Cutting strength brief introduction

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One, the origin of cutting force, cutting join forces reachs his to decompose (one) the force of origin research cutting of cutting force, to making clear further cutting mechanism, to computation power is used up, to the design of cutting tool, machine tool, clamping apparatus, reasonable to making cutting dosage, optimize parameter of cutting tool geometry to wait, have very important sense. When metallic cutting, cutting tool cuts work, make material happening is out of shape and be become to cut the force that bits place requires by treatment, call cutting force. Cutting force originates 3 respects: 1. Overcome metabolic of the flexibility that be opposite by treatment material to fight force; 2. Overcome metabolic of the plasticity that be opposite by treatment material to fight force; 3. Opposite of face of the knife after overcoming the attrition force that cuts area of the knife before bits is right and cutting tool is crossed the surface and already machined the attrition force between the surface. (2) close cutting blade is in cutting join forces and the intention of join forces Fr that its disclose them on advanced knife face. Measure to facilitate the effect that analyses cutting force is mixed, the size of computational cutting force, normally join forces Fr, be in by advocate the axis of athletic speed direction, dimensional rectangular coordinates that cuts deep direction and feed direction to make is decomposed on Z, Y, X it is mutual and perpendicular Fz, Fy and Fx3 into 3 component of force. 1, advocate cutting force Fz (tangential force) : Advocate the component of force of direction of athletic cutting speed. Fz is a the largest component of force, it consumed cutting general power 95% the left and right sides, it is design and the main basis of use cutting tool, use at checking computations machine tool, clamping apparatus the intensity of main component and stiffness and power of machine tool electromotor. 2, cut fight force Fy greatly (radial load) : Cut the component of force of deep direction. Fy does not consume power, but in the machine tool the inadequacy of machining complex tigidity that place of one cutting tool comprises one clamping apparatus checks one work, it is to cause oscillatory abundant to want an element. Nextpage3, feed fights force Fx (axial force) : The component of force of feed direction. Fx consumed general power 5% the left and right sides, it is system of feed of checking computations machine tool main 0, component intensity and rigid basis. Note: Be opposite in milling plane, afore-mentioned component of force also call: Fr -- tangential force, Fy -- radial load, Fx -- axial force. 2, the determine and cutting force often encounters in the experience formula production of cutting force, experiment computation of cutting force. At present the theoretical calculation formula of cutting force can offer qualitative analysis to use only. Because formula of computation of cutting force Fz is in oversight temperature, stress, Ⅲ is out of shape the area is out of shape with attrition the condition such as force issues derivation to come out, reason cannot be used at computation. And seek cutting power simpler practical method is to use the appearance that measure power to measure the experimental formula that after go out or passing a test, arranges to get directly. 1, measuring a principle with what measure power instrument to measure cutting force to measure power instrument is to use cutting master piece to use what what produce on the stretch component of the appearance that measure power to be out of shape, or after the charge that action generates on piezocrystal passes changeover, numerate the value of Fz, Fx, Fy. In automation production, still can use the signal that measures force to pass move plant to arise to optimize with monitoring cutting process. The working principle that presses the appearance that measure power can be divided mix for mechanical, hydraulic pressure electric the appearance that measure power. At present commonly used is resistor meet an emergency piece type measures power instrument. If plan institute is shown, resistor meet an emergency piece type measures power instrument by sensor 1, bridge circuit 2, appearance of meet an emergency (amplifier) 3 with recorder 4 composition. Sensor is a stickup on elastomer resistor meet an emergency piece changeover component, make through it the change of cutting force is changed into the change of n. resistor meet an emergency piece join becomes bridge circuit, when meet an emergency piece when resistance changes, criterion bridge is lopsided, generated electric current or output of voltage question mark, appearance of meet an emergency of classics of this question mark magnifies, show by Ji Luyi come. Pass demarcate to be able to make the relation chart between n and cutting force. Measuring the n that the basis when force records, can go up from demarcate chart the cutting force of fish correspondence is numeric. The experience formula of force of Nextpage2, cutting is current, people had gathered data of much cutting force test, to machining a method commonly, if turning, aperture adds labour and milling,waited to already established the experience formula that can use directly. The method of the experiment that measure power has only factor law and much element way, use only factor method normally. Secure other experiment condition namely, change back penetration of a cutting tool to measure Ap and feed F respectively when cutting, numerate from the appearance that measure power corresponding cutting force is numeric, request a function relation between them according to arranging through number next. The turning force test that establishs through cutting force experiment is formulary, its are general the form is: Attention: Formula of cutting force experiment is beg below specific experimental requirement come out. When computational cutting force, if cutting condition and experimental condition not agree with, need to amend coefficient KF by, it is the correction coefficient product that included a lot of factors. Correction coefficient also is to use experimental method to beg. 3, power of unit cutting force, cutting and unit cutting power 1, P of unit cutting force: It is to point to what place of area of excision unit cut arises advocate cutting force. Can express with next type: Type makes clear on, p of unit cutting force and feed F are concerned, it increases as feed F and reduce. P of unit cutting force does not suffer back penetration of a cutting tool to measure the effect of Ap. P of unit cutting force can check manual, use P of unit cutting force to calculate advocate cutting force Fz is relatively simple and easy and intuitionistic. 2, cutting power Pm: Use up the power in cutting process to call GB of cutting power Pm(to be Po) . Cutting power is force Fz and the power the sum that Fx spends, because Fy direction does not have displacement, do not consume power so. Then Pm=(FzVc+Fxnwf/1000) × 10-3 among them: Pm, cutting power (KW) ; Fz, cutting force (N) ; Vc, cutting speed (M/s) ; Fx, feed force (N) ; Nw, workpiece rotate speed (R/s) ; F, feed (Mm/s) . The 2nd on the right side of the equality sign in type is to consume the power in feed motion, it takes general power 5% the left and right sides, can skip not plan, then Pm=FzVc × 10-3 is pressed on after type gets cutting power, if want the power of computer bed electromotor (PE) so that choose machine tool electromotor when, still should consider efficiency of machine tool drive. In type of M of η of PE ≥ Pm/ : η M, the transmission efficiency of the machine tool, take commonly for 0.

