UNIT-I PLANING MACHINES

Planning machine

Planing machine

Another view of Planer

Table Movement in Planer

Table Movement in Planer- another view

What is a planer ? A Machine which produces flat surfaces Consists a stationary housing for holding the tools A table holding the work reciprocates Large works, that con not be accommodate on shapers The tool is stationary but the work moves

Planer - working principle The table on which work is clamped is imparted a reciprocating movement Cutting takes place during the forward stroke of table During return stroke the cutting tool is slightly lifted Tool is fed for each forward stroke TOOL WORK Work is fixed on Table

WORKING PRINCIPLE – contd. Table is driven by an electric motor Length of table stroke can be adjusted Speed of return stroke is also regulated

Principle of operation of a planer

Classification of planers 1. Double housing Planer 2. Open side Planer 3. Pit type Planer 4. Edge Planer or Plate Planer 5. Divided Table Planer

Double housing planer: It is the Standard model & most widely used Very heavy and robust Has a bed and two vertical housings are fixed Table moves along the guide ways of the bed Housing supports cross rail & tool heads. Cross rail carries two tool heads Tool head carries tools

A double housing planer

Open side planer It has only one supporting column (housing) Area larger than the table can be planed Cross rail is mounted as a Cantilever Tool holders are mounted on Cross rail Stroke length of bed is controlled by adjustable dogs

Open side planer

PIT Planer Columns and cross rail carrying tool head move longitudinally on massive rail above the work table Bed is recessed in the floor Loading and unloading of jobs is easy Used for Planing heavy & large jobs Table and work piece resting on it are stationary and the tool reciprocates

Edge / plate planer Specially designed for squaring or beveling the edges of heavy steel plates for pressure vessels Carriage supporting the tool is moved back and front direction Cutting can take place during both directions of carriage travel Operator stands on the platform & operates

Divided table planer Also known as Tandem planer Planer has two tables on the bed Table may be reciprocated together or separately Each table reciprocates under different tool head For continuous production, small work pieces clamped on one table are being machined, another is stationary and can be used for setting up fresh works Used for quick & continuous production

Planing machine - parts COLUMN CROSS RAIL TOOL HEADS Feed Mechanism TABLE BED

Main Parts of Planing machine 1. Bed 2. Table 3. Housing or Column 4. Cross rail 5. Tool heads 6. Driving Mechanism 7. Feed Mechanism

Constructional details of a planer CROSS MEMBER COLUMN COLUMN CROSS RAIL TOOL HEADS Feed Mechanism TABLE BED

Parts of planer

Parts of planer

1. Bed Large box like casting Length is nearly twice the table length Consists guide ways on which table moves Houses the driving mechanism of table Made of Cast Iron

2.Table Also called Platen Large rectangular casting mounted on bed ways Holds the work & reciprocates along bed ways Top surface has T slots Work is clamped on T slots

3.Housing or Column Large vertical structures on each side of the bed Supports cross rail on which tool heads are mounted Also supports the mechanism for operating the tool heads Made of Cast Iron

4. Cross rail A rigid casting mounted horizontally on the column Can be moved up & down by elevating screw Carries two slides with tool heads Tool heads can be moved horizontally on the guide ways of cross rail

5. Tool heads Contains tool posts for holding the tools Tool post (clapper block) is hinged to the head During return stroke cutting tool will be lifted Tool heads can be swiveled through 60º on either side of its vertical position

Specifications of a Planer 1. Distance between the two housings 2. Height between Table & cross rail at its uppermost position 3. Maximum length of table travel 4. Number of Speeds & feeds available

Specifications of a Planer- contd. 5. Power input 6. Floor space required 7. Type of Drive 8. Net weight of the Machine

Mechanism Introduction A Planing Machine produces flat surfaces The Table holding the Work reciprocates There should be some mechanism to move the Table in reciprocating motion, and Table to move quick during idle stroke

Mechanisms to drive the Table (QRM) 1. Open & Cross belt drive 2. Reversible motor drive 3. Hydraulic drive

1.Open & Cross belt drive Mechanism Loose Pulley Fast Pulley Pulleys on Shaft Counter Shaft Open belt Cross belt 19 - Table Belt shifter 18. Trip dog 17. Belt shifter lever 9,12 Loose Pulleys Rack 13 - Bull gear shaft 10,11 Fast Pulleys 14 - Bull gear Change gears Feed disc

