Machining method for deep and narrow grooves on aluminum-magnesium casing

Abstract

This invention discloses a method for machining deep and narrow grooves on an aluminum-magnesium casing. First, a pre-drilling process is performed within the waist-shaped groove using a drill bit of the same width as the groove. This removes most of the excess material, significantly reducing the subsequent milling allowance, improving machining efficiency, and facilitating chip removal during milling. This avoids chip breakage due to poor chip removal and dimensional deviations caused by tool sticking. Then, a variable-speed, half-circle, stepped layer milling method is used to machine to the designed dimensions. High feed rates are used on straight sections to greatly improve machining efficiency, while low feed rates are used on smooth transition sections to prevent tool breakage. The subsequent milling operation incorporates a small portion of the allowance from the previous milling of the sidewall, effectively finishing the first layer of sidewalls while significantly reducing the number of layer milling marks. Compared to existing layer milling methods, this method ensures the groove width, meets the groove wall roughness requirements, and greatly improves machining efficiency.

Description

Technical Field

[0001] This invention relates to the field of machining technology, and in particular, to a method for machining deep and narrow grooves on an aluminum-magnesium casing. Background Technology

[0002] Currently, aluminum-magnesium alloy casings for aero engines are readily machinable, allowing for the fabrication of numerous gas / oil passages. To maximize the capacity of some oil passage outlets, a slotted structure is frequently employed. For example, the slotted structure... Figure 1 As shown, due to the complex distribution of air / oil passages on the casing, there are deep and narrow waist-shaped grooves. The width of these grooves ranges from 3mm to 5mm, and the depth ranges from 20mm to 100mm. Currently, the common machining method is to use a small milling cutter with the same width as the waist-shaped groove for layer milling. However, due to the small cutter diameter, long cutting edge, and the narrow and deep waist-shaped groove, chip removal is poor, easily leading to tool breakage. Furthermore, this results in poor tool rigidity, causing tool deflection and vibration during layer milling. The tool marks in each layer are quite obvious and deep, leading to non-compliant groove width dimensions and insufficient surface roughness. In addition, because the layer milling path for waist-shaped grooves has corner characteristics, the machining speed cannot be too high to ensure machining accuracy at the corners. Moreover, the poor chip removal within the waist-shaped groove makes it difficult to increase the machining speed. Therefore, the current layer milling method for waist-shaped grooves has low machining efficiency. Summary of the Invention

[0003] This invention provides a method for machining deep and narrow grooves on aluminum-magnesium casings, which solves the technical problems of easy tool breakage, poor machining quality, and low machining efficiency in the existing method of machining waist-shaped grooves on aluminum-magnesium casings using small milling cutters of equal width for layer milling.

[0004] According to one aspect of the present invention, a method for machining deep and narrow grooves on an aluminum-magnesium casing is provided, comprising the following:

[0005] Pre-drill holes in the waist-shaped groove using a drill bit with a diameter equal to the groove width;

[0006] The milling process is carried out using a variable speed half-circle stepped layer milling method to achieve the design dimensions, and the diameter of the milling cutter is smaller than the width of the waist-shaped groove.

[0007] Furthermore, the number of pre-drilled holes is calculated based on the following formula:

[0008] n = [L / D]

[0009] Where [] represents rounding, n represents the number of pre-drilled holes, L represents the longest length of the waist-shaped groove, and D represents the groove width.

[0010] Furthermore, multiple pre-drilled holes are distributed at equal intervals from both sides of the waist-shaped groove toward the middle.

[0011] Furthermore, the process of machining to the design dimensions using the variable speed half-circle stepped layer milling method specifically involves:

[0012] Starting from the transition point between the smooth transition section and the straight section, the milling cutter descends directly without lifting the cutter after completing the first half-circle contour and completes the second half-circle contour. The first half-circle contour includes a straight section and a smooth transition section, and the second half-circle contour includes another straight section and another smooth transition section. The feed rate of the milling cutter in the straight section is greater than the feed rate in the smooth transition section. The milling cutter continuously performs half-circle step-like layer milling. When the last layer is reached, the milling cutter moves around the contour of the waist-shaped groove to process the waist-shaped groove to the design size.

