L4

Fundamental approach (8 steps)

1. Design a special machinig operation to study chip formation process. Set variables such as cut thickness, material shear stress, chip length ratio. 2. Develop mathematical models of cutting process 3. Study tool life phenomena 4. Establish analyses for predicting tool life 5. Study surface finish phenomena 6. Establish analyses for predicting surface finish 7. Develop cost and time per component for each operation 8. Develop optimization analysis for selecting cutting conditions.

Basic turning operations (5 of them)

1. Facing 2. Contour turning 3. Chamfering 4. Cut off 5. Threading

Advantages of fundamental approach

1. Gives a better understanding of cutting phenomenon 2. Basic data and notions can be used in analyses of the various machining operations.

Disadvantages of empirical approach

1. Many calculations 2. Data only useful for the particular machninig operation 3. Results do not attempt to answer the question 'why' - only the 'what' is given.

Two kinds of cutting fluids mainly used

1. Mineral or vegetable-oil based (in low speed lubricating regime) 2.Water based (an emulsion with high heat counducting capacity)

Advantages of empirical approach

1. Quick and practical means of obtaining relevant performance data 2. Empirical equations are relatively simple 3. A number of variable are allowed

Milling operations:

1. Slab milling 2. Slotting 3. Face milling 4. Profile milling 5. Pocket milling

Disadvantages of fundamental approach

1. Slow because of the detailed work required. 2. Quantitative basic data has to be obtained in the required form 3, It is hard to predict adequate theories and analyses for many practical machining operations.

Performance Measures and Criteria

1. Tool life, time to tool failure 2. Surface finish and roughness 3. Component production rate 4. Shape and size variation 5. Forces and power

Two main functions of cutting fluids

1.Coolant at relatively high cutting speed 2.Lubricant at relatively low cutting speed

Cutting parameters

1.Cutting speed 2.Feed 3.Depth of cut

Effect of high cutting temperatures on machined job are

1.Dimensional inaccuracy of the job due to thermal distortion 2.Surface damage by oxidation, buring, and rapid corrosion. 3.Induction of tensile residual stresses and micro at the surafce/subsurface.

Cutting temperatures are important because high temperatures

1.Reduce tool life 2.Extremely high temperatures are dangerous for machine operator 3.Can cause inaccuracies in work part dimensions due to thermal expansion of work piece material.

Abrasive processes?

Abrasive processes - material removal by hard, abrasive particles, e.g., grinding. Grinding chips usually range in thickness from 0.0025mm to 0.25mm

Material removal has three basic elements required:

Cutting tool, work piece, machine tool which supports the tool and the work piece which provides relative motion

Hot macining is benefical for what kind of materials?

For the materials which are very hard and hardenable like high manganese steel.

Machining?

Machining - material removal by a sharp cutting tool, e.g., turning, milling, drilling. Removal of macroscopic chips in the form of ribbons or particles having a thickness of from about 0.025mm to 2.5 mm

Removal processes divided into main three groups

Machining, abrasive processes and non-traditional processes

Nontraditional processes?

Nontraditional processes -various energy forms other than sharp cutting tool to remove material

Cutting temperature has a controlling influence on the rate of [] and [].

tool wear, friction between chip and tool

Objectives of machining processes:

Physically feasible, technologically as effcient and economical, the process must be capable of competing with other manufacturing processes.

Counterboring?

Provides a stepped hole, in which a larger diameter follows smaller diameter partially into the hole

Tapping?

Used to provide internal screw threads on an existing hole, Tool called a tap

Reaming?

Used to slightly enlarge a hole, provide better tolerance on diameter, and improve surface finish

Types of drilling

reaming, tapping, counterboring