Le blog de willy

吸波材料一般由基體材料和吸收介質複合而成，能將投射到它表面的電磁波能量吸收，並通過材料的介質損耗使電磁波能量轉化成為熱能或其他形式的能量。好的吸波材料具有質輕、耐溫、耐濕和抗腐蝕等性能，現今電子零件輕薄短小趨勢，其吸波材料發展也朝向”材料薄、重量輕、頻段寬、強度強”等。

吸波材料特性：

• 最大限度地使入射電磁波進入到吸波材料內部，從而減少電磁波的直接反射。
• 吸波材料對入射電磁波能產生有效吸收或衰減，即產生電磁損耗，使電磁波能量轉化為熱能或其他形式能，從而使電磁波在介質中被最大限度地吸收。

吸波材料分類：

• 按研究時期可以分成傳統吸波材料和新型吸波材料
  傳統型按其微波損耗機理分為：電阻型吸波材料、電介質型吸波材料和磁介質型吸波材料。鐵氧體、鈦酸鋇、金屬微粉、石墨、碳化矽、導電纖維等屬傳統吸波材料，它們通常都具有吸收頻帶窄、密度大等缺點。其中鐵氧體吸波材料和金屬微粉吸波材料研究較多，性能也較好。
  新型吸波材料包括：納米材料、多晶鐵纖維、手性材料、導電高聚物吸波材料、等離子體吸波材料和可見光、紅外及雷達兼容吸波材料等。新型吸波材料包括納米材料、手性材料、導電高聚物、多晶鐵纖維及電路模擬吸波材料等，它們具有不同于傳統吸波材料的吸波機理。其中納米材料和多晶鐵纖維是眾多新型吸波材料中性能最好的2種。
• 從吸波原理上可以分成電吸收型、磁吸收型
• 吸波材料大體可以分成塗層型、板材型和結構型
• 從結構上可以分為吸收型、干涉型和諧振型等吸波結構
  吸收型吸波材料本身對雷達波進行吸收損耗，基本類型有複磁導率與複介電常數基本相等的吸收體、阻抗漸變“寬頻”吸收體和衰減表面電流的薄層吸收體；干涉型則是利用吸波層表面和底層兩列反射波的振幅相等相位相反進行干涉相消，如1／4波長“諧振”吸收體，這類材料的缺點是吸收頻帶較窄
• 吸波材料的損耗機制分類
  • 電阻型損耗：此類吸收機制與材料的導電率有關的電阻性損耗，即導電率越大，載流子引起的宏觀電流（包括電場變化引起的電流以及磁場變化引起的渦流）越大，從而有利於電磁能轉化成為熱能。
  • 電介質損耗：它是一類與電極有關的介質損耗吸收機制，即通過介質反復極化產生的“摩擦”作用將電磁能轉化成熱能耗散掉。電介質極化過程包括：電子雲位移極化，極性介質電矩轉向極化，電鐵體電疇轉向極化以及壁位移等。
  • 磁損耗：此類吸收機制是一類與鐵磁性介質的動態磁化過程有關的磁損耗，此類損耗可以細化為：磁滯損耗，旋磁渦流、阻尼損耗以及磁後效效應等，其主要來源是與磁滯機制相似的磁疇轉向、磁疇壁位移以及磁疇自然共振等
• 吸波材料應用：
  吸波材料應用於各類電子產品，如電視、音響、VCD機、電腦、遊戲機、微波爐、移動電話中，可以使電磁波洩露降到國家衛生安全限值（10微瓦每平方釐米）以下，確保人體健康。將其應用于高功率雷達、微波醫療器、微波破碎機，能保護操作人員免受電磁波輻射的傷害。

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.

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.

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.	--	--

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.

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

Bewise Inc., being a professional manufacturer of various cutting tools, is endeavoring to make excellent products. We are very experienced in custom-made tools, and good at solving customers’ problems when they meet difficulties and troubles. Through everlasting research and practices, we understand thoroughly about different materials of cutters and cutting tools.

BW's popular products for tool series including circular saw, carbide cutting tool, saw blade, wood saw blade, special tool,side milling cutter, …etc; For machines we have spiral tube cooler, cutter grinder, and the latest design and advanced powder forming machine / pelletizer. Bewise is a superior manufacturer and supplier of cutter production and machinery industry.

There are two grades of cemented carbide, tungsten carbide and tungsten steel.

One is pure carbide and anti hole types. Pure carbide contains carbides and cobalt only, with best strength and anti-wear characteristics, and its strength and abrasion resistance will be reduced by adding any other substances, it is usually used for cutting cast iron and non-ferrous metal materials. But the pure carbide cannot endure high temperature, its scrap will stick on the cutter blade face easily during high heat, which causes the flank depression by its diffusion. Carbide added tantalum carbide and titanium carbide is with high temperature resistance because these two ingredients are with higher melting point than tungsten carbide, relatively its strength and anti-ear characteristics are lower than pure carbide.

tungsten steel material properties:

tungsten steel tool suitability:

Reference Information Source: tool designed Huang Rongwen

Bewise Inc., being a professional manufacturer of various cutting tools, is endeavoring to make excellent products. We are very experienced in custom-made tools, and good at solving customers’ problems when they meet difficulties and troubles. Through everlasting research and practices, we understand thoroughly about different materials of cutters and cutting tools.

BW's popular products for tool series including circular saw, carbide cutting tool, saw blade, wood saw blade, special tool,side milling cutter, …etc; For machines we have spiral tube cooler, cutter grinder, and the latest design and advanced powder forming machine / pelletizer. Bewise is a superior manufacturer and supplier of cutter production and machinery industry.