Automatic plate feeding and discharging machine
Patent Information
- Application Number
- CN202522474113.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-21
- Publication Date
- 2026-09-22
- Estimated Expiration
- 2035-11-21
AI Technical Summary
这种设计不仅增加了设备的生产成本，而且由于涉及多种运动部件和驱动方式的协调，会影响整体上料效率
[0012]1、通过动力机构工作，带动与动力机构动力连接的转动盘旋转，进而使得开设在转动盘上的导滑槽周向转动，在导滑槽的转动过程中改变与滑动槽处的重合区域，进而使连接在滑动槽与导滑槽处的移动架部分沿着滑动槽的轨迹左右上下移动，从而通过吸附机构吸附下方的待加工板材与加工后的板材移动，操作连贯流畅，能够提升生产效率，满足生产需求。
Smart Images
Figure CN224783254U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of sheet metal processing technology, and more specifically, to an automatic sheet metal loading and unloading machine. Background Technology
[0002] Sheet metal refers to flat, rectangular sheets of material made to standard sizes, primarily metal sheets produced by forging, rolling, or casting. It is classified into thin plates, medium plates, thick plates, and extra-thick plates. When sheet metal is moved to processing equipment, it is transferred to the loading / unloading mechanism via a transport mechanism. The loading / unloading mechanism facilitates the transfer of sheet metal between the transport mechanism and the processing equipment.
[0003] Specifically, firstly, the feeding cylinder drives the feeding lifting plate to descend, allowing the suction cup to pick up the material. Then, the feeding cylinder drives the feeding lifting plate to rise. Next, the feeding motor drives the suction cup moving plate horizontally via the feeding screw, moving the material to the conveying guide position and releasing it. To complete both the vertical and horizontal movement of the material, both the feeding motor and the feeding cylinder are required. This design not only increases the production cost of the equipment but also affects the overall feeding efficiency due to the coordination of multiple moving parts and driving methods.
[0004] Therefore, an automatic board loading and unloading machine is needed to solve the above problems. Utility Model Content
[0005] The summary section of this application is intended to provide a brief overview of the concepts, which will be described in detail in the detailed description section below. This summary section is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.
[0006] To address the technical problems mentioned in the background section, some embodiments of this application provide an automatic sheet metal loading and unloading machine, comprising: a feeding mechanism, a placement platform, a processing conveyor platform, a discharging mechanism, a worktable, a moving frame, and a power platform. The feeding mechanism and the discharging mechanism are double-layered conveyor platforms, arranged horizontally. The placement platforms are arranged horizontally at the adjacent ends of the feeding mechanism and the discharging mechanism. A processing conveyor platform is fixed at the adjacent ends of the two placement platforms. A worktable is located directly above the processing conveyor platform. The worktable is arranged in a double-layered manner, with a moving frame slidably fitted at the front end of the worktable. An adsorption mechanism is connected and installed at the lower end of the moving frame. A power mechanism is connected and installed at the rear end of the worktable. A rotating disk is connected and fitted at the front end of the power mechanism. The rotating disk is connected and fitted with the moving frame. The worktable includes an outer plate and an inner plate arranged horizontally. A through cavity is opened at the inner end of the outer plate. The inner plate is located at the through cavity. A sliding groove is provided between the outer plate and the inner plate. A guide groove is provided on the rotating disk.
[0007] Furthermore, the rotating disk is disposed between the two outer plates, and a fixed frame is provided between the outer plate at the rear end and the inner plate. A fixed rod is fixed between two adjacent outer plates. A rotating cylinder is rotatably connected to the outer periphery of the fixed rod. A driven wheel is fixed to the outer periphery of the rotating cylinder. A driving wheel is powered to the front end of the power mechanism. The driving wheel meshes with the driven wheel. A sliding cavity is provided above the outer plate at the front end. The moving frame is connected to the sliding groove and the guide groove.
[0008] Furthermore, the upper end of the movable frame is provided with a telescopic slide rod that can extend and retract vertically. The slide cavity is slidably connected to the telescopic slide rod. Two symmetrical push plates are installed below the main rod of the movable frame. The two push plates are located between the two sets of adsorption mechanisms on the left and right. The lower end of the push plate is lower than the lowest end of the adsorption mechanism. The adsorption mechanism includes a sleeve part and a suction cup part. The suction cup and the sleeve part are connected by a spring. A sliding insert rod is fixed on the movable frame. The sliding insert rod extends backward and inserts into the sliding groove and the guide groove.
