Production Process Unit Test 2

Q1. Elements of Lathe

PARTS OF THE LATHE MACHINE

The lathe machine is consist of the following six basic elements

1. Bed 2.Head Stock 3.Tailstock

4. Carriage 5.Lead Screw 6.FeedDrive

1. BED

The bed is the base of the lathe. The top of the bed has two guide ways to provide the support and the sliding surfaces for the carriage and the tailstock. The bed is made up of cast iron. The function of bed is to support all other elements of the lathe.

2. Head stock

The head stock is permanently fastened to the left hand end of the lathe bed. The function of head stock is to support the spindle and to house the main drive. Spindle is the hollow rotating shaft used for holding the work piece Main drive is used to drive the spindle and to change the spindle speed .the main drive is powered by an electric motor.

3. Tailstock

The tailstock is located at the right hand end of the lathe bed..It can be moved along the guide ways on the lathe bed and can be clamped in any position on the lathe bed..It is used to hold the dead centre which can support the long work piece during machining and to hold the tool like drills .

4. Carriage

The carriage is located between the head stock and the tailstock of the lathe bed . It slides along the guide ways on the lathe bed..The function of carriage is to hold the cutting tool and to give the longitudinal or cross feed to the cutting tool.

5. Lead screw

Lead screw is the long threaded shaft driven by the feed drive..It is used for giving the mechanized motion of the carriage for cutting threads on the work piece.

6. Feed drive

Feed drive is the unit used for transmitting the power and the motion from the main drive to the lead screw with require reduction ratio.

Explanation of the standard components of most lathes:

• Bed: Usually made of cast iron. Provides a heavy rigid frame on which all the main components are mounted.
• Ways: Inner and outer guide rails that are precision machined parallel to assure accuracy of movement.
• Headstock: mounted in a fixed position on the inner ways, usually at the left end. Using a chuck, it rotates the work.
• Gearbox: inside the headstock, providing multiple speeds with a geometric ratio by moving levers.
• Spindle: Hole through the headstock to which bar stock can be fed, which allows shafts that are up to 2 times the length between lathe centers to be worked on one end at a time.
• Chuck: 3-jaw (self centering) or 4-jaw (independent) to clamp part being machined.
• Chuck: allows the mounting of difficult workpieces that are not round, square or triangular.
• Tailstock: Fits on the inner ways of the bed and can slide towards any position the headstock to fit the length of the work piece. An optional taper turning attachment would be mounted to it.
• Tailstock Quill: Has a Morse taper to hold a lathe center, drill bit or other tool.
• Carriage: Moves on the outer ways. Used for mounting and moving most the cutting tools.
• Cross Slide: Mounted on the traverse slide of the carriage, and uses a handwheel to feed tools into the workpiece.
• Tool Post: To mount tool holders in which the cutting bits are clamped.
• Compound Rest: Mounted to the cross slide, it pivots around the tool post.
• Apron: Attached to the front of the carriage, it has the mechanism and controls for moving the carriage and cross slide.
• Feed Rod: Has a keyway, with two reversing pinion gears, either of which can be meshed with the mating bevel gear to forward or reverse the carriage using a clutch.
• Lead Screw: For cutting threads.
• Split Nut: When closed around the lead screw, the carriage is driven along by direct drive without using a clutch.
• Quick Change Gearbox: Controls the movement of the carriage using levers.
• Steady Rest: Clamped to the lathe ways, it uses adjustable fingers to contact the workpiece and align it. Can be used in place of tailstock or in the middle to support long or unstable parts being machined.
• Follow Rest: Bolted to the lathe carriage, it uses adjustable fingers to bear against the workpiece opposite the cutting tool to prevent deflection.

Q2 Types of Milling Machine

Q3. List various parts of planer machine & write various operations performed on it.

Parts of Planer

A standard double housing planer has the following main parts.

(i) Bed
(ii) Work table
(iii) Column or housing
(iv) Cross rail
(v) Saddle
(vi) Tool head
(vii) Driving and feed mechanism.

Bed :-

The bed of a planer must be a element or casting twice as

long as the table. The bed acts as the foundation of the machine.

The other parts are attached to, or supported by the bed. The bed

has accurately finished ways on which the worktable slides. The

gearing or hydraulic cylinder for driving the table is housed under

the bed.

(ii) Worktable :-

The table is a heavy rectangular casting, which carries the work by a very long hydraulic cylinder or by a pinion gear driving a rack which is fastened under the center of the table.

