刀具的使用

不管刀具設計得如何，或用什麼材料製成，刀具的製造商都應該提供切削速度和每齒進給量的初始值。如果沒有這些資料，就應該向製造廠家的技術部門諮詢。廠商 應該熟知他們的產品在進行全寬度開槽銑削、外廓銑削、插銑或斜坡銑削時的能力如何，因為許多標準銑刀大多數不能完成這樣多的加工工序。比如，如果銑刀沒有 足夠大的第二後角，則斜坡銑削的斜角就要減小。

很明顯，如果超出刀具的加工能力，將導致刀具的損壞。插銑也是一樣，如果不能將切屑及時地從槽底排出，切屑將會受到擠壓，之後刀具也將損壞。總之，銑削加工高溫合金時，這些情況對刀具壽命都是不利的。

如果認為減慢進給速度可延長刀具壽命，事實證明是錯誤的。典型的例子就是在切第一刀時，會發現材料相當硬。如果把進給量減小 ( 如可轉位銑刀的每齒進給量減至 0.025~0.5 mm ) ，刀具切削刃將強烈地摩擦工件，結果是刀具很快或是立即損壞。摩擦能引起工件表面的加工硬化，為避免加工硬化，切第一刀時應保持一定的切削負荷 ( 0.15~0.2 mm/ 每齒進給量 )。

切削深度取決於多種因素，如刀具設計，刀片高度、刀具剛性、刀具總長、機床馬力等。但當刀具的後角和前角為 5°~11° 正值時，最適於加工粘度大的材料。立銑刀的螺旋角應該在 35°~50° 之間。這些銑刀的傾斜刀刃有鋸削作用，能形成理想的切屑並帶走切削熱。

當然，難切削材質時，適當的切削速度也非常重要。它決定了在切削區產生熱量的多少。推薦的速度範圍從較低的 12~15 m/min ( 對高速鋼銑刀 ) 到 23~37 m/min ( 對硬質合金銑刀 )，再到180~245 m/min 或更高( 對陶瓷銑刀 )。增加進給量和切削深度也會增加切削熱，因相應地增加了切削力和刀具與工件的接觸面積。

根據銑削難切削材質時的應力和切削力，應選擇由K40~K50硬質合金作為銑刀刀片的基體，並採用帶有耐熱性能高的氮鋁鈦塗層。使用這類硬質合金牌號的刀片進行銑削 加工，可取得很好的加工效果。在較低的切削速度下，採用碳氮化鈦塗層進行加工，其效果也不錯。

如果在加工中，刀具使用不當，即使用最好的基體和塗層，也不會取得好的加工效果。比如，在零件上要銑出一個深度為 2~5mm 的槽，想分三次走刀加工出來。一般在這個加工過程中 CAM 系統將顯示為三次切深都一樣。由於工件重複地接觸刀具上同一部位，最終相同的切深將使塗層上產生一個缺口，一旦這個缺口劃穿了塗層，就會損傷基體，致使刀 具損壞。

因此在銑削加工中，選取適當的切削深度 ( 一般在 0.5~0.60mm ) ，在銑削時，防止工件重複接觸刀片同一部位，這樣才能延長刀具的壽命。

刀具在銑削鎳基合金時破損較快?

鎳系合金中鎳和鉻是兩個主要添加成分，增加鎳能增加材料韌性，加入鉻可提高材料的硬度，再加上其他成分的平衡，據此就可以預測刀具的磨損情況。加工鎳基合金，其刀具費用較高，其費用為銑削一般鋼材的5~10倍。

毋庸質疑，在銑削鎳基合金時，熱量是影響刀具壽命的最重要的因素，因為即使最好的硬質合金刀具，也會被過高的切削熱所毀壞。產生極高的切削熱，不僅僅是銑削鎳合金才遇到的問題。所以銑削這些合金時，需要對熱量加以控制。

另外，瞭解應用各種形式的刀具 ( 高速鋼刀具、硬質合金刀具或陶瓷刀具 ) 加工時所產生的熱量值，也是非常重要的。 許多刀具的損壞還與其他因素有關，不合格的夾具和刀柄都可能縮短刀具壽命。當夾緊的工件剛性不足，切削時產生移動時，可能會引起硬質合金基體的斷裂。有時 會沿切削刃產生小的裂縫，有時還會從硬質合金刀片上崩裂，無法繼續進行切削。

