Manufacturing Test 2

Name the three most common machining processes

1. turning - it is a machining operation which reduces the diameter of the workpiece to produce cylindrical parts of required dimensions. 2. drilling - carried out in drilling machine to create a hole in the given workpiece. 3. Milling - used to machine flat surfaces with the help of a milling cutter

What is a blind hole?

A blind hole is a hole which does not pass throughout the work piece (that is, the hole does not reach the other face of the work piece) after operations such as reaming, drilling, and milling.

What is the distinguishing feature of a radial drill press?

A radial drill press has a radial arm in which the drilling head can be moved and clamped.

What are the abrasive processes technologically and commercially important?

Ability of closed tolerances and excellent surface finish. It can be used on hard and soft materials. The dimensions of the product can be given very close tolerance.

What are the five basic parameters of a grinding wheel?

Abrasive material - material which is used to remove a large amount of material from the work part. Grain size - depends upon the material removal rate and better surface finish. Bonding material - used to bind abrasive grains and create integrity in the structure and shape of grinding wheel. Wheel structure - combination of abrasive grains, bond material, and pores in the grinding wheel. The wheel structure not only depends upon the hardness and toughness, but also the spacing of grain and density. Wheel grade - refers to the hardness of the bonded material. Measured on scale to find the grade ranges between hard and soft.

What are some of the new problems introduced by machining dry

Abscense of chip removal benefits in grinding and milling operation. Overheating of tool may cause damage to parts. Quality might be affected. Large capital is required to set up a dry machining operation.

What is the chemical formula of the ceramic material used in almost all ceramic cutting tools

Al2O3

What are the principal abrasive materials used in grinding wheels?

Aluminum oxide (Al2O3); silicon carbide (SiC); Cubic Boron Nitride (cBN); diamond

What is roughing in machining?

An operation that removes large amount of material in a single pass of cutting tool. It is done with lower cutting speed. Very high depth of cut is given. Feed Rate is very high. It is done in the initial stage.

What are the parameters that have the greatest influence in determining the ideal surface roughness Ri in the turning operation?

Average surface roughness depends on feed and nose radius. See equation in notebook.

Name the seven elements of tool geometry for a single point cutting tool

Bake rake angle, side rake angle, end relief angle, side relief angle, side cutting edge angle, nose radius, end cutting edge angle

name the various ways in which a work part can be held in a lathe?

Between centers - headstock and tailstock hold it in place. Chuck - three or four jaws fixed on its outside diameter. Collet - holds work part by using tapered outer collar. Faceplate - Holds an irregular or cylindrical work part by using clamps to grasp the parts.

Name the two main categories of cutting fluid according to function

Coolants - to minimize effects of heat. Lubricants - reduce friction, transfer heat, transmit power, prevent rust.

The unit cost in a machining operation is the sum of four cost terms. What are they?

Cost of part handling time, cost of machining time, cost of tool change time, tooling cost

What are the parameters of a machining operation that are included within the scope of cutting conditions?

Cutting conditions are the conditions which decide the production rate, surface finish, and material removal rate. Cutting conditions are cutting speed - relative speed between speed of cutting tool and surface speed of workpiece. Feed - relative peed at which the cutting tool advances the workpiece. Depth of cut - thickness of the tool which moves into the workpiece

What abrasive material would one select for grinding a cemented carbide cutting tool?

Diamond wheel because is it a fine diamond particle which does not lose its strength, and can provide smooth and fine cuts.

Why can diamond cutting tools not be used to machine steel and other ferrous metals?

During cutting operation of steel and ferrous materials with diamond cutting tools, the carbon atoms present in the diamond reacts with the ferrous in the material and changes its composition which is not desirable.

Broaching is performed using a rotating multitooth cutting tool? True or false?

False; the rotation of multiple tooth is not taking place during the broaching process.

What are the methods by which cutting fluids are applied in a machining operation

Flooding - steady stream of fluid directly at the tool work or tool chip interface point of the machining operation Mist application - refers to water based cutting fluids. In this application the fluid is ordered at the work in the form of a high speed mist supplied by a pressurized air stream. Manual operation - using paint brush, the cutting fluid is applied mamually in between the workpiece and tool

What are the three mechanisms of grinding wheel wear?