[0009] Furthermore, the upper end of the power platform is provided with a transfer platform, the power platform is provided with a power source, and a belt drive mechanism is connected between the power source and the transfer platform. Guide rails and ball sliders are fixedly installed on the front and rear sides of the power platform and the transfer platform. A guide rod and a lead screw are connected to the placement platform. The lower end of the lead screw is connected to a power mechanism to control its rotation. The guide rod and the guide rail are in sliding engagement. The ball slider is threadedly connected to the lead screw. A material rack is placed above the transfer platform. Two sets of symmetrical front and rear abutment plates are fixedly provided on the upper end of the material rack. A plate is placed between the two sets of abutment plates.
[0010] Furthermore, each of the two sets of abutment plates has a guide cavity at its close end, and the bottom of the material rack has a limiting cavity communicating with the guide cavity. Each of the two sets of abutment plates has an abutment strip that slides into contact with it. The upper end of the abutment strip has a chamfer. The abutment strip and the abutment plate are fixedly connected with a sliding block. The sliding block slides into contact with the guide cavity and can abut against the upper side of the limiting cavity.
[0011] The beneficial effects of this application are as follows:
[0012] 1. The power mechanism drives the rotating disk connected to the power mechanism to rotate, which in turn causes the guide groove on the rotating disk to rotate circumferentially. During the rotation of the guide groove, the overlapping area with the sliding groove changes, which in turn causes the moving frame part connected to the sliding groove to move left, right and up and down along the trajectory of the sliding groove. This allows the adsorption mechanism to adsorb the material to be processed and the processed material below. The operation is smooth and continuous, which can improve production efficiency and meet production needs.
[0013] 2. During the process of the adsorption mechanism moving and attaching to the board, two symmetrically arranged push plates on the left and right sides can quantitatively push the board on both sides, thereby preventing the lower board from gradually shifting during the adsorption and movement of the upper board, and preventing the lower board from falling due to gradual shifting. In addition, the adsorption mechanism is equipped with a spring-assisted height self-adaptation, which can automatically adjust according to the change of material stacking height, and is suitable for boards with different stacking heights, ensuring continuous production. Attached Figure Description
[0014] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application.
[0015] Furthermore, throughout the accompanying drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the elements are not necessarily drawn to scale.
[0016] In the attached diagram:
[0017] Figure 1 This is a schematic diagram of the overall structure according to one embodiment of this application;
[0018] Figure 2 yes Figure 1 A schematic diagram of the workbench, moving frame, and adsorption mechanism in the embodiment;
[0019] Figure 3 yes Figure 2 A schematic diagram of the hidden lines of the workbench, moving frame and power mechanism in the embodiment, viewed from the front.
[0020] Figure 4 yes Figure 3 A schematic diagram of the rotating disk portion in the embodiment;
[0021] Figure 5 yes Figure 3 A schematic diagram of the external appearance of the movable frame portion in the embodiment;
[0022] Figure 6 yes Figure 3Removed in the example Figure 4 and Figure 5 A partial sectional view of the rear section;
[0023] Figure 7 This is a schematic diagram of the external appearance of the power platform in the embodiment;
[0024] Figure 8 yes Figure 7 An exploded view of the material rack section in the embodiment.
[0025] Figure label:
[0026] 10. Feeding mechanism; 11. Placement platform; 12. Processing conveyor platform; 13. Discharge mechanism; 14. Workbench; 15. Moving frame; 16. Adsorption mechanism; 17. Power mechanism; 20. Rotating disk; 21. Outer plate; 22. Inner plate; 23. Sliding groove; 24. Fixed frame; 25. Fixed rod; 26. Rotating cylinder; 27. Driven wheel; 28. Driving wheel; 29. Guide groove; 30. Sliding cavity; 31. Telescopic slide rod; 32. Push plate; 33. Sliding insert rod; 40. Power platform; 41. Transfer platform; 42. Guide frame; 43. Ball bearing slider; 44. Material rack; 45. Abutment plate; 46. Guide cavity; 47. Limiting cavity; 48. Abutment strip; 49. Chamfer; 50. Sliding block; 51. Guide rod; 52. Lead screw. Detailed Implementation
[0027] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.
[0028] It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.
[0029] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are used only to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.
[0030] It should be noted that, in the description of this disclosure, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0031] It should be noted that, in this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0032] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".
[0033] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.
