数控液压拉伸垫关键技术的研究

发布时间：2018-04-15 09:16

本文选题：数控液压拉伸垫 + 预加速　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：拉伸垫是一种压力机配套装置,其作用是压紧工件边缘防止冲压时工件起皱。传统的拉伸垫采用以下三种结构形式:空气拉伸垫、液压拉伸垫、液压空气混合缓冲拉伸垫。现今,机械压力机正向着大行程、大吨位、高速度的方向发展,传统的拉伸装置已经不能满足新型压力机深拉伸、大吨位、低振动的工艺技术要求。为适应压力机的发展,将精确的数控技术与液压相融合,得到新型的拉伸垫——数控液压拉伸垫。数控液压拉伸垫的功能特点可以使压力机生产冲压次数更高、冲压质量更好、冲压噪声更小。因此,以数控液压拉伸垫的功能设计为例,对拉伸垫预加速功能、冲压过程中改变压边力功能(冲压材料与模具之间的摩擦力)、拉伸垫下极限位置闭锁功能进行研究,为数控液压拉伸垫的设计提供有效的帮助。因而,具有一定的参考价值。本文针对数控液压拉伸垫的关键功能——拉伸垫下行预加速控制。从拉伸垫与滑块的接触速度入手针对有/无预加速功能,分析主液压缸内的压力波动峰值和压力平稳时间。运用速度反馈控制数控液压垫拉伸垫的预加速值,确定数控液压拉伸垫的预加速相对于滑块速度的相对系数为80%左右。无预加速功能情况下,系统压力波动出现时间早,且产生二次阶跃,峰值大,压力平稳时间在370ms;有预加速功能情况下,压力波动出现在与滑块接触的时刻,且无二次阶跃变化,压力变化峰值低,压力平稳时间为140ms;从而,确定数控液压拉伸垫预加速功能使用速度和位置反馈控制方案。基于压力反馈研究数控液压拉伸垫的变压边力控制,确定在冲压板材时改变拉伸垫压边力的液压系统结构,调整四个压边缸压力。通过对冲压钢板的模拟,对压边缸内部压力峰值变化与平稳时间进行分析,确定压边缸设计和其压力反馈控制方案。采用位置反馈研究数控液压拉伸垫的位置闭锁控制,使拉伸垫在滑块运动到冲压下极限位置时,可以锁定不动待滑块返程500ms后复位。明确其不跟随滑块返程运动的设计原则;通过对拉伸垫无闭锁、有下移闭锁和有下移闭锁取料位几种情况的分析,得到压力变化曲线,为解决数控液压拉伸垫闭锁问题提供位置反馈的解决方案。
[Abstract]:Tension pad is a press supporting device, its function is to press the workpiece edge to prevent the workpiece wrinkle.The traditional drawing pad adopts the following three types of structure: air tension pad, hydraulic tension pad and hydraulic air mixed buffer tension pad.Nowadays, the mechanical press is developing towards the direction of long stroke, large tonnage and high speed. The traditional drawing device can no longer meet the technical requirements of deep drawing, large tonnage and low vibration of the new press.In order to adapt to the development of press, the precise numerical control technology is combined with hydraulic pressure, and a new type of drawing pad-numerical control hydraulic drawing pad is obtained.The function characteristic of NC hydraulic drawing pad can make the press produce higher punching times, better stamping quality and less punching noise.Therefore, taking the function design of numerical control hydraulic drawing pad as an example, this paper studies the function of pre-acceleration of drawing pad, changing the function of blank holder force (friction between stamping material and die, locking function of limit position under tension pad) during stamping.For the numerical control hydraulic drawing pad design to provide effective help.Therefore, it has certain reference value.This paper aims at the key function of NC hydraulic tension pad-the downlink pre-acceleration control of the drawing pad.Based on the contact speed between the tension pad and the slider, the peak pressure fluctuation and the pressure stationary time in the main hydraulic cylinder are analyzed.The speed feedback is used to control the pre-acceleration value of the NC hydraulic cushion drawing pad, and the relative coefficient of the pre-acceleration of the NC hydraulic tension pad relative to the speed of the slider is determined to be about 80%.In the case of no pre-acceleration function, the pressure fluctuation of the system appears earlier, and produces the second step, the peak value is large, and the pressure stable time is 370 Ms. In the case of pre-acceleration function, the pressure fluctuation occurs at the time of contact with the slider, and there is no second step change.The peak value of pressure change is low and the pressure stationary time is 140 Ms. Therefore, the speed and position feedback control scheme of the pre-acceleration function of numerical control hydraulic tension pad is determined.Based on pressure feedback, the variable blank holding force control of NC hydraulic drawing pad is studied, and the hydraulic system structure of changing the blank holder force during stamping is determined, and the pressure of four blank holder cylinders is adjusted.Through the simulation of punching steel plate, the peak pressure change and stationary time of the blank holder cylinder are analyzed, and the design of the blank holder cylinder and its pressure feedback control scheme are determined.The position locking control of the NC hydraulic tension pad is studied by position feedback. When the slider moves to the limit position under the punching position, the tension pad can be locked and reset after the slider returns to the 500ms.The design principle of the return movement of the slider is made clear, and the pressure change curve is obtained by analyzing the situation that the tension pad has no latch, there is a downshift latch, and the material level is taken with a downshift latch.It provides a position feedback solution for solving the lock problem of NC hydraulic tension pad.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH137;TG659

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