Gantry machining center ram design method and ram

Abstract

The present invention relates to the field of machine tool design. Disclosed are a gantry machining center ram design method and a ram. The method comprises: driving a ram to move along guide rails in a Z-axis direction; recording the X-axis displacement of a spindle mounting surface to obtain a simulation curve; performing linear fitting on the basis of front-segment data of the curve; calculating a difference between a fitted line and the simulation curve; recording a position at which the difference is greater than or equal to a threshold as a dangerous position and optimizing same; applying equal global acceleration; recording strains at different positions of the ram; taking a point at which the strain is greater than a threshold as a dynamic load dangerous point; enabling the ram to circularly and quickly move at the highest speed in the Z-axis direction; measuring the strain of the dynamic load dangerous point in a vertical direction; and determining a point at which the strain is greater than a preset value as a dangerous point and optimizing same. By means of the steps, the straightness of a ram in a Z-axis direction can be predicted and controlled at a design stage, thereby improving the design reliability and efficiency, enhancing the ability of the ram to resist a dynamic load, improving the precision retaining ability, achieving high feeding stability of the designed ram in the Z-axis direction, and satisfying the requirement of high-speed movement.

Description

A ram design method and ram for a gantry machining center Technical Field

[0001] The present invention relates to the field of machine tool design, in particular to a ram design method and a ram for a gantry machining center. Background Art

[0002] The ram is the fundamental structural component of a gantry machining center, housing the spindle and spindle motor. Gantry machining centers typically feature guide rails mounted on the back or side of the ram, which is then mounted on a saddle via guide rail sliders. The saddle is typically wall-mounted vertically or tilted at a 45° angle.

[0003] Existing ram designs fail to account for the significant loads experienced when operating with a large Z-axis travel and the weight of the spindle, main motor, or ram itself. Static loads can easily degrade the straightness of the ram guide rails. Dynamic inertia during Z-axis movement can lead to plastic deformation of the ram over extended machine tool use, resulting in reduced accuracy. Ram deformation can also cause lead screw deformation, impacting feed stability. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, one of the objectives of the present invention is to provide a gantry machining center ram design method capable of calibrating the ram's static accuracy and improving the ram's ability to resist dynamic loads.

[0005] In order to overcome the deficiencies of the prior art, a second object of the present invention is to provide a ram with high static precision and strong dynamic load resistance.

[0006] One of the purposes of the present invention is achieved by the following technical solution:

[0007] A ram design method for a gantry machining center comprises the following steps:

[0008] Modeling: Establish a finite element model including the ram, saddle, guide rail, slider, lead screw, and lead screw nut. Set a fixed constraint on the Y-axis slider mounting surface of the saddle. The ram and the guide rail are bound together, the guide rail and the slider are inseparable, the slider and the saddle are bound together, the saddle and the lead screw nut are bound together, and the lead screw nut and the saddle are connected via the lead screw.

[0009] Straightness analysis: Gravity is applied to the entire model, driving the ram to move along the guide rail in the Z axis. The X-axis displacement of the spindle mounting surface at the end of the ram is recorded to obtain a simulation curve of the X-axis displacement of the spindle mounting surface and the Z-axis travel. The data of the first 40%-50% segment of the simulation curve is used for linear fitting to obtain a fitting line. The difference between the fitting line and the simulation curve is calculated. When the difference is greater than or equal to a threshold, the position is recorded as a dangerous position.

[0010] Straightness optimization: Optimize the dangerous positions in the straightness analysis, and re-model and re-analyze the optimized model until the difference between the fitted straight line and the simulation curve is less than the threshold;

[0011] Dynamic load strain analysis: Apply an equal global acceleration based on the maximum acceleration of the machine tool's Z-axis, record the tensile or compressive strain at different positions of the ram, and identify the point where the tensile or compressive strain exceeds the threshold as the dynamic load danger point. Install a unidirectional strain gauge at the dynamic load danger point, and move the ram in a rapid cycle along the Z-axis at the fastest speed. Measure the tensile or compressive strain in the vertical direction at the dynamic load danger point and record the maximum value.

[0012] Dynamic load strain optimization: When the maximum value is greater than the preset value, it is judged as a dangerous point. The dynamic load dangerous point is optimized and the optimized model is re-modeled, and straightness analysis and dynamic load strain analysis are performed until the straightness and dynamic load strain meet the requirements.

