Titanium alloy milling needs the right conditions
Compared with most other metal materials processing, titanium processing is not only more demanding, but also more restrictive.This is because the metallurgical properties and material properties of titanium alloys may have a serious impact on the cutting action and the material itself.However, if the right tool is selected and used correctly, and the machine tool and configuration are optimized to the optimal state according to the titanium processing requirements, then these requirements can be fully met and satisfactory high performance and perfect results can be obtained.Many problems encountered in traditional titanium processing are not inevitable, as long as the influence of titanium properties on the processing process is overcome, success can be achieved.
Titanium's properties make it an attractive component material, but many of these properties also affect its workability.Titanium has an excellent strength-weight ratio and is usually only 60% as dense as steel.Titanium has a lower coefficient of elasticity than steel, so it has a harder texture and better deflection.Titanium also has better corrosion resistance than stainless steel and lower thermal conductivity.These properties mean that titanium will produce higher and more concentrated cutting forces during machining.It is easy to produce vibration and lead to the cutting vibration;In addition, it is easy to react with cutting tool material during cutting, thus aggravating crescent depression wear.In addition, its thermal conductivity is poor, because the heat is mainly concentrated in the cutting area, so the tool processing titanium metal must have high thermal hardness.
Stability is the key to success
Some machining workshops find it difficult to process titanium effectively, but this view does not represent the trend of modern machining methods and tools.Part of the problem is that titanium is a new technology and lacks experience.In addition, difficulties are often related to expectations and the experience of the operator, especially those who are used to working with materials such as cast iron or low-alloy steel, which generally have very low processing requirements.Titanium, by contrast, seems to be more difficult to process because the same tool and the same rate cannot be used and the tool life is different.Even compared to some stainless steels, titanium is still more difficult to process.We can certainly say that the processing of titanium metal must take different cutting speed and feed as well as certain preventive measures.In fact, compared with most materials, titanium is a completely direct processing of materials.As long as the titanium workpiece is stable, the clamping is firm, the machine tool is selected correctly, the power is right, the working condition is good, and is equipped with iso 50 spindle with short tool overhang, all problems will be solved - as long as the cutting tool is correct.
However, in the actual milling process, the requirements for titanium metal processing are not easy to meet, because the ideal stability conditions are not always available.In addition, many titanium parts have complex shapes and may contain many fine or deep cavities, thin walls, bevels, and thin supports.To successfully process such a part, you need to use a large overhang, small diameter tool, which will affect the tool stability.Potential stability problems often occur when titanium is processed.
You have to think about vibration and heat
The non-ideal environment also includes other factors, one of which is that most machine tools are currently fitted with is040 spindles.If the machine tool is used with high intensity, the new tool state cannot be maintained for a long time.In addition, if the part structure is more complex, it is usually difficult to effectively clamp.The challenge does not end there, of course. The cutting process must sometimes be used for full groove milling, side cutting or contour milling, all of which may (but not necessarily) produce vibration and poor cutting conditions.It is important that when setting up a machine tool, attention must always be paid to improving stability to avoid the tendency of vibration.Vibration can cause blade breakage, blade damage and unpredictable and inconsistent results.One improvement is the use of multiple clamps to bring the part closer to the spindle to help offset the vibration.
Since the titanium metal can maintain its hardness and strength at high temperatures, the cutting edge will encounter high forces and stresses, coupled with the high heat generated in the cutting area, which means that work hardening is likely to occur, which can lead to certain problems, especially for subsequent cutting processes.Therefore, the selection of the best indexable blade and groove shape is the key to the success of processing.Past history has shown that the fine grain non-coated blade grades are very suitable for titanium processing;Today, blade grades coated with PVD titanium can greatly improve performance.
Accuracy, condition and correct cutting parameters
The accuracy of tool runout in axial and radial direction is also important.For example, the cutting edges around the milling cutter can quickly become damaged if the blade is not properly mounted into the cutter.When cutting titanium, other factors, such as poor tool manufacturing tolerances, wear and tool damage, defective or poor handle quality, machine spindle wear, etc., can greatly affect tool life.Observations show that these factors are responsible for 80% of all cases of poor processing performance.Although most people prefer to use a positive front corner groove, a slightly negative front corner groove can actually remove material with a higher feed and feed up to 0.5mm per tooth.But this also means that the best stability must be maintained, that is, the machine should be very strong, and the clamping should be extremely stable.
Except for milling (had better use round blade), should avoid to use 90 Angle, doing so usually helps to improve the stability and overall performance, especially when used under shallow cut deep, when making a deep cavity milling, a recommended practice is through the tool by the handle and the use of variable length of cutting tools, rather than using a single length in the whole process of the long knives.
Adjusting the cutting parameters to overcome the vibration caused by reducing feed per tooth is a traditional solution, but this approach is not appropriate as it can have a catastrophic impact on tool life and cutting performance.Indexable blades require a certain amount of cutting edges to be rounded to increase cutting edge strength and obtain better adhesion of the coating.
When milling titanium, the tool is required to operate at least a minimum feed - usually 0.1mm per tooth.If there is a tendency to throw vibration, blade damage or reduced tool life problems will be inevitable.Possible solutions include accurately calculating the feed per tooth and ensuring that it is at least 0.1mm.
The spindle speed can also be reduced to achieve the initial feed rate.If the minimum feed per tooth is used and the spindle speed is incorrect, the impact on tool life can be as high as 95%.Reducing spindle speed usually increases tool life.
Once a stable operating condition is established, the spindle speed and feed can be increased correspondingly to obtain the best performance.Another option is to take some of the blades out of the milling cutter or to choose a milling cutter with fewer blades.