The phrase speed and feed or feed and speed refers to two separate speeds in machine tool practice, cutting speed and feed rate . They are often regarded as a couple due to their combined effect on the cutting process. Each, however, can also be considered and analyzed in its own right.
Cutting speed (also called surface velocity or just speed ) is the difference in speed (relative speed) between the cutting tool and the workpiece surface is operating. This is expressed in units of distance along the surface of the workpiece per unit of time, usually the surface of the foot per minute (sfm) or meters per minute (m/min). Feed rate (also often styled as a solid compound, feed rate , or simply called feed ) is the relative speed at which the cutter is advanced along the work piece ; the vector is perpendicular to the velocity vector. The feed rate unit depends on the motion of the tool and the workpiece; when the workpiece is spinning ( for example , in rotating and boring), the unit is almost always spaced per spindle distance (inches per revolution [in/rev or ipr] or millimeter per revolution [mm/rev]). When the workpiece does not rotate (eg, , in milling), the unit is usually distance per time (inches per minute [in/minute or ipm] or millimeters per minute [mm/min]), although distance per revolution or per cutter gear is sometimes also used.
If variables such as cutter geometry and machine tool stiffness and tooling settings can be maximized maximally (and reduced to negligible constants), only the power shortage (ie kilowatt or horsepower) available for the spindle will prevent the maximum use of the speed and feed possible for workpiece material and cutting material provided. Of course, in reality, other variables are dynamic and can not be ignored; but there is still a correlation between available power and the feed and speed used. In practice, the lack of stiffness is usually a limiting constraint.
The phrase "speed and feed" or "feed and speed" has sometimes been used metaphorically to refer to the details of the plan's execution, which only the skilled technician knows (which is different from the designer or manager).
Video Speeds and feeds
Cut speed
The cutting speed can be defined as the rate at the surface of the workpiece, regardless of the machining operation used. The cutting speed for mild steel 100 ft/min is the same whether the cutting speed passes through the workpiece, as in the counter operation, or the cutting speed that travels through the workpiece, as in the mill. operation. Cutting conditions will affect the value of this surface velocity for mild steel.
Schematically, the velocity on the workpiece surface can be regarded as a tangential velocity on the cutter interface, that is, how fast the material moves across the cutting edge of the tool, even though the "focused surface" is a topic with valid answers. In drilling and milling, the outer diameter of the tool is a widely agreed surface. In transforming and boring, the surface can be defined on both sides of the depth of the piece, ie the initial surface or the final surface, with no definition "wrong" as long as the person involved understands the difference. An experienced engineer summed this up succinctly as "my diameter turned from" versus "the diameter I turned to." He uses "from" instead of "to", and explains why, while admitting that some others do not. The focusing logic on the largest diameter involved (drill OD or final plant, the initial diameter of the changed workpiece) is that it is where the highest tangential velocity, with the largest heat generation, is the main driver of wear.
There will be optimal cutting speed for each material and set of machining conditions, and spindle speed (RPM) can be calculated from this speed. Factors affecting the calculation of cutting speed are:
- Materials done (steel, brass, tool steel, plastic, wood) (see table below)
- Cutting material made of (Carbon steel, high speed steel (HSS), carbide, ceramic)
- The economic life of cutter (cost for regrind or new purchase, compared to the number of parts produced)
The cutting speed is calculated based on the assumption that optimal cutting conditions exist. These include:
- Metal removal rate (final cut that removes small amount of material can be run at an improved speed)
- Full and constant flow of fluid cutting (adequate cooling and watering chips)
- Machine stiffness and tool settings (vibration or chat reduction)
- Cutting continuity (compared to cutting off , such as working on rectangular piece of material in lathes)
- Material condition (factory scale, hard spots due to white cast iron formed in castings)
Cutting speed is given as a set of constants available from the manufacturer or material supplier. The most common materials are available in reference books or charts, but will always be subject to adjustment depending on cutting conditions. The following table provides cutting speed for the selection of common materials under a set of conditions. The condition is the age of chisel 1 hour, dry cutting (no cooling), and on the medium bait, so it seems wrong according to the circumstances. This cutting speed may change if, for example, adequate cooling is available or an increase in HSS value is used (such as those including cobalt).