[0013] Furthermore, during the semi-circular stepped layer milling process:

[0014] The area removed during the first milling operation is (A×d+πD) 2 / 8+πd 2 / 8)×C;

[0015] The area removed by the second milling is the sum of the remaining area in the first layer and the area removed by the second milling. The remaining area in the first layer is [A×(Dd)+πD]. 2 / 8-πd 2 / 8)×C, the second layer of milling removal area is (A×d+πD) 2 / 8+πd 2 / 8)×C;

[0016] The area removed by the third milling is the sum of the remaining area in the second layer and the area removed by the third milling. The remaining area in the second layer is [A×(Dd)+πD]. 2 / 8-πd 2 / 8)×C, the third layer milling removal area is (A×d+πD) 2 / 8+πd 2 / 8)×C;

[0017] The area removed by the Nth milling is the sum of the remaining area of ​​the (N-1)th layer and the area removed by the Nth layer milling, where the remaining area of ​​the (N-1)th layer is [A×(Dd)+πD]. 2 / 8-πd 2 / 8)×C, the milling removal area of ​​the Nth layer is (A×D+πD) 2 / 4)×C;

[0018] Where A represents the length of the straight segment, D represents the groove width, d represents the diameter of the milling cutter, and C represents the depth of cut per layer.

[0019] Furthermore, the ratio of the feed rate of the end mill in the straight section to the feed rate in the smooth transition section is between 3 and 8.

[0020] Furthermore, the ratio of the feed rate of the end mill in the straight section to the feed rate in the smooth transition section is between 7 and 8.

[0021] Furthermore, the ratio of the end mill's diameter to the slot width is between 0.6 and 0.9.

[0022] Furthermore, the ratio of the end mill's diameter to the slot width is between 0.8 and 0.9.

[0023] Furthermore, the pre-drilling process employs a pecking drill method.

[0024] The present invention has the following effects:

[0025] The present invention discloses a method for machining deep and narrow slots on aluminum-magnesium casings. First, a pre-drilling hole is made in the slot using a drill bit with a diameter equal to the slot width. This drilling removes most of the allowance, significantly reducing the allowance for subsequent milling and improving machining efficiency. Furthermore, the drilled hole facilitates chip removal during milling, preventing cutter breakage due to poor chip removal and dimensional deviations caused by tool sticking. Then, a variable-speed, half-circle, stepped layer milling method is used to machine to the designed dimensions. A high feed rate is used on straight sections, greatly improving machining efficiency, while a low feed rate is used on smooth transition sections to prevent tool breakage. Moreover, the subsequent milling operation includes a small portion of the allowance from the previous milling of the sidewall, effectively finishing the first layer of sidewalls while significantly reducing the number of layer milling marks. Compared to existing layer milling methods using a cutter with a diameter equal to the slot width, this method ensures the slot width, meets the required surface roughness, and greatly improves machining efficiency.

[0026] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 This is a schematic diagram of the dimensions of the waist-shaped groove structure.

[0029] Figure 2 This is a schematic flowchart of a preferred embodiment of the present invention for processing deep and narrow grooves on an aluminum-magnesium casing.

[0030] Figure 3 This is a schematic diagram of pre-drilling holes in a waist-shaped groove in a preferred embodiment of the present invention.

[0031] Figure 4This is a schematic diagram of a milling cycle of the entire contour of the waist-shaped groove in a preferred embodiment of the present invention.

[0032] Figure 5 This is a schematic diagram of a semi-circular stepped layer milling process in a preferred embodiment of the present invention. Detailed Implementation

[0033] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0034] like Figure 2 As shown, a preferred embodiment of the present invention provides a method for machining deep and narrow grooves on an aluminum-magnesium casing, including the following:

[0035] Step S1: Use a drill bit with a diameter equal to the width of the groove to pre-drill holes in the waist-shaped groove;

[0036] Step S2: Use a variable speed half-circle step milling method to process to the design size, and the diameter of the milling cutter is smaller than the width of the waist-shaped groove.