Grain Fracture - when a portion of the grain breaks off, but the rest of the grain remains bonded in the wheel. Attritious wear - dulling of individual grains, resulting in flat spots and rounded edges. Bond fracture - the individual grains are pulled out of the bonding material.

Identify 3 basic forms of sawing operation

Hacksawing - process in which the metals are cut in forward stroke by hacksaw machine. Bandsawing - process in which work pieces are cut in return stroke by means of a continuous metal band using a bandsaw blade. Circular sawing - it is a process in which wood or other materials are cut by means of rotating a saw blade continuously.

Name some abrasive operations available to achieve very good surface finishes

Honing - produces a finish hole with accuracy. Lapping - process to produce accurate surface finish with smoothness. Hand lapping - abrasive roll is kept between two surfaces. Machine lapping - abrasive is used on a softer material as pitch to produce a hard lap to cut a harder material. Super finishing - process used to produce a mirror like finished surface. Polishing and buffing - produces a smooth surface by removing burrs and scratches.

Define planning

In this operation, work piece which moves linearly is clamped on the table and tool is fixed. Heavy duty operation. Large cutting force is transferred to table. Multi-point cutting tool is used during operation.

Define prismatic parts in machining

It has a block or flat shape; this geometry involves linear or rotating tool motion to remove material from a linear motion of the work part. Some examples are milling, shaping and sawing.

Define Rotational parts in machining

It has a cylindrical or disc like shape; this geometry involved cutting tool to remove material from a rotating part; some examples are turning and boring.

Define external broaching

It is used either as push type or pull type depending upon the operations. It is used to produce gear teeth and splicer jobs. An internal spur gear tooth is used. Low cost.

Define engine lathe

Lower range of speed of headstock. Tailstock carries only one tool for turning a job. Time needed to complete the work part is more, and costly products are produced. Only one cutting tool can be handled at a time.

What is finishing in machining?

Removes very less thickness of material in order to give better surface finish. It is done with higher cutting speed. Very less depth of cut is given. Feed rate is very less. It is done at the final stage. (less as in less than roughing)

Name some of the steps that can be taken to reduce or eliminate vibrations in machining?

Machining vibrations is the problem of instability which results in waviness. Some steps to reduce the vibrations are: add stiffness to resist deformation. During the machining cutting operation, periodic cutting forces are generated; at that time, the feed and depth of cut must be reduced. Change in cutter design reduces cutting forces.

define cemented carbide used as cutting tools

Made from tungsten carbide using powder metallurgy techniques with cobalt as the binder. Used to machine cast irons and nonsteel materials.

What is meant by the designation 12in x 36 in lathe

Means there is a 12 inch swing (largest diameter a work piece can hold in a lathe) and 36 in is the distance between centers

What is the physical interpretation of the parameter C in the taylor tool life equation?

Parameter C is the cutting speed with respect to one-minute of tool life. It depends upon the cutting condition, tool material, and work material.

Define Tapping

Process in which internal threads are made by the use of tapping tools. The feel of the tool is non-linear in motion across the inside surface of the work part. Done on a drilling machine.

What is truing, in reference to grinding wheels?

Process of making a grinding wheel round and concentric. When the wheel is rotating, very little material is removed by diamond-pointed tool which is fed slowly against the wheel.

What is dressing, in reference to grinding wheels?

Process to clean the periphery of the grinding wheels, and to remove the dull abrasives grains to smoothen the surface. The aim of dressing is to balance the grinding wheels when they are out of roundness.

How is the power required in a cutting operation related to cutting force?

See notebook

Identify the four forces that act on the chip in orthogonal cutting but cannot be measured directly in an operation

See notebook

How does creep feed grinding differ from conventional grinding?

See notebook and powerpoint

Describe in words what the merchant equation tells us

Shear plane angle increases when rake angle, a, increases. Shear plane angle increases when friction angle, B, decreases.

