In most cases, the focus of improving production efficiency is to improve the cutting edge. After the cutting ability of the cutting edge is improved, the production efficiency can be continuously improved. However, due to the different characteristics of different parts, tool overhang has become one of the most important factors in machining. We are increasingly concerned about the performance of cutting edge cutting vibration. There is a tool overhang that tends to vibrate, but in most cases, this problem can be avoided by very slight cutting and the tool slowly approaching the workpiece, but at the expense of cutting efficiency. If the tool must enter the hole or cavity, a flexing force is generated, which can cause a tendency to vibrate.
Long overhanging tool
In today's machining sector, long tool overhangs are required for inner-hole turning, boring, cutting and grooving, and milling operations, and are increasingly used. In some cases, the same workpiece may require multiple types of operations. To date, many of the long-swing applications have low levels of processing performance and only meet the most basic requirements for parts that can be machined. That is, no cutting vibrations occur, and no mention can be made of production efficiency. Because of the vibration of the tool, it can easily lead to a decrease in processing safety, poor part quality, high noise levels, short tool life, and even machining of waste. Therefore, it is often only possible to use cutting parameters that are lower than the cutting edge capability, which increases processing costs and leads to longer production times.
In the milling process, due to the intermittent cutting action, vibration tends to occur during processing. Due to the use of long overhang tools, more and more milling processes tend to oscillate. Many methods can temporarily avoid the tendency to induce vibrations, such as using the correct milling cutter and tool path. However, when the overhang of the tool (distance between the spindle end shank flange and the cutting edge) exceeds three times the diameter of the shank, if a product that meets existing standards is to be machined, additional measures are required.
With the ever-increasing demand for tool overhangs that are four times or more tool-heavy during milling, we are eager to overcome the effects of vibration because vibration limits production efficiency. In particular, since the axial depth of cut and the feed rate have to be kept at a low level, the metal removal rate has not been exerted as it should be. In many cases, long overhangs must be used for either milling or hole turning. For example, on a multitasking machine tool, the B-axis spindle usually prevents the tool from approaching the workpiece, so you must use a tool with a longer overhang.
In order to overcome the tendency of vibration, we need to use more high-tech means to manufacture damping handles, which helps to better and more accurately minimize the amplitude. In other words, we can accurately determine the type of vibration in a field and the required damping damping settings. In the latest research and development work, when we design and apply vibration reduction technology, we combine a large number of professional technical means and experience to achieve a smoother metal cutting at higher processing speeds.
It is not possible to eliminate the vibration completely during processing, but it is now completely possible to reduce it to the lowest level without any influence on the process. Using advanced simulation methods, equipment, and measurement systems, combined with a deep understanding of structural dynamics, can completely eliminate the adverse effects of forces on the tool. This R&D work not only achieves the vibration reduction function, but also can more accurately find the specific tool overhang function.
For the milling process, the use of new standard shanks does not affect the machining performance due to tool overhang. The standard adapter minimizes the typical amplitude of the two different overhang ranges. There are currently two types of vibration-reducing handles of different lengths, which are respectively dedicated to the milling operations of up to 4 to 5 times the shank diameter and 6 to 7 times the shank diameter. Custom vibration damping handles can make the milling cutter rods longer. (The tool overhang referred to in this document refers to the distance between the spindle end shank flange and the knife edge.) These shanks are suitable for the most common areas of milling over long tool overhangs. Adopting the new system can increase production efficiency and greatly shorten the investment return time of the handle.
The milling adapter allows for increased axial depth of cut and infeed. This can greatly increase the potential for productivity, and brings high-efficiency milling possibilities to feature features such as cavities that exceed the machining range, such as when using slot cutters that are larger than the shank. The potential of new products can extend tool overhangs, or extend tool overhangs while increasing productivity.
Inner hole turning
Internal hole turning will involve tool overhangs more extensively. The hole of many parts is very deep, and the requirements for mast overhang are very strict. The overhang range is 4 to 14 times the diameter of the boring bar. The correct selection and application of the tool play a decisive role in the result of the operation, because the turning of the inner hole is very sensitive to vibration. One advantage of the Silent Tools damper mast is that the damper mechanism is located as close as possible to the cutting edge. This mounting method can quickly respond to any vibration tendency.
