Design of Flexible Tooling Fixture for Thin-walled
Design of Flexible Tooling Fixture for Thin-walled
Today, I will share a design push on the flexible tooling fixture for thin-walled aluminum alloy check fixture processing. In the automobile main model inspection tool, many parts belong to large-scale aluminum alloy complex thin-walled structural parts, and the thickness is much smaller than the length and width dimensions. The material removal rate of the thin-walled overall structural parts is more than 90%, the average thickness is 4mm, and the thickness of local areas is less than 1mm. Due to the poor rigidity and weak strength of thin-walled parts, it is extremely easy to deform during processing, which makes the processing difficult, and it is difficult to guarantee the processing quality of the parts.
Because the thin wall of the workpiece is a curved surface, and the entire surface is the surface to be processed, ordinary clamps are not convenient for clamping curved surfaces, but also
It is easy to interfere with the milling cutter, so in actual processing, the auxiliary support fixture usually used is Yoyogi, Yoyogi is a composite resin material, which has good cutting performance and is relatively easy to process into support bars of various heights. The top of the Yoyogi support bar is covered with a small wedge-shaped Yokogi block, and then the Yoyogi top and the workpiece, the Yoyogi bottom end and the table are bonded with 502 glue to prevent movement during processing.
However, Yoyogi supports have the following disadvantages: long production preparation time; support positions are determined empirically, and they are inconsistent and uncontrollable.
Precision; Poor rigidity and insufficient support stability; Most of the contact methods of the wood and the workpiece are line contact, and the contact position is on the curved edge of the workpiece. The support effect is not ideal; It needs to be cleaned with organic solvent acetone. Long-term inhalation of acetone is not good for workers' health.
One. Structure and Function Analysis of Flexible Tooling Fixture
According to the size of the hood simulation block in the vehicle's main model check fixture, a preliminary tooling system model as shown in Figure 2 was made. The
The model is not a layout of the flexible tooling system, but only reflects the structural features that the flexible tooling system should include, including: base structure, sliding structure, support structure, and clamping structure. The sliding structure is driven by a hydraulic control system, including related hydraulic control mechanisms. The clamping structure performs suction clamping by a vacuum suction method, including a vacuum power source such as a vacuum pump.
Base structure: Set the positioning reference according to the positioning criteria to ensure the positioning accuracy of the workpiece and connect the carriers of each structure at the same time.
Sliding structure: Includes all guide rails, sliders, telescopic mechanisms on the fixture, and driving functions in the system for flexible positioning.
The hydraulic mechanism is used to realize the flexible positioning of the fixture in the three directions of X, Y and Z.
Supporting structure: The supporting structure in the system is composed of the telescopic mechanism of the clamp and the top bead group on the clamp head.
to make. The top bead makes point contact with the curved surface of the workpiece. In general, only the contact deformation at the positioning element will cause the workpiece position to shift, and the contact deformation at the clamping element will not directly affect the workpiece shift. The contact here is a contact at the clamping element and does not take into account the deformation caused by the contact.
The top bead material is LY12 aluminum alloy, which is adhered to the inside of the suction cup by 502 glue. The top of the bead is ball-shaped, and the bottom is cylindrical, which is convenient for clamping during processing. The design of the suction cup and the bead plays a supporting and damping role in the milling process.
The ball head structure at the top of the bead is always in point contact with the surface of the curved thin-walled part, which can well adapt to various curved structures. But and
Not all curved surfaces can be absorbed, and there are certain requirements for curvature. As shown in Figure 4, ideally, assuming that the surface of the workpiece is infinitely smooth, the minimum radius at which the suction cup and the bead can hold the workpiece is 10.5mm. However, due to the roughness of the workpiece surface and other factors, the minimum radius to meet the normal adsorption of the workpiece More than 10.5mm.
Clamping structure: It consists of a vacuum suction cup (as shown in Figure 5) and a vacuum pump at the top of the lifting column. The vacuum chuck should have sufficient flexibility and fit to meet the adsorption requirements of the workpiece surface. The selection of the vacuum pump should make the suction cup have sufficient adsorption force on the workpiece to reduce the deformation caused by vibration or warpage during processing.
Computer system in the application of flexible tooling
Computer control system for planning and decision-making of the entire flexible tooling system based on workpiece coordinate information files and generating
The corresponding control instructions are sent to the corresponding actuators. The computer control system can not only realize the movement control of each support unit, but also the optimization calculation of the layout of each support mechanism on the workpiece, thereby realizing the automation of the entire flexible tooling system.
The flexible tooling system designed in this paper is suitable for the machining of the main model check fixture and other thin-walled parts of aluminum alloy curved surfaces. According to the actual working conditions in the milling clamping, four kinds of flexible clamps with height specifications are designed. According to the data provided by Shanghai Shenmo Company, the clamping time of the tooling is 1/3 of the Yogi type, and the workpiece processing accuracy is increased by 20%, which has greater practicality. In addition, most of the tooling design uses standard modular structure. Reduced manufacturing and maintenance costs.