The settlement of problem of dot of protruding of piston pin aperture measure

004 ～ 0.

006mm; Appearance precision demand is higher, the general cylinder that sell aperture is spent for 0.

0015mm; Demand of exterior surface roughness is higher, it is Ra0 commonly.

2 ～ 0.

4; And most product sells aperture to ask in group. Different level land increased above element car piston pin the treatment difficulty of aperture. The piston of Great Wall GW413EF that my company produces and south steam N4 piston ever had produced piston pin to assemble difficult question early or late. Additional, the car piston that partial belt sells an oily aperture also because sell an oil aperture and sell aperture to intersect dot of place occurrence protruding causes piston pin aperture the invalidation of different form. The graph is shown 1 times to sell an oil aperture and sell aperture to intersect to be in occurrence protruding to nod and make piston pin and the between lubricating oil that sell aperture film is destroyed, dry attrition produces a large number of quantity of heat, bring about the melt of this place and stick together finally. Graph 1 sell an oil aperture and sell aperture to intersect the problem of above of the invalidation that sell aperture that the protruding dot of place poses our end selects an issue for protruding of piston pin aperture, to this my company established special project group, form a reason to undertake an analysis to its, put forward feasible settlement measure. Case study passes careful research analysis, sell all sorts of elements of aperture treatment considering the influence, be like: Material of clamping apparatus of machine tool, tool, piston, metallographic, heat treatment and environment, we reach the following conclusion: 1.

Respect of machine tool, tool (1) the material of boring lever majority that my company uses is 45# steel character, its oneself stiffness is low, treatment car kind piston place uses boring shank diameter lesser, suffer in machining a process bend, turn round and compress load to combine action to be able to produce vibration. (2) block inside some car pistons narrower, its width is less than a side to sell the width of aperture, wide choice exists when boring two knives at the same time the phenomenon of penetration of a cutting tool, bring about thereby sell aperture to stand by lumen brim to handle occurrence protruding station. (3) the bench drill precision that treatment sells an oily aperture low, rotate speed is slow, and use treatment for the hand for the most part, sell an aperture to cannot achieve higher treatment quality. 2.

The reason of the respect such as material of piston of piston material qualitative respect, metallographic and heat treatment makes piston finished product is out of shape in the generation after be being deposited for long, risk alkaline (annul inside aperture) wait for blemish, cause piston pin aperture to wear sell difficulty. 3.

Machine a respect (1) Kong Jia man-hour, if broach blade grinds quality poor, broach is not sharp may cause a Kong Zhou to surround stress to center, in follow-up working procedure these stress get releasing, form protruding place thereby. (2) when aperture of essence of life is machined, treatment arrives selling an oily aperture is interrupted cutting, suffer the effect of boring lever tigidity and cutting tool quality, cause easily in sell an oily aperture to export side to form protruding place. (3) boil pressure sell Kong Shi, although can nod the protruding that forms in treatment temporarily,press, but just let this a little bit produce flexibility to be out of shape, in follow-up memory process, this protruding dot can rebound slowly again come out. From south in light of the test case of steam N4 and piston of Great Wall GW413EF, this kind rebounds to be mirrorred with respect to very can apparent ground after a month come out. Nextpage (4) because product line is used now,shed production, not was in between working procedure goods, this also causes the treatment stress of rough machining working procedure to cannot get be releasinged adequately, cause certain effect to the quality of finish machining. (5) the treatment that sell aperture uses dry cutting, without compulsive refrigeration, also put in certain influence to machining quality. 4.

Environmental problem (1) when production, product line issues treatment in normal temperature, the effect that suffers environmental temperature is bigger, control of difference in temperature masters not easily. (2) piston pin aperture uses 20 ℃ constant temperature to detect, but leader plant assembles the spot is normal temperature, the as a result of piston pin coefficient of expansion when winter air temperature is inferior is smaller than the piston, also can assemble to piston pin cause certain effect. Solve measure to pass pair of above reasons to undertake integration analysis, combine our company current situation, we made corresponding settlement measure, specific as follows: 1.

Craft file is improved get those who sell an oily aperture process to change Dao Pin second unified it is 200 / second; The knife of essence of life that boring of essence of life sells aperture process changes Dao Pin second unified for 10 000 / second (the equipment, cutting tool theory that is in whack to fall is referenced data) . In the meantime, after selling a Kong Jia to be versed in arrangement sells aperture in thick boring, undertake, can eliminate the partial stress that sells a Kong Zhou to surround. 2.