Ordinary steel masts are ideal for four-fold diameter overhangs. Solid carbide boring bars are suitable for applications with six times the diameter. For longer overhangs, the inner hole turning requires the use of a damper mast. Steel damper boring bars are used to machine holes with 10 times the overhang diameter. Reinforced cemented carbide damping boring bars are used for over 14 times diameter overhangs. Cutting and thread cutting usually use lower overhangs. In addition, the vibration characteristics of the mechanism of all machine tools are different, that is, the same cutting machining occurs at different frequency points due to the different characteristics of the machine tool itself. Therefore, it is important to develop a vibration-reducing standard tool that can operate normally in as large a frequency range as possible.
Aperture
In the process of taking vibration damping measures, the diameter of the used aperture and the boring bar vary greatly. The standard tooling system has a machining diameter of 10 to 250 mm, while the custom tool product covers a larger diameter.
There are three reasons for the use of vibration reduction masts for internal hole turning: maintaining small tolerances and excellent surface quality, minimizing machining time with the minimum number of passes, and using competitive and economical machining rates. At this time, production efficiency and safety are the most critical, because the competition of many parts of the manufacturing process is very fierce.
Now, the combination of the boring bar and the cutting head in the turning of the inner hole will benefit the machining. For small diameter machining with an aperture of less than 20 mm, two types of T and D inserts can be used to optimize the ongoing process at hand, for example, when the tolerance limits are very small and hard part turning. For the case where the hole diameter is greater than or equal to 20 mm, interchangeable cutting heads can be used, which provides great flexibility, high safety, and easy tool clamping.
It is very important to use high-pressure cooling technology when turning the bore. By adding coolant nozzles behind the cutting edge, chip control and discharge can be improved. The aim is to make full use of coolant equipment on the machine. The shank with a fixed nozzle ensures that the coolant is accurately sprayed into the cutting area, which improves chip breaking performance and discharges the chip breaking out of the hole and onto the conveyor belt. A quick-change tool holder system is used on the turning center. This system can usually be designed with a high-pressure cooling water supply nozzle. Conveniently uses high-pressure cooling water to blow the chips away from the processing area. These devices have built-in fittings and fluid supply tubes, and when an external pipe must be used, the tool change time can be very long. The optimized cutting unit is equipped with preset fixed nozzles, thereby reducing the assembly time of the machine tool.
Using the right method for internal hole turning can make a big difference in processing performance, safety, and machining results. For example, Sandvik Coromant's three-pass approach, where the programmed part includes a programming diameter larger than the required diameter. When it takes 30 minutes or more to process repeatedly to obtain a fine range of small tolerances, turning through the inner hole of Sandvik Coromant can be completed in less than five minutes. The advantage is particularly obvious. The reason why the processing time can be greatly shortened is that it eliminates the need for a lot of unnecessary, small-depth deep-rooted trial and error processing.
Because the cutting edge is not properly involved in the cutting and the measurement process needs to be stopped several times, the production efficiency is low and the cutting process is unstable, which will destroy the hole's machining accuracy. This machining method minimizes the correct number of cuttings and is suitable for overhanging in 3 to 4 times the diameter of the inner hole turning, in which the tool diameter ≥ 13 mm, suitable for a variety of material types, can use normal or recommended cutting parameter.
The method used now is to solve the vibration problem that has a negative impact on processing, which is totally different from the previous method. Although solving problems is still part of the application of these tools, our focus is on increasing productivity, ensuring process safety, and consistent quality.
The overall stability of the system is improved by increasing the rigidity of the system or by increasing the amount of damping of the system through the use of dampening tools. The use of the most rugged and stable tool holder system, such as the Coromant Capto interface, which conforms to the ISO standard, has no effect on the “system” parts. The natural frequency of the machine tool is another important factor of the "system". In order to achieve comprehensive optimization, consider improving the different structures of individual machine tools to increase overall stability.
Large masts with Coromant Capto C10 connections can be used for internal hole turning with diameters greater than 100 mm and up to 10 times the diameter of a hole, turning high quality holes at high metal removal rates. Quick change function can quickly install the mast with high accuracy. The mast is mainly used for flat lathes and heavy-duty machining of relatively large holes at large turning centers.