Ranking machinability
Rating machinability of a material tries to measure the machinability of various materials. This is expressed as a percentage or a normal value. The American Iron and Steel Institute (AISI) determines the machinability ratings for various materials by running back-test at 180 feet surface per minute (sfpm). Then arbitrarily assigned 160 Brinell B1112 steel machinability ratings of 100%. The machinability rating is determined by measuring the weighted average of normal cutting speed, surface finish, and tool life for each material. Note that materials with machinability ratings of less than 100% will be more difficult for machines than B1112 and materials and grades over 100% will be easier.
The machinability rating can be used in conjunction with the equations of Taylor's life tool, VT n = C to determine the cutting speed or tool life. It is known that B1112 has 60 minute chisel life with cutting speed 100 sfpm. If the material has a machinability value of 70%, it can be determined, with the foregoing, that to maintain the same chisel life (60 min), the cutting speed should be 70 sfpm (assuming the same tooling is used).
When calculating for copper alloys, engine ratings arrive assuming a value of 100 out of 600 SFM. For example, phosphor bronze (grade A-D) has a machinability rating of 20. This means that bronze phosphorus runs at 20% at 600 SFM or 120 SFM. However, 165 SFM is generally accepted as a 100% base rating for "grading steels".
Maps Speeds and feeds
Spindle speed
spindle speed is the rotation frequency of engine spindle, measured in revolutions per minute (RPM). The preferred velocity is determined by working backward from the desired surface velocity (sfm or m/min) and combining the diameter (workpiece or cutter).
Spindle can hold:
- Material (as in a screw machine)
- Drill bits are drilled
- Milling cutter on milling machine
- Router bit in the wood router
- Cutting or forming knife in wood forming or spindle spindle
- Grinders on a grinding machine.
- Or maybe hold the chuck, which then holds the workpiece on the lathe. In this case, the tool is often a stationary tool, although there are many exceptions, such as in grinding mills.
Excessive spindle speed will cause wear and tear of the appliance, damage, and may cause a chat tool, all of which can lead to potentially hazardous conditions. Using the right spindle speed for materials and equipment will greatly improve the life of the chisel and the quality of the final surface.
For certain machining operations, cutting speed will remain constant for most situations; therefore the spindle speed will also remain constant. However, facing, forming, separating, and resting operations on a lathe or screw involves machining of an ever-changing diameter. Ideally, this would mean changing the spindle speed when cutting cuts across the workpiece surface, resulting in a constant surface velocity (CSS). The mechanical arrangements for CSS effects have been around for centuries, but they have never been applied generally to machine tool controls. In the pre-CNC era, CSS ideals were ignored for most jobs. For the unusual work that demands it, special pain is taken to achieve it. The introduction of CNC-controlled lathes has provided a practical, everyday solution through automated CSS. By using the machine software and the variable speed electric motor, the lathe can increase the spindle RPM as the cutter draws closer to the center of the section.
The grinding wheels are designed to run at maximum safe speeds, the speed of the spindle grinding machine may vary but this should only be changed by taking into account the safe working speed of the wheels. When the wheel wears it, its diameter will decrease, and its effective cutting speed will decrease. Some grinders have provisions to increase spindle speed, which corrects the loss of this cutting ability; However, increasing the speed beyond the wheel rankings will destroy the wheel and create serious harm to life and limbs.
In general, spindle speed and feed rate are less important in woodworking than metalworking. Most woodworking machines include electric saws such as circular saws and band saws, jointers, planer thickness spinning at fixed RPM. In such machines, cutting speed is adjusted through the feed rate. The required feed rate may vary greatly depending on motor strength, hardness of wood or other material being worked on, and the sharpness of the cutting tool.
In woodworking, the ideal feed rate is that it is slow enough not to clog the motor, but fast enough to avoid burning the material. Certain woods, such as black cherry and maple, are more susceptible to burning than others. Appropriate feed rates are usually obtained by "feeling" if the ingredients are fed, or by trial and error if the power feeder is used. In thicknessers (planers), wood is usually fed automatically through rubber or corrugated steel rollers. Some of these machines allow varying feed rates, usually by replacing pulleys. Slower feed rates usually result in smoother surfaces because more pieces are made for each length of wood.
