# Error of machining fixed position is analysed (on)

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(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