當然，這種崩裂刃具也可能是因為硬質合金太硬或切削負荷太大所致。這時應考慮採用高速鋼刀具進行加工，以減少崩裂。當然，高速鋼刀具又不能像硬質合金那 樣承受較高的熱量。

在加工開始前，加強夾具的剛性，不僅延長了刀具的壽命，而且還提高了工件表面質量，減少了加工誤差。 同樣刀柄選擇不當，也會縮短刀具壽命。如把柄徑為 3.175mm 的立銑刀裝在銑刀刀柄裏，由於緊固螺釘的作用，使刀具和刀柄之間的配合間隙偏到一邊，刀具中心偏離刀柄回轉中心，使銑刀工作時的徑向 跳動增加，致使銑刀每個刀齒的切削負荷不均衡。這種切削狀態對刀具很不利，特別是在銑削鎳基合金與含有添加到材料中的其他元素可能有：矽、錳、鉬、鉭、鎢等，值得注意的是鉭和鎢也是用來製造硬質合金的主要成分，它們能有效地提高硬質合金的性能，但是這些元素加入到工件材料中，就使它變地難以銑削加工時更加突出。

通過使用改善了刀具裝卡偏心度的刀柄，如液壓卡頭、熱裝卡頭，能使切削作用更均衡、更平穩，減少了刀具磨損，提高了表面質量。選擇刀柄時應遵循一個原則，就是刀柄要盡可能的短。這些對刀具和工件的夾持要求，對銑削任何材料都適用。

沖壓加工介紹

沖壓加工根據材料的變形特點分： 分離加工方式、成形加工方式

分離加工方式

沖裁加工方式是指使板料按一定的輪廓綫斷裂分離而獲得一定形狀、尺寸的沖壓件的加工方式。分離加工方式主要有沖孔、落料、 切斷、切舌、切邊、剖切、整修及精沖等。

anticlockwise milling and clockwise milling

Milling is one of the most common and most widely used processing methods, and for roughing milling of the various structural components and fine milling is almost by end milling. There are two ways, clockwise and anticlockwise milling, according to the cutting direction. The movement of the cutting edge and work piece is in the opposite direction or same direction, divided into the two kinds of conventional milling and climb milling.

Anticlockwise Milling:

Milling direction and feed in the opposite direction (milling against the feed) is anticlockwise milling; chip caused from the bottom into upper, so we also call it as up milling; Since the traditional processing and milling mostly used this way, so we also called it as conventional milling.

Characteristics of anticlockwise milling:

1. Chip shape is from thin to thick, and cutter afford force from light into heavy, which may prevent the cutter fracture by the impact.
2. Suitable for milling casting black surface.
3. Can be used in the old milling machine, no screw invalid gap movement.
4. More friction, the blade is easy to blunt, short life.
5. Easy shaken, the machined surface is rough, poor machining accuracy.
6. The device is not easy to settle, which is not suitable for milling thin parts.
7. More energy consumption.

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Clockwise milling:

The milling and feed in the same direction (milling with the feeds) called clockwise milling; Due to cutting action is from no-machining face of work piece into down place (chips from thick into thin), so it is called down milling or climb milling.

Characteristics of climb milling:

1. Chip is from thick into thin, cutter affords force from heavy into light, easy to cause fracture by impact.
2. Not suitable for milling castings, forgings, and the surface of the work piece with fish scale shape.
3. The milling machine shall have a gap eliminator, or easy to produce screw invalid gap movement.
4. Processing less friction, longer life of the cutter edge.
5. Easy chucking, no vibration, and high accuracy of the machined surface.
6. The device is easy to settle, it’s suitable for milling long thin work pieces.
7. Less feed consumption.

In most of the milling case, in addition to the casting of the first milling and old milling Lo-gap chopping device need to use the anticlockwise milling, down milling is better than conventional milling.

Cutting Reference Data for End Mills of Various Materials

Effective working solution depends on correct cutters, operation method, and technology.
Usual cutting conditions and major influence factors of CNC machines.

