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  • 中頻點焊機與工頻點焊機的區別
  • 本站編輯:杭州先創熱熔設備廠發布日期:2019-10-18 19:02 瀏覽次數:
中頻逆變點焊機與傳統工頻交流焊機相比的優勢
 
      優勢主要提示:與傳統的工頻交流點焊機相比,中頻逆變點焊機運行的能源成本比工頻交流點焊機節約近1/3,適合自動化運用,控制智能化程度高,適應材料范圍廣,尤其能夠得到穩定、可靠的焊點質量。
 
與傳統的工頻交流點焊機相比,中頻焊機運行的能源成本比工頻焊機節約近1/3,適合自動線運用,控制智能化程度高,適應材料范圍廣,尤其能夠得到穩定、可靠的焊點質量。
 
       隨著汽車行業的快速發展,汽車車身結構的安全性及新材料的運用對車身的焊接工藝提出了新的挑戰。對于帶涂層的鋼板、涂膠的鋼板、多層板及不同材質板等條件下的焊接,傳統的工頻點焊機難以滿足焊接要求,應運而生的是各種先進的焊接工藝及焊接設備,如中頻逆變焊機、螺母輸送機等。
      近年來,國外部分生產汽車批量大的企業將中頻點焊機器人和伺服技術點焊機器人應用于轎車白車身焊裝線。尤其在歐洲,中頻點焊機器人使用量已占40%,并擴大到鋁合金轎車車身的點焊作業。在國內中頻點焊機在各大汽車廠中也得到了越來越廣泛的應用,如一汽大眾、奇瑞汽車、北京現代、東風日產等廠家都已將中頻焊機運用于自動線焊接或人工點焊。
 
     與傳統的工頻焊機相比,中頻焊機大的優點在于直流極性好、焊接質量好。以RexrothPSQ6000的中頻焊機在奇瑞汽車A5白車身生產線的運用為例,來說明中頻點焊機良好的焊接質量性能。
 
      在A5白車身生產線的骨架總拼工位,由機器人使用工頻焊機焊接。此工位的左右側圍門檻處,有10個焊點為四層板焊接,四層板總厚度達到5.5mm,此處焊點的焊接質量很不穩定。當焊接電流過大時,會引起焊點過燒或焊點燒穿;當焊接電流調小時,又會引起弱焊或虛焊。無論如何調整焊接參數,都無法得到穩定良好的焊點質量,因為此處不僅板厚、鋼板層數多,而且裝配時有一定的裝配間隙,而工頻焊機并不能根據實際的裝配狀態對焊接參數進行自動的調整來保證焊接質量。對此,中頻逆變焊機正好能克服工頻焊機的缺陷。
 
     在使用中頻焊機之前,技術人員采用四層板試板分別用工頻焊機和中頻焊機進行焊接試驗觀察焊接質量。四層板的試驗材料為:(1.8+1.5+1.5+0.8)mm組合的4塊冷軋低碳鋼板,焊鉗電極直徑16mm,焊接參數經過多次試驗優化.
 
     從表1可見對于多層板的焊接,無論從操作環境,還是從焊點質量及其穩定性,中頻焊機的焊接性能都明顯優于工頻焊機。由于中頻焊機的電流非常接近直流電流,焊接時沒有電流峰值,焊接過程中熱量增加比較穩定無波動,因此焊接飛濺很少,甚至幾乎沒有。所以中頻焊機的操作環境較工頻焊機操作環境好很多,并且中頻焊機的電流熱效率高于交流電流,故中頻焊機焊接的焊點熔核直徑比工頻焊機的大1~2mm。
      隨后在A5車身側圍門檻處用工頻焊機和中頻焊機進行四層板焊點的焊接,試驗結果與用試板做的試驗結果基本吻合,具體車身焊點見圖1。用中頻焊機焊接的5個焊點熔核均在5~6mm之間,用工頻焊機焊接的3個焊點的熔核在3~4mm之間。
 
      通過一段時間的現場驗證,中頻焊機焊接A5側圍門檻處四層板焊點焊接質量合格,且質量穩定,顯著優于工頻焊機的焊接質量。如此優良的焊接質量不僅與中頻焊機的直流極性有關,還與它的控制系統有重要的關系。中頻焊機擁有功能強大的監控軟件,智能化程度高。它采用了恒功率控制技術和伺服運動控制器(氣動元件),可以對焊接電流、焊接時間、焊接功率及焊接的壓力等進行全閉環控制。
 
