Introduction
CNC machined components are the backbone of every industry. One of the biggest challenges seen in computer numerical control (CNC) machining is tool deflection. The problem area of this challenge is that it creates machine chatter and impairs the finish of the surface or the machine part. It could also create errors in dimensional accuracy. As a standard practice the tool is placed on the raw material block. However the counter pressure of the material when the operational force of the full tool acting on it,tends to deflect the tool in unknown directions. This impacts the accuracy as well as the smooth finish of the surface. Hence CNC machining operations have to focus a great deal on tool alignment and the counter pressure of surfaces of the materials. Since tool reflection is a common error it needs solutions that ensure the causes are identified. In the following sections the factors that need to be taken care of to minimize tool deflection are discussed in detail.
Tool deflection and its impact on machined components
When the cantilevered position of the CNC machine tool is displaced from its alignment it causes tool deflection. The problem area is the placement of the tool inside the chuck and the free movement of the operating side of the tool or the cantilever.
Surface of the material throws a resisting force to the operating end causing the errors. Along with the resisting force the CNC tool is also under stress from other operational forces. This causes stiffness and especially when it is not able to sustain the impact of the external forces. Eventually the tool will deflect from the alignment.
The errors caused by the tool reflection are: the tool or the workpiece will fail, the life cycle of the tool is diminished, the dimensional accuracy of the product is lost, and the smooth finish of the surface is destroyed.
How to prevent tool deflection?
The fact of the matter is tool deflection cannot be completely avoided. However some strategies can be used to minimize the deflection. The CNC machined components machinists have the experience to test the strategies and lower tool deflection.
- Shorten the length in overhang
The objective of this strategy is to control the distance between the tip of the operating tool and the CNC tool. The tool when mounted on the cantilever beam experiences stress in the vertical and horizontal directions externally. This load stress theory is important in a cantilever beam. The length has to be shortened to overcome tool deflection. When the overhang length is short, then the bend stress also becomes minimal. Hence it has no additional impact on the bend stress to move the tip away from the workpiece.
- Strengthen tool core
The strength of a tool is its core area and it is dependent on the length of the flute and its reach. The difference between the length of the flute in fact defines the rigidity of the core. Hence in CNC machines the long flute tools are expected to have a long life in radial consistency. The ideal diameter has to be thick. This gives the material the wall to absorb any stress due to shearing and continue to be rigid.
- Improve tool stiffness
It is a standard practice to use high speed steel in CNC machining tools. But despite the course strength of the speed Steel machining operations are likely to impact with higher load. This also leads to many tools to deflect from its chuck. Therefore this one of the solutions in consideration to make the tool stepher and improve the course strength is carbide. In carbide tools it when carbide is used to manufacture these tools it is 3 times more than the ordinary high speed. But the limitation of carbide is that it is very b r i t t l e. Hence it can be used only to reduce the deflection. When carbide tools are used the operator has to pay great attention to avoid the tool snapping.
Tool deflection can be controlled in a CNC machine by these three Strategies to improve the life expectancy of the tool.
