High-rigidity lead screw pre-stretching structure and method for heavy machine tool

Abstract

The high-rigidity lead screw pre-stretching structure comprises a lead screw fixing end and a lead screw stretching end, and the lead screw fixing end is composed of a positioning plate, a coupling, a fastening wedge block, a thin nut, a thick nut, a left support, two thrust bearings, a needle bearing, two bearing seats and a power source; the lead screw stretching end is composed of a wedge block, a thin nut, a thick nut, a thrust bearing, a needle bearing, a bearing seat, a spacer bush and a right support. The lead screw pre-stretching method comprises the steps that the heating belt is wound to the position, close to the stretching end, of the lead screw, a sensing rod of the temperature sensor is fixed in the heating belt on the lead screw, the dial indicator is fixed to the main body piece, the indicator hand makes contact with the end of the lead screw, the heating belt heats the lead screw to reach the thermal elongation delta L of the lead screw, heating is stopped, and a nut at the stretching end is rapidly and manually screwed to complete operation. The structure is compact, the stability is high, the pre-stretching method is rapid and accurate in operation, measurement is visual, and the requirements of a heavy machine tool for high reliability and high precision of pre-stretching of the ball screw are met.

Description

Technical Field

[0001] The invention relates to a high-rigidity lead screw pre-stretching structure and method for a heavy-duty machine tool, belonging to the technical field of heavy-duty machine tools. Background Art

[0002] Due to the characteristics of heavy-duty machine tools, such as large load-bearing capacity and large cutting force, the ball screws configured in the transmission system are generally large in size, and are greatly affected by friction heat generation and thermal expansion and contraction characteristics of materials. During operation, they produce large elastic deformations themselves, resulting in feed deviations, which affect the positioning accuracy and processing quality of the machine tools. The conventional practice is to pre-stretch the screw after the screw structure chain is assembled, monitor the screw end with a meter, and stretch the screw to the pre-stretching amount by tightening the round nut on the screw to offset the thermal elongation caused by the temperature rise during the actual operation of the screw. During stretching, under the action of mechanical impact force, the meter value will often change. At the same time, because the original pre-stretching structure is that the screw bracket is directly assembled on the main part, and is fastened to the main part by its own screws and pins, the assembly rigidity is insufficient during stretching, and the screw bracket is often deformed by force and a slight displacement causes the three-point accuracy of the adjusted screw to change. Especially for the pre-stretching of large-sized screws, due to the need for greater prestress, the system rigidity of the existing screw pre-stretching structure is obviously insufficient. To solve this problem, we urgently need to develop a high-rigidity screw pre-stretching structure and method for heavy machine tools. This project is included in the provincial major scientific and technological achievement transformation project with contract number CG23017. Summary of the invention

[0003] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides a high-rigidity lead screw pre-stretching structure and method for heavy-duty machine tools, a lead screw fixed end structure is provided at the left end of the lead screw, the left end of the lead screw is fixed on the main body, and the right end of the lead screw is set as an adjustable end structure, and the left and right end brackets of the lead screw adopt an embedded internal force-enhancing structure, that is, the two brackets are respectively embedded in the grooves sunken in the main body, and the two brackets are firmly fixed on the main body through the dual force-enhancing action of the wedge block and the screw without generating external force, so as to avoid loosening and instability of the transmission system under the action of alternating loads, calculate the maximum thermal elongation of the lead screw when working, electrically heat and extend the lead screw to the maximum elongation when the lead screw is working, and then manually adjust the position of the round nut on the adjustable end of the lead screw to complete the pre-stretching of the lead screw. The present invention provides a high-rigidity lead screw pre-stretching structure through design, which solves the problem that the lead screw holder is often deformed due to insufficient rigidity and slight displacement leads to changes in the accuracy of the three points of the adjusted lead screw. At the same time, by applying the physical principle of thermal deformation of the lead screw, the present invention solves the problems that mechanical stretching is laborious and inefficient, and the stretching amount is inconvenient to monitor. The present invention can meet the requirements of high rigidity, high reliability and high precision for pre-stretching of ball screws in heavy machine tool drive systems. In addition, the ball screw stretching structure is compact and stable, and the pre-stretching method is precise and convenient to operate, and the measurement is intuitive and accurate.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a high-rigidity lead screw pre-stretching structure and method for heavy machine tools, including a lead screw fixed end and a lead screw stretching end and a pre-stretching method. The lead screw fixed end is composed of a positioning plate, a coupling, a fastening wedge, a thin nut, a thick nut, a left bracket, two thrust bearings, a needle bearing, two bearing seats, and a power source. The left side of the positioning plate is connected to the power source through a positioning stop, and the output shaft of the power source is connected to the left end of the lead screw through a coupling. The positioning plate is fixed on the left end face of the main body, the left bracket is embedded in the front groove of the main body, the right side is fitted with the front groove, the lower side of the left side is a 45° inclined surface in contact with the inclined surface of the wedge block, the wedge block is connected to the main body with a screw, and the left bracket is locked in the front groove of the main body by tightening the screw. The left bracket is provided with a boss, and the left and right sides are respectively provided with thrust bearings and bearing seats, and the needle bearings are connected in the middle. The needle bearings and the two bearing seats are connected to the lead screw, and the left side of the bearing seat is connected with a thick nut and a thin nut in turn, and the two nuts are connected to the lead screw through threads. The stretching end is composed of a wedge, a thin nut, a thick nut, a thrust bearing, a needle bearing, a bearing seat, a spacer, and a right bracket. The right bracket is embedded in the rear groove of the main body, the left side is fitted with the rear groove, and the lower right side is a 45° inclined surface that contacts the inclined surface of the wedge. The wedge is connected to the main body with screws, and the screws are tightened to lock the right bracket in the rear groove of the main body. The spacer, needle bearing, bearing seat, and thrust bearing are connected in sequence in the right bracket. The spacer, needle bearing, and bearing seat are connected to the lead screw. The thick nut and thin nut are connected to the right side of the bearing seat in sequence, and the two nuts are connected to the lead screw through threads.