    恒功率控制技術是對次級電流和次級電壓進行監控,通過調整焊接時間和焊接電流保證每一個焊接熔核的輸入功率相等,因此它可以有效補償焊接分流、焊接裝配不良、焊接母材成分變化等非機器擾動因素。它根據焊接的條件,選取一個標準試板,建立一條電流和電阻的樣本曲線,然后在實際的焊接工作中,根據實際的焊接電阻對實際的焊接電流和焊接時間進行補償焊接板件之間有膠水干擾的一個焊接參數曲線圖,紅色曲線是實際的焊接電流-時間曲線,與它部分重合的黑色曲線是焊接樣本的焊接電流-時間曲線,綠色曲線是實際的焊接電阻-時間曲線,與它部分重合的黑色曲線是焊接樣本的焊接電阻-時間曲線。樣本為沒有膠水的同樣鋼板的焊接,當焊接板件之間有膠水時,板件電阻大大高于樣本電阻,故焊接電流在開始段突然增大,使膠水層被擊穿,同時損失的焊接電流以延長焊接時間得到補償,保證了焊點的質量。圖3為焊接板件之間有涂層干擾的一個焊接參數曲線圖,曲線含義與圖2相同,當焊接板件之間有涂層干擾時,控制系統通過增加焊接電流來進行補償。
     由于中頻焊機具備以上兩方面的優點,故其焊接質量控制遠遠優于工頻點焊機。但是它的缺點是價格比普通工頻焊機高6~8倍,一次性投資大。然而,它的綜合性能將決定它的應用程度,下面看一下它的綜合性能,與普通的工頻焊機相比,它有以下幾個特點(其參數見表2):
 
1.中頻焊機焊接電流接近完全直流,由于沒有明顯的峰值電流,熔核尺寸穩定擴大,幾乎沒有飛濺,焊接質量穩定、熱效率高。與工頻焊機相比,中頻逆變焊機焊接電流可降低40%,電極使用壽命大大延長。
 
2.中頻焊機變壓器重量和體積小,輸入功率低,便于采用連變壓器式焊鉗。當運用于機器人點焊操作時,可使機器人的負荷減輕,而工頻焊機在自動線上運用時則需要負載能力更強的機器人。
 
3.中頻點焊機的響應速度僅為工頻焊機的1/20,電流能夠更快地達到設定值,更準確地分析參數,焊接質量控制更準確。
 
4.中頻點焊機三相負荷均衡,功率因數高(0.9左右),節能。而兩相工頻焊機,工作時很難保證相電壓之間的均衡,功率因數低(0.6左右),三相工頻焊機則很難實現恒流輸出。
 
5.中頻點焊機適用多種材料及異種金屬的焊接,如鋁合金、不銹鋼、高強度鋼板等材料。另外,對于鍍鋅板和普通多層板的焊接,其焊接質量也遠高于工頻焊機的焊接質量。而工頻焊機只適應焊接性能好的材料,如低碳鋼板。
Advantages of intermediate frequency inverter spot welder over traditional power frequency ac welder
 
 
 
Advantages main tips: compared with the traditional power-frequency ac spot welding machine, the energy cost of the operation of the medium-frequency inverter spot welding machine is nearly 1/3 less than that of the power-frequency ac spot welding machine. It is suitable for automation, highly intelligent control and wide range of materials, especially for stable and reliable welding spot quality.
 
 
 
Compared with the traditional power frequency ac spot welding machine, the energy cost of the operation of the intermediate frequency welding machine is nearly 1/3 less than that of the power frequency welding machine. It is suitable for the application of the automatic line, has a high degree of intelligent control and a wide range of materials. In particular, it can obtain stable and reliable welding spot quality.
 
 
 
With the rapid development of automobile industry, the safety of automobile body structure and the application of new materials pose new challenges to the welding process of automobile body. For the welding with coated steel plate, coated steel plate, multilayer plate and different materials, the traditional industrial frequency spot welding machine is difficult to meet the welding requirements, the emergence of a variety of advanced welding technology and welding equipment, such as intermediate frequency inverter welding machine, nut conveyor and so on.
 
In recent years, some foreign enterprises which produce large quantities of automobiles have applied intermediate frequency spot welding robot and servo spot welding robot to the welding line of car body in white. Especially in Europe, the use of intermediate frequency spot welding robot has accounted for 40%, and expanded to aluminum alloy car body spot welding operations. In the domestic medium frequency spot welding machine has been more and more widely used in the major automobile factories, such as faw-volkswagen, chery automobile, Beijing hyundai, dongfeng nissan and other manufacturers have used the medium frequency welding machine in automatic line welding or manual spot welding.
 
 
 
Compared with the traditional industrial frequency welder, the main advantages of the intermediate frequency welder are good polarity and welding quality. Take the application of RexrothPSQ6000 intermediate frequency welder in chery automobile A5 body in white production line as an example to illustrate the good welding quality performance of intermediate frequency welder.
 
 
 
The skeleton of A5 body in white assembly line is welded by a frequency welder. At the enclosed threshold on the left and right sides of this station, there are 10 welding spots for four-layer plate welding. The total thickness of the four-layer plate reaches 5.5mm, and the welding quality of the welding spots here is very unstable. When the welding current is too large, it will cause the solder burn or solder burn through; When the welding current is adjusted, weak welding or virtual welding will be caused. No matter how to adjust the welding parameters, it is impossible to obtain a stable and good welding spot quality, because here not only is the plate thickness and the number of steel plates are many, but also there is a certain gap in the assembly, and the power frequency welder cannot automatically adjust the welding parameters according to the actual assembly state to ensure the welding quality. In this regard, the intermediate frequency inverter welding machine can just overcome the defects of the industrial frequency welding machine.
 
