顺铣与传统铣削

Milling cutters are generally multi-tooth cutting tools. Due to the involvement of multiple teeth in cutting simultaneously and the longer cutting edges enabled, higher material removal rates can be achieved for higher productivity. Different milling cutters allow the machining of flat surfaces, grooves, slots, steps and complex contours, as well as gear teeth, threads, spline shafts and other shaping applications.

Grooving Tool Structures

For indexable grooving inserts:

（1）The geometry of Indexable Milling Cutters

An indexable milling cutter has one main helix angle and two lead angles, an axial lead angle, and a radial lead angle.

径向导程角γf主要影响切削功率，而轴向导程角γp影响切屑形成和轴向力的方向，当γp为正值时，工件上会产生爬坡切削。

导程角（前刀面）：

负导程角：用于钢、钢合金、不锈钢和铸铁。

正导程角：用于粘合材料和一些高温合金。

定心导程角：用于齿轮切削、切槽、仿形铣刀和成形铣刀。

应尽可能使用负导程角。

（2）The geometry of Milling Cutters

1. Positive angle-positive angle

   切削轻，排屑顺畅，但切削刃强度较低。适用于加工软质材料、不锈钢、耐热钢、普碳钢、铸铁。对于小功率机床、刚性不足的加工系统以及容易形成积屑瘤的地方应优先选用。

   优点： 1. 切削顺畅 2. 排屑顺畅 3. 良好的表面粗糙度

   缺点： 1.切削刃强度低 2.不利于切入接触 3.工件与机床工作台脱离

2. Negative angle-negative angle

   抗冲击性高，采用负角刀片，适合铸钢、铸铁、高硬度、高强度钢的粗铣削。但切削动力消耗较高，要求加工系统具有优良的刚性。

   优点： 1. 切削刃强度 2. 生产率 3. 将工件推向机床工作台

   缺点：1.切削力较大2.切屑堵塞

3. Positive angle- negative angle

   切削刃抗冲击能力较强，切削刃也较锋利。适用于加工钢、铸钢和铸铁。也适用于重型加工。

   优点： 1. 排屑顺畅 2. 有利的切削力 3. 更广泛的应用范围

（3）Cutter tooth pitch

1、细齿距：进给速度快，铣削力较大，容屑空间小。

2、标准螺距：常规进给速度、铣削力、排屑空间。

3、粗齿距：低速进给，铣削力较小，容屑空间较大。

如果铣刀没有配备专用修光刃刀片，则表面粗糙度取决于每转进给量是否超过刀片上修光刃面的宽度。

Types and Uses of Milling Cutters

Milling cutters can be classified based on tooth structure into end mills and face mills. Based on the relative position of teeth and the cutter axis, there are cylindrical cutters, side and face cutters, form cutters, etc.

Categorized by tooth shape, there are straight, spiral, angular and curved tooth types. Classification by tool construction includes solid, clamped, indexed, inserted and brazed types.

But the most common classification is by cutting-edge back geometry

Milling cutters with tangential teeth can be divided into the following types:

(1) Face milling cutters. They include whole face milling cutters, inserted tooth face milling cutters, and machine adjustable position face milling cutters. They are used for coarse, semi-fine and fine machining of various flat surfaces, steps, etc.

(2) Side milling cutters. They are used for machining step surfaces, side surfaces, grooves, cavities, various shaped holes on workpieces, and internal and external curved surfaces. If side milling cutters are simply classified, they can be divided into left-hand and right-hand types. Now many people still don’t understand the concept of left-hand and right-hand.

First of all, to determine whether a cutter is left-handed or right-handed, you can use the following method. Facing the vertically placed milling cutter, if the gullet rises from the left bottom to the right top, it is right-handed; if the gullet rises from the right bottom to the left top, it is left-handed. For right-handed, you can also use the right-hand rule – bend the four fingers to indicate the direction of rotation, with the thumb pointing in the direction of ascent as right-handed. The helical gullet plays a role in chip removal and also constitutes the front angle and front part of the milling cutter.

