Face mill (older) (CNC Programing)
Face milling is a machining operation that controls the height of the machined part. For most applications, face milling is a relatively simple operation, at least in the sense that it usually does not include any difficult contouring motions. The cutting tool used for face milling is typically a multi tooth cutter, colled a face mill, although end mills may also be used for certain face milling operations, usually within small areas. The top sufaces machined with a face mill are generally perpendicular to the axis of the facing cutter. In CNC programming, the face milling operations are fairly simple, although two important considerations are critical:
a) selection of the cutter diameter
b)inital starting position of the tool in relation to the part
(Peter Smid, CNC Programming handbook, second edition, page227)
Face Mill (Newer) (Better)
On small machines it's best to use a small-diameter cutter and take multiple passes. A large-diameter cutter requires too much horsepower and leads to undesirable small feed rates and depth of cuts. If the cutter has double positive rake angles, cutting forces are reduced significantly and productivity goes up . Coarsepitch cutters have bigger chip pockets and fewer teeth in the cut. A differential-pitch cutter has unequally spaced teeth, which cuts down on vibration and chatter. Climb milling is always recommended, because the chip is thick as the cutter enters the workpiece and thin on exit. The thin exit chip gives extended tool life.
Optimum width of cut is two thirds of the diameter of the cutter. Centrally positioned cutters result in an alternating cutting force, which can cause vibration. To optain a better surface finish, exchange one of the regular inserts with a wiper insert. A wiper insert protrudes below the other inserts by approximately .002 in. The width of this inser should be approximately one third greater than the distance the cutter travels per revolution. This wider insert then removes the tool marks left by the other inserts.
Difficult-to-machine materials such as high-alloy steels, austenic stainless steels, titanium alloys and heat resistant super-alloys often machine easiest when round inserts are used. The round inserts give max edge strength and limits the chip thickness. Start with a low cutting speed and increase it if possible. The more difficult a material is to machine, the lower the cutting speed should be. Use flood coolant. For titanium, mist coolanty is preffered. Round inserts aren't only effective cutting tools for exotic materials but can be used on all materials. Round inserts with a positive rake have an effective shearing cutting action. The large radius also provides an outstanding surface finish. For machining hardened steel, using a CBN polycrystalline insert in a face mill gives excellent results. A high-quality surface finish and a workpiece cool to the touch can be expected. (R. Kibbe, W. White et. all. Machine Tool Practices 9th edition pg.538)
Difficult-to-machine materials such as high-alloy steels, austenic stainless steels, titanium alloys and heat resistant super-alloys often machine easiest when round inserts are used. The round inserts give max edge strength and limits the chip thickness. Start with a low cutting speed and increase it if possible. The more difficult a material is to machine, the lower the cutting speed should be. Use flood coolant. For titanium, mist coolanty is preffered. Round inserts aren't only effective cutting tools for exotic materials but can be used on all materials. Round inserts with a positive rake have an effective shearing cutting action. The large radius also provides an outstanding surface finish. For machining hardened steel, using a CBN polycrystalline insert in a face mill gives excellent results. A high-quality surface finish and a workpiece cool to the touch can be expected. (R. Kibbe, W. White et. all. Machine Tool Practices 9th edition pg.538)
------------------------------------------------------------
End mill (older ) (CNC Tools)
End mills are the most common tools used for peripheral milling. There is a wide selection of end mills available for just about any conceivable machining application. Traditional end mills come in metric and english sizes, variety of diameters, styles number of cutting flutes, numerous flute designs, special corner designs, shanks, and tool material compositions.
Some of the most common machining operations that can be performed with an end mill – HSS, cobalt, solid carbide or an indexable insert type:
Peripheral end milling and contouring
Milling of slots and keyways
Channel groves, face grooves and recesses
Open and closed pockets
Facing operations for small areas and thin walls
Counterboring
Spotfacing
Chamfering
Deburring
(Peter Smid, CNC Programming handbook, second edition, page275)
End Mill (Newer) (Better)
The most frequently used cutting tool for the vertical milling machine is the end mill. End mills are so named because their primary cutting is done on their end both in plunge and traverse milling. End mills may have 2, 3, 4 or more flutes and may be right-or left-hand cutting. to determine the cutting direction of an end mill, observe the cutter from its cutting end. A right hand cutter will cut while turning in a ccw direction. A left-hand cutter will cut turning in a cw direction. the direction of flute twist or helix may also be right-or- left hand. For example, a right-hand helix twist to the right.
