The biggest feature of the square shoulder milling cutter (see fig. 4-41) is that it has a main deflection angle of 90 °, which makes it have the following advantages: economy, flexibility and reliability.
Square shoulder milling cutter includes square shoulder end milling cutter, square shoulder face milling cutter, etc.
Fig. 4-41 typical square shoulder milling cutter
1. Features of square shoulder milling cutter
With square shoulder milling, a true 90 ° straight sidewall can be obtained.
The main deflection angle of 90 ° also means the increase of cutting impact force.
If it is not compensated by reasonably selecting the material of cemented carbide and the geometric angle of cutting edge, these impact forces will lead to the destruction of cutting edge and cutting vibration.
As shown in fig. 4-42, generally speaking, the direction of the feed force should be along the spindle direction of the machine tool, so as to avoid vibration and bending of the milling cutter.
The direction of the feed force depends on the size of the main deflection angle.
A small main deflection angle is more favorable for the direction of the feed resistance.
However, a square shoulder milling cutter with a 90 ° main deflection angle may cause the radial component of the cutter body to increase, making the feed force deviate from the direction of the spindle to a large extent, which needs to be compensated by selecting the correct geometric angle of the cutting edge and cutting conditions.
Fig. 4-42 radial force of square shoulder milling cutter
The square shoulder milling cutter (see fig. 4-43) accounts for the largest proportion in today’s milling process due to its high metal removal rate.
Similarly, under the requirements of productivity, reliability and quality, the square shoulder milling cutter has been continuously improved.
Square shoulder face milling can be used in many end milling applications that require face, edge and groove cutting.
Square shoulder milling can be carried out with traditional square shoulder milling cutter, end milling cutter, long edge milling cutter and three face edge milling cutter.
Since there are many options, it is necessary to carefully consider the processing requirements to make the best choice.
At present, there are two main directions in improving these milling processes:
One is to achieve higher metal removal rate, especially on smaller machine tools;
The other is to achieve better surface quality through one-time cutting.
Fig. 4-43 square shoulder milling
2. Selection of square shoulder milling cutter
（1） Precautions for selecting square shoulder milling cutter
For square shoulder milling strategy and tool selection, 90 ° main deflection angle is a limiting factor.
This requires correct selection of processing conditions for compensation.
The best combination of cutting conditions (high safety, high productivity and low production cost) is the combination of large back feed, large feed and medium cutting speed.
When the machine tool is overloaded, it is necessary to reduce the back feed, which has priority over reducing the feed.
Generally speaking, the following points shall be paid attention to when selecting the square shoulder milling cutter:
(1) The radial back cutting amount should not exceed 30% of the tool diameter (for safety reasons).
If the radial back cutting amount is less than 30% of the tool diameter, the axial back cutting amount can be equal to the cutting edge length (for safety reasons, it should not exceed 80%).
When the radial back cutting amount exceeds 30%, the axial back cutting amount shall not exceed 30% of the cutting edge length.
If the back feed or feed is limited by machining conditions (part size, machine power, tool or part stability), productivity can be improved by increasing the cutting speed.
(2) The average chip thickness and cutting speed are used to optimize the machining process, especially when the radial back feed is smaller than the tool diameter (no more than 30%).
The selection of cutting tools and inserts (cemented carbide material, geometric angle and size) should be consistent with the selected cutting parameter combination.
(3) The clamping of the tool should be as short and as firm as possible, and always select the tool diameter as large as possible to meet the processing requirements.
(4) Dense tooth cutter has small chip space, but it has high stability and can adopt high feed speed.
When the radial undercut is less than 30% of the tool diameter, the best choice is the dense tooth tool.
For groove milling, the tools with standard tooth pitch and sparse teeth are the best choice.
(5) If the requirement of surface roughness is not high, the feed speed should be selected as high as possible.
Especially when machining stainless steel, super alloy and titanium alloy, in order to avoid surface hardening, it is necessary to increase the feed rate. However, the maximum feed per tooth must not be exceeded.
（2） Application and precautions of square shoulder milling cutter
The square shoulder milling cutter can be used in many occasions (see fig. 4-44), including insert milling, slope milling, circular interpolation milling, spiral interpolation milling, drilling and face milling.
As shown in table 4-13, shoulder milling, edge milling (peripheral milling) and square shoulder milling with thin wall and inclined wall are selected as examples to briefly describe the application and precautions of square shoulder milling cutter.
Fig. 4-44 application
a) Insert milling
b) Slope milling
c) Spiral interpolation milling
e) Long overhang
f) Unstable condition
Table 4-13 application of square shoulder milling
|Processing occasion||Apply tool||matters needing attention|
|Shallow shoulder||1. square shoulder milling cutter 2 Square shoulder vertical milling||1. large radial cutting is allowed for shallow notch 2 The oversize shoulder tool option provides optimal accessibility when milling shallow shoulders deep|
|Deep shoulder||1. Square shoulder end milling cutter; 2 Square shoulder milling cutter; 3 Corn milling cutter||1. For those shoulders in deep position, the extension rod with interface can be used;2. Generally, the corn milling cutter is a good solution for the application of deep, large and heavy square shoulder milling. The corn milling cutter milling shoulder has two characteristics: (1) high metal removal rate (2) it is usually used for rough milling, because the final surface texture depends on the high feed side milling.|
|Edge milling||1. square shoulder end milling cutter; 2 Corn milling cutter;3 Trihedral edge milling cutter.||Thin edges are usually machined with end mills, while deeper or thicker edges are machined with end mills by repeating the “square shoulder milling” path or using the corn milling tool for one pass. A key factor in edge milling is to achieve an appropriate feed per tooth f|
|Thin wall and inclined wall||Square shoulder end mill||1. The machining strategy of the thin-wall part will change with the height and thickness of the wall. Generally, the forward milling is used;2 In all working conditions, the number of tool paths will be determined by the size of the wall and the axial back cutting amount, taking into account the stability of the tool and the wall;3 High speed technologies, i.e. small a/a and high V, are usually used to facilitate the milling of thin walls because they reduce the tool take-up time and thus reduce impact and deflection.|
|Arc cut in||1. Square shoulder end milling cutter 2. Square shoulder milling cutter||1. Gentle cutting is necessary to avoid vibration and prolong tool life, especially when milling shoulder;2. The tool is programmed as cut in; Always make the chip thickness generated at the outlet Zero: this will ensure both a high feed and a long tool life;3. This method is most suitable for milling around the external fillet, because it can avoid sharp changes in cutting;4. For arc cutting, keep the tool continuously.|