[0034] Reference Figure 1-3An automatic sheet metal loading and unloading machine includes: a feeding mechanism 10, a placement platform 11, a processing conveyor 12, a discharging mechanism 13, a worktable 14, a moving frame 15, and a power station 40. The feeding mechanism 10 and the discharging mechanism 13 are double-layered conveyor platforms, arranged symmetrically on the left and right. Two placement platforms 11 are symmetrically located at the adjacent ends of the feeding mechanism 10 and the discharging mechanism 13. Two power stations 40 are located above the two placement platforms 11. A processing conveyor 12 is fixedly mounted at the adjacent ends of the two placement platforms 11. The processing conveyor 12 extends rearward, with its rear end extending to the processing mechanism for processing. A worktable 14 is located directly above the processing conveyor 12. The worktable 14 is designed with two layers at the front and back. A movable frame 15 is slidably fitted at the front end of the worktable 14. Multiple extension rods (four are shown in the figure) are fixed at the lower end of the movable frame 15, which are distributed left and right. There are two sets of extension rods distributed left and right. The extension rods are arranged to extend forward and backward, and an adsorption mechanism 16 is connected and installed on the extension rods. A power mechanism 17 is connected and installed at the rear end of the worktable 14. A rotating disk 20 is connected to the front end of the power mechanism 17. The rotating disk 20 is connected and fitted with the movable frame 15. The worktable 14 includes an outer plate 21 and an inner plate 22 distributed at the front and back. A connecting rod is fixed between the two outer plates 21. A through cavity is opened at the inner end of the outer plate 21. The inner plate 22 is located at the through cavity. A sliding groove 23 is provided between the outer plate 21 and the inner plate 22. A guide groove 29 is provided on the rotating disk 20.
[0035] The power table 40 first moves to the placement table 11 via the lower feeding mechanism 10. Then, the power mechanism 17 controls the moving frame 15 to move left and right, so that the adsorption mechanism 16 below the moving frame 15 comes into contact with the board at the power table 40. The adsorption mechanism 16 adsorbs the board below and moves it to the processing conveyor table 12. The processing conveyor table 12 moves the board to the processing position for processing. After the adsorption mechanism 16 descends, it can adsorb the processed board and move it to the placement table 11 on the right. During this process, the adsorption mechanism 16 on the left will drive the board to be processed on the left to be processed on the processing conveyor table 12 for processing. After the board with the board to be processed on the power table 40 is cleared, it is transported to the left via the transport platform of the upper feeding mechanism 10. After the power table 40 on the right has collected the processed board, it is transported to the right via the transport platform of the lower discharging mechanism 13. The transport platform of the upper discharging mechanism 13 transports a new board collection frame to the left.
[0036] Reference Figure 3-6A rotating disk 20 is positioned between two outer plates 21. Two symmetrically positioned fixed frames 24 are located between the outer plate 21 and the inner plate 22 at the rear end. The fixed frames 24 extend laterally and are fixedly connected to the rear end faces of the outer plates 21 and the inner plate 22. A fixed rod 25 is fixed between two adjacent outer plates 21. A rotating cylinder 26 is rotatably connected to the outer periphery of the fixed rod 25. A driven wheel 27 is fixed to the outer periphery of the rotating cylinder 26. A driving wheel 28 is connected to the front end of the power mechanism 17. The driving wheel 28 meshes with the driven wheel 27. A sliding cavity 30 is formed above the outer plate 21 at the front end. There is a front-to-back overlapping area between the guide groove 29 and the sliding groove 23. A movable frame 15 is connected to the sliding groove 23 and the guide groove 29. The power mechanism... In operation, the motor at the power mechanism 17 provides power, which is then transmitted to the drive wheel 28 after being reduced and increased in torque by the reducer. This drives the drive wheel 28, which is connected to the power mechanism 17, to rotate. Under the meshing of the drive wheel 28 and the driven wheel 27, the rotating disk 20 is rotated through the rotating cylinder 26, which is fixedly connected to the rotating disk 20 and the driven wheel 27. This causes the circumferential position of the guide groove 29 to change, which in turn causes the front and rear overlap areas of the guide groove 29 and the sliding groove 23 to change. Specifically, the moving frame 15 connected to the sliding groove 23 and the guide groove 29 moves counterclockwise along the trajectory of the sliding groove 23. The loading and unloading of the board is achieved through the sliding of the moving frame 15 on the sliding groove 23 and the adsorption control of the adsorption mechanism 16.
