Error of machining fixed position is analysed (on)

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The place before be like is narrated, to assure the treatment precision of workpiece, before workpiece is machined, must locate correctly. Alleged and correct fixed position, except should restrict necessary freedom to spend, correctly option fixed position is standard with fixed position component besides, the error limits less than that the error that still should make the orientation way place of the choice arises allows in workpiece. This section is the fixed position error that mensurable analytic computation locates means place arises namely, in order to decide whether the orientation way of a choice is logical. The element that workpiece machining error causes when use clamping apparatus includes 4 following fields: (1) the error that concerns in the fixed position on clamping apparatus with workpiece, call D of Δ of fixed position error; (2) the error that concerns in the installation on the machine tool with clamping apparatus, call A of mounting error Δ ; (3) the error that concerns with component of clamping apparatus fixed position with cutting tool, call adjust error Δ T; (4) the error that concerns with treatment process, call G of process error Δ . Include machine tool and cutting tool error among them, be out of shape sum of errors measures an error to wait. To make sure the treatment of workpiece asks, the K of δ of treatment public errand that workpiece should not exceed after afore-mentioned errors are synthesized, namely this section of   of K of δ of ≤ of G of Δ of T + of Δ of A + of Δ of D + of     Δ is analysed first locate in clamping apparatus with workpiece concerned error, the content that locates the error is concerned namely. What cause by fixed position is same the design that approves work is standard on treatment dimension direction most upheaval quantity, call fixed position error. When K of δ of 1/3 of ≤ of D of Δ of fixed position error, think the orientation way of make choice of is feasible commonly. One, the cause that the account that fixed position error produces and computation cause fixed position error has two: Because fixed position is standard,one is as fiducial as the design not coincide, call fiducial not coincide error (fiducial not agree with error) ; 2 because locate,be deputy production error and cause the displacement with standard fixed position, call fiducial displacement error. (one) fiducial not because fixed position is standard,coincide error reachs computation as fiducial as the design not coincide and the fixed position error that cause is called fiducial not coincide error, will express with Δ B. Graph 3 -61a is shown for spare parts diagram, in breach of the mill on workpiece, treatment dimension is A, B. Graph 3-61b is treatment sketch map, workpiece locates with underside and E face, c is affirmatory cutting tool and clamping apparatus pair of knife dimension of mutual position, the position of the in machining a process C in a batch of workpiece is changeless. The design that machines dimension A is standard it is F, fixed position is standard it is E, both not coincide. Be in when one by one of a batch of workpiece on clamping apparatus when fixed position, suffer the effect of S /2 of δ of ± of dimension S, working procedure is standard the position of F is fluctuant, the size of the fluctuant influence A of F, cause an error to A, this error is fiducial not coincide error. Apparent and fiducial not the size of coincide error should be equal to fixed position fiducial as fiducial as the design not coincide and the machines dimension fluctuant range that create, by graph 3-61b knowable: S of   of   of S of δ of Δ B =A Max-A Min =S Max-S Min= is fixed position fiducial E and design are standard the space size between F. When the way that should devise standard fluctuant way and treatment measure is same, fiducial not coincide error is equal to fixed position fiducial as fiducial as the design a public errand of dimension, be like graph 3-61, it is δ S when the public errand of S, namely S of δ of B = of     Δ (3-2)   should design standard fluctuant way and treatment dimension direction to have one included angle (its included angle is β ) when, fiducial not coincide error is equal to fixed position fiducial what as fiducial as the design span is machining dimension direction to go up from dimension public errand is umbriferous, namely β of Cos of × of S of δ of B = of     Δ (3-3)   should locate fiducial as fiducial as the design between the combination that has a few relevant measure, should be the dimension public errand that connects related each on treatment dimension direction umbriferous take and, namely I of the δ in     type -- fixed position is standard as fiducial as working procedure between the public errand that dimension connects related each (Mm) ; β I -- the included angle between the direction of δ I and treatment dimension direction (0) . Type (3-4) it is fiducial not the general computation type of B of coincide error Δ .

