CN111843618B - Large structural member window frame thickness machining error compensation method - Google Patents
Large structural member window frame thickness machining error compensation method Download PDFInfo
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- CN111843618B CN111843618B CN202010767279.1A CN202010767279A CN111843618B CN 111843618 B CN111843618 B CN 111843618B CN 202010767279 A CN202010767279 A CN 202010767279A CN 111843618 B CN111843618 B CN 111843618B
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Abstract
The invention discloses a large structural member window frame thickness processing error compensation method, which comprises the following steps: firstly, preprocessing a window position on a part, and processing the window position to half of the design size of the window; step two, measuring the thickness of the corresponding position of the periphery of the window frame, and calculating the thickness difference; thirdly, calculating an included angle before and after the part window is deformed by the numerical control machining center according to the thickness difference and the longitudinal height of the window; fourthly, the numerical control machining center calculates the cutting depth according to the included angle before and after deformation; and fifthly, automatically adjusting the feed track and the cutting depth of the cutter by the numerical control machining center, and machining the window frame. The method can process parts with various window thicknesses, can process windows with different thicknesses, and ensures that the machining size of the numerical control machine meets the design requirement. After the method is adopted, the qualified product rate of the numerical control machine is obviously increased, the production efficiency of large-scale structural members is improved, and the production cost is saved.
Description
Technical Field
The invention belongs to the technical field of aerospace precision numerical control machining, and particularly relates to a numerical control machining error compensation method for the thickness of a large structural member window frame.
Background
In the field of precision mechanical numerical control machining, the situation that a large structural part and a thin-wall part cannot be machined due to excessive deformation or the machining quality cannot meet the design requirements is often encountered. If the part deformation is too large, the part quality is unqualified and the part is scrapped, and the processing cost is increased.
The large-scale rotary thin-wall part is formed by splicing and welding three arc-shaped wall plates into a shell section, and welding an upper end frame and a lower end frame on the upper end face and the lower end face of the shell section respectively, wherein the whole part is provided with 3 longitudinal welding seams and 2 annular welding seams, and deformation is easily generated between the wall plates and between the circular shell section and the upper end frame and between the circular shell section and the lower end frame due to welding stress concentration under the action of welding stress. On the basis, the large-scale rotary thin-wall part is machined, a window is required to be opened at a position which is about 170mm away from the upper end frame, the thickness of the window peripheral opening frame is required to be accurately controlled, the thickness of the peripheral opening frame is required to be 2mm, the tolerance is controlled within 0.2mm, the inner wall and the outer wall of the part are not parallel due to large local deformation of the part after welding is completed, and therefore the thickness of the window peripheral opening frame is difficult to guarantee in the machining process, as shown in figure 1.
Aiming at the problem, the invention provides a numerical control machining error compensation method. According to the method, the thicknesses of the vertically symmetrical positions of the processed window frame are manually measured, the thickness difference is calculated, the thickness difference is input into a macro program, the numerical control machining center can automatically adjust the feed track according to the numerical control macro program, the cutting depths are different at different positions, and finally the local thickness size of the structural part is ensured to meet the design requirement.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a thickness processing error compensation method for a large structural member window frame.
The technical scheme adopted by the invention for solving the technical problems is as follows: a large-scale structural member window frame thickness machining error compensation method comprises the following steps:
firstly, preprocessing a window position on a part, and processing the window position to half of the design size of the window;
step two, measuring the thickness of the corresponding position of the periphery of the window frame, and calculating the thickness difference;
thirdly, calculating an included angle before and after the part window is deformed by the numerical control machining center according to the thickness difference and the longitudinal height of the window;
fourthly, the numerical control machining center calculates the cutting depth according to the included angle before and after deformation;
and fifthly, automatically adjusting the feed track and the cutting depth of the cutter by the numerical control machining center, and machining the window frame.
Compared with the prior art, the invention has the following positive effects:
the invention belongs to the field of precise numerical control machining, and is used for numerical control machining of a large structural member of a certain product in the aerospace industry. Because the part is a welding part and is formed by welding three wall plates and front and rear end frames, the part has larger deformation under the action of welding stress, and because the size of the design requirement is strict and the tolerance range is small, the part brings great difficulty to a numerical control machine, and the numerical control machine frequently adds and causes unqualified products. The method utilizes the advantages of a five-axis numerical control machine tool, firstly measures the thickness difference delta = delta 1-delta 2 of the symmetrical position of the window, then calculates the included angle theta = arctan (delta/h) of the deformed window and the normal window according to the height h of the window and the thickness difference delta, calculates the cutting depth delta s of each position of the window according to the value of the included angle theta, and automatically adjusts the feed path of the cutter after calculating the cutting depth of each point so as to carry out numerical control processing.
The method can process parts with various window thicknesses, can process windows with different thicknesses, and ensures that the machining size of the numerical control machine meets the design requirement. After the method is adopted, the qualified product rate of the numerical control machine is obviously increased, the production efficiency of large-scale structural members is improved, and the production cost is saved.