[0037] It is understood that the machining method for the deep and narrow grooves on the aluminum-magnesium casing in this embodiment first uses a drill bit with a diameter equal to the groove width to pre-drill holes in the waist-shaped groove. Drilling removes most of the excess material, significantly reducing the allowance for subsequent milling, which improves machining efficiency. Furthermore, the drilled holes facilitate chip removal during milling, preventing cutter breakage due to poor chip removal and dimensional deviations caused by tool sticking. Then, a variable-speed, half-circle, stepped layer milling method is used to machine to the design dimensions. High feed rates are used on straight sections, greatly improving machining efficiency, while low feed rates are used on smooth transition sections to prevent tool breakage. Moreover, each subsequent milling operation includes a small portion of the allowance from the previous milling of the sidewall, effectively finishing the first layer of sidewall while significantly reducing the number of layer milling marks. Compared to existing layer milling methods using a cutter with a diameter equal to the groove width, this method ensures the groove width, meets the groove wall roughness requirements, and greatly improves machining efficiency.

[0038] It is understood that in step S1, a set of through holes are pre-drilled in the waist-shaped groove using a pecking drilling method to ensure the machining accuracy of the through holes. Furthermore, given the characteristics of the drill bit's machining as a full-enclosure process, the number of pre-drilled holes is calculated based on the groove length and width. Preferably, the number of pre-drilled holes is calculated using the following formula:

[0039] n = [L / D]

[0040] Where [] denotes rounding, n represents the number of pre-drilled holes, L represents the longest length of the waist-shaped groove, and D represents the groove width. Furthermore, as... Figure 3As shown, the points of multiple pre-drilled holes are distributed at equal distances from both sides of the waist-shaped groove toward the middle. That is, a through hole is drilled on each of the smooth transition sections on both sides of the waist-shaped groove, and then the remaining through holes are evenly distributed between the two through holes on the left and right. This ensures that the residual part is uniform, the depth of cut is regular during subsequent milling, and the milling process is more stable. At the same time, the holes on the left and right sides can also prevent the milling cutter from being fully stressed at the cutting point during the step-type layer milling process with variable speed half-turn, which could lead to tool breakage. This prepares for subsequent layer milling without lifting the tool.

[0041] It can be understood that the process of machining to the design dimensions using the variable speed half-circle stepped layer milling method specifically involves:

[0042] Starting from the transition point between the smooth transition section and the straight section, the milling cutter descends directly without lifting the cutter after completing the first half-circle contour and completes the second half-circle contour. The first half-circle contour includes a straight section and a smooth transition section, and the second half-circle contour includes another straight section and another smooth transition section. The feed rate of the milling cutter in the straight section is greater than the feed rate in the smooth transition section. The milling cutter continuously performs half-circle step-like layer milling. When the last layer is reached, the milling cutter moves around the contour of the waist-shaped groove to process the waist-shaped groove to the design size.

[0043] Specifically, Figure 4 The diagram illustrates a milling cycle, which refers to the completion of milling the entire contour of a waist-shaped groove. For example, starting from the transition point between the right-side smooth transition section and the upper straight section, the milling cutter completes the first layer of milling in the first milling cycle after traversing the upper straight section and the left-side smooth transition section, thus completing the milling of half a circle of contour. Then, using the transition point between the left-side smooth transition section and the lower straight section as the descent point, the milling cutter descends directly into the next layer of milling without lifting off the ground. After the milling cutter completes the lower straight section and the right-side smooth transition section, the second layer of milling in the first milling cycle is completed, thus completing the milling of the other half of the contour, thereby achieving half-circle stepped layer milling. Then, at the transition between the smooth transition section on the right and the straight section on the upper side, the cutter is lowered directly without lifting the cutter to perform the second milling cycle. This process is repeated half-circle step-milling until the last milling cycle is reached. In the last milling cycle, the cutter moves directly along the contour of the waist groove to make the waist groove the design size.

[0044] Understandable, such as Figure 5 As shown, during the semi-circular stepped layer milling process:

[0045] In the first milling path, the milling cutter travels a straight segment and a smooth transition segment. The area removed in the first milling is approximately equal to (A×d+πD). 2 / 8+πd 2 / 8)×C;

[0046] In the second milling path, the milling cutter travels along another straight segment and another smooth transition segment. The removal area of ​​the second milling is the sum of the remaining area of ​​the first layer and the removal area of ​​the second layer, where the remaining area of ​​the first layer is approximately equal to [A×(Dd)+πD]. 2 / 8-πd 2 / 8)×C, the area removed by the second layer of milling is approximately equal to (A×d+πD) 2 / 8+πd 2 / 8)×C;

