In the multi-axis system, the connection method of SBR precision linear rails should be designed flexibly according to the motion demand, space layout and load characteristics. Different connection methods have their own focus on structural stability, motion precision and applicable scenarios, and can be specifically subdivided into the following categories, each of which contains connection details and adaptable scenarios:
ONE,Right Angle Lap (Orthogonal Connection)
This is the most common connection method in multi-axis systems, the core of which is to arrange two SBR precision linear rails vertically at 90° in the space through the mechanical structure to form an orthogonal axes system such as X-Y, X-Z or Y-Z, so as to construct a three-dimensional motion space.
Connection structure: Usually one axis (e.g. X-axis) is the base track, which is fixed horizontally on the frame; the other axis (e.g. Y-axis) is vertically mounted on the X-axis slider through the transition connecting plate - the connecting plate needs to be precisely adhered to the mounting surface of the X-axis slider (flatness ≤ 0.03mm) and rigidly locked with high-strength bolts (e.g. 8.8 grade socket head cap screws). The connecting plate should be precisely fitted with the mounting surface of the X-axis slider (flatness ≤0.03mm) and rigidly locked by high-strength bolts (such as 8.8-grade hexagonal bolts) to ensure that the perpendicularity error between the Y-axis track and the X-axis track is ≤0.1mm/m. If further stability improvement is needed, auxiliary support seats can be installed at both ends of the track to offset the deflection caused by the cantilever structure.
Scenario: Suitable for equipment requiring two-dimensional or three-dimensional planar motion, such as coordinate robots, automatic dispensing machines, laser engraving machines, etc. The X-axis drives the overall mechanism horizontally. For example, the X-axis drives the whole mechanism to move horizontally, and the Y-axis realizes lateral feeding on the X-axis slider, so that the two-axis linkage can complete any trajectory movement in the plane; if the Z-axis is superimposed (perpendicular to the X-Y plane), it can realize accurate positioning in the three-dimensional space (e.g., the movement of the nozzle of a 3D printer).
Parallel Lap (Coplanar Connection)
By arranging multiple SBR precision linear rails in parallel in the same plane, it can realize large-area support of loads or synchronous movement of long travel, the core is to ensure the parallelism and isometricity of each rail.
Connection structure: multiple rails should be installed along the same datum line (such as the positioning groove on the frame), the spacing of adjacent rails is determined according to the width of the load (usually 50-200mm), the parallelism is calibrated by the laser interferometer (error ≤ 0.05mm/m), and the height of top surface of the rails is adjusted by the isometric pads (difference in height ≤ 0.02mm), so as to avoid the block from stalling due to the uneven force during the slider's operation. The two ends of the rail are connected and fixed by a common end plate, and the fit between the end plate and the end surface of the rail should be strictly controlled (gap ≤ 0.01mm) to prevent the rail from having expansion and contraction stress due to temperature change.
Applicable scenarios: Mostly used in heavy load or large span movement scenarios, such as transplanting platforms of automatic production lines (load ≥500kg), large material conveying organizations. For example, under the 3-meter-long transplanting platform, 3 SBR tracks are arranged in parallel, and the load weight is shared by multiple sliders to avoid bending and deformation of a single track due to heavy load, and at the same time, the smoothness of platform movement is improved (the amplitude of vibration is ≤0.05mm during operation).
Dissimilar lap connection (non-orthogonal multi-angle connection)
According to the space limitation of the equipment or special movement track demand, the SBR track is connected in different planes with non-90° angle (such as 30°, 45°, 60°, etc.) to realize the complex spatial movement.
Connection structure: customized wedge-shaped transition bracket is required, the inclination angle of the bracket is the same as the design angle of the rail (angle tolerance ≤ 0.5°), the rail is fixed on different planes of the frame through the bracket, and the axes of the two rails are intersected or perpendicular to each other in space. In order to ensure the coordination of movement, the rail slider needs to be connected to the load through universal joints or flexible couplings to offset the additional torque caused by installation errors. If the angle is fixed and the load is large, reinforcement can be added between the rail and the bracket to enhance the structural rigidity (e.g. welded triangular support).
Applicable scenarios: suitable for space constraints or the need for inclined movement of the equipment, such as curved surface grinding robot (track along the tangent direction of the surface of the workpiece), inclined conveyor line (30 ° angle with the horizontal plane to achieve the material climbing). For example, in the solar panel inspection equipment, the SBR track can drive the inspection lens along the tilted surface of the photovoltaic panel to ensure that the lens is always perpendicular to the panel surface, thus improving the inspection accuracy.
Fourth, docking connection (renewed length connection)
when the length of single SBR track can not meet the travel demand (such as more than 6 meters), through the docking of multiple segments of the track to extend the total length, the core is to eliminate the steps and gaps at the seams, to ensure the continuity of the movement.
Connection structure: Before docking, the end face of the track needs to be precision machined (verticality ≤ 0.01mm, flatness ≤ 0.005mm) to ensure that the axes of the two sections of the track are co-linear after docking (coaxiality error ≤ 0.02mm). The joints can be "stepped" or "flat" design: stepped through the rail end of the cam and groove with positioning, to avoid lateral offset; flat type in the rail below the addition of a common transition base, the top surface of the base need to be scraped and ground to the precision of the mirror (Ra ≤), the top surface of the base should be scraped and ground to the precision (Ra ≤). The top surface of the base should be scraped to mirror precision (Ra≤0.8μm), and the two sections of the track should be pressed onto the base by bolts to eliminate the gap between the joints. After docking, the seams on the top surface of the rail should be trimmed with a special scraper to ensure that there is no obvious stutter when the slider passes through (height difference ≤ 0.005mm).
Scenario: Suitable for long-stroke linear motion equipment, such as table feeding of large CNC machine tools (stroke ≥ 10 meters), stacker tracks in automated warehouses. For example, in a 50-meter-long stacker crane track, 10 sections of 5-meter-long SBR track are butt-jointed, and the smooth treatment at the joints can ensure that the vibration amplitude of the stacker crane can be controlled within 0.1mm when it is running at 1.5m/s.
Five,Compound lap joint (multi-mode combination connection)
In the complex multi-axis system, the above multiple connection modes are used in combination to satisfy more complex movement requirements, and the core is to ensure the rigidity and coordination of each connection node.
Connection structure: Take the "right-angle + parallel" combination as an example, the X-axis adopts a parallel overlap double track structure to carry heavy loads, the Y-axis is mounted on the X-axis slider through a right-angle overlap, and at the same time the Y-axis arranges two tracks in parallel to enhance stability, and the nodes of the tracks need to be fitted with locating pins (with a clearance of H7/g6) to ensure precision repeatability after dismounting (with a gap of H7/g6). The connection nodes of each track should be equipped with positioning pins (fit clearance H7/g6) to ensure the repeatability of accuracy after disassembly (error ≤0.03mm). If it involves heterogeneous rails, it is necessary to set tension sensors at key positions to monitor whether the load distribution is even in real time and avoid overloading at a single point.
Applicable scenarios: mostly used in high-precision, high-complexity automation equipment, such as semiconductor wafer handling robots (need to realize multi-dimensional precision movement in the clean room), aerospace parts inspection equipment (need to meet the large load and micron-level positioning accuracy).
In summary, the connection of SBR precision linear rails should be centered on the three core objectives of "precision maintenance", "load bearing" and "motion coordination". In the meantime, through precision machining, calibration tools and auxiliary support structure, we can ensure that the connected rail system meets the demand of long-term stable operation.
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