A method for machining a center of an elongated hole to ensure dimensional and geometric tolerances

Abstract

The application provides a method for machining an elongated hole in a machining center to ensure the shape and position tolerances of the elongated hole, which adopts a coarse and fine combined mode to machine the elongated hole according to the size and depth of the elongated hole. In the coarse machining, a centering drill is selected to determine the coarse reference position, so that the tool is prevented from breaking and the surface roughness in the hole is ensured to establish an accurate reference for subsequent machining; in the fine machining, different types of tools are selected to perform combined cutting according to the different effects of the tool edges participating in cutting, so that the tool is protected, the tool breaking phenomenon is not prone to occur, the service life of the tool is ensured, and the size accuracy and position accuracy of the machined hole are ensured; in the final forming machining, a drill reamer is selected to perform machining, so that the hole diameter size is ensured and the roughness in the hole is ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of machining method, and relates to a method for machining a long hole in a machining center. BACKGROUND

[0002] The machining center is used to machine long holes, especially the long holes of parts in the field of intelligent ammunition. When the long hole is machined, the mechanical cutting method cannot be used due to the high hardness of the material, and only soft materials such as copper and aluminum or short steel parts with small hole diameter and depth can be machined. The size tolerance and the shape and position tolerance are strictly required, and the electric spark machining is generally used to complete the machining. However, the electric spark machining has the disadvantages of long machining time, low first-time inspection qualified rate and the need for secondary repair. When the long hole is machined by the machining center, the tool wear and the chip removal problem are important problems leading to the breakage of the drill and reamer in the machining process. SUMMARY

[0003] The purpose of the present application is to provide a method for machining a long hole in a machining center and ensuring the shape and position tolerance of the long hole. According to the characteristics of the machining center and the tool, the mechanical cutting machining of the long hole can be realized by adjusting some program parameters and the machining sequence and changing the control.

[0004] The purpose of the new technology is realized by the following technical scheme:

[0005] A method for machining a long hole in a machining center and ensuring the shape and position tolerance of the long hole, characterized in that the method comprises the following steps:

[0006] Step 1: rough machining: establishing a machining reference

[0007] 1. A center drill is used to pre-drill a positioning reference on the end face of the part;

[0008] 2. A φ5 extended drill bit is selected to cut and remove the excess material along the position of the center drill, and a certain depth is machined;

[0009] 3. A φ5.7 three-fluted extended drill bit is used for secondary rough machining, and the hole position is corrected for the first time;

[0010] Step 2: finish machining: step machining method, ensuring the size and shape and position tolerance of the long hole; 1. The long hole is finished machined in a step cutting manner, a φ6.0 slotting cutter is selected to cut and machine the position of the long hole,

[0011] 2. The φ6.0 slotting cutter completes the second correction of the hole diameter while machining the hole;

[0012] 3. After the φ6.0 slotting cutter is completed, a φ6.045 six-fluted reamer is selected to expand and ream the machined hole for the second time;

[0013] Step three: forming: complete the hole diameter and bottom cutting;

[0014] 1. Select φ6.04 long four-blade drill reamer, when machining, φ6.045x20mm stepped hole is machined in advance, then φ6.04 long four-blade drill reamer is selected to complete the final hole diameter machining work; The machining mode of four-blade drill reamer is that two four-blade drill blades participate in cutting first, and then two four-blade reamer blades cut;

[0015] After the hole diameter and hole depth machining is completed, φ6.035 two-blade cutter is selected to machine the bottom end face of the slender hole.

