The crossbeam slide seat is a crucial component of the machine tool, characterized by a complex structure and various types. Each interface of the crossbeam slide seat corresponds directly to its crossbeam connection points. However, when transitioning from a five-axis universal slide to a five-axis heavy-duty cutting slide, changes occur simultaneously in the crossbeam slide seat, crossbeam, and guide rail base. Previously, to meet market demands, large components had to be redesigned, which resulted in long lead times, high costs, and poor interchangeability.
To address this issue, a new crossbeam slide seat structure has been designed to maintain the same external interface size as the universal interface. This allows for the installation of the five-axis heavy-duty cutting slide without requiring changes to the crossbeam or other large structural components, while also satisfying rigidity requirements. Additionally, improvements in processing technology have enhanced the accuracy of the crossbeam slide seat manufacturing. This type of structural optimization, along with its associated processing methods, is recommended for promotion and application within the industry.
1. Introduction
It is well-known that the size of power and torque affects the shape of the installation cross-section of a five-axis head. The beam slide seat, which is equipped with a universal five-axis slide, can be connected to the universal modular beam via a linear rail. However, the installation cross-section for a high-power and high-torque five-axis heavy-duty cutting slide is over 30% larger than that of a conventional universal slide.
As a result, improvements are needed in the design of the beam slide seat. A key innovation in this redesign is the ability to share the same beam with the beam slide seat of the universal five-axis slide. This approach facilitates the construction of a modular platform. Additionally, it enhances overall rigidity to some extent, shortens the production cycle, significantly reduces manufacturing costs, and allows for better adaptation to market changes.
Introduction to the structure of the conventional batch-type beam slide seat
The conventional five-axis system primarily consists of large components such as the workbench, guide rail seat, beam, beam slide seat, and the five-axis slide. This discussion focuses on the basic structure of the beam slide seat, as illustrated in Figure 1. The two sets of beam slide seats are symmetrical and consist of upper, middle, and lower support plates, amounting to a total of eight components. These symmetrical beam slide seats face each other and clamp the support plates together, resulting in a “mouth”-shaped beam slide seat with an embracing structure (refer to the top view in Figure 1). The dimensions indicated in the main view represent the travel direction of the beam, while the dimensions in the left view are critical for the connection to the beam and must adhere to specific tolerances.
From the viewpoint of an individual beam slide seat, to facilitate processing, the upper and lower six groups of slider connection surfaces at the “I” shape junction—featuring a wide top and a narrow middle—are concentrated on a single processing surface. This arrangement ensures that various dimensional and geometric accuracies can be achieved through fine processing. The upper, middle, and lower groups of support plates serve merely as structural support, making them simple and practical. The cross-sectional dimensions of the five-axis slide, designed with the conventional enveloping structure, are currently 420 mm × 420 mm. Additionally, errors may arise during the processing and assembly of the five-axis slide. To accommodate final adjustments, the upper, middle, and lower support plates must maintain gaps in the closed position, which are subsequently filled with injection molding to create a hardened closed-loop structure. These adjustments can introduce errors, particularly in the enveloping crossbeam slide seat, as illustrated in Figure 1. The two specific dimensions of 1050 mm and 750 mm are crucial for connecting with the crossbeam.
According to the principles of modular design, these dimensions cannot be altered in order to maintain compatibility, which indirectly restricts the expansion and adaptability of the crossbeam slide seat. While this configuration may meet customer demands in certain markets temporarily, it does not align with the rapidly evolving market needs today.
Advantages of innovative structure and processing technology
3.1 Introduction to Innovative Structure
The promotion of market applications has provided people with a deeper understanding of aerospace processing. The growing demand for high torque and high power in specific processing parts has sparked a new trend in the industry. In response to this demand, a new crossbeam slide seat designed for use with a five-axis head and featuring a larger cross-section has been developed. The primary aim of this design is to address the challenges associated with heavy cutting processes requiring high torque and power.
The innovative structure of this new crossbeam slide seat is illustrated in Figure 2. It categorizes similarly to a universal slide and consists of two sets of symmetrical crossbeam slide seats, along with two sets of upper, middle, and lower support plates, all forming a comprehensive embracing type structure.
A key distinction between the new design and the traditional model lies in the orientation of the crossbeam slide seat and the support plates, which have been rotated by 90° compared to conventional designs. In traditional crossbeam slide seats, the support plates mainly serve a supportive function. However, the new structure integrates slider installation surfaces onto both the upper and lower support plates of the crossbeam slide seat, creating a split structure unlike that of the conventional model. This design allows for fine-tuning and adjustment of the upper and lower slider connection surfaces to ensure they are coplanar with the slider connection surface on the crossbeam slide seat.