[0005] Screw pre-stretching method: Use a heating belt to wrap around the screw near the stretching end, with a winding width of 400-500mm, fix the sensing rod of the temperature sensor in the heating belt on the screw, fix the steel ball at the stretching end of the screw, fix the dial indicator on the main body, and the needle touches the steel ball at the end of the screw. Heat the screw with the heating belt to reach its thermal elongation ΔL and stop heating. Quickly tighten the thick nut at the stretching end manually until it fits the joint surface of the bearing seat. After the screw temperature returns to room temperature, recheck the dial indicator value. The value is consistent with the thermal elongation ΔL, install the thin nut and lock it to complete the entire screw pre-stretching process.

[0006] Calculate the thermal expansion ΔL: Among them, ΔL is the thermal elongation of the screw, Ft is the pre-tensioning force, Δt is the temperature rise of the screw when it is used, L is the total length of the screw, d is the bottom diameter of the screw thread, A is the radial cross-sectional area of ​​the bottom diameter of the screw, and E is the Young's elastic modulus.

[0007] The beneficial effects of the present invention are as follows: it provides a high-rigidity lead screw pre-stretching structure and method for heavy-duty machine tools, which solves the problem of accuracy change caused by insufficient rigidity of the lead screw bracket in the prior art, and at the same time, the physical principle of lead screw heating is used during the lead screw pre-stretching to avoid the laborious, inefficient and inconvenient monitoring of the stretching amount during mechanical stretching. The structure is compact and stable, and the pre-stretching method is precise in operation and intuitive in measurement, which meets the high reliability and high precision requirements of heavy-duty machine tools for ball screw pre-stretching. It can also be used for the installation and adjustment of other structures with thermal elongation changes, and has the characteristics of simple structure, convenient and quick operation, and precise and reliable adjustment of dimensions. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0009] Figure 1 It is a schematic diagram of a high-rigidity lead screw pre-stretching structure for a heavy-duty machine tool according to the present invention.

[0010] Figure 2 yes Figure 1 Schematic diagram of the fixed end structure of the screw.

[0011] Figure 3 yes Figure 1 Schematic diagram of the screw pre-stretching end structure and pre-stretching method.

[0012] Numbers in the figure: 1. Positioning plate, 2. Coupling, 3. Wedge, 4. Thin nut, 5. Thick nut, 6. Left bracket, 7. Thrust bearing, 8. Needle bearing, 9. Bearing seat, 10. Spacer, 11. Right bracket, 12. Lead screw, 13. Power source, 14. Heating belt, 15. Induction rod, 16. Temperature sensor, 17. Steel ball, 18. Dial indicator, 19. Shoulder, 20. Main part, 21. front groove, 22. rear groove, 1201. left shoulder of the screw, 1202. right shoulder of the screw. DETAILED DESCRIPTION