[0016] The technical effect of the present application is,

[0017] During rough machining, the tool can be ensured not to break, and the surface roughness in the hole can be ensured, thereby establishing an accurate reference for subsequent machining;

[0018] During fine machining, the tool is protected, the tool breakage phenomenon is not easy to occur, the service life of the tool is ensured, and the size accuracy and position accuracy of the machined hole are ensured;

[0019] During the final forming machining, drill reamer is selected for machining, and since a certain excess is left during the previous hole diameter machining, the excess value is calculated according to the size of the selected tool, so that after the drill reamer machining, the hole diameter size and the roughness in the hole are ensured. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 : rough machining schematic diagram

[0021] Figure 2 : fine machining schematic diagram

[0022] Figure 3 : forming machining schematic diagram

[0023] Figure 4 : tool schematic diagram

[0024] Figure 5 : alloy reamer cross section schematic diagram

[0025] Figure 6 : alloy drill reamer cross section schematic diagram

[0026] Figure 7 : slotting cutter cross section schematic diagram DETAILED DESCRIPTION

[0027] A method for machining a slender hole in a machining center to ensure its shape and position tolerance, characterized in that it comprises the following steps:

[0028] Rough machining: establish machining reference

[0029] 1. Use a center drill to pre-drill a positioning reference on the upper end face of the part according to the position specified in the drawing to establish a rough reference for subsequent tool processing.

[0030] 2. Use a φ5 extended drill bit to cut along the center drill position to remove excess material, with a processing depth of 53mm;

[0031] 3. Use φ5.7 three-sided edge lengthened drill bit to perform secondary roughing and make the first correction to the hole position, which can well ensure the roughness of the inner surface of the hole and establish a rough reference for subsequent processing. At this time, the shape of the hole (such as Figure 1 )

[0032] Finishing: step processing method to ensure the size and shape and position tolerance of slender holes.

[0033] 1. Use step cutting to finish the elongated hole. Use a φ6.0 plunge milling cutter to cut the elongated hole. Step cutting can prevent the hole diameter from being deformed. Step cutting can also prevent the tool from breaking during the machining process because the tool has a longer cutting edge.

[0034] 2. The φ6.0 plunge milling cutter completes the secondary deviation correction of the hole diameter while machining the hole, ensuring the roughness inside the hole and establishing a rough reference for subsequent processing;

[0035] 3. After the φ6.0 plunge milling cutter completes the first fine hole expansion, a six-edge reamer is used to ream the newly machined hole a second time. The six-edge reamer has many cutting edges involved, so the surface roughness of the machined part is higher.

[0036] 4. Based on the hole diameter produced by the φ6.0 plunge milling cutter, we selected a φ6.045 six-flute reamer after calculation and testing to cut the inner hole of the part, ensuring the part's dimensional accuracy and surface roughness. This second round of reaming provides a precise entry point for the subsequent extended drill reamer and provides more precise protection and support for the extended tool's shank.

[0037] Forming: Complete cutting of hole diameter and bottom.

[0038] 1. Use a φ6.04 extended four-edge drill reamer to complete the final hole diameter processing. The processing method of the drill reamer is that the two drill edges are involved in cutting first, and then the two reamer edges are used for cutting. This can ensure the accuracy level of the hole inner diameter roughness;

[0039] 2. When using the φ6.04 extended four-edge drill reamer for processing, the inner wall of the pre-processed φ6.045×20mm stepped hole will not be scratched, and the problem of connection marks during the secondary processing of the stepped hole is also solved.

[0040] Since the bottom end of the elongated hole is a flat bottom, after the hole diameter and hole depth processing is completed, we select a φ6.035 two-blade tool to process the bottom end face of the elongated hole. By selecting a tool with a diameter smaller than the inner hole diameter and requiring passivation treatment for the tool side blade, the tool side blade is prevented from scratching the inner diameter of the elongated hole; the remaining material shape at the bottom of the elongated hole is inverted conical, and the material to be cut by the tool gradually increases, and the cutting resistance gradually increases. We select a two-blade expander to cut the remaining material at the bottom of the elongated hole, and the two-blade expander has small cutting force, which can prevent the tool from breaking.

