As customer requirements continue to grow, the need to deliver parts with unparalleled precision and sharp finishing becomes increasingly important. To achieve this result, professional CNC companies must minimize tool distortions. As the name suggests, tool deflection is the result of cutting forces exceeding the rigidity of the tool and causing it to bend. Tool deflection wears out the tool and exposes it to the risk of breaking. For these reasons, minimizing tool deflection is crucial to ensure part repeatability and high-quality finishing. It is also worth noting that minimizing tool distortions is economical as it reduces machine downtime. What affects machining accuracy? How to minimize the chance of tool damage? What should you pay attention to in CNC machines? We write about this below!
How the bending of the tool affects the processed object
The deflection of a tool is defined as the bending of a tool. Deformation of tools and objects occurs due to the load on the tool or object, which can cause significant changes. It occurs when cutting forces can overcome the stiffness of the tool, resulting in tool deflection. CNC machining tools have two ends. One end of the CNC machining tool can be freely held, while the other end is mounted in the tool holder. During CNC machining, the tool can exert force on the workpiece. When the CNC machining tool exerts force on the workpiece, the workpiece also exerts an opposite resistance to the tool. Several other working forces and resistances also act on the CNC machining tool. If the external force applied to the tool becomes greater than the tool's force, it can cause tool deflection. The deflection and bending of the tool have a significant impact on CNC machining.
Damage and bending of CNC tools, and machining accuracy
Bending or damage to tools causes the following complications in CNC machining:
- Tool deviation can damage the machined object or the tool itself.
- A bent tool shortens the life cycle of CNC machining. It destroys dimensional accuracy and causes numerous errors in CNC machining systems.
- Moreover, it results in a rough surface of the CNC machined object.
- Tool deviation can lead to serious dimensional errors - This greatly affects the surface being machined by CNC and can lead to potential surface damage.
- This shortens the tool's lifespan and causes it to crack - If not properly considered, tool deviation can cause part scratches.
- Tool wear may increase, and parts produced with tool deviations may be subject to variability, exceeding tolerances, or surface finish vibrations.
If you want to reduce tool deflection and achieve high-quality surface finish without sacrificing part quality, you need high-quality CNC lathes, high-quality tools, and experienced engineers to operate these machines. Tool deflection can be minimized by minimizing the distance from the tool holder to the tool tip.
How to reduce the deflection of a CNC tool?
Tool deflection in CNC machining is very common and can be catastrophic with minimal impact on part quality. Tool overhang cannot be completely avoided or prevented, but there are ways to reduce it. Cutting depth, proper endpoint, proper CNC machine programming - these are a few aspects of CNC machine care. Here are some tips to help you reduce tool deflection during CNC machining.
Increase the tool core's endurance by changing the diameter
The diameter is an important factor when considering deflection and bending, especially the core diameter. The core strength of the tool depends on its span and the length of the groove, and the difference between the span and the length of the groove can be defined as the core stiffness. Using the obtained tool, the core diameter can be used for calculations, then the core diameter becomes the neck diameter. By changing these values, the deflection of the end tool can be reduced. This can have a significant impact on the size of tools with long grooves.
Discover the difference between long grooves and long distances
Tool deformation can be minimized by understanding the key differences between tools with long grooves and long strokes. The difference in rigidity between tools with a long edge and a long reach is primarily due to the core diameter. A tool with more material is relatively stiffer than a tool with less material. In addition, tools with shorter grooves are harder and have a longer lifespan. Each type of tool has its strengths. To reduce deflection during a specific operation, the appropriate tool should be used.
Use the distance measuring tool to minimize tool deflection
Long-reach tools are most commonly used to remove material from crevices where the tool holder does not fit and cannot remove the material. The material is removed by inserting a non-cutting extension with the diameter of the tool. Deflection can be prevented by reducing the reach beyond the cutting edge to the diameter of the tool.
Application of the tool for long grooves
Tools with long grooves mainly have large cutting lengths. Tools with long grooves are most often used for creating slits in seamless walls. The size of the core diameter does not change and remains the same throughout the entire length of the cut. The larger the core diameter, the higher the likelihood of part distortion. In addition, some cutting edges may cause conical edges in the case of high feeds.
Reduce the throat length
The overhang is the length between the end of the CNC tool and the connection point. In the case of assembly as a cantilever beam, the tool must withstand bending stresses and horizontal and vertical forces. According to the theory of stress loads, shorter overhangs lead to a smaller impact of bending stresses.
Increase the rigidity of the tool
The deflection of a tool in CNC machining can be reduced by increasing the rigidity of the tool. CNC machining tools are typically made of high-speed steel. High-speed steel is often helpful in machining operations, but exposure to heavy loads can cause tool deformation. An alternative to high-speed steel tools is carbide tools, which are considered three times stiffer than high-speed tools. Carbide tools can be used to reduce deformation due to their brittle properties in CNC machines.
Summary
Generally speaking, the bending and unbending of a tool is the main cause of failures or damage to the processed product. The deformation of the tool during work can be minimized by applying certain strategies, such as reducing the distance of the tool grip from its apex and increasing its rigidity and core strength. Reducing the overhang also reduces the bending of the CNC machining tool. In order to reduce the number of failures and inaccuracies, it is worth using the best equipment and constantly participating in training to have knowledge about CNC machines and fully utilize the tools. Appropriate programming methods (using the best machining or milling program) and training the operator in this area will certainly improve functions and quality in the CNC machine, and other problems and questions related to tool bending will become irrelevant.