75 ~ 0.

85, great value applies to new machine tool, little value applies to old machine tool. 3, Ps of power of cutting of unit of Ps of unit cutting power is to point to to the power that place of Zw of unit volume metal consumes is excised inside unit time. 4, the metabolic rule of cutting force carries out a proof, the influencing factor of cutting force is very much, basically cutting tool of material of parameter of geometry of dosage of workpiece material, cutting, cutting tool, cutting tool wears away condition and cutting fluid. 1, workpiece material (1) hardness or intensity rise, cut succumb intensity τ S increases, cutting force increases. (2) plasticity or tenacity rise, cut bits to break off not easily, cut bits and before knife face attrition increases, cutting force increases. 2, cutting dosage (1) back penetration of a cutting tool is measured (cutting deepness) Ap, feed increases, cut area increases, be out of shape fight force and attrition force to increase, cutting force increases. Because carry penetration of a cutting tool on the back to measure Ap to compare feed to the influence of cutting force,be opposite the impact of cutting force is big (normally XFz=1, YFz=0.


9) , it is so in practice, when the metallic layer that needs to excise certain amount, to improve productivity, use big feed cutting deeper than be being cut greatly cutting relatively save labour saves power again. Nextpage (2) cutting speed Vc (pursues 2.

20) 1) when machining plasticity metal, cutting speed Vc is affected as be out of shape to cutting to the influence rule of cutting force same, they are caused through accumulating the action of bits tumour and attrition. (with turning 45 steel are exemple, see figure below) 2) when cutting brittleness metal, because be out of shape with attrition all lesser, change of force of the cutting when Vc of reason cutting speed is changed is not big. 3, angle of cutting tool geometry (1) before horn: Horn increases before, be out of shape reduce, cutting force is reduced. (2) tool cutting edge angle: Kr of tool cutting edge angle is in 30 ° - increase inside 60 ° limits, have main effect by the influence of cutting ply HD, make advocate cutting force Fz is reduced; Kr of tool cutting edge angle is in 60 ° - increase inside 90 ° limits, circular arc of place of point of a knife and deputy before horny influence is more outstanding, reason advocate cutting force Fz increases. Popularly, kr=60 ° - 75 ° , so Kr of tool cutting edge angle increases, advocate cutting force Fz increases. (Graph 2.

22) Kr increases, make Fy is reduced, Fx increases. Practice application, in turning axis kind spare parts, especially long and thin axis, cut the action that fights force Fy greatly to reduce, often use the lathe tool cutting of R>600 of bigger κ of tool cutting edge angle. (S of λ of 3) blade dip: λ S is lesser to Fz influence, but bigger to influence of Fx, Fy. λ S by to negative change, criterion Fx is reduced, Fy increases. Practice application, from analysis of cutting force viewpoint, should not be when cutting had chosen S of big λ of negative blade dip. It is especially below the condition with machining complex poorer stiffness, because lose S of blade dip λ ,often increased to cut the action that fights force Fy greatly and generation is oscillatory. 4, other element (1) face of cutting tool arris: Should choose lesser width, make Fy is reduced. (2) radius of cutting tool circular arc: Increase, cutting is out of shape, attrition increases, cutting force increases. (3) cutting tool wears away: Knife face wears away after increase, cutting tool becomes blunt, with workpiece extruding, attrition increases, cutting force increases. CNC Milling CNC Machining