[0037] The upper end of the movable frame 15 is provided with a telescopic slide rod 31 that can extend and retract vertically. The slide cavity 30 is slidably connected to the telescopic slide rod 31. The movable frame 15 and the rotating disk 20 are hollow. The vertical main rod of the movable frame 15 is provided with evenly distributed hollow holes to reduce weight. Two left-right symmetrical push plates 32 are installed below the main rod of the movable frame 15. The two push plates 32 are located between the left and right sets of adsorption mechanisms 16. The lower end of the push plate 32 is lower than the lowest end of the adsorption mechanism 16. The adsorption mechanism 16 includes a sleeve part and a suction cup part. The sleeve is clamped and fixed on the movable frame 15 by threaded parts through the connecting groove on the movable frame 15. The suction cup is connected to the sleeve part by a spring. A sliding insert rod 33 is fixed on the movable frame 15. The sliding insert rod 33 extends backward and inserts into the sliding groove 23 and the guide groove 29.
[0038] The movable frame 15 moves as a whole by engaging with the sliding groove 23 and the guide groove 29 via the sliding rod 33. When the overlapping position of the sliding groove 23 and the guide groove 29 changes, the movable frame 15 moves. During this process, the telescopic sliding rod 31, which can extend and retract vertically at the movable frame 15, slides horizontally with the sliding cavity 30 to prevent circumferential swaying of the movable frame 15. During the movement of the movable frame 15, a set of adsorption mechanisms 16 on the left side places the workpiece to be processed, and a set of adsorption mechanisms 16 on the right side places the processed workpiece. The push plate 32, fixedly installed at the lower end of the movable frame 15, pushes the workpiece horizontally, preventing excessive horizontal movement that could cause it to fall out of the workpiece collection frame. The adsorption mechanism 16 consists of a sleeve and a suction cup. The suction cup slides vertically on the sleeve and is connected to a spring, preventing gaps above the workpiece from preventing effective adsorption during the downward movement of the adsorption mechanism 16.
[0039] Reference Figure 1 and Figure 7-8 The upper end of the power platform 40 is equipped with a transfer platform 41. The power platform 40 contains a power source, and a belt drive mechanism connects the power source and the transfer platform 41. Guide rails 42 and ball bearing sliders 43 are fixedly installed on the front and rear sides of the power platform 40 and the transfer platform 41. A guide rod 51 and a lead screw 52 are connected to the placement platform 11. The lower end of the lead screw 52 is connected to a power mechanism to control its rotation. The guide rod 51 and the guide rail 42 are in sliding engagement. The ball bearing slider 43 is threadedly connected to the lead screw 52 to achieve vertical lifting. A material rack 44 (plate collection frame) is placed above the transfer platform 41. The upper end of the material rack 44 is fixed with two sets of symmetrical abutment plates 45. A plate is placed between the two sets of abutment plates 45. The two sets of abutment plates 45 are provided with guide sliding cavities 46 at their close ends. The bottom end of the material rack 44 is provided with a limiting cavity 47 that communicates with the guide sliding cavity 46. The two sets of abutment plates 45 are slidably fitted with abutment strips 48 at their close ends. The upper end of the abutment strips 48 is provided with a chamfer 49. The abutment strips 48 and the abutment plates 45 are fixedly fitted with sliding blocks 50 at their close ends. The sliding blocks 50 are slidably fitted with the guide sliding cavity 46 and can abut against the upper side of the limiting cavity 47.
[0040] The power table 40 is vertically movable on the placement platform 11. The material rack 44 is moved by the transfer table 41 and two transport platforms on the same plane as the power table 40. For example, if the transfer table 41 is located in the lower area above the placement platform 11, the power table 40 is not pushed upwards by the rotation of the lead screw 52. The transport platform at the lower feeding mechanism 10 can transport the material rack 44 to the top of the transfer table 41. The operation of the transfer table 41 moves the material rack 44 as follows: Figure 7As shown, the power platform 40 is placed above the transfer table 41. Under normal conditions, the guide slide 42 and the guide slide rod 51 slide up and down in cooperation, and the ball block 43 and the lead screw 52 are threaded together. When the lead screw 52 rotates with the power provided by the power source, it can drive the power platform 40 and the transfer table 41 to move upward. Thus, when the material to be processed on the material rack 44 is transported by the adsorption mechanism 16 and the height decreases, when the adsorption mechanism 16 contacts the material for the second time, the surface of the material to be processed on the material rack 44 rises.
[0041] Similarly, the power table 40 on the right moves downward under the connection of the lead screw 52. Under the sliding connection of the sliding block 50 and the guide cavity 46, the lower end of the abutment bar 48 abuts against the upper end surface of the placement table 11 during the downward movement of the material rack 44. This causes the position of the chamfer 49 to move upward first relative to the position of the abutment plate 45. The chamfers 49 on the left and right sides allow the processed material to be stored in the material rack 44.