(2) because fiducial displacement error and computation locate deputy production error and create fixed position of standard position fluctuant, add the error that is versed in dimension is caused to workpiece, call fiducial displacement error, the Y that use Δ will express. The orientation way that differs apparently and different fixed position deputy structure, its locate the computational method of standard mobile amount is different. Below, the computational method of the fiducial displacement error that analyses a few kinds of common orientation way generation: 1. The computation of fiducial displacement error when workpiece locates with plane with workpiece of   of planar fixed position is more convenient. When if pursue,the work that 3-61 place shows locates with plane, the position of fixed position tool reference plane can regard what do not change as, accordingly fiducial displacement error is 0, namely 2 of   of   of Y =0 of Δ of   of the   when workpiece locates with plane. Workpiece is sold in cylinder with round hole, workpiece of   of the fixed position on columnar arbor is sold in cylinder with round hole, the fixed position on columnar arbor, its fixed position is standard the central line that is aperture, fixed position tool reference plane is inside aperture surface. If graph 3-62 place is shown, because locate pair of influence that cooperates clearance, can make line of center of aperture of the circle on workpiece (fixed position is standard) positional happening deflection, what quantity of its center deflection is machining dimension direction to go up is umbriferous it is Y of Δ of fiducial displacement error namely. Locate the direction of fiducial deflection has two to plant likelihood: It is to be able to be on aleatoric direction deflection; 2 be can go up in some direction only deflection. Should locate fiducial when aleatoric direction deflection, its are the biggest the biggest gap that deflection quantity is direction of fixed position deputy diameter namely, namely Y =X Max=D Max of     Δ , D0 +X Min of δ of D + of δ of D 0min= (3-5) the X Max in   type -- fixed position deputy the biggest cooperate clearance (Mm) ; D Max -- work location hole is the largest diameter (Mm) ; D 0min -- cylinder is sold or the smallest diameter of columnar arbor (Mm) ; δ D -- the diametical public errand of work location aperture (Mm) ; δ D0 -- cylinder is sold or the diametical public errand of columnar arbor (Mm) ; X Min -- fixed position place requires the smallest clearance, by decide when the design (Mm) . When fiducial deflection is only way, in its shift direction quantity of the biggest deflection is the biggest gap of radius direction, namely Y = of     Δ (1/2) X Max= (1/2) (D Max-d 0min) = (1/2) (D +X Min of δ of δ D + )   (3-6) if   is fiducial when the direction of deflection and the direction that workpiece machines dimension are abhorrent, should measure fiducial deflection go up to treatment dimension direction umbriferous, umbriferous the fiducial displacement error that the value after just is this treatment dimension. When workpiece locates with columnar arbor, fixed position cooperates clearance deputily to still can make the axes of workpiece aperture happens askew, affect the positional precision of workpiece, if pursue,3-63 place is shown. Workpiece still has parallelism alignment error besides pitch public errand, namely the L 1 in type -- treatment face length (Mm) ; L 2 -- length of fixed position aperture (Mm)     (3) column is round beyond workpiece in V beyond workpiece of   of the fixed position on form piece columnar face in V when the fixed position on form piece, its fixed position is standard the axes line of columnar face outside be workpiece, face of the cylinder outside locating tool reference plane is. If not plan V form piece error, and when the appearance of only work datum plane and on size error, the fixed position of workpiece is standard can produce deflection, if pursue,place of 3 -64a, B is shown. By graph 3-64b knowable, only the influence of the D of δ of dimension public errand as a result of workpiece, make Z of work center edge to move from O 1 to O 2, be in namely Z to fiducial displacement quantity can be calculated by next type D of the δ in   type -- the diametical public errand of work location tool reference plane (Mm) ; α / 2 -- V form piece half horn (0) . The volume that displacement measures and outside public errand of columnar face diameter is concerned, accordingly to exacter location, need the round precision outside rising appropriately. V form piece good to neuter, along its so the displacement of X direction is 0. The V form that should use α =90 0 piece, fixed position is standard in Z to the treatment dimension direction that displacement quantity can be like workpiece by   of computation leaving type and Z way are same, the fiducial displacement error that goes up in treatment dimension direction is Y =O 1O 2=0 of     Δ .

D of 707 δ (3-10) if       has β of one included angle with Z on treatment dimension direction, the fiducial displacement error that goes up in treatment dimension direction is   (3) because the computational   of fixed position error locates error Δ D is by fiducial fiducial displacement error combines coincide sum of errors and do not become. Because this is when error of computational fixed position, part first B of cipher out Δ and Δ Y, get Δ D both combination next. Next circumstances can be like when combination: 1. 0 of ≠ of Δ Y, when Δ B =0, b of Δ of Δ D = (3-12)     2. Δ Y =0, ≠ of Δ B 0 when, y of Δ of Δ D = (3-13)     3. 0 of ≠ of Δ Y, ≠ of Δ B 0 when, if working procedure is standard,do not go up in fixed position tool reference plane: Y of Δ of B + of Δ of Δ D = (3-14)   if working procedure is standard go up in fixed position tool reference plane, y of Δ of ± of B of Δ of Δ D = (3-15)     " + " , " , " differentiate method is: Dimension of tool reference plane of ① analysis fixed position by big decrescent (or by small greaten) when, the fluctuant way with standard fixed position; When ② should locate dimension of tool reference plane makes similar change, establish fixed position fiducial do not move, analytic working procedure is fiducial and fluctuant direction; If ③ is both fluctuant way is same namely " + " , both and fluctuant way is opposite namely " , " . 2, the aperture of 10H7 of the φ on the spare parts that locates 3-1 of exemple of error computation example gets place of 3-65 of graph of bore with a reamer to show, workpiece locates with aperture, fixed position sells a diameter to beg: ± of 50 of working procedure dimension 0.

07mm reachs the fixed position error of parallelism. Solution: (1) ± of 50 of working procedure dimension 0.

The fixed position of B = 0mm(of 07mm is standard as fiducial as working procedure coincide)   presses type (3-5) : 0 + of D of δ of D + of δ of Δ Y = X Min =0.

021+0.

009+0.

007= 0.

037mm   criterion by type (3 - 12) Y = 0 of Δ of = of D of Δ of the   that get   .

  of 037mm   (2) parallelism 0.

The   of   of   of fixed position error of 04mm manages together,   of Δ B = 0mm presses type (3-7) : Criterion the fixed position error of parallelism is Y = 0 of Δ of D = of     Δ .

3-2 of exemple of 018mm   is shown like graph 3-66 place, with cant of milling of angle milling cutter, beg treatment dimension to be 39 ± 0.

The fixed position error of 04mm. Solution: Δ B = 0mm (fixed position is standard as fiducial as working procedure coincide)   presses type (3-11) Y =0 of Δ of the   that get   .

=0 of β of D Cos.

707 × 0.

04 × 0.

866= 0.

024mm   presses type (3-12) Y = 0 of Δ of D = of Δ of the   that get   .

024mm CNC Milling CNC Machining