在工科生心中,通常有一个概念:三维空间中的物体有六个自由度。图示为右手坐标系,其中六个自由度分别是沿X、Y、Z轴的直线运动和绕这三个轴旋转,满足右手螺旋定则。
然而,这个概念误导了人们认为“实现空间任意方向加工机床必须有6个自由度或6个轴”。事实上,不是所有实现任意角度加工的机床都需要包含6个轴。这就是问题的关键。
传统三轴机床在处理复杂表面或具有多孔结构的部件时,需要特殊夹具来使刀具从不同方向与工作件接触,并进行多次过程变换。相比之下,五轴联动数控机床可以在单一装夹下进行高速、高精度加工复杂形状部件。
五轴联动数控机床通过控制刀具位置和姿态来实现工作件加工。因此,最重要的是如何描述刀具位置和姿态。
三轴数控机床只能改变刀具位置,但其姿态固定,如立式三轴机床,其刀锥一直沿着Z軸方向。在X、Y、Z三个直线坐标值中确定刀具位置和姿态。
五轴数控机床是在三轾基础上增加两个旋转軸A、B(或C),其中任选两个。由于这两个额外的旋转軸,使得每次操作后刀具(测头)都能以不同的方式对待工作件,从而减少了使用特殊夹持装置并重复调整所需次数。此外,它们允许更快地切割材料并提供更高的精确性,因为它们能够在一个步骤中完成许多任务,而不是依赖于重新设置工具或者使用专门设计的人造器械。
至于为什么选择5-axis CNC machining而不是6-axis,有几个原因:
工作流程效率:5-axes machines are more efficient in terms of the number of setups and tool changes required to complete a job, which can lead to faster production times and lower costs.
产品质量:The ability to perform complex operations in a single setup reduces the risk of errors and increases precision, resulting in higher-quality products.
Space constraints: Many manufacturing environments have limited space, making it difficult to accommodate larger machines with additional axes.
In summary, while it may seem logical that a machine would need six axes to achieve arbitrary angles of movement, the reality is that five axes can be sufficient for most applications due to advancements in technology and design. The key factor is not just the number of axes but also how they are utilized by the CNC system.
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