[0042] The above description is merely a selection of preferred embodiments of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.
Claims
1. An automatic sheet metal loading and unloading machine, comprising a feeding mechanism (10), a placement table (11), a processing conveyor table (12), a discharging mechanism (13), a worktable (14), a moving frame (15), and a power table (40), characterized in that: The feeding mechanism (10), the discharging mechanism (13), and the two placement platforms (11) are symmetrically arranged. The processing conveyor (12) is located at the close ends of the two placement platforms (11). The power platform (40) is located on the placement platform (11). A workbench (14) is located directly above the processing conveyor (12). A movable frame (15) is slidably fitted to the front end of the workbench (14). An adsorption mechanism (16) is installed at the lower end of the movable frame (15). The rear end of the worktable (14) is connected to a power mechanism (17), and the front end of the power mechanism (17) is connected to a rotating disk (20). The worktable (14) includes an outer plate (21) and an inner plate (22). The inner end of the outer plate (21) is provided with a through cavity, and the inner plate (22) is located at the through cavity. A sliding groove (23) is provided between the outer plate (21) and the inner plate (22). A guide groove (29) is provided on the rotating disk (20). The sliding groove (23) is connected to the guide groove (29) and the moving frame (15).
2. The automatic board loading and unloading machine according to claim 1, characterized in that: A rotating cylinder (26) is rotatably connected inside the inner plate (22). A driven wheel (27) is fixed on the outer periphery of the rotating cylinder (26). A driving wheel (28) is powered and connected to the front end of the power mechanism (17). The driving wheel (28) meshes with the driven wheel (27). A sliding cavity (30) is opened above the outer plate (21) at the front end. A sliding rod (33) is fixed on the moving frame (15) and slidably connected to the sliding groove (23) and the guide groove (29).
3. The automatic board loading and unloading machine according to claim 2, characterized in that: The upper end of the movable frame (15) is provided with a telescopic slide rod (31) that can extend and retract vertically. The slide cavity (30) is slidably connected to the telescopic slide rod (31). Two left-right symmetrical push plates (32) are installed below the main rod of the movable frame (15). The two push plates (32) are located between the left and right sets of adsorption mechanisms (16). The adsorption mechanism (16) includes a sleeve part and a suction cup part that extend and retract vertically. The suction cup and the sleeve part are connected by a spring.
4. The automatic board loading and unloading machine according to claim 1, characterized in that: The upper end of the power platform (40) is provided with a transfer platform (41). The front and rear sides of the power platform (40) and the transfer platform (41) are fixedly installed with guide rails (42) and ball sliders (43). The placement platform (11) is connected with a guide rod (51) and a lead screw (52). The guide rod (51) and the guide rail (42) are slidably engaged. The ball slider (43) and the lead screw (52) are threadedly connected. A material rack (44) is placed above the transfer platform (41). The upper end of the material rack (44) is fixed with two sets of symmetrical front and rear abutment plates (45). A plate is placed between the two sets of abutment plates (45).
5. The automatic board loading and unloading machine according to claim 4, characterized in that: Both sets of abutment plates (45) have guide cavities (46) at their close ends. The bottom end of the material rack (44) has a limiting cavity (47) that communicates with the guide cavities (46). Both sets of abutment plates (45) have abutment strips (48) that slide together at their close ends. The upper end of the abutment strip (48) has a chamfer (49). The abutment strip (48) and the abutment plate (45) connected to it have a sliding block (50) that slides together with the guide cavity (46) and can abut against the upper side of the limiting cavity (47).
6. The automatic board loading and unloading machine according to claim 1, characterized in that: The outer plate (21) has two fixed brackets located at the front ends of the rotating disk (20). The outer plate (21) located at the rear end and the inner plate (22) are provided with two vertically symmetrical fixed brackets (24). The fixed brackets (24) extend to the left and right and are fixedly connected to the rear end faces of the outer plate (21) and the inner plate (22). A fixed rod (25) is fixed between two adjacent outer plates (21).
7. The automatic board loading and unloading machine according to claim 4, characterized in that: The feeding mechanism (10) and the discharging mechanism (13) are transport platforms arranged in two layers, and the power platform (40) can move up and down so that the transfer platform (41) is arranged on the same side as the upper and lower transport platforms respectively.
8. The automatic board loading and unloading machine according to claim 1, characterized in that: The movable frame (15) is hollowly disposed between the movable frame (15) and the rotating disk (20), and the vertically disposed main rod of the movable frame (15) is provided with evenly distributed hollow holes to reduce weight.