Two- flute end mills can be used for plunge cutting. these are called center cutting because they can make their own starting hole. Four flute end mills may also be center cutting. However, if these are center drilled or gashed on the end, they can't start their own holes. This type of end mill will cut only on its periphery but may be used in end milling provided the cut is begun off the workpiece or in a premachined hole or other cavity.
A three-flute end mill is a compromise between the bigger chip capacity of a two-flute and the better finishing ability of the four-flute end mill. A three-flute end mill is an excellent choice for slotting. Often, one cut with a three-flute end mill will give an acceptable surface finish. Much of the time, two of the three teeth are i the cut, giving a smooth, chatterless cutting action. A four-flute end mill is stronger than two-or three-flute end mills; this permits the use of max feed rates. A straight fluted end mill design will produce straight side cuts in slotting end eliminate a leaning keyway condition. Multiple-flute end mills produce fine finishes following a roughing cut. Acorner radius or chamfer on an end mill increases cutter life by preventing corner chipping. These end mills should be used whenever a fillet radius in a pocket is acceptable. These cutters are also called "bull-nose" end mills. (R. Kibbe, W. White et. all. Machine Tool Practices 9th edition pg.517)
------------------------------------------------------------------------
Two- flute end mills can be used for plunge cutting. these are called center cutting because they can make their own starting hole. Four flute end mills may also be center cutting. However, if these are center drilled or gashed on the end, they can't start their own holes. This type of end mill will cut only on its periphery but may be used in end milling provided the cut is begun off the workpiece or in a premachined hole or other cavity.
A three-flute end mill is a compromise between the bigger chip capacity of a two-flute and the better finishing ability of the four-flute end mill. A three-flute end mill is an excellent choice for slotting. Often, one cut with a three-flute end mill will give an acceptable surface finish. Much of the time, two of the three teeth are i the cut, giving a smooth, chatterless cutting action. A four-flute end mill is stronger than two-or three-flute end mills; this permits the use of max feed rates. A straight fluted end mill design will produce straight side cuts in slotting end eliminate a leaning keyway condition. Multiple-flute end mills produce fine finishes following a roughing cut. Acorner radius or chamfer on an end mill increases cutter life by preventing corner chipping. These end mills should be used whenever a fillet radius in a pocket is acceptable. These cutters are also called "bull-nose" end mills. (R. Kibbe, W. White et. all. Machine Tool Practices 9th edition pg.517)
------------------------------------------------------------------------
Slab Mill (Older) (CNC Still) (Better)
The plain horizontal milling machine used primarilly for machining flat surfaces is known as a slab mill. Because the basic idea is to accurately create parallel top anf bottom surfaces, it is usually not necessary to square the workpiece or workholding device to table travel.
For slabbing operations, the cutter should be wider the part being machined; this permits the operation to be completed with one pass. The cutting speed must be correct for the material being machined, and cutting fluid should be riberally applied at the point of cut. Rigidity of the setup is important. Since the cutter will be mounted on an arbor, the idea is to keep the cutter as close to the column as possible to ensure maximum rigitidy while allowing for tool clearance and for the cutter width to slightly exceed the workpiece widht.(Arthur R. Meyers,Thomas J. Slattery,Basic Machining Reference Handbook, Industrial Press Inc., 2001, p.127-128)
Slab Mill (Newer)
Cutting-tool life and machining operations are greatly influenced by the way that the cutting fluid is applied. It should be supplied in a copious stream under low pressure so that the work and cutting tool are well covered. The rule of thumb is that the inside diameter of the supply nozle should be about three-quarters the width of the cutting tool. The fluid should be directed to the are where the chip is being formed to reduce and control the heat created during the cutting action and to prolong tool life.
In slab milling, cutting fluid should be directed to both sides of the cutter by fan-shaped nozzles approximately three-quartesrs the width of the cutter.