[0041] The principle of the application is that the elongated hole has problems such as difficult chip removal, tool breakage, hole tolerance and shape tolerance exceeding, and hole roughness not meeting the drawing requirements during processing. According to the size and depth of the elongated hole, rough and fine combination is used for processing. In rough machining, a centering drill is selected to set the rough reference position, and a drill bit is selected for multiple small cutting processing. Each time a certain depth is processed, it returns to zero, and then feeds to the just processed depth and returns to zero. Repeat 3-5 times to complete the rough machining of the small hole. This can ensure that the tool does not break and can ensure the surface roughness of the hole, and establish an accurate reference for subsequent processing. In fine machining, different types of tools are selected for combined cutting according to the different effects of the tool edges participating in cutting. Since the cutting edges of the tools participating in cutting are long, step cutting is used during cutting. At the same time, according to the position of the different tools participating in cutting, the spindle speed and feed rate of the machine tool are adjusted. This protects the tool and prevents it from breaking, ensuring the service life of the tool and the size and position accuracy of the processed hole. During the final forming processing, a drill reamer is selected for processing. Since a certain amount of allowance is left during the previous processing of the hole diameter, the allowance value is calculated according to the selected tool size to ensure that the drill reamer processing ensures the hole diameter size and the hole roughness.

Claims

1. A method for ensuring the geometric tolerance of elongated holes in a machining center, characterized in that: The following steps are involved: Step 1: Rough machining: Establishing machining datum (1) Use a center drill to pre-drill a positioning reference on the upper end face of the part; (2) Use a φ5 extended drill bit to cut along the center drill position to remove excess material and process to a certain depth; (3) Use a φ5.7 three-sided edge lengthened drill bit for secondary rough machining and perform the first correction of the hole position; Step 2: Finishing: Step processing method to ensure the size and form tolerance of the elongated hole; (1) Use the step cutting method to finish the elongated hole, and use a φ6.0 plunge milling cutter to cut the position of the elongated hole. (2) The φ6.0 plunge milling cutter completes the secondary correction of the hole diameter while machining the hole; (3) After the φ6.0 plunge milling cutter is completed, a φ6.045 six-edge reamer is used to ream the processed hole for the second time; Step 3: Forming: completing the cutting of hole diameter and bottom; (1) When using a φ6.04 extended four-edge drill reamer, a φ6.045×20mm stepped hole is pre-processed, and then a φ6.04 extended four-edge drill reamer is used to complete the final hole diameter processing work; the processing method of the four-edge drill reamer is that two four-edge drill blades are involved in cutting first, and then two four-edge reamer blades are used for cutting; After the hole diameter and hole depth are processed, a φ6.035 two-edged tool is used to process the bottom end surface of the slender hole.

2. A method for machining elongated holes in a machining center to ensure their geometric tolerances according to claim 1, characterized in that: Use a center drill to pre-drill a positioning reference on the upper end face of the part at the position specified in the drawing.

3. The method for machining elongated holes in a machining center to ensure their geometric tolerances according to claim 1, characterized in that: Then use a φ5 extended drill bit to feed along the center drill position to perform cutting processing to remove excess material. The processing depth is 53mm.

4. The method for machining an elongated hole in a machining center to ensure its geometric tolerance according to claim 1, characterized in that: During rough machining, each time: machine to a certain depth and return to zero, then feed to the depth and return to zero, repeat 3-5 times to complete the rough machining of the small hole.

5. The method for machining elongated holes in a machining center to ensure their geometric tolerances according to claim 1, characterized in that: During finishing, different types of tools are selected for combined cutting according to the different roles of the tool blade in cutting.

6. The method for machining elongated holes in a machining center to ensure their geometric tolerances according to claim 1, characterized in that: The step cutting method is adopted during cutting, and the spindle speed and feed rate of the machine tool are adjusted according to the position of different tools involved in cutting.

7. The method for machining elongated holes in a machining center to ensure their geometric tolerances according to claim 1, characterized in that: During forming processing, drills and reamer are selected for processing, and the allowance value is calculated based on the selected tool size.

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