Background technology
Current national Specification: be φ 310mm with the maximum machined hole diameter of fine boring cutter for jig boring machine.Yet in reality processing, often can run into the boring of φ 360mm-large hole dimension of φ 750mm, claim that here the above hole of φ 360mm is macropore.Need to prove, about macropore, current not standard is defined, but concept ubiquity in the art, for different processing objects, some handles are also referred to as macropore processing greater than the processing of φ 150mm.
Process for macropore, if directly adopt Imitated design, hole after the boring can occur round (not oblate under the effect of the fine boring cutter cutter hub self gravitation that floats, circularity over tolerance in other words) phenomenon, the bottom of the macropore of hole can be larger, at least 0.06mm, at most 0.80mm, top is then relatively smaller, directly affects dimensional accuracy and the circularity of macropore.
About the fine boring cutter that floats, such as the fine boring cutter of standard, be illustrated in Figure of description 1 and the accompanying drawing 2, the segmental arc of Fig. 2 upper right corner dotted line represents finished surface.Among the figure, have radially square through hole at boring bar 1, be called cutter side, a combined cutter is inserted into described cutter side, is directed at described cutter side and restrained at axial and circumferential, and obviously, this structure can be subject to the impact of foregoing gravity and cause the pore-forming circularity over tolerance.
A kind of old-fashioned macropore fine boring cutter is illustrated among Fig. 3 and Fig. 4, this cutter only has a cutter head 3, it is locked in cutter side that cutter hub 2 is held out against screw 8 by one, lost unsteady ability than the fine boring cutter of above-mentioned standard, thereby overcome the problem of the circularity over tolerance that causes because floating according to Action of Gravity Field.Yet in this structure, the radial component of cutting force can only all be born by boring bar.Overhanging of boring bar is longer, can produce the deflection of nature, can therefore produce equally the problem of pore-forming circularity over tolerance, and cylindricity also can variation.
China CN201906844U has provided a kind of by improving the scheme of cutter supporting condition, taper shank outer end in being installed on the boring spindle taper hole, be provided with one heart its external diameter can be deeply by in the boring hole and external diameter approach by the cutterhead of boring hole inwall, boring cutter is installed in the cutter groove of cutterhead outer face.This structure is the length by the covert reduction boring cutter self of the size that increases the boring cutter mounting structure, improves the rigidity of boring cutter.Yet the distortion of boring cutter under this condition does not change the impact of circularity, and reason is, it is stressed basically identical except additional gravity is in each position in hole for boring cutter, can be therefore and elimination on the impact of pore-forming circularity.And can increase the distortion of boring bar because of extra heavy burden, further aggravate the problem of circularity over tolerance.
Summary of the invention
The present invention proposes further to improve on the basis of existing floating boring tool, thereby, the object of the invention is to propose a kind of macropore fine boring apparatus that can guarantee preferably hole circularity.
In order to realize goal of the invention of the present invention, the technical scheme that adopts is:
A kind of macropore fine boring apparatus, comprise that radial floating is positioned the fine boring cutter of boring bar cutter side, also comprise the force application part that acts on described fine boring cutter and make fine boring cutter compression cutter side spigot surface, thus the gravity that the frictional force between fine boring cutter and cutter side is subject to more than or equal to fine boring cutter.
According to said structure, adopt the mode of gravitational equilibrium to solve the boring cutter self gravitation to the impact of machining accuracy, show the impact on circularity that therefore causes as described in the background section.Obviously, this structure has advantages of common floating boring tool, simultaneously, because the gravity that boring cutter is subject to will be much smaller than cutting force, be fixed on version on the boring bar than boring cutter, the deflection that therefore boring bar produces is very little, can ignore the impact of machining accuracy.Therefore, can guarantee well the circularity of hole according to said structure of the present invention.
Above-mentioned macropore fine boring apparatus, described force application part are the second tension spring that an end is connected in described fine boring cutter, and the other end of this second tension spring is restrained.
Above-mentioned macropore fine boring apparatus, described the second tension spring circumferentially is arranged in boring bar one side, and its two ends are corresponding to be connected on the upper fine boring cutter that stretches out from two ends, cutter side symmetrically.
Above-mentioned macropore fine boring apparatus, described the second tension spring is connected on the described fine boring cutter by the movable joint screw.
Above-mentioned macropore fine boring apparatus also comprises self contering structure, and this self contering structure comprises and is arranged in symmetrically fine boring cutter two cutter side's external parts with the second tension spring of centripetal tension fine boring cutter.
Above-mentioned macropore fine boring apparatus, the second tension spring is provided with two at the every end left and right symmetrically of fine boring cutter cutter side external part.
The specific embodiment
Illustrate that accompanying drawing 1 to 8 is the structural representation of illustrative macropore fine boring cutter, but do not consist of limitations on claims, adopted simplified painting among the figure, only be used for clear the expression, do not represent the processing structure of actual products.
