The craft of casting pig of boring of PCBN cutting tool experiments

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One, of the problem raise my company production 3, if requirement of precision of aperture of crock of airframe of 4 crocks of diesel engine pursues 1 is shown. Material is HT250, hardness is 200-250HB. Used treatment of cutting tool of YG3 hard alloy in the past, because treatment aperture is deeper, distance of cutting tool cutting is long, cutting tool wears away fast, and production lot is big, in bore hole the problem that a few following fields basically produce in the process: The crock after 1) essence boring issues small taper greatly on aperture generation, cylinder spends short of requirement; Blade of 2) cutting tool is ground frequent, the workload that move a knife is big; 3) treatment dimension comes loose difference is big, stability is poor; 4) workpiece heat is out of shape big, the influence machines dimension precision; 5) production efficiency is low, affect production lot badly expand etc. The basic approach that solves these problems is to use data of new-style cutting tool, the wearability that raises cutting tool and cutting speed and the coefficient of friction that decrease small cutting tool and workpiece. For this, the author chose material of PCBN cutting tool, and according to its cutting function, undertook on machining center and modular machine tool craft experiments respectively, obtained very good result. Graph 1 2, boring treatment craft experiments 1 experiment condition machines an object: Aperture of airframe cylinder bushing, HT250, hardness 200-250HB; Cutting tool: PCBN is compound piece; Processability is qualitative: Finish machining; Machine equipment: XH756 machining center; Machine a condition: Do type cutting. The geometrical parameter that the influence graph of parameter of geometry of 2 cutting tool to exterior surface roughness is shown 2 times is 4 groups of different cutting tool is right the influence curve of exterior surface roughness, because the brittleness of PCBN cutting tool is bigger than hard alloy, use the part before lose edge or be being lost with increasing cutting tool combat impact strength (prevent bit fracture or rupture) , but lose arris and the accretion of the horn before losing, make the cutting of cutting tool fights force to increase, easy cause vibration of cutting tool system, affect workpiece surface surface roughness, what because this wants special attention,choose cutting tool is negative fall arris and the horn before losing. Can see in the graph, g0=0 ° is in parameter of cutting tool geometry, g01=-10 ° ～ - when 8 ° of ～ of ° of 15 ° A0=6, workpiece surface surface roughness is worth lowest, precision is highest. Because airframe bores hole,this is itself is successive cutting treatment, the horn before 0 ° are being used below the condition that allows in cutting condition and lose edge lesserly, be helpful for reducing the vibration of cutting force and cutting tool system, make cutting tool cutting light, be helpful for reducing surface roughness of treatment workpiece surface to be worth thereby. ～ of Ⅰ G0=-3 ° - ～ of ° of 5 ° G01=-20 - ～ of ° of 25 ° A0=6 ～ of ° of G01=-20 of ° of G0=0 of 8 ° Ⅱ - 8 ° of ～ of ° of 25 ° A0=6 ～ of Ⅲ G0=-3 ° - ～ of ° of 5 ° G01=-10 - 8 ° of ～ of ° of 15 ° A0=6 Ⅳ G0=0 ° , because material of PCBN cutting tool has very good thermal stability and high temperature hardness, heat conduction performance is good, coefficient of friction is small wait for a characteristic, special agree with high speed cutting. Recommend according to concerning a material, undertook cutting speed and the cutting that correspondence of exterior surface roughness concerns experiment. From the graph 2 in can see, when low speed cutting, the surface roughness value of workpiece surface is greater, as the heighten of cutting speed, the value reduces workpiece surface surface roughness stage by stage. If be with Ⅳ group cutting tool exemple when V<300m/min, ra>1.

6µm, when V>500m/min, ra<1.

25µm, because be when low speed cutting,this is, because cutting tool suffers arris or the effect of the horn before losing, the cutting of cutting tool fights force to increase, cause vibration of cutting tool system, make the value increases exterior surface roughness thereby, arrive when cutting speed heighten when fair value, of main shaft stimulate Zhen Pin rate is higher, greatly prep above machine tool - workpiece - clamping apparatus - the frequency with cutting tool inherent machining complex, cutting process is accordingly smooth, the value reduces treatment surface surface roughness apparently. But when V>800m/min later, not apparent to the influence of exterior surface roughness. The influence of 4 cutting speed to cutting tool life the mainest factor that cutting speed is life of influence cutting tool, the graph is shown 3 times fall in different cutting speed, the relation curve of cutting distance and wear extent of point of a knife, visible V ≤ when 300m/min, cutting tool wears away very fast (treatment controls airframe 12 times the indispensible and new) that grind a knife. It is after V>700m/min, point of a knife wears away slow (treatment controls machine types or forms of literature 200 times to begin to grind knife) afresh, because PCBN cutting tool is when high speed cutting,this is, produce higher cutting temperature, make be machined material bate, with the hardness between cutting tool difference increases, this kind " bate effect " the life that improved cutting tool. Graph the relation of 3 cutting distance and wear extent of point of a knife the 5 feed influence to exterior surface roughness needs to make as a result of PCBN cutting tool piece lose edge in order to avoid blade of the collapse in cutting process, the choice because of this feed cannot too small, want to be more than arris width, otherwise cutting tool cutting is pouring arris area, form the very large part before losing, go against exterior surface roughness reduce. Feed is too big, also affect exterior surface roughness likewise reduce. The graph shows the relation curve that is feed and exterior surface roughness 4 times. Can see from inside the graph, when feed F<0.