Spindle speed becomes important in the operation of routers, spindle moulders or molders, and drill. Older and smaller routers often rotate at fixed spindle speeds, typically between 20,000 and 25,000 rpm. While this speed is good for small router bits, using larger bits, say more than 1 inch (25 mm) or 25 millimeters in diameter, can be dangerous and can cause chats. Larger routers now have variable speeds and larger bits require slower speeds. Wood drilling generally uses higher spindle speeds than metal, and its speed is not so important. However, larger diameter drills do require slower speeds to avoid burning.
Cutting the feed and the speed, and the speed of the spindle coming from them, is the ideal cutting condition for the tool. If conditions are less than ideal then adjustments are made to spindle speed, this adjustment is usually a reduction in RPM to the nearest available speed, or which is considered (through knowledge and experience) to be true.
Some materials, such as useable candles, can be cut at various spindle speeds, while others, such as stainless steels, require more careful control because cutting speed is essential, to avoid overheating both cutter and workpiece. Stainless steel is one of the ingredients that works very easily hardened, therefore insufficient feed or incorrect spindle speed can cause less than ideal cutting conditions because the workpiece will quickly harden and resist the cutting action of the tool. The application of liberal cutting fluids may improve the conditions of this cutting; However, the selection of the right speed is a critical factor.
Spindle speed calculation
Most metalworking books have nomograms or spindle speed tables and feed rates for various cuters and workpieces; Similar tables may also be available from the manufacturer of the cutters used.
Spindle speed can be calculated for all machining operations after SFM or MPM is known. In most cases we deal with cylindrical objects such as milling cutters or rotating workpieces in the lathe so we need to determine the velocity at the edges of this round object. This velocity at the periphery (the point on the circumference, moving past the stationary point) will depend on the spin speed (RPM) and the diameter of the object.
One analogy would be skateboarders and cyclists who travel side by side along the way. For certain surface speeds (the speed of these pairs along the way), their rotation speed (RPM) of wheels (great for skaters and small for cyclists) will be different. This rotational speed (RPM) is what we calculate, given the fixed surface velocity (velocity along the road) and the known value for their wheel sizes (cutter or workpiece).
The following formula can be used to estimate this value.
Approximation
RPM yang tepat tidak selalu diperlukan, pendekatan dekat akan bekerja (menggunakan 3 untuk nilai ).
misalnya untuk kecepatan potong 100Ã, ft/menit (pemotong baja HSS polos pada baja ringan) dan diameter 10Ã, inci (pemotong atau benda kerja)
dan, untuk contoh menggunakan nilai metrik, di mana kecepatan potong adalah 30 m/menit dan diameter 10 mm,
Run
Namun, untuk perhitungan yang lebih akurat, dan dengan mengorbankan kesederhanaan, rumus ini dapat digunakan:
give menggunakan contoh yang same
Dan menggunakan contoh yang sama seperti di atas
Where:
- RPM is the rotational speed of the cutter or workpiece.
- Speed ​​ is the recommended cutting speed of material in meters/min or feet/min
- Diameter in millimeters or inches.
Feed rate
The feed rate is the speed at which the cutter is fed, ie, forward to the workpiece. This is expressed in units of distance per revolution to spin and bore (usually an inch per revolution or millimeter per revolution). This can be stated for grinding too, but it is often expressed in units of distances per time for grinding (typically inches per minute [ ipm ] or millimeters per minute ), taking into consideration how many teeth (or flutes) the cutter then determines what it means for each tooth.
Feed rate depends on:
- Device type (small drill or large drill, high speed or carbide, boxtool or recess, thin-form instrument or width form tool, knurl slide or turret straddle knurl).
- The desired final surface.
- Power is available on the spindle (to prevent stalling the cutter or workpiece).
- Machine stiffness and tool settings (ability to withstand vibration or chat).
- Workpiece strength (high feed level will break down the thin pipe wall)
- The characteristics of the material being cut, the flow of the chip depends on the type of material and the feed rate. The ideal shape of the chip is small and breaks faster, bringing heat from the appliance and working.