The term name of selecting in the description of example may comprise specific structure or characteristic, but only with the technical conditions that are expressed in example, should not consist of restriction to the technical scheme that the present invention requires.
As Tool Design, at first, must find a kind of structural shape of the best; Secondly, reasonably select material and the angle of cutter; At last, constantly perfect in practice.Only in this way just can design qualified, gratifying cutter, the macropore fine boring cutter also is like this.
1. the structure of general fine boring cutter
Fine boring tool used more than 60 year in the lathe manufacturing, had formed national standard.
As illustrated in fig. 1 and 2, fine boring cutter, namely cutter hub 2 consists of with the cutter head 3 that is fixed on the overhanging end of cutter hub and additional adjustment member among the figure, version belongs to adjustable structure, in the dependence, relatively moving of lower right boring cutter hub adjusted the size of hole dimension in the actual processing, fine boring cutter can radially slide in boring bar 1 cutter side (cutter side surface accuracy IT7), double cutting edge is radial symmetric structure, can form the effect of symmetrical extruding, thereby, so that the balance of the radial component of cutting force, be suitable for the processing request of surface roughness Ra=0.8 μ m endoporus, the dimensional accuracy of endoporus can be controlled at the H6 level.
Embodiments of the invention all keep the basic floating structure of floating boring tool shown in attached Fig. 1 and 2, satisfy the balance of the radial component of cutting force.
2. the structure of old-fashioned macropore fine boring cutter
As previously mentioned, the macropore fine boring cutter structural difference that can see on the market at home is little, shown in Fig. 3 and 4, the fine boring tool of this structure is a kind of cutter of present more use, and the background technology part is relatively clearly described, such cutter can only carry out the endoporus processing of general precision, and surface roughness does not reach the specification requirement of drawing.In order to overcome the sagging factor that causes that endoporus is not round of fine boring cutter deadweight, fine boring cutter and boring bar 1 adopt the wide boss radial location of 6mm, hold out against the structure that screw 8 holds out against the right boring cutter hub, owing to can not floating of boring cutter, also adopt the boring of hilted broadsword sword, do not had the effect of symmetrical extruding.So, the boring of hilted broadsword sword is only suitable in the processing request of surface roughness Ra 〉=3.2 μ m endoporus, the mobile radial feed of realizing in the elongated slot of cutter head 3 on cutter hub 2, realize fine setting by adjusting screw 7, adjust the left and right screw thread that two kinds of pitch are arranged on the screw 7, pitch is 1.25 and 1, and the differential pitch that obtains like this is 0.25mm, adjust screw 7 and whenever turn around, cutter head 3 advances or retreats 0.25mm.The radially adjustment of fine boring cutter is also similar, usually also all is to adjust by being similar to the version of adjusting screw 7.
As previously mentioned, old-fashioned macropore fine boring cutter shown in Fig. 3 and Fig. 4 is the boring of hilted broadsword sword, can not reach the endoporus processing request of surface roughness Ra=0.8 μ m, therefore, all adopt the floating boring tool structure according to embodiments of the invention, as shown in Figure 5 and Figure 6, adopt the double-sided blade structure can form the effect of symmetrical extruding.
Referring to Figure of description 5, in the upper and lower bilateral symmetry of fine boring cutter four tension springs 9 have been installed, rely on screw 10 and pulling block 11 centripetal tension fine boring cutters, can make fine boring cutter be in the centering position of balance.
9 one-tenth whole left-right symmetry of four tension springs and symmetrical structure up and down can make boring cutter obtain reasonable stress.
The mode that adopts latch to be connected between pulling block 11 and the fine boring cutter can be used as long as bearing pin inserts pin-and-hole, and mounting or dismounting conveniently.
Said latch connects, as shown in Figure 7, performance more clearly, screw 10 be a kind of head end with the screw of pin-and-hole, the connecting portion of tension spring 9 can directly insert pin-and-hole.This screw can be called the movable joint screw.Eyelet bolt/nail refers generally to GB 798 eyebolt/nails and moral mark (DIN) 444 eyebolt/nails.Certainly, in this programme, the head of screw is mainly used in the connection of tension spring, therefore, be not limited to the movable joint screw here, what it will be apparent to those skilled in that knows, the tension spring connecting portion mostly is hook/ring portion, obviously, bolt/ailhead can form a limiting section, above tension spring can hang over.
Round in order to eliminate the sagging boring aperture that causes of fine boring cutter deadweight, the phenomenon of circularity over tolerance has adopted tension spring 12 to strain the version of fine boring cutters in the example in other words.In Fig. 6, tension spring 12 axially is configured in boring bar one side, and two ends are connected on the fine boring cutter by screw 13, applies a quantitative frictional force between the cutter side of fine boring cutter and boring bar, can offset the part weight of fine boring cutter.The specific design step is as follows:
For national standard φ 310mm fine boring cutter, can not produce the not round phenomenon in boring aperture, by practice, φ 340mm fine boring cutter can not produce above-mentioned situation yet, and the appearance and size of fine boring cutter is 30x60x340, and material is 45#, YG8.