(F. Krar, A.Gill, P. Smid, Technology of Machine Tools 6th edition pg. 268 )
---------------------------------------------------------------------
Fly Cutter (Older) (Cutting Tool)
For drilling large holes in pipe or sheet metal, twist drills are not suitable because of the drill tends to dig into the work or the hole is too large to be cut by a standard-size drill. Large holes are cut in thin metal by a hole cutter. Saw- type cutters of this design can be obtained in a wide range of sizes. For very large holes in thin metal a fly cutter is used. Such a cutter consists of tool bits held in a horizontal holder that can accommodate a range of diameters. Both cutters cut in the same path but one is set slightly below the other.
(Amstead, B.H., Ostwald P.F., Begeman, M.L., Manufacturing Processes, 8th Edition, John Wiley & SOns, Inc, pg.510)
Fly Cutter (Newer)
A fly-cutter is a single-point tool often consisting of a high-speed or carbide tool secured in an appropriate holder. Altough a fly-cutter isn't truly and end mill, it's used for end milling applications. Flycutters are often used to take light face cuts from large surface areas. The tool bit in the flycutter must be properly ground to optain the correct rake and clearence angles for the material being machined. Flycutters may also be used for boring operations. Care must be exercised when using a flycutter. When the tool is revolving, the inserted cutting tool becomes almost invisible and can injure the operator. (W. White et. all Machine Tool Practices 9th ed. pg.520 )
-------------------------------------------------------------------
Ball Nose Cutter (Older) (CNC Tool)
Ball nose end mills are among the most commonly and extensively used cutting tools on CNC milling machines and machining centres. They are essential for production of sculptured surfaces required on components such as dies and moulds. Many times these surfaces need ball nose end mills of quite small diameters to cover all the features in the mould. They are subjected to deflection at cutting edge which results in chatter and lower metal removal rates. Normally, solid high speed steel or solid carbide cutters are used. Any breakage or wear results in costly regrinding or replacement of the cutters. To obviate these drawbacks many designs of ball nose end mills with indexable/throwaway inserts have come into vogue. In these type of cutters, an insert of special configurations having the required ball nose radius is clamped in a pocket milled in the body of the end mill. This weakens the cutter at the critical section thus increasing the deflections and reducing the material removal rate.
(Murty R.L., Srihari G., Rao C.S.P., Proceeding of 17th All India Manufacturing Technology Design and Research Conference p.81)
Ball Nose Cutter (Older) (CNC Tool)
Ball nose end mills are among the most commonly and extensively used cutting tools on CNC milling machines and machining centres. They are essential for production of sculptured surfaces required on components such as dies and moulds. Many times these surfaces need ball nose end mills of quite small diameters to cover all the features in the mould. They are subjected to deflection at cutting edge which results in chatter and lower metal removal rates. Normally, solid high speed steel or solid carbide cutters are used. Any breakage or wear results in costly regrinding or replacement of the cutters. To obviate these drawbacks many designs of ball nose end mills with indexable/throwaway inserts have come into vogue. In these type of cutters, an insert of special configurations having the required ball nose radius is clamped in a pocket milled in the body of the end mill. This weakens the cutter at the critical section thus increasing the deflections and reducing the material removal rate.
(Murty R.L., Srihari G., Rao C.S.P., Proceeding of 17th All India Manufacturing Technology Design and Research Conference p.81)
Ball Nose (Newer)
These types of bits differ from end mills in that the geometry of the end of the bit's rounded. These bits are also available in various types and are often used in areas such as decorative fluting, engraving and in 3D finish work.
The ball-nosed milling cutter has recently emerged as an important cutting tool in machining industrial moulds since it can be employed to create complicated surfaces by numerical control (NC) machine systems. Ball-nosed milling cutters of different specifications are in high demand as NC system technology is gaining in popularity. The cutting edge of common ball-nosed milling cutters is as simple as a plane, and this causes many problems in machining. For example, swarf removal is difficult, swarf gathers around the cutting edge and then blocks up the cutter. This causes a arouses high wear rate and affects the surface precision of the workpiece. Work has therefore begun on ball-nosed milling cutters with S-shaped cutting edges.
(A. Overby, CNC Machining Handbook, pg.20)( A Manufacturing Model of S-Shaped Ball-Nosed Milling Cutter and Error Analysis in Realisation in Industry Y. T. Wang1, Q. S. Bao1 and Y. Y. Tang2)
No comments:
Post a Comment