[0013] Furthermore, in the steps of optimizing the dangerous positions in the straightness analysis and optimizing the dynamic load dangerous points, the optimization specifically includes: adding guide rails on the side, increasing the number of sliders on the guide rails, increasing the wall thickness near the dangerous points, setting reinforcing ribs on the left and right walls, optimizing the size and position of the window according to the stress diagram, and setting longitudinal reinforcing ribs on the front and rear walls, and optimizing any one or more of the above simultaneously.

[0014] Furthermore, in the optimization step, reinforcing ribs are provided on the left and right walls, and the reinforcing ribs are in a cross shape.

[0015] Furthermore, the optimization step includes setting reinforcing ribs on the left and right walls and adjusting the height and thickness of the reinforcing ribs.

[0016] Furthermore, in the straightness analysis step, a threshold value of a difference between the fitting straight line and the simulation curve is 0.2 μm.

[0017] The second object of the present invention is achieved by adopting the following technical solution:

[0018] A slide is designed using any of the above-mentioned slide design methods for a gantry machining center, wherein the rear wall of the slide is provided with two guide rails, and two sliders are installed on each guide rail on the rear wall; the left wall and the right wall are respectively provided with one guide rail, and three sliders are installed on the guide rails of the left wall and the right wall; the front wall is provided with multiple windows, and the multiple windows are located at both ends of the front wall to avoid the dangerous points.

[0019] Furthermore, the rear wall and the front wall are variable wall thickness structures, and the dangerous points of the rear wall and the front wall are located in the middle. The wall thickness at the dangerous points is the largest, and the wall thickness gradually decreases towards the upper and lower ends. The maximum wall thickness is between 30 and 40 mm, and the minimum wall thickness is between 20 and 25 mm.

[0020] Furthermore, the rear wall and the front wall are provided with longitudinal reinforcing ribs, and the longitudinal reinforcing ribs extend to the edge of the window.

[0021] Compared with the prior art, the present invention provides a gantry machining center ram design method that drives the ram to move along the guide rail in the Z axis, records the X-direction displacement of the spindle mounting surface at the end of the ram, obtains a simulation curve of the X-direction displacement of the spindle mounting surface and the Z-axis stroke, uses the data of the first 40%-50% segment of the simulation curve to perform linear fitting to obtain a fitting straight line, calculates the difference between the fitting straight line and the simulation curve, and when the difference is greater than or equal to a threshold, records the position as a dangerous position and optimizes the structure of the dangerous position; by applying equal global acceleration, records the tensile or compressive strain at different positions of the ram, and converts the tensile or compressive strain at different positions of the ram into a suitable value. The point where the compression strain is greater than the threshold is regarded as the dynamic load danger point. A unidirectional strain gauge is installed at the dynamic load danger point, and the slide is moved in a cycle at the fastest speed on the Z axis. The tensile or compressive strain in the vertical direction of the dynamic load danger point is measured and the maximum value is recorded. When the maximum value is greater than the preset value, it is judged as a danger point and the dynamic load danger point is optimized. Through the above steps, the Z-axis straightness of the slide can be predicted and controlled in the design stage, thereby improving the reliability and efficiency of the design; improving the ability of the slide to resist dynamic loads and improving the accuracy retention; the designed slide has high Z-axis feed stability and meets the needs of high-speed movement. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a flow chart of a ram design method for a gantry machining center according to the present invention;

[0023] FIG2 is a schematic structural diagram of a finite element model in the ram design of a gantry machining center according to the present invention;

[0024] FIG3 is a perspective view of the ram of the finite element model of FIG2 ;

[0025] FIG4 is another perspective view of the ram of FIG3 ;

[0026] FIG5 is a perspective cross-sectional view of the ram of FIG3 ;

[0027] FIG6 is a schematic diagram showing the difference between the calculated fitting line and the simulation curve in the straightness analysis of the gantry machining center slide design method of the present invention.