What are the two basic categories of cutting tools in machining? Give an example of machining operations that use each tooling type

Single point and multipoint cutting tool. Single point is used in shaping, boring, and turning operations. Multi point is used in drilling and milling operations.

What does the term size effect mean in metal cutting?

Specific energy required to cut a unit volume of material varies with respect to size of the chip

What is the name of the most common process for cutting internal threads

Tapping process

Define conventional surface grinding

The action of cutting is grinding wheel. The workpiece reciprocates under the rotating grinding wheel about a horizontal axis to complete the process. Used for light stock removal rate.

Define peripheral milling

The axis of the tool is parallel to the movement or feed of the work part. The operation performed by the cutting edges in peripheral milling is on the outside edge of the revolving cutter.

define face milling

The axis of the tool is perpendicular to the movement or feed of the work part. The operation performed by the cutting edges in face milling is on the outside edge and end edge of the revolving cutter.

Which cutting speed is always lower for a given machining operation, cutting speed for minimum cost or cutting speed for maximum production rate? why?

The cutting speed is lower for minimum cost because of the following conditions: When tool change time increases, the cutting speed decreases. When cutting speed is lower, tool life increases; and thus it is not necessary to change the tool frequently. Maximum cutting speed is always greater than minimum cutting speed because the tooling cost pushes the optimum speed value down to the left.

What distinguishes material removal processes from other manufacturing processes?

The difference is that something is being removed in machining rather than something being added.

Define conventional knee-and-column machine

The table of this machine can be swiveled horizontally in x, y, and z directions. This machine is used for forming keyways, cutting gears, milling cutters, and cutting dovetail.

Why are cutting fluid filter systems becoming more common and what are their advantages?

They reduce fluid disposal cost as disposal is much less when a filter is placed. Lower maintenance of machine tool. Longer tool life. They reduce health hazards by cleaning cutting fluids.

What is a turning center?

This machining involved turning process by means of turning tool. Work piece rotated and tool is fixed. Used for cutting rotated work pieced with turning tool. Profile turning and automatic tool indexing.

Identify some of the common compounds that form the thin coatings on the surface of coated carbide inserts

TiN, TiC, Al2O3

What are the two principal aspects of cutting tool technology>

Tool material - chosen based on maximum stress handled by the tool, along with maximum cutting temperature and wear effect of machining process. Tool geometry - concerned with the optimizing of shape and size of the cutting tool, to perform given machining operation, in order to achieve good accuracy and geometry of the finished product.

What are the factors on which the selection of feed in a machining operation should be based?

Tooling - using a hard of softer material. Rouging/finishing - roughing refers to high feed and finishing refers to low feed. Feed when roughing - limitations on feed in roughing are based on cutting forces, horsepower, and set up rigidity. Material removal rate is maximized when feed is more. Finishing - the most important factor for surface finish is feed because it produces a better surface finish.

What are the two principal location on a cutting tool where tool wear occurs?

Top rake face - generally faces crater wear. Crater weal forms when the chip slides against the surface, and causes elevated temps and stresses at tool-chip contact to produce wearing action. Flank - suffers from flank wear. Principally due to abrasion, flank wear is caused by movement of the workpiece past the clearance face of the tool.

Identify three desirable properties of a cutting-tool material

Wear resistance - there are many types of wear in cutting operation such as abrasive wear, adhesive wear, and surface finish on tool. Toughness - refers to the ability of the material to regain energy without failing. It is usually a combination of ductility and strength in the material. Hot hardness - The property of the material to regain its hardness at a high temperature environment in which the tool works.

grinding creates high temps. How is temperature harmful in grinding?

When a material is removed from abrasie wheel at high temperature, residual stresses affect distortion of material shape. At high temperature surface, burns and crack occur. At high temperature, material become soft and weak; and it results in corrosion.

Why do costs tend to increase when better surface finish is required on a machined part?