 
 
Before using the intermediate frequency welder, the technician USES the four layer plate test plate to conduct the welding test with the frequency welder and the intermediate frequency welder respectively to observe the welding quality. The test materials of the four layers are :(1.8+1.5+1.5+0.8) mm cold rolled low carbon steel plates with electrode diameter of 16mm. The welding parameters have been optimized through multiple tests, and the final test results are shown in table 1.
 
 
 
As can be seen from table 1, the welding performance of the intermediate frequency welder is obviously better than that of the industrial frequency welder, no matter from the operating environment or the quality and stability of the welding spot. Since the current of the intermediate frequency welder is very close to the dc current, there is no peak current during welding, and the heat increase during welding is relatively stable without fluctuation, so there is little or even no spatter during welding. Therefore, the operating environment of the intermediate frequency welder is much better than that of the industrial frequency welder, and the current thermal efficiency of the intermediate frequency welder is higher than that of the ac current. Therefore, the diameter of the welding spot of the intermediate frequency welder is 1 ~ 2mm larger than that of the industrial frequency welder.
 
Then, the welding of the four-layer plate welding spot was carried out by the frequency welder and intermediate frequency welder at the threshold of the side wall of A5 body. The test results were basically consistent with the test results made by the test plate. The specific welding spot of the body was shown in figure 1. The core of 5 welding spots with intermediate frequency welder is 5 ~ 6mm, and the core of 3 welding spots with labor frequency welder is 3 ~ 4mm.
 
 
 
After on-site verification for a period of time, the welding quality of the four-layer plate welding spot at the girth threshold of side A5 welded by the intermediate frequency welder is qualified and stable, which is significantly better than the welding quality of the industrial frequency welder. Such excellent welding quality is not only related to the dc polarity of the intermediate frequency welder, but also to its control system. Intermediate frequency welding machine has powerful monitoring software, high intelligence. It adopts constant power control technology and servo motion controller (pneumatic components), which can control the welding current, welding time, welding power and welding pressure.
 
 
 
Constant power control technology is to monitor the secondary current and voltage, and ensure that the input power of each weld nugget is equal by adjusting the welding time and welding current. Therefore, it can effectively compensate for non-machine disturbance factors such as welding shunt, welding assembly failure, and change of welding base material composition. First it according to the welding conditions, the selection of a standard test plate, build a current and resistance of the sample curve, and then in the actual welding work, according to the actual resistance welding of actual welding current and welding time compensation have glue between the welding plate interference graph of a welding parameters, the red curve is the actual welding current - time curve, and it is the black curve parts overlap welding sample welding current - time curve, the green curve is the actual welding resistance - time curve, and it is the black curve parts overlap welding sample welding resistance - time curve. The sample is the welding of the same steel plate without glue. When there is glue between the welded plates, the resistance of the plate is much higher than that of the sample. Therefore, the welding current suddenly increases in the beginning section, which causes the glue layer to be broken down. Figure 3 is a graph of welding parameters with coating interference between welded plates. The meaning of the curve is the same as that in figure 2. When there is coating interference between welded plates, the control system compensates by increasing welding current.
 
Because the intermediate frequency welding machine has the advantages of the above two aspects, its welding quality control is far superior to the power frequency spot welding machine. But its disadvantage is that the price is 6 ~ 8 times higher than ordinary industrial frequency welder. However, its comprehensive performance will determine the degree of its application. The following is its comprehensive performance. Compared with ordinary industrial frequency welder, it has the following characteristics (see table 2 for its parameters) :
 
 
 
1. The welding current of intermediate frequency welder is close to full dc. Due to the absence of obvious peak current, the size of molten core expands steadily with almost no splash. Compared with power frequency welder, the welding current of intermediate frequency inverter welder can be reduced by 40%.
 
 
 
2. Medium frequency welding transformer weight and volume small, low input power, easy to use even transformer type welding tongs. When applied to the robot spot welding operation, can reduce the load of the robot, and the machine in the automatic line when the use of the need for a stronger load capacity of the robot.
 
 
 
3. The response speed of intermediate frequency spot welder is only 1/20 of that of industrial frequency welder. The current can reach the set value faster, analyze parameters more accurately and control welding quality more accurately.
 
 
 
4. Intermediate frequency spot welding machine three-phase load balance, high power factor (about 0.9), energy saving. While two-phase frequency welder, it is difficult to ensure the balance between phase voltage and power factor is low (about 0.6), and it is difficult to achieve constant current output of three-phase frequency welder.
 
 
 
5. Intermediate frequency spot welding machine is suitable for welding various materials and different metals, such as aluminum alloy, stainless steel, high strength steel plate and other materials. In addition, the welding quality of galvanized sheet and common multilayer sheet is much higher than that of power frequency welder. The frequency welder is only suitable for the material with good welding performance, such as low carbon steel plate.