The motor driving the pinion gear is of reversible type with variable speed. The upper surface of the table has T slots in it to facilitate the clamping of the work or vises and special fixtures with Tools. The top surface of the table also has accurate holes for supporting the stop pins etc.

The side of the table has a groove for clamping planer reversing dogs at different positions. In some planers, hydraulic bumpers are fitted at the end of the bed to avoid the table from overrunning.

(iii) Column or housing :-

The frame of the planer is the same hollowbox type used on large milling machines. The frame is basically two heavy columns fastened together at the top with a large bracing section and fastened at the bottom to the machine bed.

This creates a very strong, rigid structure which will handle heavy loads without deflection. On a double housing planer, two housings or columns rise vertically at the sides of the machine. They support the cross rail and house the elevating screws and controls for the machine.

(iv) Cross rail :-

The cross rail is a heavy box or similar construction. It is mounted in a horizontal position on the vertical ways of the housing. It slides up and down on veer or flat ways, controlled by hand or by power operated screws. These cross rails are so heavy that they are counterweighted, with either cast-iron weights or hydraulic cylinders, in order that they may be moved easily and positioned accurately.

After being positioned, they are clamped in place. The purpose of the cross rail is to carry the vertical tool heads which by means of feed screws may be moved from left to right. It is very essential that the cross rail, when clamped, be parallel to the table for obtaining accurate machined surfaces.

(v) Saddle :-

The saddle is fitted to the ways of the cross rail. On its front surface are ways to which the tool head is fitted, together with a vertical feed screw that provides for a vertical movement of the tool head. There are two saddles one for the left tool head, the other for the right tool head. Each one may be operated independently of the other.

(vi) Tool head :-

The tool head of a planer is similar to that of a shaper both in construction and in operation. The tool head is attached to the saddle which contains the tool post which. in turn, holds the cutting tool. The tool post is hinged to the head so that on the return movement of the table the cutting tool will be raised and ride on the top of the work.

This saves the cutting edge of the tool from being damaged and permits the automatic traverse feed to operate without interference. A feed screw is provided to move the tool head with respect to work. The tool head can be swiveled for taking angular cuts. There are four tool heads, two in vertical position on the cross rail, and the other two known as side tool heads mounted one each on the two columns below the cross rail.

Linear planing[edit]

The most common applications of planers and shapers are linear-toolpath ones, such as:

Generating accurate flat surfaces. (While not as precise as grinding, a planer can remove a tremendous amount of material in one pass with high accuracy.)^[2]

Cutting slots (such as keyways).

It is even possible to obviate wire EDM work in some cases. Starting from a drilled or cored hole, a planer with a boring-bar type tool can cut internal features that don't lend themselves to milling or boring (such as irregularly shaped holes with tight corners).

Helical planing[edit]

Although the archetypal toolpath of a planer is linear, helical toolpaths can be accomplished via features that correlate the tool's linear advancement to simultaneous workpiece rotation (for example, an indexing head with linkage to the main motion of the planer). To use today's terminology, one can give the machine other axes in addition to the main axis. The helical planing idea shares close analogy with both helicalmilling and single-point screw cutting. Although this capability existed from almost the very beginning of planers (circa 1820),^[3] the machining of helical features (other than screw threads themselves) remained a hand-filing affair in most machine shops until the 1860s, and such hand-filing did not become rare until another several decades had passed.

Prevalence of current use[edit]

Planers and shapers are now obsolescent, because other machine tools (such as milling machines, broaching machines, and grinding machines) have mostly eclipsed them as the tools of choice for doing such work. However, they have not yet disappeared from the metalworking world. Planers are used by smaller tool and die shops within larger production facilities to maintain and repair large stamping dies and plastic injection molds. Additional uses include any other task where an abnormally large (usually in the range of 4'×8' or more) block of metal must be squared when a (quite massive) horizontal grinder or floor mill is unavailable, too expensive, or otherwise impractical in a given situation. As usual in the selection of machine tools, an old machine that is in hand, still works, and is long since paid-for has substantial cost advantage over a newer machine that would need to be purchased. This principle easily explains why "old-fashioned" techniques often have a long period of gradual obsolescence in industrial contexts, rather than a sharp drop-off of prevalence such as is seen in mass-consumer technology fashions.

Q4. Gear Hobbing

Unknown

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Production Process 2, Unit test 2

Sunday, 5 April 2015

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