The requirements of CNC machine tools for NC cutting tools

 

The requirements of CNC machine tools for CNC cutting tools

The structure of CNC turning tools is generally two kinds of organic clamp type and integral welding type. The materials that are widely used are mainly cemented carbide, which has high hardness and good steel toughness. Cemented carbide is generally used for high-speed turning, and high-speed steel is generally used for low-speed turning.

The CNC lathe can be used for both roughing and finishing. In order to enable rough machining to be processed with a larger cutting depth and a larger feed rate, the CNC turning tool is required to have high strength and good durability. Fine turning is first to ensure the machining accuracy, so the tool is required to have high precision and good durability. In order to reduce the tool change time and facilitate tool setting, machine clamp tools should be used as much as possible.

The turning tools used in CNC turning are generally divided into three categories, namely, pointed turning tools, arc turning tools and forming turning tools. A turning tool characterized by a straight cutting edge is generally a sharp-cutting tool. The tool tip of this type of turning tool is mainly composed of straight lines and secondary cutting edges, such as 90° internal and external turning tools, left and right face turning tools, grooving turning tools, and various external rounds with very small tool tip chamfers. Inner hole turning tool. When machining parts with this type of turning tool, the contour shape of the part is mainly obtained by the displacement of an independent tool tip or a linear main cutting edge, which is completely in principle with the contour shape of the parts obtained during machining of the other two types of turning tools. different.

The arc-shaped turning tool is a special turning tool for CNC machining. It is characterized in that the shape of the cutting edge constituting the main cutting edge is a circular arc with small roundness error or line profile error. Each point of the arc blade is the tip of the arc-shaped turning tool. Therefore, the tool position point is no longer on the arc, but on the center of the arc. The turning tool arc radius is theoretically independent of the shape of the processed part, and can be flexibly determined or confirmed after measurement as required.

When the tip of some pointed or shaped turning tool has a certain arc shape, it can also be used as this type of turning tool. The arc-shaped turning tool can be used for turning inner and outer surfaces, and is especially suitable for turning various smoothly connected forming surfaces.

Forming turning tools are commonly known as model turning tools, and the contour shape of the processed parts is completely determined by the shape and size of the turning tool blade. In CNC turning processing, common forming turning tools include small radius arc turning tools, non-rectangular turning tools and thread turning tools. In CNC machining, the forming turning tool should be used as little as possible or not. When it is really necessary to select it, it should be explained in detail in the process preparation document or the processing procedure sheet.

THE STRUCTURE OF CNC TURNING TOOL

The machine clamp can be indexed to the composition of the turning tool
According to the different clamping structure, it can be divided into the following forms
Eccentric
The eccentric clamping structure uses an eccentric spindle at the upper end of the screw to clamp the blade on the tool bar. The structure relies on eccentric clamping and the screw is self-locking. The structure is simple and easy to operate, but it cannot be positioned bilaterally. When the eccentricity is too small, the precision of the blade manufacturing is required to be high. If the eccentricity is too large, the blade is easy to loosen under the impact of cutting force, so the eccentric clamping structure is suitable for continuous and smooth cutting.

Leveraged
The lever-type clamping structure applies the principle of leverage to clamp the blade. When the screw is turned, the clamping force is generated by the lever, so that the blade is positioned on the side of the slot. When the screw is unscrewed, the blade is loosened, and the semi-cylindrical spring plate can keep the position of the shim. The structure is characterized by high positioning accuracy, firm clamping, reasonable force, and convenient application, but it has poor manufacturability.
　　
The inner hole of the blade is positioned on the pin of the blade slot. When the pressure block with a bevel is pressed down by the compression screw, one side of the wedge abuts against the boss on the tool bar, and the other side pushes the blade to the cylindrical pin of the middle hole of the blade Press the blade up. The structure is characterized by simple and convenient operation, but low positioning accuracy, and the clamping force is opposite to the cutting force.
　　
Wedge type clamping structure
Regardless of the clamping method used, the blade must meet the following conditions when clamping:
①The clamping and positioning of the blade should conform to the principle of positioning and clamping of the cutting force, that is, the resultant force of the cutting force must act on the periphery of the blade supporting surface.
②The positioning of the peripheral dimensions of the blade must meet the three-point positioning principle.
③The resultant force of cutting force and clamping force on the positioning base surface (blade and cutter body) must be greater than the alternating force that causes the blade to leave the positioning base surface due to cutting vibration.