[0013] like Figures 1 to 3As shown, a heavy machine tool high rigidity lead screw pre-stretching structure and method. It includes a lead screw fixed end and a lead screw stretching end and a pre-stretching method. The lead screw fixed end is composed of a positioning plate 1, a coupling 2, a fastening wedge 3, a thin nut 4, a thick nut 5, a left bracket 6, two thrust bearings 7, a needle bearing 8, two bearing seats 9, and a power source 13. The left side of the positioning plate 1 is connected with a power source 13 through a positioning stop, and the output shaft of the power source 13 is connected to the left end of the lead screw 12 through a coupling 2. The positioning plate 1 is fixed on the left end face of the main body 20, and the left bracket 6 is embedded in the front groove 21 of the main body 20, and the right side is in contact with the front groove 21. The lower side of the left side is a 45° inclined surface that contacts the inclined surface of the wedge block 3. The wedge block 3 is connected to the main body 20 with a screw, and the left bracket 6 is locked in the front groove 21 of the main body 20 by tightening the screw. The left bracket 6 is provided with a boss 19, and thrust bearings 7 and bearing seats 9 are provided on the left and right sides respectively, and needle bearings 8 are connected in the middle. The needle bearings 8 and two bearing seats 9 are connected to the lead screw 12, and the left side of the bearing seat 9 is connected with a thick nut 5 and a thin nut 4 in sequence, and the two nuts are connected to the lead screw 12 through threads. The stretching end is composed of a wedge block 3, a thin nut 4, a thick nut 5, a thrust bearing 7, a needle bearing 8, a bearing seat 9, a spacer 10, and a right bracket 11. The right bracket 11 is embedded in the rear groove 22 of the main part 20, with the left side fitting with the rear groove 22, and the lower side of the right side is a 45° inclined surface in contact with the inclined surface of the wedge block 3. The wedge block 3 is connected to the main part 20 with screws, and the screws are tightened to lock the right bracket 11 in the rear groove 22 of the main part 20. The spacer sleeve 10, needle roller bearing 8, bearing seat 9, and thrust bearing 7 are connected in sequence in the right bracket 11. The spacer sleeve 10, needle roller bearing 8 and bearing seat 9 are connected to the screw 12. The thick nut 5 and the thin nut 4 are connected in sequence on the right side of the bearing seat 9, and the two nuts are connected to the screw 12 through threads.

[0014] The specific operation steps are as follows: 1. First, install the positioning plate 1, wedge block 3, left bracket 6, and right bracket 11 at the corresponding positions of the main part 20, tighten the wedge block 3 to lock each bracket, align the three points of the positioning plate 1, left bracket 6, and right bracket 11 with the upper side busbar of the guide rail of the main part 20 so that the parallelism is no more than 0.01 / 500mm, and the consistency of the centers of the three points reaches 0.01mm, pre-pin them for positioning and then remove them. 2. Install the fixed end: Assemble the two thrust bearing 7 tightening rings on both sides of the boss 19 of the left bracket 6 on the bearing seat 9, install the needle bearing 8 and the thrust bearing 7 loose rings on both sides in the left bracket 6, insert the bearing seat assembly into the screw 12, fix the left bracket 6 assembly in the front groove 21 of the main part 20, and screw the wedge block 3 to double lock the left bracket 6 in the front groove 21 through the screw and the wedge surface. Tighten the left thick nut 5 to lock the left bracket 6 and the bearing seats 9 on both sides to complete the installation of the left bracket. The thick nut 5 is locked until there is no gap between the thrust bearings 7 on both sides of the left bracket 6, the bearing seat 9 and the left shoulder 1201 of the screw, so that the screw 12 can rotate freely and without movement, and then install the thin nut 4 to fix and lock the thick nut 5. 3. Install the stretching end: install the thrust bearing 7 tightening ring on the bearing seat 9, install the spacer sleeve 10 on the right end of the screw 12, install the needle bearing 8 and the thrust bearing 7 loose ring in the right bracket 11, fix the right bracket 11 in the rear groove 22 of the main part 20, tighten the wedge block 3 until the right bracket 11 and the rear groove 22 are in close contact with each other, install the needle bearing 8 and the bearing seat 9 in turn, tighten the thick nut 5 to lock the right bracket 11 and the bearing seat 9, the spacer sleeve 10 and the right shoulder 1202 of the screw until the screw rotates freely without movement, and the thin nut 4 at the outer end is not installed yet.

