PRODUCT DESIGN

Feed gearbox Lathe

The feed gearbox or quick-change gearbox is fitted directly below the head stock assembly. Power from the lathe spindle is transmitted through gears to the quick-change gearbox. This gear box contains a number of different sizes of gear which provides a means to change the rate of the feed, and the ratio between the revolutions of the head stock spindle and the movement of the carriage for thread cutting by altering the speed of motion of feed rod or lead screw.

The arrangement which are employed in feed gear boxes to obtain multiple speeds and different rates of feed are:

1.Sliding gear mechanism

2.Sliding clutch mechanism

3.Gear cone and tumbler gear mechanism

4.Sliding key mechanism

5.Combination of any two or more of the above

Feed rod

The feed rod is a long shaft that has the key way extending from the feed box across and in front of the bed. The power is transmitted from the lathe spindle to the apron gears through a feed rod via large number of gears. The feed rod is used to move the carriage or cross-slide for turning, boring, facing and all other operations except thread cutting.

Lead screw

The lead screw is a long threaded shaft used as a master screw, and is brought into operation only when threads have to be cut. In all other times the lead screw is disengaged from the gear box and remains stationary, but this ma be used to provide motion for turning, boring, etc. in lathes that are not equipped with a feed rod.

Apron Mechanism

The apron mechanism is used for transforming rotary motion of the feed rod and the lead screw into feed motion of the carriage. The mechanism also ensures that when the half nut is engaged with the lead screw the worm drops down disconnecting the feed motion. This arrangement is called foolproof arrangement and saves the machine from any damage.

fr. NTTF ( NETTUR TECHNICAL TRAINING FOUNDATION)

RIVETS

A rivet is a fastener that has a head and a shank and is made of a deformable material.

It is used to join several parts by placing the shank into holes through the several parts and creating another head by upsetting or deforming the projecting shank.

During World War II, Rosie the Riveter was a popular cartoon character in the United States. No better image can illustrate the advantages of riveted joints.These are

1. Low cost

2. Fast automatic or repetitive assembly

3. Permanent joints

4. Usable for joints of unlike materials such as metals and plastics

5. Wide range of rivet shapes and materials

6. Large selection of riveting methods, tools, and machines

Riveted joints, however, are not as strong under tension loading as are bolted joints (see Chap. 22), and the joints may loosen under the action of vibratory tensile or shear forces acting on the members of the joint. Unlike with welded joints, special sealing methods must be used when riveted joints are to resist the leakage of gas or fluids.

Joseph E. Shigley

Professor Emeritus

The University of Michigan

Ann Arbor,Michigan

Source: STANDARD HANDBOOK OF MACHINE DESIGN

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Tunnel gate and Runner

Tunnel gate is usually conical beheaded, overhanging one side sloping cavity or product. Gate hole diameter d must Consider the weight of the product, the condition of cross-section with long-bends and runners. As a measure taken beginning 0.8 mm to around 10 grams of product weight. After the trial if showed signs are too small gate, gate be enlarged as needed.

Runner is a conduit between the nozzle on the end of the barrel with a cavity in the mold. Melting plastic in the room at the end of the barrel which is the injection, flow through the hole nozzle, sprue holes, conduit or runner, gate and finally enter into the cavity, because it will be a product. Moderate plastic that fills the channels along the runner and sprue, is a waste that must be removed from the mold along with the current product expenditures.

Because it is a waste, then the mold with a cavity much, cavity layout and conditions runner distribution must be considered, in order to get the runner channels as short as possible. With a short runner channel, cross-sectional runner can be made smaller, so the weight of materials that become waste (know by heart) would be small, given the weight - the channel cross section x length x channel density.

Condition of cross section and channel length of the sprue runner each cavity are cultivated together, so that received an injection pressure of each cavity so that the filling of each same acvity balanced.

Traditional Engineering Design

Traditional engineering design is a linear approach divided into a number of steps. For example. a six-step process might be divided into problem identification, preliminary ideas. refinement. analysis. documentation.

and implementation. (Sec Figure 1.12.) The design process moves through each step in a sequential manner; however. if problems arc encountered. the process may return to a previous step. This repetitive action is called iteration or looping. Many industries use the traditional

engineering design process: however. a new process is developing that combines some features of the traditional process with a team approach that involves all segment.~ of a business.

The Engineering Design Process

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