Left-handed milling cutters are generally chosen only when high-precision machining is required. Left-handed milling cutters are generally used in the processing of mobile phone keys, thin film switches, LCD panels, acrylic mirrors and other high-precision machining. But for some requirements that are highly demanding, especially for the production and machining of some mobile phone keys or electrical device panels, where the accuracy and surface smoothness requirements are very high, a downward milling left-turning cutter should be selected to avoid problems such as tool marks, burrs on cut edges, etc.

(3) Slot milling cutters. They are used for milling slots, etc.

(4) Groove milling cutters and saw blade milling cutters. They are used for milling various grooves, sides, steps and sawing.

(5) Special groove milling cutters. They are used for milling various special groove shapes, including form milling cutters, half-moon keyway milling cutters, swallowtail groove milling cutters, etc.

(6) Angle milling cutters. They are used for milling straight grooves, helical grooves, etc. on tools.

(7) Die milling cutters. They are used for milling various forming surfaces such as protrusions and depressions on dies.

(8) Gang milling cutters. They comprise a set of several milling cutters combined for milling complex forming surfaces, surfaces of different parts of large workpieces and wide flats.

Triangular saw blade milling cutters: For some milling cutters require heavy grinding while maintaining the original shape at the front, their back uses triangular saw blade forms, including disc groove milling cutters, convex semi-circular, concave semi-circular milling cutters, double angle milling cutters, forming milling cutters etc.

顺铣与传统铣削

There are two methods of milling relative to the workpiece feed direction and spindle rotation direction of the milling machine:

The first is conventional milling, where the rotation direction of the milling cutter and the cutting feed direction are the same. When starting to cut, the milling cutter will immediately engage the workpiece and remove the last chip.

The second is climb milling, where the rotation direction of the milling cutter and the cutting feed direction are opposite. Before starting to cut, the milling cutter must slip on the workpiece for a distance, starting with zero cutting thickness and reaching maximum cutting thickness at the end of the cutting.

During milling with three-flute, some side or face mills, the cutting forces will act in different directions. When face milling, the milling cutter is positioned exactly on the outside of the workpiece, so the direction of cutting forces must be paid particular attention. In conventional milling, the cutting force presses the workpiece against the table, while in climb milling the cutting force moves the workpiece away from the table.

Since conventional milling gives the best cutting effect, it is usually the first choice. Only when there are issues like backlash in the machine tool or problems that cannot be solved by conventional milling, climb milling will be considered. Ideally, the diameter of the milling cutter should be slightly larger than the workpiece width, and the axis of the milling cutter spindle should always be kept at a slight distance from the centerline of the workpiece. When the tool is positioned directly on the cutting center, burrs are very likely to form.

As the cutting edge enters and exits cutting, the direction of radial cutting forces will constantly change, which may cause vibration of the machine spindle and damage to the insert. The cutting edge may also break and the machined surface will be very rough. If the milling cutter is slightly offset from the center, the direction of cutting forces will no longer fluctuate – the milling cutter will gain a kind of preload.

When the milling cutter insert enters cutting each time, it needs to bear the impact load of cutting, and the load size depends on the chip cross-section, workpiece material and cutting type. Whether the cutting edge and workpiece can engage correctly during entry and exit is an important issue.

When the axis of the milling cutter is completely outside the width of the workpiece, the initial impact force during entry is borne by the outermost tip of the insert, which means the initial impact load is borne by the most sensitive part of the tool. The cutter also leaves the workpiece with the tip, which means from the start of cutting to leaving, the cutting force always acts on the outermost tip until the impact is unloaded.

When the centerline of the milling cutter is exactly on the edge line of the workpiece, the impact load reaches the maximum during entry and exit when the chip thickness reaches the maximum and the insert disengages from cutting.

When the axis of the milling cutter is within the width of the workpiece, the initial impact load along the cutting edge during entry is borne by a part farther away from the most sensitive tip, and the insert also exits cutting relatively smoothly during retract.

For each insert, the way the cutting edge leaves the workpiece when exiting cutting is important. The remaining material near the exit may somewhat reduce the gap between inserts. When the chip disengages from the workpiece, an instant tensile force will be generated along the front cutting face of the insert and often produces burrs on the workpiece. This tensile force endangers safety in dangerous situations.