[0015] Screw pre-stretching method: Use heating belt 14 to wrap around the screw 12 near the stretching end, with a winding width of 400-500mm, fix the sensing rod 15 of the temperature sensor 16 in the heating belt 14 on the screw 12, fix the steel ball 17 at the stretching end of the screw 12, fix the dial indicator 18 on the main body 20, and the needle touches the steel ball 17 at the end of the screw. Heat the screw 12 with the heating belt 14 to reach its thermal elongation ΔL and stop heating. Quickly tighten the thick nut 5 at the stretching end manually until it fits the joint surface with the bearing seat 9. After the temperature of the screw 12 returns to room temperature, recheck the value of the dial indicator 18. The value is consistent with the thermal elongation ΔL, install the thin nut 4 and lock it to complete the entire screw pre-stretching process.

[0016] Calculate the thermal expansion ΔL: Among them, ΔL is the thermal elongation of the screw, Ft is the pre-tensioning force, Δt is the temperature rise of the screw when it is used, L is the total length of the screw, d is the bottom diameter of the screw thread, A is the radial cross-sectional area of ​​the bottom diameter of the screw, and E is the Young's elastic modulus.

Claims

1. A high-rigidity lead screw pre-stretching structure for heavy machine tools, comprising a lead screw fixed end and a lead screw stretching end, characterized in that: The screw fixed end is composed of a positioning plate (1), a coupling (2), a fastening wedge (3), a thin nut (4), a thick nut (5), a left bracket (6), two thrust bearings (7), a needle bearing (8), two bearing seats (9), and a power source (13). The left side of the positioning plate (1) is connected to the power source (13) through a positioning stop. The output shaft of the power source (13) is connected to the left end of the screw (12) through the coupling (2). The positioning plate (1) is fixed on the left end surface of the main body (20). The left bracket (6) is embedded in the positioning plate (1). The front groove (21) of the main body (20) is fitted with the front groove (21) on the right side, and the lower side of the left side is a 45° inclined surface that contacts the inclined surface of the wedge block (3). The wedge block (3) is connected to the main body (20) by screws, and the screws are tightened to lock the left bracket (6) in the front groove (21) of the main body (20). The left bracket (6) is provided with a boss (19), and thrust bearings (7) and bearing seats (9) are provided on the left and right sides respectively, and a needle bearing (8) is connected in the middle. The needle bearing (8) and two bearing seats (9) The lead screw (12) is connected to the left side of the bearing seat (9), and the thick nut (5) and the thin nut (4) are connected to the lead screw (12) in sequence. The two nuts are connected to the lead screw (12) through threads. The lead screw stretching end is composed of a wedge block (3), a thin nut (4), a thick nut (5), a thrust bearing (7), a needle bearing (8), a bearing seat (9), a spacer (10), and a right bracket (11). The right bracket (11) is embedded in the rear groove (22) of the main body (20), the left side is in contact with the rear groove (22), and the lower side of the right side is a 45° inclined surface that is in contact with the wedge block (3 ) inclined surfaces are in contact, the wedge block (3) is connected to the main body (20) with a screw, and the screw is tightened to lock the right bracket (11) in the rear groove (22) of the main body (20). The spacer sleeve (10), the needle roller bearing (8), the bearing seat (9), and the thrust bearing (7) are connected in sequence in the right bracket (11). The spacer sleeve (10), the needle roller bearing (8) and the bearing seat (9) are connected to the lead screw (12). The right side of the bearing seat (9) is connected in sequence with a thick nut (5) and a thin nut (4). The two nuts are connected to the lead screw (12) through threads.

2. A method for pre-stretching a high-rigidity lead screw for a heavy machine tool, characterized in that: A heating belt (14) is wound around the lead screw (12) near the stretching end, with a winding width of 400-500 mm. The sensing rod (15) of the temperature sensor (16) is fixed in the heating belt (14) on the lead screw (12). A steel ball (17) is fixed to the stretching end of the lead screw (12). A dial indicator (18) is fixed to the main body (20) so that the needle touches the steel ball (17) at the end of the lead screw. The lead screw (12) is heated by the heating belt (14) until its thermal elongation ΔL is reached and heating is stopped. The thick nut (5) at the stretching end is quickly and manually tightened until it fits the joint surface of the bearing seat (9). After the temperature of the lead screw (12) returns to room temperature, the value of the dial indicator (18) is rechecked. The value is consistent with the thermal elongation ΔL. The thin nut (4) is installed and locked to complete the entire lead screw pre-stretching process. Calculate the thermal expansion ΔL: Among them, ΔL is the thermal elongation of the screw, Ft is the pre-tensioning force, Δt is the temperature rise of the screw when it is used, L is the total length of the screw, d is the bottom diameter of the screw thread, A is the radial cross-sectional area of ​​the bottom diameter of the screw, and E is the Young's elastic modulus.

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