[0028] In the figure: 10, slide; 11, window; 12, spindle mounting surface; 13, reinforcing rib; 20, guide rail; 30, slider; 40, slide saddle. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be another intermediate component through which it is fixed. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be another intermediate component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be another intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] Referring to FIG1 , a method for designing a ram for a gantry machining center includes the following steps:

[0033] Modeling: Create a finite element model including the ram 10, saddle 40, guide rail 20, slider 30, lead screw, and lead screw nut. Set a fixed constraint on the Y-axis slider 30 mounting surface of the saddle 40. The ram 10 and guide rail 20 are bound together, the guide rail 20 and slider 30 are inseparable, the slider 30 and saddle 40 are bound together, the saddle 40 and lead screw nut are bound together, and the lead screw nut and saddle 40 are connected via a lead screw.

[0034] Straightness analysis: Gravity is applied to the entire model, driving the ram 10 to move along the guide rail 20 in the Z axis. The X-axis displacement of the spindle mounting surface 12 at the end of the ram 10 is recorded, and a simulation curve of the X-axis displacement of the spindle mounting surface 12 and the Z-axis travel is obtained. The data of the first 40%-50% segment of the simulation curve is used for linear fitting to obtain a fitting line. The difference between the fitting line and the simulation curve is calculated. When the difference is greater than or equal to the threshold, the position is recorded as a dangerous position.

[0035] Straightness optimization: Optimize the dangerous positions in the straightness analysis, and re-model and re-analyze the optimized model until the difference between the fitted straight line and the simulation curve is less than the threshold;

[0036] Dynamic load strain analysis: Apply a global acceleration equal to the maximum acceleration of the machine tool's Z-axis, and record the tensile or compressive strain at different locations on the ram 10. Points where the tensile or compressive strain exceeds the threshold are considered dynamic load risk points. Install a unidirectional strain gauge at these dynamic load risk points, and cyclically move the ram 10 at maximum speed along the Z-axis. Measure the tensile or compressive strain in the vertical direction at these dynamic load risk points, and record the maximum value.

[0037] Dynamic load strain optimization: When the maximum value is greater than the preset value, it is judged as a dangerous point. The dynamic load dangerous point is optimized and the optimized model is re-modeled, and straightness analysis and dynamic load strain analysis are performed until the straightness and dynamic load strain meet the requirements.

[0038] Specifically, during the straightness analysis step, a curve is drawn showing the relationship between the X-axis displacement of the spindle mounting surface 12 at the end of the ram 10 and the Z-axis travel. The first half of the curve is approximately straight, while the second half is curved due to variations in the ram's straightness (as shown in Figure 6). A straight line is fitted using displacement data from the first 40% to 50% of the Z-axis travel and extended to the entire travel range, serving as a reference line. Within the travel range, the difference between the simulated straightness curve and the reference line is the simulated straightness value. Points where the difference between the two curves is greater than or equal to the threshold of 0.2 μm are recorded as static load risk points.

[0039] Specifically, the straightness optimization step involves optimizing any one or more of the following: adding guide rails 20 to the sides, increasing the number of sliders 30 on the guide rails 20, increasing the wall thickness near the critical point, installing reinforcing ribs 13 on the left and right walls, optimizing the size and position of the window 11 based on the stress diagram, and installing longitudinal reinforcing ribs on the front and rear walls. The ribs 13 on the left and right walls are crisscross-shaped. The optimization step also includes adjusting the height and thickness of the ribs 13.

[0040] Specifically, in the dynamic load strain optimization step: the tensile and compressive strains of the dynamic load dangerous point are compared with the standard value. The material is cast iron, and the strain standard value is specified as 0.02%. When the maximum strain is greater than 0.02%, it is judged as a dangerous point.

[0041] The present application also relates to a ram. The ram design method for the gantry machining center is described above. The ram 10 has two guide rails 20 on its rear wall, with two sliders 30 mounted on each guide rail 20. The left and right walls each have one guide rail 20, with three sliders 30 mounted on the guide rails 20 on the left and right walls. The front wall has multiple windows 11 located at both ends of the front wall to avoid dangerous spots. The rear and front walls have variable wall thickness structures, with the dangerous spots located in the middle. The wall thickness at the dangerous spots is greatest, and gradually decreases toward the upper and lower ends. The maximum wall thickness is between 30 and 40 mm, and the minimum wall thickness is between 20 and 25 mm. The rear and front walls are provided with longitudinal reinforcing ribs 13, which extend to the edges of the windows 11.