Tooling improves basically be lever of boring of aperture of essence of life: The purpose is the tigidity that increases boring staff and circumgyrate precision. Pass a large number of experiments to prove, in equal treatment the condition falls, hard alloy is treatment small diameter, high accuracy aperture the boring lever stuff with good integral performance, hard alloy (YG6X) of boring lever fight brace up it is good that function wants pole of more qualitative than 45# steel boring much, can make exterior surface roughness is reduced, treatment surface does not have Zhen Wen. The graph is shown 2 times is the rod of hard alloy boring that my company uses at present. Consider lever of hard alloy boring is machined not easily, because this is on solder of front of lever of hard alloy boring the knife head lever of material of a paragraph of T7A, facilitating outfit places cutting tool. This boring lever by knife head lever (material: T7A) , arbor (material: YG6X) with bit body (material: 40Cr) 3 parts composition. Bit body heat treatment asks: 30 ～ 35HRC, exterior hair is blue, arbor and bit body interference 0.

05 ～ 0.

08mm press fitting, knife head lever and place of arbor copper solder must assure to solder quality (3 000r/min of arbor rotate speed, if sealing off and sequential serious) . The circumstance that if some product essence boring sell aperture to machine existence,two knives interfere, need to design lengthen boring staff, the penetration of a cutting tool when making sure thick knife and knife of essence of life are different. Graph lever of boring of 2 hard alloy (lever of 1- knife head; 2- arbor; 3- bit body) 3.

Cutting tool improves thick knife of aperture of essence of life by the cutting tool of PCD of instead of hard alloy cutting tool that uses now. PCD cutting tool has coefficient of friction low, coefficient of thermal conductivity is tall and hardness is advanced characteristic, can grind a sharp cutting blade point, reduce cutting force greatly, be helpful for raising the precision that cutting machines, also reduce the demand that machines machine tool stiffness to nicety at the same time, the treatment quality that improved thick knife not only, reduced the frequency that change a knife second, and rose to machine efficiency, prolonged the service life of cutting tool. Consider treatment asks, the norms that chooses PCD thick knife is 15mm of φ 6mm × (R=0.

2mm) . Graph 3 for sketch map of PCD thick knife. The horn before cutting tool of PCD thick knife is 5 ° , α of the horn after cutting tool is used answer hind horn, it is 12 ° , 15 ° respectively, cutting tool first flank is wide 0.

2 ～ 0.

3mm. Below the circumstance with advanced certain part, lesser the first hind horn can make wedge horn β increases, cutting tool intensity rises; The 2nd hind horn increases, face of the knife after be helpful for reducing and sell the between round face attrition inside aperture and interference. Tool cutting edge angle and deputy slant horny semmetry distributings, r=0 of circular arc of point of a knife.

2mm. The cutting deepness that assumes as a result of PCD boring cutter is very small, of cutting tool advocate the cutting part of deputy cutting blade is assumed by circular arc of point of a knife actually (have Xiu Guang effect at the same time) . Nextpage4 of thick knife of graph 3 PCD.

Although the influence of temperature control temperature cannot cause car piston pin directly aperture machines what protruding nods to form, but the assembly that the difference of temperature can affect car piston directly, the outfit that causes car piston sells difficulty. Accordingly, we took necessary step in the control respect of temperature. We to many car piston pin aperture has temperature corrective experiment, according to offerred fundamental data, made relevant control way, summary gave the rule that diameter of Kong Zhi of car piston pin changes along with temperature. Sell formula of aperture diameter correction to be: Sell =6 of Kong Ce value of a quantity.

× of 68 × 10-6 is measured to sell aperture diameter × (20 ℃ - actual temperature) for example: To selling hole size the requirement is φ 18 +0.

014 +0.

The temperature when the piston of 008 is being machined is amended see next tables. Temperature of diameter of Kong Zhi of some car piston pin is corrective (unit: Mm) 5.

Detect respect essence is measured room detect annul when there is the piston that sells an aperture inside aperture, sell aperture circularity for accurate report, must detect through selling the circularity with an aperture sectional center, a Kong Gai will be sold to live with scotch tape when measuring, adhesive plaster cuts out norms: Do not be more than an aperture diameter + of 2mm square piece. We undertook epilogue above measure experiment in great quantities, avoided what protruding of piston pin aperture selects an issue successfully to happen again, apply successfully already at batch production now. Henceforth, as engine low discharge those who reach dynamical sex, economy and dependability is ceaseless rise, to the treatment of the piston precision asks also will taller and taller. While we are summing up experience, also devote oneself to to raise the treatment level of the piston ceaselessly, to enhance company overall competition ability indefatigable effort. CNC Milling CNC Machining