Thread whirlwind milling is a machining method of milling thread from workpiece with carbide forming cutter installed on high-speed rotating cutter head.
High speed thread milling device matched with horizontal lathe or Swiss lathe is usually required, and there are also special whirlwind milling machine tools.
It is named for its high milling speed (up to 400m/min), fast machining efficiency and cutting spatter like a whirlwind in the machining process.
Whirlwind milling can realize dry cutting, heavy load cutting, difficult to machine materials and ultra-high speed cutting, with low power consumption.
The surface roughness value can reach Ra=0.8 μ m.
When whirlwind milling, the spindle speed of the machine tool is slow, so the machine tool has high motion precision and good dynamic stability.
It is an advanced thread processing method.
1. Characteristics of whirlwind milling thread
Compared with other thread processing methods, whirlwind milling has the following advantages:
(1) High processing efficiency, more than 10 times higher than the traditional processing efficiency.
(2) Due to the forming process, the product is formed with one tool, and the eccentric cutting does not need to retreat the tool, with high precision.
(3) The whirlwind milling transformed from lathe does not change the lathe structure, the spiral angle is adjustable, and the installation is convenient;
Save the cost of investment in special aircraft equipment.
(4) The surface roughness value can reach Ra=0.8 μ m.
The machining accuracy is improved by 2 levels.
(5) The lathe axial feed is slow, easy to operate, and can reduce the professional skills of workers.
2. Working principle of whirlwind milling
The whirlwind milling needs to complete five machining movements in the machining process, as shown in fig. 4-115.
Fig. 4-115 machining movement form of whirlwind milling
(1) The cutter head drives the carbide forming cutter to rotate at a high speed (main motion).
(2) The spindle of the machine tool drives the workpiece to rotate slowly (auxiliary movement).
(3) The whirlwind milling moves along the axial direction of the workpiece according to the screw pitch or lead of the workpiece. (feed movement).
(4) Radial motion of whirlwind milling (cutting motion).
(5) Within a certain angle range, the whirlwind milling also has a degree of freedom (rotary motion) for adjusting the spiral angle.
3. Classification and application of whirlwind milling
(1) The cutting forms of whirlwind milling are divided into internal milling method and external milling method.
Their characteristics and application scope are shown in table 4-25.
Table 4-25 method of whirlwind milling thread
scope of application
Whirlwind milling external thread
Internal milling method
1. The cutting is stable;
2. The thread surface roughness value is small;
3. Long tool life;
4. Chip removal is difficult;
5. Workpiece diameter is limited by the structure of machine tool and cyclone milling device.
1. Suitable for milling threads with thread rise angle ≤ 5 “;
2. Thread diameter <100mm.
External milling method
1. The cutting vibration is larger than that of the internal milling method;
2. The surface roughness value of thread is larger than that of internal milling method;
3. Low tool life.
1. Threads with thread rise angle >5 °;
2. Thread diameter >100mm.
Whirlwind milling internal thread
1. Smooth cutting;
2. The rotation diameter ratio is 0.6~0.7.
Internal thread with diameter ≥ 100mm
Note: the rotation direction of the workpiece shown by the solid line in the fig. is forward milling, and the direction shown by the dotted line is reverse milling.
(2) Whirlwind milling can process bone screw, lead screw, worm and screw parts, as shown in fig. 4-116.
Fig. 4-116 parts processed by whirlwind milling
4. Implementation mode of whirlwind milling
(1) Special whirlwind milling machine:
Although this method has high precision and wide processing range, it requires a large amount of investment in special equipment and poor flexibility.
It can not complete a series of other processing procedures such as subsequent turning milling and drilling that can be processed by the walking machine.
After the appearance of the power tool holder for the whirlwind milling of the walking machine, the special machine has been completely eliminated in the processing of bone screws, small worms, micro small lead screws and other fields.
(2) Horizontal lathe + whirlwind milling cutter base:
This method is a transformation method adopted in China.
The investment is small but relatively low-end.
It can only process large parts such as lead screws.
It can not process micro parts such as bone screws, and the accuracy is limited.
(3) Swiss type walking machine + whirlwind milling cutter base:
This method only needs to install a whirlwind milling cutter base on the walking machine, with high precision, NC automatic processing, wide processing range and no need to purchase special machine tools, low investment and high efficiency.
And it can complete a series of subsequent processing procedures such as turning, milling and drilling, and realize unattended and efficient processing;
It is the most advanced processing solution for bone screws, small worms and other parts.
5. Selection of thread whirlwind milling cutter
In the steam turbine industry, the machining of cylinder split screw hole is one of the most difficult problems in machining technology.