The main structure is now composed of two sets of symmetrical crossbeam slide seats, with the upper, middle, and lower support plates arranged in a “T” shape, featuring a wider top and a narrower bottom. The dimensions of 1160mm and 1200mm on the left side of Figure 2 extend in the direction of crossbeam travel, while the key shared dimensions of 1050mm and 750mm remain consistent with those of the conventional crossbeam slide seat.
This design allows the new crossbeam slide seat to completely share the same open crossbeam as the conventional version. The patented process used for this new crossbeam slide seat involves filling and hardening the gap between the support plate and the crossbeam slide seat using injection molding, thus forming an integral embracing structure that can accommodate a 600mm x 600mm five-axis heavy-duty cutting slide.
As indicated in the left view of Figure 2, the upper and lower slider connection surfaces on the crossbeam slide seat that secures the five-axis heavy-duty cutting slide create a split structure. Due to potential processing errors, the slider positioning surface and other dimensional and geometric accuracy aspects may not lie on the same horizontal plane, complicating the processing. In light of this, appropriate process improvements have been implemented to ensure qualified assembly accuracy for this split structure.
3.2 Coplanar Grinding Process Description
The semi-finishing of a single beam slide seat is completed by a precision milling machine, leaving only the finishing allowance. It needs to be explained here, and only the finishing grinding is explained in detail. The specific grinding process is described as follows.
1) Two symmetrical beam slide seats are subject to single-piece reference grinding. The tooling is illustrated in Figure 3. The finishing surface, referred to as surface A, serves as the positioning surface and is clamped onto the guide rail grinder. The reference bearing surface B and the process reference surface C are ground to ensure that their dimensional and geometric accuracy meet the requirements specified in the drawing.
2) To address the challenge of processing the non-coplanar error in the structure mentioned above, we have specifically designed four fixed support equal-height block tools and two bottom support equal-height block tools. The value of 300 mm is crucial for the equal height measurements and must be processed according to the specifications provided in the drawing to ensure uniform height. This is illustrated in Figure 4.
3) Two sets of symmetrical beam slide seats are clamped together face-to-face using special tooling (see Figure 5). Four sets of fixed support blocks of equal height are connected to the beam slide seats through their mounting holes. Additionally, two sets of bottom support blocks of equal height are calibrated and fixed in conjunction with the reference bearing surface B and the process reference surface C. This setup ensures that both sets of symmetrical beam slide seats are positioned at an equal height relative to the bearing surface B, while the process reference surface C is used to verify that the beam slide seats are properly aligned.
After the coplanar processing is completed, the slider connection surfaces of both sets of beam slide seats will be coplanar. This processing occurs in a single pass to guarantee their dimensional and geometric accuracy.
Next, the assembly is flipped to clamp and position the previously processed surface, allowing the grinding of the other slider connection surface. During the grinding process, the entire beam slide seat, secured by the tooling, is ground in a single pass. This approach ensures that each slider connection surface achieves the desired coplanar characteristics.
Comparison and verification of static stiffness analysis data of beam slide seat
4.1 Division of plane milling force
In metal cutting, the CNC milling lathe force during plane milling can be divided into three tangential components that act on the tool. These component forces are crucial indicators for assessing the cutting rigidity of machine tools. This theoretical data verification is consistent with the general principles of static stiffness tests. To analyze the forces acting on the machining tool, we employ the finite element analysis method, which allows us to transform practical tests into theoretical assessments. This approach is used to evaluate whether the design of the beam slide seat is appropriate.
4.2 List of plane heavy cutting parameters
Cutter diameter (d): 50 mm
Number of teeth (z): 4
Spindle speed (n): 1000 rpm
Feed speed (vc): 1500 mm/min
Milling width (ae): 50 mm
Milling back cutting depth (ap): 5 mm
Feed per revolution (ar): 1.5 mm
Feed per tooth (of): 0.38 mm
The tangential milling force (fz) can be calculated using the formula:
\[ fz = 9.81 \times 825 \times ap^{1.0} \times af^{0.75} \times ae^{1.1} \times d^{-1.3} \times n^{-0.2} \times z^{60^{-0.2}} \]
This results in a force of \( fz = 3963.15 \, N \).
Considering the symmetrical and asymmetrical milling factors during the machining process, we have the following forces:
- FPC (force in the X-axis direction): \( fpc = 0.9 \times fz = 3566.84 \, N \)
- FCF (force in the Z-axis direction): \( fcf = 0.8 \times fz = 3170.52 \, N \)
- FP (force in the Y-axis direction): \( fp = 0.9 \times fz = 3566.84 \, N \)
Where:
- FPC is the force in the direction of the X-axis
- FCF is the force in the direction of the Z-axis
- FP is the force in the direction of the Y-axis
4.3 Finite element static analysis
The two cutting five-axis slides need a modular construction and must share the same beam with a compatible opening interface. Therefore, the rigidity of the beam slide seat is crucial. As long as the beam slide seat does not experience excessive displacement, it can be deduced that the beam is universal. To ensure the static rigidity requirements, relevant cutting data will be gathered to perform a finite element comparative analysis on the displacement of the beam slide seat.