When better surface finish is required on a machined part, grinding operation is used because it is a large scale material removal process. On the other hand, forming and machining processes such as honing and lapping cannot produce good dimensional accuracy. So grinding, honing, and lapping together contribute to product costs.

Why are specific energy values so much higher in grinding than in traditional machining processes such as milling?

When material is removed in the form of small chip, it causes 10 times higher to remove each unit of volume of material. Due to high negative rake angles increase, there is more deformation in removal of chips and thus more specific energy is required. Due to the use of wear flats, high friction is caused that increases the specific energy.

Identify the mechanisms by which cutting tools wear during machining.

abrasion - it refers to mechanical wearing due to the presence of hard particles in the work material, and thus removing some portions of the tool. Adhesion - occurs when two metals come into contact in high temps and pressure. Diffusion - refers to the process of transfer of atoms about a close contact region between two materials. Occurs at the tool-chip region, leading to tool surface hardness.

What is pocket milling?

an operation to move material from shallow pockets into flat parts using flat faced bottom end mills of one or more in number.

What are the principal lubricating mechanisms by which cutting fluids work?

boundary lubrication - helps in friction reduction and protection against wear. Extreme pressure lubrication - in this condition, the lubricant may vaporize due to heat. Extreme pressure additives such as chlorine, sulphur, and chlorise are used with lubricants to solve this problem.

why are the ceramic cutting tools generally designed with negative rake angles

ceramic material possesses properties of low shear and tensile strength but excellent compressive strength. This property means it is best to use a negative rake angle to load the tool in compression. Also helps in reduction of the cost per unti weight for very hard materials

What is wheel structure?

combination of abrasive grains, bond material, and pores in the grinding wheel. The wheel structure not only depends upon the hardness and toughness, but also the spacing of grain and density. the pores in the wheel structure are used to hold the grinding fluid.

Explain 4 types of chip in metal cutting?

continuous chip - formed when ductile metal is machined at high cutting speed. Gives a good surface finish but produces high heat. Discontinuous chip - formed when hard, brittle materials are machined at low cutting speed. It gives a poor finish but produces less heat. Continuous chip with built up edge (BUE) - when ductile metal is machined at low cutting speed conintuous chip is formed and some portion of work part is adhered to the rake surface of the tool. Serrated chips - formed when metals are machined at high cutting speed. Formed due to alternate low and high shear strain at the tool-chip interface.

What does the term thread chasing refer to?

cut threads on lathe with multipoint cutting tool that comprises several single point tools banked together in a single tool.

Dry machining is being considered by machine shops because of certain problems inherent in the use of cutting fluids. What are the problems associated with the use of cutting fluids?

cutting fluids become begrimed or polluted over time with lots of unwanted substances such as tramp oil, machine oil, cigs, food, small chips. These unwanted substances do not allow cutting fluids to perform their function of lubrication as well. Dry machining - does not contain cutting fluid, and it eliminates the problems of cutting fluid contaminiation, disposal, and filtration. Thus, they are considered by machine shops.

name the four categories of cutting fluid according to chemistry

cutting oils, emulsified oils, chemical fluids, semi-chemical fluids

What are some of the reasons why machining is commercially and technologically important

easy to obtain varieties of geometric shapes to the product; can provide a good surface finish for all types of materials; close tolerances can be easily achieved.

Name the three modes of tool failure in machining

fracture failure - it occurs due to sudden impact of excessive force at the cutting tool point leading to failure by brittle fracture. Temperature failure - tool fails when the cutting temperature exceeds the design cutting temp of tool. Due to overheat, material softens at cutting tool point. Gradual wear - repeated use fo a tool results in gradual wear rate and loss of tool shape. Due to gradual wear in a tool, tool cutting efficiency is decreased.

What are the basic factors that affect surface finish in machining?

geometric factors - three machining parameters which find the surface geometry of a machined part. they are: type of machining operation - type of geometry indicates the machining operation used to produce the surface. cutting tool geometry and feed - cutting tool geometry and feed are combined together to form surface geometry. Work material factors - built up edge effects, the work surface is damaged due to the curling back of chip into the work. The work surface is damaged due to the curling back of chip into the work. Vibration and machine tool factors - include vibration in the machine tool to produce waviness in the work surface.