[0042] The above embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patented invention. It should be noted that those skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention. These variations and improvements are equivalent modifications and improvements to the above embodiments based on the essential technology of the present invention and fall within the scope of protection of the present invention.

Claims

1. A ram design method for a gantry machining center, characterized in that: The following steps are involved: Modeling: Establish a finite element model including the ram, saddle, guide rail, slider, lead screw, and lead screw nut. Set a fixed constraint on the Y-axis slider mounting surface of the saddle. The ram and the guide rail are bound together, the guide rail and the slider are inseparable, the slider and the saddle are bound together, the saddle and the lead screw nut are bound together, and the lead screw nut and the saddle are connected via the lead screw. Straightness analysis: Gravity is applied to the entire model, driving the ram to move along the guide rail in the Z axis. The X-axis displacement of the spindle mounting surface at the end of the ram is recorded to obtain a simulation curve of the X-axis displacement of the spindle mounting surface and the Z-axis travel. The data of the first 40%-50% segment of the simulation curve is used for linear fitting to obtain a fitting line. The difference between the fitting line and the simulation curve is calculated. When the difference is greater than or equal to a threshold, the position is recorded as a dangerous position. Straightness optimization: Optimize the dangerous positions in the straightness analysis, and re-model and re-analyze the optimized model until the difference between the fitted straight line and the simulation curve is less than the threshold; Dynamic load strain analysis: Apply an equal global acceleration based on the maximum acceleration of the machine tool's Z-axis, record the tensile or compressive strain at different positions of the ram, and identify the point where the tensile or compressive strain exceeds the threshold as the dynamic load danger point. Install a unidirectional strain gauge at the dynamic load danger point, and move the ram in a rapid cycle along the Z-axis at the fastest speed. Measure the tensile or compressive strain in the vertical direction at the dynamic load danger point and record the maximum value. Dynamic load strain optimization: When the maximum value is greater than the preset value, it is judged as a dangerous point. The dynamic load dangerous point is optimized and the optimized model is re-modeled, and straightness analysis and dynamic load strain analysis are performed until the straightness and dynamic load strain meet the requirements.

2. The ram design method for a gantry machining center according to claim 1, characterized in that: In the steps of optimizing the dangerous positions in the straightness analysis and optimizing the dynamic load dangerous points, the optimization specifically includes: adding guide rails on the side, increasing the number of sliders on the guide rails, increasing the wall thickness near the dangerous points, setting reinforcing ribs on the left and right walls, optimizing the size and position of the window according to the stress diagram, and setting longitudinal reinforcing ribs on the front and rear walls, and optimizing any one or more of the above at the same time.

3. The ram design method for a gantry machining center according to claim 2, characterized in that: The optimization step is to set reinforcing ribs on the left and right walls, and the reinforcing ribs are in a cross shape.

4. The ram design method for a gantry machining center according to claim 2, characterized in that: The optimization step includes setting reinforcing ribs on the left and right walls, and also includes adjusting the height and thickness of the reinforcing ribs.

5. The ram design method for a gantry machining center according to claim 1, characterized in that: In the straightness analysis step, the threshold value of the difference between the fitting straight line and the simulation curve is 0.2 μm.

6. A ram designed using the ram design method for a gantry machining center according to any one of claims 1 to 5, characterized in that: The rear wall of the slide is provided with two guide rails, and two sliders are installed on each guide rail on the rear wall. The left wall and the right wall are respectively provided with one guide rail, and three sliders are installed on the guide rails of the left wall and the right wall. The front wall is provided with multiple windows, and the multiple windows are located at both ends of the front wall to avoid the dangerous points.

7. The ram according to claim 6, wherein: The rear wall and the front wall are variable wall thickness structures. The dangerous points of the rear wall and the front wall are located in the middle. The wall thickness at the dangerous points is the largest, and the wall thickness gradually decreases toward the upper and lower ends. The maximum wall thickness is between 30 and 40 mm, and the minimum wall thickness is between 20 and 25 mm.

8. The ram according to claim 6, wherein: The rear wall and the front wall are provided with longitudinal reinforcing ribs, and the longitudinal reinforcing ribs extend to the edge of the window.

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