	Introduction	Formula
Cutting Data V(m/min)	Cutting speed is decided by the diameter of end mills and its rpm		V=Cutting speed(m/min) D=diameter(mm) N=rpm of one min of end mills(min-1)
Feed speed F(mm/min)	Feed speed is the speed of relative one of work piece. Feed rate per flute is important for multi-flute end mills.		F=Feed speed per minute z= number of flute f= Feed volume per flute
Cutting depth a(mm)	Cutting depth is the thickness of flute machining on work piece. We always increase cutting depth to achieve its efficiency, but it is too deep to short tool life. It’s better to give proper cutting depth per flute, don’t increase feed rate and cutting depth together.	--	--
Feed rate per flue f(mm/刃)	Once a flute to cut	--	--
Cutting width b(mm)	Vibration caused by diameter of end mill, width of work piece, flute numbers, and cutting width.	--	--

Cutting Speed

Work Material	High Speed Steel	Carbide – rough cutting	Carbide – fine cutting
Cast iron (soft)	32	50-60	120-150
Cast iron (hard)	24	30-60	75-100
Malleable cast iron	24	30-75	50-100
Steel (soft)	27	30-75	150
Steel (hard)	15	25	30
Aluminum alloy	150	95-300	300-1200
Yellow Steel (soft)	60	240	180
Yellow Steel (hard)	50	150	300
Bronze	50	75-150	150-240
Copper	50	150-240	240-300
Hard Rubber	60	240	450
Fiber	40	140	200

Feed volume each side

Working Material			Face cutter		End Mill		Spiral flute flat end mill		Side Cutter		Milling Cutter		Metal gap cutter
			HSS	Carbide	HSS	Carbide	HSS	Carbide	HSS	Carbide	HSS	Carbide	HSS	Carbide
Cast Iron	HB150-180		0.4	0.5	0.2	0.25	0.32	0.4	0.23	0.3	0.13	0.15	0.10	0.13
	HB180-220		0.32	0.4	0.18	0.2	0.25	0.32	0.18	0.25	0.1	0.13	0.08	0.1
	HB220-300		0.28	0.3	0.15	0.15	0.20	0.25	0.15	0.18	0.08	0.1	0.08	0.08
Malleable cast iron, Cast iron			0.3	0.35	0.15	0.18	0.25	0.28	0.18	0.2	0.1	0.13	0.08	0.1
Carbon steel	Cutting steel		0.3	0.4	0.15	0.2	0.25	0.32	0.18	0.18	0.23	0.13	0.08	0.1
	Soft steel, Steel		0.25	0.35	0.13	0.18	0.20	0.28	0.15	0.2	0.08	0.1	0.08	0.1
Alloy Steel	Annealing robust steel	HB180-220	0.20	0.35	0.10	0.18	0.18	0.28	0.13	020	0.08	0.1	0.05	0.1
		HB220-300	0.15	0.3	0.08	0.15	0.13	0.25	0.10	0.18	0.05	0.10	0.05	0.08
		HB300-400	0.10	0.25	0.05	0.13	0.08	0.2	0.08	0.15	0.05	0.08	0.03	0.08
	Stainless steel		0.15	0.25	0.08	0.13	0.13	0.20	0.10	0.15	0.05	0.08	0.05	0.08
Al-Mg Alloy			0.55	0.5	0.28	0.25	0.45	040	0.32	0.30	0.18	0.15	0.13	0.13
Brass, Bronze		speedy cutting	0.55	0.5	0.28	0.25	0.45	0.4	0.32	0.3	0.18	0.15	0.13	0.13
		ordinary	0.35	0.30	0.18	0.15	0.28	0.25	0.20	0.18	0.10	0.10	0.10	0.18
		hard	0.23	0.25	0.13	0.13	0.18	0.2	0.15	0.15	0.08	0.08	0.05	0.08
Coppper			0.30	030	0.15	0.15	0.25	0.23	0.18	0.18	0.10	0.10	0.08	0.08
Plastics			0.32	0.38	0.18	0.18	0.25	0.30	0.20	0.23	0.10	0.13	0.08	0.10