Define turret lathe

head stock has more range of speed. Tailstock carries six sided-big nut for turning a job. Time required to complete the work part is less, and economical products are produced. The tool post can hold four tools indexed by 90 degrees and one more rear tool; in addition, it can also carry extra four tools.

Define shaping

in the operation, work piece which is stationary is clamped on table and tool moves linearly. This operation is suitable for light duty. A large cutting force is transferred to tool. A single point cutting tool is used during operation.

Describe up milling

in this process, the direction of work part and rotation of cutter are opposite to each other. When unwanted materials in the form of chips are removed from the work part by means of cutter, the size of the starting chip becomes thing; this increases the thickness during sweep of the cutter. The length of the chip is more. The direction of cutter force componet must be upward in order to hold the work piece against the fixed table.

describe down milling

in this process, the direction of work part and rotation of cutter are parallel to each other. When unwanted materials in the form of chips are removed from the work part by means of cutter, the size of the starting chip becomes thick; this decreases during the sweep out of the cutter. The length of chip is less. The direction of cutter force componet must be downward in order to hold the work piece against the fixed table.

Why is the orthogonal cutting model useful in the analysis of metal machining?

it alters the complex 3D metal machining situation into a simple 2D. It simplifies the analysis of selection of tool for different cutting operations. Very simple tool geometry.

define generating in machine part geometry

it is a process in which the work part is determined by feed trajectory of cutting tool. The material is removed by speed motion, but the shape of the work part is determined by feed motion. The feed trajectory involved variation in depth or width of the cut during operation.

Define dead center

it is fixed with the tailstock. Relative motion between work and dead center, so friction is developed. It is generally used at lower speeds.

Define internal broaching

it is mostly used as a pull type. It is used to produce holes, internal, gears, and splines. An external spur gear tooth is used. High cost.

Define profile milling

kind of end mill in which the outer periphery of a flat part is cut. The shape of the slot that is cut is determined in the work. The order of machining process in profile milling is roughening cut, semi finishing, and finishing.

Describe the turning process

machining process carried out on a lathe machine to remove excess material from the surface of the rotating work part by using single point cutting tool to produce round shaped parts.

Define cerments used as cutting tools

made from combinations of TiC, TiN and TiCN with nickel. Cerment tools are used to machine steels, strain steels, and cast irons.

What are the three basic categories of material removal processes? What is material removal?

metal removal - machining process in which metal is removed in the form of a chip to get the finished product; three basic processes are conventional machining - it uses the sharp edge cutting tools for machining process. Abrasive machining - it uses hard, abrasive particles impinged into a tool for machining process. Non-concentional machining - uses thermal, electrical or mechanical energy for machining process rather than conventional cutting tools.

Name some of the important mechanical and physical properties that affect the machinability of a work material

microstructure - the metal with identical microstructures contains similar machining properties. Heat treatment - to achieve desired properties in metals, often passed through a heating and cooling operation in their solid state. Hardness - increase in hardness also increases the abrasive wear of tool, and reduces the tool life. Strength - if the material strength increases, cutting forces, specific energy and cutting temps increase. Ductility - Low carbon steel has relatively low hardness, in so ductile to machine well. High ductility results in tearing of the metal, and results in tearing of the metal, and results in poor finish.

What kind of machining operation is gear hobbing?

milling

What is a machine tool?

powered machine that is used to make relative movements between cutting tool and work part in order to accomplish metal removal or forming process.

Define threading

process in which external threads are made by the use of a single point cutting tool. The feel of the tool is linear in motion across the outside surface of the work part. Done on a lathe machine

Define forming in machine part geometry

process in which the work part is shaped geometrically by the cutting tool. The material is removed by the speed motion, but the shape of the work part is determined by cutting edge of the tool. The feed trajectory involved depth of the cut to the final penetration into the work after the completion of feed motion.