Drawings
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic illustration of a shell segment with non-parallel inner and outer walls due to deformation;
FIG. 2 is a schematic diagram of the angle θ caused by the non-parallel inner and outer walls;
FIG. 3 is a schematic view of a milling window cutting depth change point location;
fig. 4 is a schematic diagram of the window milling tool operation.
Detailed Description
The embodiment of the invention provides a method for processing the peripheral thickness of a window of a large-sized rotary thin-wall part.
The involved key entities mainly comprise three parts: numerical control machining center (macro procedure), cutter, work piece.
The technical principle is as follows: according to the thickness values (delta 1 and delta 2) of two symmetrical positions of the peripheral opening frame of the measuring window and the longitudinal distance (h) of the window, according to the calculation formula of the included angle: and theta = arctan (delta/h), calculating an included angle between the actual position and the theoretical position of the inner wall and the outer wall at the outlet frame by the numerical control macro program, adjusting the cutting depth according to the calculated theta value, and processing the circumferential thickness of the whole window, as shown in fig. 1 and 2.
The points at which the cutting depth needs to be adjusted are 10 points in total. As shown in fig. 3.
The size of the inner frame of the window is as follows: 2x1 x 2y1, outer frame dimensions 2x 2x 2y2, the coordinates of the points of the outer frame at the chamfer tangents are equal to the inner frame coordinate values, for example: the vertical coordinate y1 of the points is equal to the height from the datum line of the inner frame to the upper edge; the horizontal coordinate values of the point (v) and the point (i) are x1, the distance from the datum line to the left edge of the inner frame is equal, and the like. The coordinate values of each point are as follows:
(iii) point coordinate values (x 2, 0), the (v) point coordinate values (-x 2, 0),
fourthly, point coordinate values (x 2, y 1) and seventh point coordinate values (-x 2, y 1),
point coordinate values (x 1, y 2), point coordinate values (-x 1, y 2),
ninthly point coordinate values (-x 2, -y 1), and (x 2, -y 1),
the r point coordinate values (-x 1, -y 2), the r point coordinate values (x 1, -y 2).
The depth of cut is set to be as,
(iv) points and (iv) points of depth of cut Δ s1= y1 tan θ,
the cutting depth of points (v) and (v) is Δ s2= y2 tan θ,
the cutting depths Δ s3= -y1 × tan θ at the ninthly and the ② points,
depth of cut Δ s4= -y 2= tan θ at points r and r.
The tool performs a cutting operation based on a feed path set by the θ value in the numerical control macro program, as shown in fig. 4.
The working principle is as follows:
the method comprises the following steps: firstly, preprocessing the position of a window on a part, processing the position to half of the design size of the window, measuring the thickness of the corresponding position on the periphery of a window frame, and calculating the thickness difference.
Step two: and inputting the thickness difference into a numerical control macro program, and automatically adjusting the feed track and the cutting depth by a numerical control machining center to machine the window frame.
The principle is as follows: the numerical control machining center calculates an included angle theta before and after the part window is deformed according to the thickness difference delta and the longitudinal height h of the window,
calculating the formula: θ = arctan (Δ δ/h) (formula one);
and the numerical control machining center calculates the cutting depth by using a formula II according to the included angle theta: Δ s = y tan θ (formula two);
and the numerical control cutter automatically adjusts the cutting depth according to the calculation result, so that the part is adaptively processed, and the processing quality requirement is finally met.
The processing flow of the peripheral thickness dimension of the mouth frame is as follows:
in order to ensure that the excessive cutting is not carried out, the cutting depth of each feed is as small as possible, so that a ball-end cutter with the diameter phi 4 is selected as a cutter. In order to make the milled window frame smoothly transit, a feed method of milling along the circumferential direction of the window edge is selected. According to the calculation results of the first formula and the second formula, the cutter starts cutting from the point I, the cutting depth is delta s4, the cutter starts cutting to the point II, the cutter smoothly transitions to the point II, the cutter deepens cutting gradually in the process of round corner milling, and the cutting depth delta s3 reaches the point II. From the point II to the point III to the point IV, the cutting tool still deepens cutting, and the cutting depth reaches delta s1 when the cutting tool reaches the point IV. From the fourth point to the fifth point, the cutter is in smooth transition, the cutting depth is still increased, the cutting depth when reaching the fifth point is delta s2, the cutting depth is unchanged from the fifth point to the sixth point, the cutting depth gradually becomes shallow from the sixth point to the seventh point, when reaching the seventh point, the cutting depth is recovered to delta s1, when reaching the seventh point, the cutting depth gradually becomes shallow from the seventh point to the eighth point, the cutting depth is equal to the cutting depth of the seventh point and is recovered to delta s3, when reaching the seventh point, the cutter is in smooth transition, the cutting depth is still reduced, when reaching the third point, the cutting depth is changed to delta s4, and when reaching the fifth point, the cutting depth is unchanged, so far, the cutter finishes cutting for one circle of the window frame. And calculating the time required by the macro program to run according to the difference between the designed thickness dimension and the actual thickness, namely the machining allowance to be removed until the cutting is finished, wherein the thickness dimension meets the requirement.
