Posted On: September 28, 2020
Tool deflection is one of the common challenges in CNC machining. It can instigate machine chatter, ruin the surface finish of a machined part, mess up the dimensional accuracy, etc. Generally, the tool is firmly placed in the chuck but often during the operation, the material’s opposing force surpasses the operational force of the tool it pushes or deflects the tool in an unexpected direction. However, the accuracy, surface finish, and CNC machining operation depend on tool alignment up to some extent. Therefore, if tool deflection occurs, it can cause several errors in the CNC machining process. This is why one must have a complete understanding of what tool deflection is, what are its causes, and strategies to reduce it. This post discusses all of these factors for minimum tool deflection possible.
An Overview of Tool Deflection and its Impact on CNC Machining
Tool deflection is exactly what its name says. It is the deflection of the tool from its expected alignment. The CNC machining tool is gripped between the chuck in a cantilever position. This means one end of the tool is held inside the chuck and the other operating end of the tool is free or cantilevered. Since in CNC machining operations, the tool consistently exerts a force against the workpiece, the workpiece material also offers resisting force. Along with the resisting force, the CNC tool is impacted by different operational forces, therefore if the tool stiffness does not sustain external forces, the tool deflects from its set alignment.
The tool deflection can certainly cause the following errors in CNC machining.
- Catastrophic failure of either tool or workpiece
- Tool life-cycle depletion
- Dimensional inaccuracy
- Rough surface finish or potential surface damage
Strategies to Prevent or Reduce Tool Deflection
Although tool deflection is not 100% avoidable, it still can be reduced by using some strategies and tactics. The CNC machinist can adopt the following tried and tested strategies to reduce tool deflection while working.
- Minimize Overhang Length:
The distance between the clutching point of a CNC tool and the operating tip of a tool is called overhang length. Since the tool is mounted as a cantilever beam, it is always subjected to bending stress and external vertical and horizontal forces. According to the load-stress theory for a cantilever beam, the shorter the overhang length, the lower is the bend stress impact. Based on this concept itself, the minimization of overhang length of the tool helps in the reduction of tool deflection.
- Enhance Tool Core Strength:
The core strength of a tool depends on its flute length and reach. The difference between flute length and reach defines the rigidity of the core. Therefore, for radial consistent CNC machining operations, long flute tools perform well. The core diameter if kept thick, offers more material wall to absorb shear stress therefore, the core strength and rigidity increase ultimately.
- Enhance Tool Stiffness:
Generally, CNC machining tools are made of high-speed steel (HSS). High-speed steel is good for machining operations but on exposure to higher stress load, the HSS tools are prone to deflection. Carbide tools are a considerable solution over HSS tools since carbide is 3 times more rigid than HSS. However, carbide is a brittle material, it can be used for the reduction of deflection. If carbide tools are used, the operator needs to pay attention if the tool breaks.
These are the strategies of reduction in tool deflection during CNC machining. However, a quality CNC machine, premium quality tool, and an experienced operator can ultimately help in the reduction of tool deflection. Therefore, one must source CNC machining services from trusted organizations like BDE, Inc. The company is recognized for its high-quality CNC part production services and precision CNC machining services.
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