• Uses single-point cutting tool.

• nvolves a reciprocating motion between the tool and workpiece.

• Produces plane or sculpted surfaces.

• !eaves parallel feed marks.

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Working principle of a planing machine

•  The machine used for this process is known as

a planer. The si"e of the planer is determined by

the largest workpiece that can be machined on it.

The principle involved in machining of a #ob in

 planer is a reverse case of shaper. The work is

rigidly held on the work table or platen of the

machine. The tool is held vertically in the tool

head mounted on the cross-rail. The work table

together with #ob is made to reciprocate past the

vertically held tool. The inde$ed feed%after each

cut% is given to the tool during the idle stroke of

the table.

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Main parts of a planner•   Bed.

•   Table or platen.

•   &ousing or column. Cross-rail.

•   Tool-heads.

•   Controls.

Types of planer

•   'tandard or double housing planer.

•   (penside planer.

•

  Planer miller.

•   Plate planer.

•   Pit planer.

•   )ivided table planer.

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Working of a butler planing machine

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Driving mechanism

*our different methods are as follows:

•

  Crank drive.

•   Belt drive.

•   )irect reversible drive.

•   &ydraulic drive.

  Feeding mechanism

The hori"ontal feed is given by moving the tool-head along the cross-rail and vertical

feed%to vary the depth of cut% is imparted by moving the vertical slide of the tool-head

By means of the down feed screw.

•   +atchet and pawl feed mechanism.

•   *riction disc feed mechanism.

•   ,lectrical feed mechanism.

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Work holding devices

ost of the #obs can be directly held on the machine table with the help of some

general types of fi$tures such as:

•   ices.

•   T bolts.

•

  Clamps.•   'tops.

•   /ngle plates and irons.

•   Braces.

•   'top blocks.

•   blocks.

•   Planer #acks.

•   blocks.

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Planing operations

The only difference with the shaper is that a shaper can machine only small work%

whereas a planer is specially designed for large work. The common type of work 

machined in planer are: the bases ans tables of all kinds of machine tools% large

structures%frames of different engines and identical pieces of work which may be small

in si"e but large in number.The common operations are:

•   Planing flat hori"ontal surface.

•   Planing vertical surfaces.

•   Planing at an angle and machining dovetails.

•   Planing curved surfaces.

•   Planing slots and grooves.

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Cutting speed, feed and depth of cut

•   Cutting speed- the cutting speed of a planer is the rate at which the metal is

removed during the forward cutting stroke. Commonly used planers usually employ

a cutting speed of 0-12 metres per minute and a return speed of about 34metres per

minute.

•   *eed- the feed in planing machine is the distance the tool head travels at the

 beginning of each cutting stroke e$pressed in mm per double stroke.

•   )epth of cut- it is the thickness of metal removed in one cut and is measured by the

 perpendicular distance between the machined and nonmachined surface e$pressed

in mm.

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Precautions

•

  5e should protect machine table from burrs and irregularities of the workpieces.•   Use of crane in fi$ing the workpiece should be done carefully.

•   *or the surfacing work the tool head is set vertically.

•   'afety clutch must be provided for feed and

 power rapid traverse.

•   Use of vertical power rapid traverse for feeding the table should never be allowed.