[0047] In the third milling path, the cutter's travel path is the same as the first milling path. The removal area of ​​the third milling is the sum of the remaining area of ​​the second layer and the removal area of ​​the third layer, where the remaining area of ​​the second layer is approximately equal to [A×(Dd)+πD]. 2 / 8-πd 2 / 8)×C, the area removed by the third layer of milling is approximately equal to (A×d+πD) 2 / 8+πd 2 / 8)×C;

[0048] In the Nth milling path, the milling cutter travels one circle along the groove profile. The area removed in the Nth milling is the remaining area of ​​the (N-1)th layer plus the area removed by the Nth layer milling. The remaining area of ​​the (N-1)th layer is approximately equal to [A×(Dd)+πD]. 2 / 8-πd 2 / 8)×C, the milling removal area of ​​the Nth layer is (A×D+πD) 2 / 4)×C.

[0049] Where A represents the length of the straight segment, D represents the groove width, d represents the diameter of the milling cutter, C represents the depth of cut per layer, and d < D.

[0050] It is understood that when the present invention uses the variable speed half-circle stepped layer milling method for milling, the milling content of the next layer includes a small portion of the allowance of the side wall after the previous layer is milled. This not only serves the purpose of finishing the side wall of the first layer, but also greatly reduces the number of layer milling tool marks. Compared with the layer milling method of equal-width slots, it can ensure the slot width dimension and well meet the roughness requirements of the slot wall.

[0051] Furthermore, in existing layer milling methods using equal-width slot cutters, to ensure the stability of the slot width, a full-circle contour layer milling method is generally used. This means the cutter travels one full circle along the contour of the slot each time, and milling requires a feed rate consistent with the smooth transition section. However, when milling along the straight section, the cutter uses only a single cutting edge, with the tool contacting a single line. In contrast, when milling along the smooth transition section, multiple cutting edges participate, with approximately 1 / 4 of the tool's side surface in contact. Moreover, the contact area increases as the tool diameter approaches the slot width. Therefore, the force-bearing area on the tool is larger in the smooth transition section, resulting in significantly greater force than in the straight section. Consequently, the feed rate in the smooth transition section is slower to prevent tool breakage. Thus, existing layer milling methods using equal-width slot cutters have slow feed rates and low machining efficiency when milling along the slot contour. In this invention, a variable-speed, half-circle stepped layer milling method is used. The feed rate of the cutter in the straight section is significantly greater than that in the smooth transition section, thereby greatly improving machining efficiency. For example, the total machining time for existing layer milling is t1 = [(2A+πD) / (S×f1)]×(H / C), while the total machining time for the variable speed half-circle stepped layer milling of this invention is t2 = [2A / (S+f2)+πD / (S×f1)]×(H / 2C), where f2 represents the feed rate of the straight section, f1 represents the feed rate of the smooth transition section, S represents the spindle speed, and H represents the groove depth. In this invention, since the feed rate f = Z×n×f z Where Z is the number of teeth on the milling cutter, n is the spindle speed, and f z This refers to the feed per tooth. In the circular arc segment, multiple cutting edges participate in the cutting, resulting in a large tool contact area and high force. To prevent tool breakage in the circular arc segment, the spindle speed n1 in the circular arc segment is approximately (0.2 to 0.5) times the spindle speed n2 in the straight line segment, and the feed per tooth f in the circular arc segment... z1 ≈ (0.2~0.5) times the feed rate per tooth of the straight segment f z2 Therefore, f2 >> f1. Thus, for a layer milling cycle, the machining time of the variable speed half-circle stepped layer milling is less than half of the existing layer milling machining time. Moreover, the number of layers processed in the layer milling cycle of the present invention is only half of that of the existing layer milling. Therefore, t2 < t1 / 4. Compared with the existing layer milling method, the variable speed half-circle stepped layer milling method of the present invention improves the machining efficiency by at least 75%.

[0052] Optionally, the ratio of the feed rate of the end mill in the straight section to the feed rate in the smooth transition section is between 3 and 8. More preferably, the ratio is between 7 and 8. For example, the feed rate in the smooth transition section is 20 mm / r to 30 mm / r, and the feed rate in the straight section is 150 mm / r to 240 mm / r.