Define turning operation

process of producing an external cylindrical shape using single point cutting tool. Tool angle is very important part of concern for successful turning operation. Therefore, tool set up at an angle is a must to produce high degree of accuracy in shape of work. This process can only be done on lathe machine.

Define boring operation

process to produce an enlarged and finished hole using single point cutting tool to an existing hole. Tool is not set at an angle as boring operation requires digging of tool inside the work piece. This process can be done on a lathe or milling machine.

What are the functions of a grinding fluid?

reduces friction by lubrication; removes heat from work zone, and increases material removal rate; reduces wear of grinding wheel; used to wash away the chips from the work piece.

What is an orthogonal cutting operation?

refer to a type of cutting in which the cutting edge is normal to the cutting speed direction.

What is the specific energy in metal machining?

refers to the amount of energy required to cut a unit of material from the workpiece. Also called unit power.

What is wheel grade?

refers to the hardness of the bonded material. Measured on scale to find the grade ranges between hard and soft. Soft materials are used where the material removal is less, and the hard materials are used where the material removal is more. Grading system from A (soft) to Z (hard)

What is machining?

refers to the process in which metal is removed form the material in order to obtain the desired dimensions of a product

Define live center

rotates in the bearing of the tailstock. No relative motion between work and live center, so not friction is developed. It is generally used at higher speeds.

Identify 2 forces that can be measured in orthogonal cutting

see notebook

What is the relationship between the coefficient of friction and friction angle?

see notebook

identify the three alternative ways of holding and presenting a cutting edge for a single point cutting tool during machining

solid tools - tool geometry shape is made by grinding the solid shank of tool. Brazed insert - cemented carbide materials are brazed to the shank of the tool. Mechanically clamped insert - inserts of carbide and cemented carbides are clamped mechanically to the tool shank.

What is tool chip thermocouple?

technique used to find the temp generated at tool-chip interface.

Define abrasive belt grinding

the action of cutting is of abrasive particles which are bonded to a flexible belt. Workpiece is pressed against the belt by the support of platen to complete the process. Used for heavy stock removal rate.

Define machinability

the capability of a workpiece material to be removed with ease by using machine tools.

What can a mill-turn center do that a conventional turning center cannot?

the mill turn center is a CNC milling machine in which the cylindrical job is fixed to a specified angle to machine the outside surface of the job by milling cutter. On the other hand, a conventional turning center is a cnc lathe machine which is capable of cutting rotated work pieces by means of turning tool; they do not have the capacity to stop th work part at an angular position.

What is the physical interpretation of the parameter n in the taylor tool life equation/

the relative constant for a given tool material and it is the slope of plot between cutting speed and tool life.

Define universal milling machine

the table of this machine can be swiveled horizontally about vertical axis at my angle. This machine is used for cutting angular shapes and helixes on work parts.

What is centerless grinding?

the workpiece is kept between the grinding wheel and moving wheel on a work rest. Both wheel rotate in the same direction. The grinding wheel is a stationary wheel which roates at high speed on a fixed axis, so the direction of force to be applied on workpiece should be down against the work rest.

What is machining center?

this machining involved milling process by means of willing cutter. Work piece is stationary and tool moves. It is used to machine the surface of the work parts with milling cutter tool. The axes of machining center are x,y, and z directions on a CNC milling machine. Operations performed on this machine are surface porfiling, profile milling and pocket milling.

What are the criteria by which machinability is commonly assessed in a production machining operation?

tool life - period of time that a cutting tool can function properly before failing. Forces and power - limit of tools to perform specific machining operation over a given work piece to avoid any crack and fractures. Surface finish - surface texture that consists of three components: lay, surface roughness and waviness. Easy of chip disposal - it is a process which includes disposal of chip and garbage obtained in the machining operation.

What are some of the tool life criteria used in production machining operations?

total cutting time, failure of cutting tool, visual observation of wears like crater and flank, sound problem in tool, work piece count, increased power consumption, degradation of surface finish.

Name some important bonding materials used in grinding wheels?

vitrified bond, silicate bond, rubber bond, shellac bond, and resinoid bond