Traditional machining methods generally use slotted taps.
Because different sizes of thread require different sizes of taps, tap machining has the limitations of high manufacturing cost, low production efficiency, and difficult to control the surface roughness of the workpiece.
Shanghai steam turbine works uses the three-axis linkage function of CNC gantry milling and CNC boring and milling machines to whirlwind milling threads.
By changing the size of cutter compensation, the milling thread specification can be controlled.
During cutting, the spindle of the machine tool drives the tool bar to rotate rapidly at 700 ~ 1400r/min, and at the same time, with the interpolation rotation of the X and Y axes, the milling cutter feeds upward from the hole bottom along the thread pitch direction.
This processing method will not affect the machined thread surface due to chip, and the surface roughness value of both sides of the thread can reach Ra ≤ 3.2 μ m。
Whirlwind milling can process threads of different diameters, different pitches, left-right rotation, meter and inch systems.
The minimum processing range of thread diameter is M42, and the maximum is only limited by the Y-axis range of the machine tool.
M270 has been processed on CNC gantry milling × 3.
As shown in fig. 4-117.
Fig. 4-117 whirlwind milling of large threads by using the three-axis linkage function of CNC machine tool
When some thread diameters are greater than 120mm, there are two types of milling thread arbors:
One is an integral type, that is, the taper handle and the cutter bar are made into a whole, and the whirlwind milling cutter and blade are installed;
The second is ABS extension rod type, that is, the taper handle and cutter rod are connected by ABS, so the length and diameter of the extension rod can be arbitrarily selected according to the depth and specification of the screw hole, and then the whirlwind milling cutter is installed.
Compared with the two, the latter is obviously more flexible.
The whirlwind milling insert adopts a convertible blade.
The cutting part of the blade is usually 60 °, with 4 cutting edges, which can be applied to thread cutting of various pitches.
The cutting amount of each tooth of the convertible blade depends on the ratio of the shank diameter to the shank length.
Generally, the best or shortest ratio is selected.
The diameters available for ABS shank internal thread whirlwind milling cutter produced by Harbin Yigong and Mianyang tools are φ25mm, φ32mm, φ40mm, φ 50mm, φ63mm, φ80mm , and φ100mm and other specifications.
6. Typical product introduction
One process completes rough machining and finish machining.
The newly developed Hao en worm whirlwind milling process can optimize the existing whirlwind milling process and increase benefits.
Hao’en has developed a set of milling tools with the new concept of whirlwind milling and layered milling.
These are specially designed for machining worm and thread with larger allowance.
In order to achieve this goal, an independent pre machining blade is added, and the workpiece can be machined to the specified outer diameter.
For a tool with 9 blades, the layered milling concept uses differentiated rough and finish machining so that each cutting edge can share the same cutting amount, which means that each cutting edge can obtain a significantly longer service life.
The finish machining cutting edge can produce smooth thread tooth surface within the optimized machining range.
No matter how the outer diameter of the workpiece is, it can be combined with cutting edges of various profiles to extend the tool life and produce the best worm and thread.
Hao en worm gear whirlwind cutting can be used to process single line, multi line threads and various profiles.
Moreover, the precision polished S271 double-edged indexable blade is customized for different thread shapes and processing materials.
The indexable blade is installed in a blade seat with appropriate size and high stability.
The blade seat can be installed not only on the new modular whirlwind milling cutter head, but also directly on the power tool seat of the machine tool.
The worm whirl milling is carried out with a hao’en whirl milling tool with 9 blades.
The rough machining blade can process the workpiece to the specified outer diameter.
Subsequently, the finishing blade ensures high accuracy of the geometric dimensions of the thread tooth surface (see fig. 4-118).
Fig. 4-118 whirlwind milling tool
Hao’en whirlwind cutting technology is a cost-effective processing method, which uses M271 type tools with 6 or 9 blades to process single line, multi line external threads and various shapes.
If the processing time is very short, compared with thread processing, the whirlwind cutting on the walking lathe has a significant advantage.
The newly developed modular tool system has a base bracket and an annular tool box, which can provide customers with a large number of combination options tailored to a variety of walking lathes and drives on the market.
The high-precision S271 system allows customers to choose between traditional rotary cutting (with 6 or 9 indexable blades in each annular magazine) or new type worm whirlwind cutting (with 9 indexable blades in each annular magazine, including 3 rough machining blades and 6 finish machining blades).
Suitable machining / driving devices and tool combinations can be easily found through the tool configuration on the horn website.
Accurate cutting data can also be obtained with the help of the new HCT cutting data calculator (see fig. 4-119).
Fig. 4-119 flexible modular design during whirlwind cutting