Volume V
1=30x60x340=0.000614 (m
3)
Weight G
1=γ V=7.8x 0.000614=4.8 (kg)
Hence one can see that, and floating boring is safe under the deadweight of 4.79kg.
Fine boring cutter weight in the example is illustrated in figure 8 as the force diagram of fine boring cutter.
Cutting data: cutting speed V=30m/min, amount of feeding f=2mm, boring depth d=0.125mm, mechanical efficiency η=0.8 is to the boring drag Ks=130kg/mm of cast iron HT250
2, so, boring power P=2d f V Ks/(60x 102x η)
=2x0.125x2x30x130/(60x102x0.8)=?0.4(kw),
Boring rotation speed n=1000x60xV/(3.14xD)=1000x60x30/(3.14x750)=764 (r/min)
Boring torque M=9.55x10
6P/n=9.55x10
6X0.4/764=5 x 10
3(N.mm)
Fine boring cutter acts on normal pressure F=M/d on the boring bar=5 x 10
3/ 270=19 (N)
Fine boring cutter acts on the boring force F on the workpiece
1=M/d
1=5 x 10
3/ 750=6.7 (N)
For 30x60 cutter side: shear strength τ=F/S=19/(30x60)=0.011 (MPa)
So the cutting output of fine boring cutter is little, resistance to cutting is low, adopts 50x80 side only to gain in weight, intensity, rigidity surplus, and the appearance and size of Novel precise boring cutter is 30x60x750, material is 45#, YG8,
Volume V=30x60x750=0.00135 (m
3)
Weight G=γ V=7.8x 0.00135=10.5 (kg)
As shown in Figure 8, go out 8-φ 30 lightening cores at the right boring cutter hub,
Volume V
1=3.14x30
2/ 4x30 x8=0.00017 (m
3)
Weight G
1=γ V=7.8x 0.0017=1.3 (kg)
Fine boring cutter weight becomes G-G
1=9.2kg.
Below be the method that fine boring cutter is eliminated deadweight:
Because the fine boring cutter deadweight is 9.2kg, and floating boring is safe under the deadweight of 4.8kg, the frictional resistance that also just must produce 4.4kg overcomes, so no matter fine boring cutter be in vertically, level or any position, the pressure that fine boring cutter imposes on inner hole of workpiece can greater than 4.8kg, not guarantee the security of floating boring.Designed an additional force at this, made cutter side's part of boring cutter and boring bar have the frictional force of 4.4kg.
We know, the material of boring cutter and boring bar is 45#, 40Cr, belong to the steel to steel contact, in the situation that oil lubrication is arranged, confficient of static friction is μ=0.11.
∵ frictional force f=μ N
∴ additional force N=f/ μ=4.4/0.11=40 (kg)
Adopt standard component Q81-3 cylinder tension spring, select the specification of d=3, D=16,
When t2=4.3, pulling force P2=42.7kg.This moment, pulling force satisfied instructions for use, can the balance fine boring cutter impact of deadweight.
In an example, the method for Novel precise boring cutter self-balancing:
Adopt standard component Q81-3 cylinder tension spring, select the specification of d=2, D=16,
When t2=3.5, pulling force P2=10kg,
This moment, pulling force satisfied instructions for use, the pulling force of upper and lower tension spring is about 20kg, the fine boring cutter deadweight is 9.2kg, because the pulling force of spring is greater than more than 2 times of fine boring cutter deadweight, this moment, spring oscillator made the situation of stressed effect from without spring the time fully different, the factor of the gravity sag of fine boring cutter is weakened, and no matter any orientation has realized the automatic centering of fine boring cutter under the effect of spring force.As can be seen from Figure 5, in order to make fine boring cutter be in the position of automatic centering, can adjust the depth position of screw, need when using for the first time repeatedly to adjust, in case centering is just with screw locking (such as gluing or tight fit) no longer dismounting on boring bar, 4 tension springs 9 are fixed on no longer dismounting on the screw simultaneously, have so just guaranteed the position of the long-term automatic centering of using of fine boring cutter.
Form about the frictional force between fine boring cutter and cutter side, we know that there are four faces cutter side, just can satisfy this requirement when one of them face of fine boring cutter and cutter side or two faces produce friction in theory, and select to have arbitrariness.Simultaneously, the generation of frictional force need to have the normal pressure of the respective face of acting on.Thereby as can be known, the force application part that produces this normal pressure selects to have the larger free degree.
Can configure so in an example, boring bar compression axially is set or tension spring acts on described fine boring cutter and can obtain needed frictional force.This moment, tension spring can be arranged on the outside of boring bar, certainly, because boring bar is hollow, also can be arranged on boring bar inside.