Being more competitive in machining turned parts and multitasking parts means keeping pace with the cutting edge of cutting tools and cutting methods. The process that most manufacturers need to perform is usually the cutting of bars, tubes and mechanical parts. Since it is often the first or last step, it is necessary to continue optimization. So how does tool development now address the challenge and how best to solve the cut-off problem?
First, we must establish the best cutting process. When analyzing the cutting process, the first is to classify according to the batch size. When choosing a tool, consider versatility and specificity. For applications where there are multiple or even one variation of a single part, a common tool is often required. In volume production, special tools are required to establish specific processes with the highest possible price/performance, safety and quality consistency. For medium-volume applications, high productivity and safety with the smallest number of suitable tools is its most important feature.
When looking for the right tool, the cut should be considered as a combination of the three basic factors: the blade overhang required to cut the diameter, the tool width will be affected by the overhang, and the tool width will affect the possible feed of the tool. The rate, while the feed rate determines the time required to complete the process. In addition, the feed rate also determines the blade geometry a€“ the sharp blade geometry is suitable for low feeds, while the robust insert geometry is suitable for high feeds.
Feeding is also related to processing conditions. Processing conditions can be evaluated by stability levels, material conditions, and type of cut to determine if the condition is good, general, or harsh. Workpiece materials can also affect machining conditions and the choice of insert grades and cutting parameters.
Second, it is necessary to establish the type of tool holder and tooling system that is most suitable for the process. The diameter of the workpiece is critical and the shank is directly related to the required depth of cut. Most cutting depths are in the medium processing range of 6 to 28 mm at the time of cutting, and the depth of cut is 28 to 55 mm for deep cutting, and 0.25 to 6 mm for shallow cutting.
When choosing a tool holder, it is necessary to balance versatility and stability. Batch size and operational changes will also affect the selection direction. Since the tool overhang can be set to suit different diameters, the tool that adjusts the blade can be used for a variety of workpiece diameters. On the other hand, the shank with integral reinforced blade is only suitable for a range of diameters, but provides maximum strength.
Furthermore, it is necessary to determine the optimal step for blade selection at the time of cutting. The cutting edge guides the tool during cutting and controls the chip while determining the formation of flash and burrs. The quality of the interface between the relatively thin blade and the shank is fundamental to tool stability. In order to maintain stability, a good track and V-shaped blade holder structure is required, and it is preferred to use it with a relatively long blade.
The width of the blade varies depending on the cutting depth of the cutting tool. A small cutting depth (workpiece diameter) can be used with a thin blade, while a larger cutting depth requires a wider blade to ensure strength. The number of insert holders on the shank corresponds to the width of the insert. Each system has its own specific blade width range. For example, CoroCut single and double-edged systems have 8 different blade widths ranging from 1.5 to 8 mm, while CoroCut 3 Suitable for shallow cutting, there are 3 blade widths ranging from 1 to 2 mm.
When selecting the insert geometry and grade for the process, the most appropriate combination of cutting edge sharpness, strength and width should be established to ensure the highest possible feed per revolution for higher production efficiency. The sharp blade geometry is easy to cut, requiring less machine power and minimizing vibration trends. The rugged trough has a larger negative rake angle and the cutting edge is enhanced to withstand the more demanding cutting and roughing operations and achieve higher feed rates.
For blade grade selection, the cutting edge strength should be prioritized to ensure the safety of the cutting process. This means that resilience should be prioritized rather than sharper and harder troughs and grades. Secondly, for the operating factors and processing conditions, to ensure the desired surface quality and feed rate, the grade should continue to be improved to make the blade more wear-resistant for higher feed rates and longer tool life.
Then, the burrs and burrs should be minimized when cutting. Burr formation is a control issue in the cutting process. The rake angle of the cutting edge (principal angle) largely determines the formation of the burr. The 0?° lead angle generally produces the most straight cutting path and the best surface quality, but leaves burrs at the end of the cut. After the severed portion is dropped and the cutting edge passes through the center of the workpiece, the beveled edge minimizes or completely cuts the burr. Since it is easy to control the tool from the expected straight tool path, a cutting edge with a large rake angle can have a negative impact on the straightness of the slit. Therefore, although it is appropriate to consider the 10?° and 15?° rake angles for the low feed groove shape from the sharp side, a moderate bevel edge (5?°) is usually the best choice.
The sharpness of the cutting edge plays an important role in limiting the formation of flash. Grinded positive rake cutting edges minimize flash, while solid grooves with large rounded tips make it easy to form flash, especially when using large feed rates. An additional pass after cutting with the same tool or finishing tool is one of the solutions for optimum productivity.
Finally, for good shut-off, a suitable and adequate supply of coolant and its direction are often critical. A tool block with an integrated coolant supply is a solution. In addition, coolant supply from below can extend tool life and improve chip control. When the bar is cut, the diameter of the workpiece being cut becomes smaller and becomes close to zero when it reaches the center. The cutting speed is thus significantly reduced, thereby increasing the tendency of the built-up edge to form on the cutting edge, which in turn has a negative impact on tool life. Increasing the spindle speed and reducing the feed rate by a few millimeters before passing through can compensate for this adverse effect.
For highly competitive cut-off applications, optimized feed rates are a priority, and feeds largely determine the level of productivity. Feeding also means that chip formation can be controlled by changing the feed during cutting, dwelling or plunging. It is also possible to minimize the vibration tendency and increase the feed rate when reducing the cutting speed. The feedrate should also be set for the correct tool pressure to ensure a straight tool path and reduce it before the end of the cut to avoid forced cuts while ensuring safety during intermittent cutting. Therefore, the combination of feed, blade and shank is a critical optimization factor when cutting.
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