[0053] Optionally, the ratio of the milling cutter's diameter to the slot width is between 0.6 and 0.9. Preferably, the ratio is between 0.8 and 0.9. It is understood that to achieve semi-circular stepped contour milling, the milling cutter's diameter d must be smaller than the slot width D. However, if the milling cutter's diameter d is too small, the tool's rigidity will be poor, making it prone to breakage. Therefore, to balance tool rigidity and the requirements of semi-circular stepped contour milling, this invention controls the ratio of the milling cutter's diameter to the slot width to be between 0.8 and 0.9.

[0054] It is understood that the machining method for deep and narrow grooves on aluminum-magnesium casings of the present invention has been improved by changing the machining strategy and optimizing the machining parameters. The deep groove through hole adopts the method of first pre-drilling a row of holes, and then using variable feed to descend step by step without lifting the tool to machine to the design size, which effectively avoids the phenomena of tool vibration, tool deflection and tool breakage that are easy to occur during the machining process, and at the same time greatly improves the machining efficiency.

[0055] It is understood that the present invention also addresses a certain intake casing. Figure 1 The deep and narrow groove shown has been machined, and the specific process is as follows:

[0056] (1) Based on the characteristics of full-enclosure machining, the number of pre-drilled holes is determined by the groove length, where number = [longest groove distance / drill diameter]. The holes are evenly distributed, extending from both sides towards the center. Therefore, one Ф3 drill bit is used to pre-drill one Ф3 hole at the center of each of the two semicircles, employing a pecking drilling method. The machining procedure is as follows:

[0057] (T75 ZT D=3.)

[0058] N90M6

[0059] N19M6

[0060] N20 D1

[0061] N21 CYCLE832(0.01,_ORI_FINISH,1)

[0062] N22 MCM_MILL

[0063] N23 STOPRE

[0064] N24 G54D1Y1100

[0065] N25 G0 A-90B=DC(0)

[0066] N26 TRAORI(2)

[0067] N27 CYCLE832(0.01,1,1)

[0068] N28 FFWON

[0069] N29 CYCLE800(0,"TC1",220000,54,0,0,0,0,-90,0,0,0,0,0,,1)

[0070] N30 STOPRE

[0071] N160G00G90G54X-41.249Y-4.481S2000M3B90.F240

[0072] N170G00Z500.D1

[0073] N180MCALL CYCLE83(500.,39.1,0,2.,,,0.,,,,1,1,3,3,,0)

[0074] N190X-41.249Y-4.481

[0075] N200X-40.294Y-9.897

[0076] N210MCALL.

[0077] (2) Using a Ф2.5 carbide end mill, a variable feed, non-retractable layer milling process is employed. Specifically, the feed is reduced to F26 at the arc transition points and increased to F180 at the straight sections. Simultaneously, after each arc section is completed, the feed is lowered by 0.5mm to proceed to the next layer milling section. The machining procedure is as follows:

[0078] (T15 XD D=2.5)

[0079] N6210T15

[0080] N6220M6

[0081] N6230CYCLE800()

[0082] N6240G500D1

[0083] N6250M94

[0084] N6260M92

[0085] N6270CYCLE832(0.001,_FINISH,1)

[0086] N6280CYCLE800(0,NJMTW,100000,57,X,Y,Z,A,0,0,0,0,0,-1,100,1)

[0087] N1424 G00Z300.M08

[0088] N1425 G00G90G57X-40.294Y-9.897B0S3600M3

[0089] N1426 G00Z3.

[0090] CC_IMD_WRITE("OACM",0,0,0,29)

[0091] N1427 R1=1

[0092] N1428 R2=0

[0093] ;(WHILE[#1LT50]DO1)

[0094] N1429 MA1:

[0095] N1430 R2=-0.5*R1

[0096] N1431 G01Z=R2F180

[0097] N1432 G01G64G41D1 X-39.998Y-9.845F180.