This analysis will simultaneously conduct finite element static analysis on both beam slide seat assemblies. This document focuses specifically on a detailed analysis of the new structure of the beam slide seat, omitting the specifics of the original sliding seat analysis. It is important to note that while the universal five-axis machine cannot handle heavy cutting, fixed-angle heavy-cutting inspections and high-speed cutting acceptance for “S” parts are often conducted during acceptance tests. The cutting torque and cutting force in these instances can be comparable to those in heavy cutting.
Based on years of application experience and actual delivery conditions, it is the author’s belief that other large components of the universal five-axis machine fully meet the requirements for heavy-cutting resistance. Therefore, conducting a comparative analysis is both logical and routine. Initially, each component is simplified by removing or compressing threaded holes, radii, chamfers, and small steps that could affect mesh division. The relevant material properties of each part are then added, and the model is imported into the simulation for static analysis.
In the parameter settings for the analysis, only essential data such as mass and force arm are retained. The integral beam slide seat is included in the deformation analysis, while other parts like the tool, five-axis machining head, and heavy-cutting five-axis slide are considered rigid. The analysis focuses on the relative displacement of the beam slide seat under external forces. The external load incorporates gravity, and three-dimensional force is applied to the tooltip simultaneously. The tooltip must be defined in advance as the force loading surface to replicate the tool length during machining, while ensuring the slide is positioned at the end of the machining axis for maximum leverage, closely simulating actual machining conditions.
The aluminum components are interconnected using a “global contact (-joint-)” method, and boundary conditions are established through line division. The beam connection area is illustrated in Figure 7, with grid division shown in Figure 8. The maximum unit size is 50 mm, the minimum unit size is 10 mm, resulting in a total of 185,485 units and 367,989 nodes. The total displacement cloud diagram is presented in Figure 9, while the three axial displacements in the X, Y, and Z directions are depicted in Figures 10 to 12, respectively.
The two cutting five-axis slides need a modular construction and must share the same beam with a compatible opening interface. Therefore, the rigidity of the beam slide seat is crucial. As long as the beam slide seat does not experience excessive displacement, it can be deduced that the beam is universal. To ensure the static rigidity requirements, relevant cutting data will be gathered to perform a finite element comparative analysis on the displacement of the beam slide seat.
This analysis will simultaneously conduct finite element static analysis on both beam slide seat assemblies. This document focuses specifically on a detailed analysis of the new structure of the beam slide seat, omitting the specifics of the original sliding seat analysis. It is important to note that while the universal five-axis machine cannot handle heavy cutting, fixed-angle heavy-cutting inspections and high-speed cutting acceptance for “S” parts are often conducted during acceptance tests. The cutting torque and cutting force in these instances can be comparable to those in heavy cutting.
Based on years of application experience and actual delivery conditions, it is the author’s belief that other large components of the universal five-axis machine fully meet the requirements for heavy-cutting resistance. Therefore, conducting a comparative analysis is both logical and routine. Initially, each component is simplified by removing or compressing threaded holes, radii, chamfers, and small steps that could affect mesh division. The relevant material properties of each part are then added, and the model is imported into the simulation for static analysis.
In the parameter settings for the analysis, only essential data such as mass and force arm are retained. The integral beam slide seat is included in the deformation analysis, while other parts like the tool, five-axis machining head, and heavy-cutting five-axis slide are considered rigid. The analysis focuses on the relative displacement of the beam slide seat under external forces. The external load incorporates gravity, and three-dimensional force is applied to the tooltip simultaneously. The tooltip must be defined in advance as the force loading surface to replicate the tool length during machining, while ensuring the slide is positioned at the end of the machining axis for maximum leverage, closely simulating actual machining conditions.
The precision turned components are interconnected using a “global contact (-joint-)” method, and boundary conditions are established through line division. The beam connection area is illustrated in Figure 7, with grid division shown in Figure 8. The maximum unit size is 50 mm, the minimum unit size is 10 mm, resulting in a total of 185,485 units and 367,989 nodes. The total displacement cloud diagram is presented in Figure 9, while the three axial displacements in the X, Y, and Z directions are depicted in Figures 10 to 12, respectively.
After analyzing the data, the cloud chart has been summarized and compared in Table 1. All the values are within 0.01 mm of each other. Based on this data and prior experience, we believe that the crossbeam will not experience distortion or deformation, allowing for the use of a standard crossbeam in production. Following a technical review, this structure was approved for production and successfully passed the steel test cutting. All precision tests of the “S” test pieces met the required standards.
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Post time: Nov-06-2024