Open & Cross belt drive Mechanism Used for smaller capacity machines Table is moved by gears & rack attached under the table Counter shaft at the top of housing has 2 pulleys These Pulleys transfer power to main shaft(Driving) Main shaft drives the table by rack & pinion

Open & Cross belt drive Mechanism 2 Sets of fast & loose pulleys are mounted on driving shaft at one end and pinion is on another end RETURN STROKE: Smaller fast pulley is used for backward motion of table (Quick motion) It is connected by open belt drive The open belt passes over small fast pulley to get Quick return The Cross belt is on loose pulley so it will not drive

Open & Cross belt drive Mechanism FORWARD STROKE: Bigger fast pulley is driven by cross belt drive It is used to drive the table during cutting stroke Open belt is on loose pulley At the end of cutting stroke, cross belt is shifted from fast pulley to loose pulley Simultaneously open belt is shifted from loose pulley to fast pulley This is achieved by trip dog which operates belt shifting lever Thus the direction of movement is automatically reversed

Rack & Pinion used to move Table

2. Reversible Motor Drive Mechanism Electric motor drives the bull gear through gear trains Motor is coupled to D.C. generator When motor is started, generator supplies power to reversible motor

Reversible Motor Drive Mechanism Reversible motor causes the planer table to move At the end of stroke, trip dog operates the switch which reverses the direction of table Speed of cutting stroke is reduced by regulating the field current of the generator

Reversible Motor Drive Diagram A.C.driving motor Reversible motor Generator Motor field resistance Exciter Motor field Reversing switch Generator field

3.Hydraulic Drive of Planer TABLE Operating Cylinder Speed Control

Forward Stroke of Table During cutting stroke, oil is pumped into LHS of cylinder As the area is less due to presence of piston rod, less force acts So the table moves slowly in cutting stroke At the end of each stroke trip dog operates a lever Lever actuates the control valve of circuit TABLE

Return Stroke of Table Oil is pumped into the Operating cylinder Cylinder contains piston & piston rod The other end of piston rod is connected to the Table During return stroke, oil is pumped into RHS of cylinder More force acts on the piston & it moves quickly TABLE

Cycle Repeated Flow of oil is changed from one side to the other side of cylinder The length of stroke can be varied by adjusting the distance between trip dogs

Planer Operations 1.Planing Horizontal Surfaces 2. Planing Vertical Surfaces 3. Planing Angular Surfaces / Dovetails 4. Planing Curved surfaces 5. Planing Slots, key ways & Grooves

Planing Horizontal Surfaces Fix the work properly on the table Set the required cutting speed Give required feed of the tool Give suitable depth of cut for rough cuts Finishing the job by giving less depth of cut

Planing Horizontal Surfaces CLAPPER BLOCK TOOL WORK PLANER TABLE

Planing Vertical Surfaces Fix the job on the table firmly Align the surface to be machined properly Vertical side is adjusted perpendicular to the table Swivel the apron away from the job Switch on the machine Rotate down feed screw by hand to give down feed

Planing Vertical Surfaces PLANER TABLE WORK

Planing Angular Surfaces Main angular planing is to make dove tails & V grooves Set the work on the table Swivel the tool head to the required angle Set apron away from work Give down feed as per requirement

Planing Angular Surfaces

Planing Formed Surfaces Fix up a square nose tool in tool head Required form is obtained by feeding the tool simultaneously in both hor. & ver. Directions Give suitable depth of cut This can also be done with the aid of a special fixture

Planing Formed Surfaces TOOL WORK PLANER TABLE

Planing Slots & Grooves Fix up the job on the table suitably Fix Slotter tools in tool heads Give feed using down feed screw Move the tool by the required amount to get uniform slots / grooves

Cutting Rack or Splines PLANER TABLE WORK

Comparison between planer and shaper Heavier, more rigid costlier machine. Requires more floor area. Work reciprocates horizontally. Tool is stationary during cutting. Heavier cuts and coarse feeds can be employed. Work setting requires much of skill and take longer time. Several tools can be mounted and employed simultaneously, usually four as a maximum facilitating a faster rate of production. Used for machining large size work pieces. A comparatively lighter and cheaper machine. Requires less floor area. Tool reciprocates horizontally Work is stationary during cutting. Very heavy cuts and coarse feeds cannot be employed. Clamping of work is simple and easy. Usually one tool is used on a shaper. Used for machining small size work piece comparatively