[0098] N1433 G01X-40.953Y-4.429

[0099] N1434 G01X-41.077Y-4.235F26

[0100] N2360 G01X-41.301Y-4.185

[0101] N2370 G01X-41.494Y-4.309

[0102] N2380 G01X-41.544Y-4.533

[0103] N1435 G01F180

[0104] N1436 R1=R1+1

[0105] N1437 R2=-0.5*R1

[0106] N1438 G01Z=R2

[0107] N1439 G01X-40.589Y-9.949F180

[0108] N1440 G01X-40.466Y-10.143F26

[0109] N2410G01X-40.241Y-10.193

[0110] N2420G01X-40.048Y-10.069

[0111] N2430G01X-39.998Y-9.845

[0112] N1441 G01G60G40X-40.294Y-9.897F180

[0113] N1442 R1=R1+1

[0114] N1443 IF R1<60GOTOB MA1

[0115] (END1)

[0116] N1444 G00Z200.

[0117] The final machined deep and narrow groove meets the dimensional accuracy requirements of the design.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for machining deep and narrow grooves on an aluminum-magnesium casing, characterized in that, Includes the following: Pre-drill holes in the waist-shaped groove using a drill bit with a diameter equal to the groove width; The milling process is carried out using a variable speed half-circle stepped layer milling method to achieve the design dimensions, and the diameter of the milling cutter is smaller than the width of the waist-shaped groove. The process of machining to the design dimensions using the variable speed half-circle stepped layer milling method is as follows: Starting from the transition point between the smooth transition section and the straight section, the milling cutter descends directly without lifting the cutter after completing the first half-circle contour and completes the second half-circle contour. The first half-circle contour includes a straight section and a smooth transition section, and the second half-circle contour includes another straight section and another smooth transition section. The feed rate of the milling cutter in the straight section is greater than the feed rate in the smooth transition section. The milling cutter continuously performs half-circle step-like layer milling. When the last layer is reached, the milling cutter moves around the contour of the waist groove to process the waist groove to the design size. During the semi-circular stepped layer milling process: The area removed in the first milling operation is (A×d+πD) 2 / 8+πd 2 / 8)×C; The area removed by the second milling is the sum of the remaining area in the first layer and the area removed by the second milling, where the remaining area in the first layer is [A×(Dd)+πD 2 / 8-πd 2 / 8)×C, the second layer of milling removal area is (A×d+πD) 2 / 8+πd 2 / 8)×C; The area removed by the third milling is the sum of the remaining area in the second layer and the area removed by the third milling. The remaining area in the second layer is [A×(Dd)+πD]. 2 / 8-πd 2 / 8)×C, the third layer milling removal area is (A×d+πD) 2 / 8+πd 2 / 8)×C; The area removed by the Nth milling is the remaining area of ​​the (N-1)th layer plus the area removed by the Nth layer milling, where the remaining area of ​​the (N-1)th layer is [A×(Dd)+πD 2 / 8-πd 2 / 8)×C, the milling removal area of ​​the Nth layer is (A×D+πD) 2 / 4)×C; Where A represents the length of the straight segment, D represents the groove width, d represents the diameter of the milling cutter, and C represents the depth of cut per layer.

2. The method for machining deep and narrow grooves on an aluminum-magnesium casing as described in claim 1, characterized in that, The number of pre-drilled holes is calculated based on the following formula: n=[L / D] Where [] represents rounding, n represents the number of pre-drilled holes, L represents the longest length of the waist-shaped groove, and D represents the groove width.

3. The method for machining deep and narrow grooves on an aluminum-magnesium casing as described in claim 2, characterized in that, Multiple pre-drilled holes are distributed at equal intervals from both sides of the waist-shaped groove toward the middle.

4. The method for machining deep and narrow grooves on an aluminum-magnesium casing as described in claim 1, characterized in that, The ratio of the feed rate of the milling cutter on the straight section to the feed rate on the smooth transition section is between 3 and 8.

5. The method for machining deep and narrow grooves on an aluminum-magnesium casing as described in claim 1, characterized in that, The ratio of the feed rate of the end mill in the straight section to the feed rate in the smooth transition section is between 7 and 8.

6. The method for machining deep and narrow grooves on an aluminum-magnesium casing as described in claim 1, characterized in that, The ratio of the end mill diameter to the slot width is between 0.6 and 0.

9.

7. The method for machining deep and narrow grooves on an aluminum-magnesium casing as described in claim 1, characterized in that, The ratio of the end mill diameter to the slot width is between 0.8 and 0.

9.

8. The method for machining deep and narrow grooves on an aluminum-magnesium casing as described in claim 1, characterized in that, The pre-drilling process uses a pecking drill method.

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