沖壓介紹

沖壓
利用安裝在壓力機上的沖模對材料施加壓力，它是在常溫（冷態）下

鋁合金的加工切削特性

工業鋁合金零件的加工對刀具有很高的要求， 尤其是航空工業中的鋁合 金，刀具在具有高性價比的同時還必須滿足高質量加工的需求。由於整體 硬質合金刀具具有非常鋒利的切削刃和槽型，其在鋁合金精加工中切削力 小，並且具有容屑空間大，排屑順暢等優點，因此整體硬質合金刀具逐漸 取代了傳統的高速鋼刀具。

鋁合金介紹

以鋁為基的合金總稱。主要合金元素有Cu、Si、Mg、Sn，次要有鎳、鈦、鉻、鋰等。鋁合金密度低，塑性好可加工成型材，具有優良導電性、導熱性和抗腐蝕性， 添加一定 元素形成的合金在保持純鋁質輕等優點的同時還能具有較高的強度。 這樣使得其 “比強度”勝過很多合金鋼，成為理想的結構材料，廣泛用於機械製造、運輸 機械、動力機械及航空工業等方面，飛機的機身、蒙皮、壓氣機等常以鋁合金制 造，以減輕自重。採用鋁合金代替鋼板材料的焊接，結構重量可減輕50%以上。
鋁合金加工方式分類：按照加工方法分形變鋁合金和鑄造鋁合金。

The cutter materials and their contrast

This list includes eight cutter materials and their contrast as below:

1. Mono Diamond)
2. CO PCD
3. Si PCD
4. PCBN
5. Si3N4
6. SiC
7. WC
8. Steel

The cutter materials and their contrast
material		Mono Diamond	CO PCD	si PCD	PCBN	Si3N4	SiC	WC	Steel
properties
Density	g/cm3	3.52	3.8~4.10	3.4	4~4.20	3.2	3	15	7.8
Knoop Hadrness	kg/mm2	6000~9000	5000~8000	5000	2700~3200	1800	2200	1500	560
Toughuess	Mpam-2	3.4	6.1~8.9	6.9	4.1~7.2	6.4	4	11	46
Compression Strength	Mpa	2000	7700	4200	3800	6800	7000	5400	1850
Tensile strength	Mpa	2600	1300	600	500	470	400	1100	1760
Thermal Expansion	10-6/°C	0.8~4.8	1.5~3.8	3.8	3.5~4.2	3.5	3.8	4.3~5.6	11.2~14.3
Thermal Conductivity	w/mk	600~1200	560	120	150	30	40	80	50
Friction		0.05~0.10	0.1	0.1	0.1	0.2	0.2	0.2	0.8

The cutting tool for hardening material above HRC50

There are higher requirements and more difficulties for many hardened molds. Hence general carbide cutters cannot reach such request of accuracy. Therefore, it should pay more attention to selection of cutting tools for hardened material.

Since hardening material which HRC is above 50, with higher hardness, the carbide cutter is difficult to meet the processing requirements, it will cause badly wear even break after CNC machining for about ten minutes. General carbide cutters cannot reach the request accuracy because the hardened mold is with higher requirement and difficulty.

Some points for choosing cutters for machining hardened materials as below:

1. Select super micro grain carbide rod and design high rigid tool body to ensure toughness and rigidity of the tool.
2. Select the blade the design of the large helix angle ranging from sub-and four-blade design so that the cutters may reach radial beating with heavy cutting within high-speed and high hardness cutting.
3. Choose carbide cutter with new crystal coating. PVD coating almost cannot be used in high hardness cutting.. the crystal coating may solve it basically about the high temperature / acid resistance / wear / and longer tool life.
4. Cooperate with the powerful tool companies to get their further technical supports and tool configuration, reducing the procurement chain and purchasing costs.

Good carbide cutters with high rigidity of the tool body and new type coating may get high efficiency, precision, and longer tool life. From pre-hardened steel to hardened steel, during high-speed, and high efficient processing; from rough to high precision machining, to achieve a long life; high precision; high quality processing makes it is easier to proceed high-speed and high rigid machining.

Article reference source : NewMaker

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