NEWS INFORMATION
在激光切割機中對于切割精度較高或厚度較大的零件，須掌握和解決幾項關鍵技術。焦點位置控制就是其中之一。激光切割的優(yōu)點之一是光束的能量密度高，所以焦點光斑直徑盡可能的小，以便產生一窄的切縫。因為聚焦透鏡焦深越小，焦點光斑直徑就越小，對于高質量的切割，有效焦深還和透鏡直徑及被切材料有關。因此控制焦點相對于被切材料表面的位置很重要。
由于激光功率密度對切割速度影響很大，透鏡焦長的選擇是個重要問題。激光束聚焦后光斑大小與透鏡焦長成正比，光束經短焦長透鏡聚焦后光斑尺寸很小，焦點處功率密度很高，對材料切割很有利;但它的缺點是焦深很短，調節(jié)余量小，一般比較適用于高速切割薄型材料。由于長焦長透鏡有較寬焦深，只要具有足夠功率密度，比較適合切割厚工件。
在確D使用何種焦長的透鏡以后，焦點與工件表面的相對位置對保障切割質量尤為重要。由于焦點處功率密度高，大多數(shù)情況下，切割時焦點位置剛處在工件表面，或稍微在表面以下。在整個切割過程中，確保焦點與工件相對位置恒定是獲得穩(wěn)定的切割質量的重要條件。有時，透鏡工作中因冷卻不善而受熱從而引起焦長變化，這就需要及時調整焦點位置。
當焦點處于合適位置時，割縫小、效率高，切割速度可獲得好的切割結果。在大多數(shù)應用情況下，光束焦點調整到剛處于噴嘴下。噴嘴與工件表面間距一般為1.5mm左右。
在激光應用過程中，常常碰到聚焦等問題，常見確定焦點位置的簡便方法有三種：
(1)打印法：使切割頭從上往下運動，在塑料板上進行激光束打印，打印直徑較小處為焦點。
(2)斜板法：用和垂直軸成一角度斜放的塑料板使其水平拉動，尋找激光束的較小處為焦點。
(3)藍色火花法：去掉噴嘴，吹空氣，將脈沖激光打在不銹鋼板上，使切割頭從上往下運動，直至藍色火花較大處為焦點。
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In laser cutting machines, several key technologies must be mastered and solved for parts with high cutting precision or large thickness. Focus position control is one of them. One of the advantages of laser cutting is that the energy density of the beam is high, so the focal spot diameter is as small as possible to create a narrow slit. Because the focal depth of the focusing lens is smaller, the focal spot diameter is smaller. For high quality cutting, the effective depth of focus is also related to the lens diameter and the material being cut. It is therefore important to control the position of the focus relative to the surface of the material being cut.
Since the laser power density has a great influence on the cutting speed, the choice of lens focal length is an important issue. After the laser beam is focused, the spot size is proportional to the focal length of the lens. After the beam is focused by the short focal length lens, the spot size is small, and the power density at the focus is high, which is good for material cutting. However, its shortcoming is that the depth of focus is very short and the adjustment margin is adjusted. Small, generally suitable for high-speed cutting of thin materials. Since the telephoto long lens has a wide focal depth, it is suitable for cutting thick workpieces as long as it has sufficient power density.
After determining which focal length lens to use, the relative position of the focus to the surface of the workpiece is particularly important to ensure the quality of the cut. Due to the high power density at the focus, in most cases, the focus position at the time of cutting is just at the surface of the workpiece, or slightly below the surface. Ensuring a constant relative position of the focus to the workpiece throughout the cutting process is an important condition for obtaining a stable cutting quality. Sometimes, the lens is heated due to poor cooling and causes a change in focal length, which requires timely adjustment of the focus position.
When the focus is in the proper position, the slit is small, the efficiency is high, and the cutting speed can obtain a good cutting result. In most applications, the beam focus is adjusted just below the nozzle. The distance between the nozzle and the surface of the workpiece is generally about 1.5 mm.
In the laser application process, there are often problems such as focusing, and there are three convenient ways to determine the focus position:
(1) Printing method: The cutting head is moved from top to bottom, and laser beam printing is performed on the plastic plate, and the smaller diameter is the focus.
(2) Inclined plate method: The plastic plate obliquely placed at an angle to the vertical axis is horizontally pulled to find the smaller portion of the laser beam as the focus.
(3) Blue spark method: remove the nozzle, blow the air, and pulse the laser on the stainless steel plate to move the cutting head from top to bottom until the blue spark is larger.