Claims (3)
1. A large-scale structural member window frame thickness machining error compensation method is characterized by comprising the following steps: the method comprises the following steps:
firstly, preprocessing a large structural member window position to be processed to half of the design size of the window;
step two, measuring the thickness of the corresponding position of the periphery of the window frame, and calculating the thickness difference;
step three, calculating an included angle theta = arctan (delta/h) before and after the window of the large structural member is deformed by the numerical control machining center according to the thickness difference and the longitudinal height of the window, wherein delta is the thickness difference of two symmetrical positions of a peripheral opening frame of the window, and h is the longitudinal distance of the window;
fourthly, the numerical control machining center calculates the cutting depth according to the included angle before and after deformation;
step five, automatically adjusting the feed track and the cutting depth of the cutter by the numerical control machining center, and machining the window frame, wherein:
(1) the feed track is that cutting is finished for one circle of the window frame from the first point, sequentially passes through the second point to the tenth point and then passes through the tenth point to the first point; wherein, each point coordinate value is as follows:
a third point coordinate value (x 2, 0), an eighth point coordinate value (-x 2, 0),
a fourth point coordinate value (x 2, y 1), a seventh point coordinate value (-x 2, y 1),
a fifth point coordinate value (x 1, y 2), a sixth point coordinate value (-x 1, y 2),
a ninth point coordinate value (-x 2, -y 1), a second point coordinate value (x 2, -y 1),
a tenth point coordinate value (-x 1, -y 2), a first point coordinate value (x 1, -y 2);
wherein: the size of the window inner frame is 2x1 x 2y1, and the size of the window outer frame is 2x 2x 2y 2;
(2) the cutting depth of each point is as follows:
the depth of cut as 1= y1 tan theta at the fourth and seventh points,
the depth of cut as 2= y2 tan theta at the fifth and sixth points,
the cutting depths as 3= -y 1= tan θ of the ninth point and the second point,
the depth of cut deltas 4= -y 2x tan theta at the tenth point and the first point,
the depth of cut at the third point and the eighth point was 0.
2. The large structural member window frame thickness machining error compensation method according to claim 1, characterized in that: the cutting process of one circle of the window frame comprises the following steps:
the cutter starts cutting from a first point, the cutting depth is delta s4, the cutter starts to feed to a second point, the cutter smoothly transits to the second point, the cutter gradually deepens cutting in the process of fillet milling, and the cutting depth delta s3 is reached to the second point; from the second point to the third point and then to the fourth point, the cutter still deepens cutting, and the cutting depth reaches delta s1 when reaching the fourth point; the tool smoothly transits from the fourth point to the fifth point, the cutting depth is still increased, the cutting depth when reaching the fifth point is Δ s2, the cutting depth is unchanged from the fifth point to the sixth point, the cutting depth gradually becomes shallow from the sixth point to the seventh point, the cutting depth returns to Δ s1 when reaching the seventh point, the cutting depth gradually becomes shallow from the seventh point to the eighth point and further to the ninth point, the cutting depth is equal to the cutting depth of the second point when reaching the ninth point and returns to Δ s3, the cutting depth is still decreased from the ninth point to the tenth point, the cutting depth becomes Δ s4 when reaching the tenth point, and the cutting depth is unchanged from the tenth point to the first point, so that the tool finishes cutting a round of the window frame.
3. The large structural member window frame thickness machining error compensation method according to claim 1, characterized in that: the tool is a spherical head tool with the diameter phi 4, and a feed method of circumferential milling along the edge of the window is adopted to ensure smooth transition of the milled window frame.
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| US5678964A (en) * | 1995-08-10 | 1997-10-21 | Dashevsky; Leon G. | Method of determining slide straightness and for providing a straight reference surface for a machine tool |
| CN102430765A (en) * | 2011-10-28 | 2012-05-02 | 湖北三江航天险峰电子信息有限公司 | Self-adaptive compensation method for detecting turning error of large part of rotary body |
| CN104759942A (en) * | 2015-04-22 | 2015-07-08 | 华中科技大学 | Online milling deformation measurement and complementation machining method for thin-walled part |
| CN107511516A (en) * | 2017-07-26 | 2017-12-26 | 北京理工大学 | A kind of prediction and compensation method of micro-groove machining deformation error |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US5678964A (en) * | 1995-08-10 | 1997-10-21 | Dashevsky; Leon G. | Method of determining slide straightness and for providing a straight reference surface for a machine tool |
| CN102430765A (en) * | 2011-10-28 | 2012-05-02 | 湖北三江航天险峰电子信息有限公司 | Self-adaptive compensation method for detecting turning error of large part of rotary body |
| CN104759942A (en) * | 2015-04-22 | 2015-07-08 | 华中科技大学 | Online milling deformation measurement and complementation machining method for thin-walled part |
| CN107511516A (en) * | 2017-07-26 | 2017-12-26 | 北京理工大学 | A kind of prediction and compensation method of micro-groove machining deformation error |
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