2mm/r, f>0.

When 4mm/r, exterior surface roughness all bad. Graph the relation of 4 feed and exterior surface roughness 6 cut pursue greatly to the influence of cutting tool life show 5 times, to cut deep the relation curve with cutting tool wear extent, should cut deep lesser when, wear extent of point of a knife is bigger (go up to Dao Yi in optics measure) , in Ap>0.

After 3mm, wear extent is reduced apparently, show gently ascendant trend later, because cut,this is deep lesser when, cutting tool is in attrition cutting position, use bigger cut deep when, because enough quantity of heat undertakes bate to cutting area metal () of metallic bate effect, make cutting tool wears away speed is reduced. But cut deep quantity to be chosen too greatly, bring about force of finish machining cutting and cutting area to increase again, those who affect exterior surface roughness reduce. Graph 5 cut deep the relation with cutting tool wear extent 3, the logical choice of parameter of cutting tool geometry and cutting dosage can see from afore-mentioned test results, parameter of the most reasonable cutting tool geometry sees a table 1. The other angle basis such as tool cutting edge angle needs to decide. Reasonable cutting dosage sees a table 1. ° of L 0 of dip of blade of Re Mm of point of a knife of A0 of the horn after G0 of the horn before expressing parameter of geometry of 1 cutting tool loses arris G01 to pour arris wide Br Mm - 10 ° ～ - 15 ° 0.

2 ～ 0.

8 ° of ～ of 3 6 ° 0.

4 ～ 0.

8 0 ° expresses 2 cutting dosage F Mm/r of feed of cutting speed V M/min cuts 1000 0 of ～ of deep Ap Mm 500.

25 ～ 0.

4 >0.

Workpiece of treatment of cutting tool of contrast of aperture of crock of treatment of cutting tool of 3 watches 3 PCBN counts a cylinder of Ra µm of exterior surface roughness to spend Mm dimension to come loose productivity of poor limits Mm / H YG3 25 3.

2 ～ 1.

6 0.

015 ～ 0.

035 0.

045 5 PCBN 160 1.

6 ～ 0.

8 0.

008 ～ 0.

020 0.

020 30 experiments according to this result, my factory undertakes on boring machine of DV3480 vertical combination cutting of cylinder bushing aperture experiments, discovery although V=700m/min, the machining complex of the machine tool also produces bigger vibration, because modular machine tool is designed,this is (especially main shaft and cutting tool system) itself is incommensurate high speed cutting, according to the graph 3 show cutting distance and concern of cutting tool wear curve, choice V=500m/min cutting experiments, parameter of cutting tool geometry is Alexandrine, feed F=0.

3mm/r, cut deep Ap=0.

4mm, test result is favorable. The watch is shown 3 times for PCBN and experiment of cutting of hard alloy cutting tool contrast is expressed. 4, trial verdict and note 1 trial verdict looks from afore-mentioned cutting test cases, the cutting experiment of aperture of crock of airframe of machine of much crock of boring of PCBN cutting tool is successful, already machined many 4000 on assorted boring machine, use effect is very good. Because A used high speed cutting, big feed, cutting efficiency is tall, improved productivity 6 times, can reduce manufacturing cost greatly. B used high speed cutting, reduce exterior surface roughness to be worth 1 class above. C PCBN cutting tool has very tall hardness and wearability, improved cutting tool service life 4 times above; Reduced treatment dimension to come loose difference and cylinder spend an error; Reduced tone knife to wear knife number, managing auxiliary time. 2 notes A issues cutting in high speed as a result of PCBN cutting tool, because of this machine tool - workpiece - clamping apparatus - stiffness of cutting tool machining complex is close friends, prevent oscillatory influence to machine precision and hit a knife. Brittleness of B PCBN cutting tool is bigger, answer to apply in successive and smooth cutting to machine a circumstance as far as possible, can use at this moment 0 before horn. When occurrence interrupted cutting, it is especially when stiffness is insufficient, should use lose the arris, horn before losing to burst apart in order to avoid where a thing can be put to best use. Deepness of cutting of C PCBN cutting tool cannot exceed 35% of knife head. D PCBN is compound piece cutting tool can solder, can undertake several times weighing grinding, PCBN is compound piece quality is close friends, otherwise meeting generation bedding face accumulates collapse blade. Blade of E PCBN cutting tool is ground also is crucial, the very important person after going up to be ground with blade of diamond emery wheel is rubbed in common tool labour is abrade, best use entrance (Japan) or Dalian manage is versed in the university is developed exceed blade of strong cutting tool to grind machine, have drop feed and trim the function such as light without feed grinding, emery wheel, be helpful for what cutting tool blade grinds quality and manufacturing efficiency rising, the blade when still can reducing cutting tool grinding at the same time grinds a quantity, raise cutting tool blade to wear a number, improve cutting tool service life namely. 50 times magnifier should be used to check edge blade to grind quality when F blade is ground, in order to raise cutting tool service life and the surface roughness that reduce treatment surface. CNC Milling