- Threads per inch (TPI) for taps, head off, and scrolling tools.
- Cut Width. Each time the cut width is less than half the diameter, a geometric phenomenon called Chip Thinning reduces the actual chipload. Feeding feeds need to be improved to compensate for the chip's thinning effect, both for productivity and to avoid scouring that reduces the life of the chisel.
When deciding what level of feed is used for a particular cutting operation, the calculation is quite easy for a single point cutter, since all the cutting work is done at one point (done by "one tooth", as is). With a milling machine or jointer, where multi-tipped/multi-fluted cutting tools are involved, the desired feed rate becomes dependent on the number of teeth on the cutter, as well as the amount of material per tooth desired to be cut (expressed) as a chip load). The larger the number of cutting edges, the higher the allowable feed rate: for a cutting edge to work efficiently it must throw enough material to cut rather than rub; it must also do its fair share of work.
Spindle speed ratio and feed rate control how aggressive the pieces are, and the nature of the swarf is formed.
The formula for determining feed rate
This formula can be used to determine the level of feed that the cutter carries in or around the work. This will apply to the cutter on the milling machine, drill press and a number of other machine tools. It will not be used on the lathe to rotate the operation, since the feed rate on the lathe is given as feed per revolution.
Where:
- FR = feed rate calculated in inches per minute or mm per minute.
- RPM = is the speed calculated for the cutter.
- T = Number of teeth on the cutter.
- CL = chip load or feed per tooth . This is the size of the chips that each cutter gear uses.
Cutting depth
The cutting speed and feed rate come together with cutting depth to determine the level of material removal , which is the volume of workpiece material (metal, wood, plastic, etc.) that can removed per unit of time
The linkage of theory and practice
The selection of analog velocity and feed with other examples of applied science, such as meteorology or pharmacology, that theoretical modeling is necessary and useful but can never fully predict the reality of a particular case because of the large multivariate environment. Just as the weather forecast or drug dose can be modeled with fair accuracy, but never with complete certainty, the engineer can predict with graphs and the approximate formula of speed and value of the feed that will work best on a particular job but can not know the optimal value right up to the job. In CNC machining, programmers typically accelerate and feed maximally adjusted feeds as calculations and general guidelines can provide. The operator then refines the values ​​when running the machine, based on the scene, sound, odor, temperature, tolerance tolerance, and cutting-edge life. Under proper management, revised values ​​are captured for future use, so when the program runs again later, this work does not need to be duplicated.
Like meteorology and pharmacology, however, the linkage of theory and practice has evolved over the decades when the balance theory part has become more advanced thanks to information technology. For example, an effort called the Machine Tool Genome Project works to provide the computer modeling (simulation) needed to predict optimum velocity-and-feed combinations for certain settings in Internet-connected stores with little local experiments and testing. Instead of the only option is the measurement and testing of the equipment's own behavior, it will benefit from the experience and simulation of others; in a sense, rather than 'reinventing the wheel', it will be able to 'make better use of existing wheels developed by others in remote locations'.
Examples of academic research
Speed ​​and feed have been studied scientifically since at least the 1890s. This work is usually done in an engineering laboratory, with funding coming from three basic roots: corporations, governments (including their military), and universities. The three types of institutions have invested large sums of money in the cause, often in collaborative partnerships. Examples of such work are highlighted below.
In the 1890s to the 1910s, Frederick Winslow Taylor made a famous (and seminal) back-and-forth experiment. He developed the Taylor Equation for Tool Life Expectancy.
Scientific studies by Holz and De Leeuw of the Cincinnati Milling Machine Company do milling cutters what F. W. Taylor has done for one-point cutter.
"After World War II, many new alloys were developed.New standards are needed to improve American productivity [US] Metcut Research Associates, with technical support from the Air Force Materials Laboratory and the Army's Laboratory of Science and Technology, published the first Machinery Data Handbook in the year 1966. The suggested speeds and feeds given in this book are the result of extensive testing to determine the optimal chisel life under controlled conditions for each day of matter, operation and violence. "
Source of the article : Wikipedia
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