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【点焊机】基础知识-荣仕杰焊接百科
作者: 编辑: 来源: 发布日期: 2020.05.07
信息摘要:
(内容来自百度百科)点焊机按照用途分,有万能式(通用式)、专用式按照同时焊接的焊点数目分,有单点式、双点式、多点式按照导电方式分,有单侧的、…

(内容来自百度百科)点焊机按照用途分,有万能式(通用式)、专用式;按照同时焊接的焊点数目分,有单点式、双点式、多点式;按照导电方式分,有单侧的、双侧的;按照加压机构的传动方式分,有脚踏式、电动机-凸轮式、气压式、液压式、复合式(气液压合式);按照运转的特性分,有非自动化、自动化;按照安装的方法分,有固定式,移动式或轻便式(悬挂式);按照焊机的活动电极(普通是上电极)的移动方向分,有垂直行程(电极作直线运动)、圆弧行程;按照电能的供给方式分,有工频焊机(采用50赫兹交流电源)、脉冲焊机(直流脉冲焊机、储能焊机等)、变频焊机(如低频焊机)。

点焊机

当工件和电极一定时,工件的电阻取决与它的电阻率.因此,电阻率是被焊材料的重要性能.电阻率高的金属其导电性差(如不锈钢)电阻率低的金属其导电性好(如铝合金)。因此,点焊不锈钢时产热易而散热难,点焊铝合金时产热难而散热易.点焊时,前者可用较小电流(几千安培),而后者就必须用很大电流(几万安培)。电阻率不仅取决与金属种类,还与金属的热处理状态、加工方式及温度有关。
为了保证熔核尺寸和焊点强度,焊接时间与焊接电流在一定范围内可以相互补充。为了获得一定强度的焊点,可以采用大电流和短时间(强条件,又称硬规范),也可采用小电流和长时间(弱条件,也称软规范)。选用硬规范还是软规范,取决于金属的性能、厚度和所用焊机的功率。对于不同性能和厚度的金属所需的电流和时间,都有一个上下限,使用时以此为准。
电极压力对两电极间总电阻R有明显的影响,随着电极压力的增大,R显著减小,而焊接电流增大的幅度却不大,不能影响因R减小引起的产热减少。因此,焊点强度总随着焊接压力增大而减小。解决的办法是在增大焊接压力的同时,增大焊接电流。

分类
点焊机按用途可以分成万能式(通用式、专用式)点焊机;
按同时焊接的焊点数目分为:有单点式、双点式、多点式;
按导电方式分为:单侧的、双侧的;
按加压机构的传动方式分为:脚踏式、电动机-凸轮式、气压式、液压式、复合式(气液压合式);
按运转的特性分为:非自动化、自动化;
按安装的方法分为:固定式,移动式或轻便式(悬挂式)点焊机;
按焊机的活动电极(普通是上电极)的移动方向分为:垂直行程(电极作直线运动)、圆弧行程。
工作原理编辑
点焊的工艺过程为开通冷却水;将焊件表面清理干净,装配准确后,送入上、下电极之间,施加压力,使其接触良好;通电使两工件接触表面受热,局部熔化,形成熔核;断电后保持压力,使熔核在压力下冷却凝固  形成焊点;去除压力,取出工件。焊接电流、电极压力、通电时间及电极工作表面尺寸等点焊工艺参数对焊接质量有重大影响。
点焊机利用正负两极在瞬间短路时产生的高温电弧来熔化电极间的被焊材料,来达到使它们结合的目的。点焊机的结构十分简单,说白了就是一个大功率的变压器,将220V交流电变为低电压,大电流的电源,可以是直流的也可以是交流的。电焊变压器有自身的特点,就是具有电压急剧下降的特性。
在焊条引燃后电压下降,电焊机的工作电压的调节,除了一次的220/380电压变换,二次线圈也有抽头变换电压,同时还有用铁芯来调节的,可调铁芯。电焊机一般是一个大功率的变压器,系利用电感的原理做成的。电感量在接通和断开时会产生巨大的电压变化,利用正负两极在瞬间短路时产生的高压电弧来熔化电焊条上的焊料。来达到使它们结合的目的。
点焊是焊件装配接接头,并压紧在两电极之间,利用电阻热熔化母材金属,形成焊点的电阻焊方法。点焊多  用于薄板的连接,如飞机蒙皮、航空发动机的火烟筒、汽车驾驶室外壳等。点焊机焊接变压器是点焊电器,它的次级只有一圈回路。上、下电极与电极臂既用于传导焊接电流,又用于传递动力。冷却水路通过变压器、电极等部分,以免发热焊接时,应先通冷却水,然后接通电源开关。电极的质量直接影响焊接过程、焊接质量和生产率。电极材料常用紫铜、镉青铜、铬青铜等制成;电极的形状多种多样,主要根据焊件形状确定。安装电极时,要注意上、下电极表面保持平行;电极平面要保持清洁,常用砂布或锉刀修整。焊接循环点焊和凸焊的焊接循环由四个基本阶段(点焊过程):
(1)预压阶段——电极下降到电流接通阶段,确保电极压紧工件,使工件间有适当压力。
(2)焊接时间——焊接电流通过工件,产热形成熔核。
(3)维持时间——切断焊接电流,电极压力继续维持至熔核凝固到足够强度。
(4)休止时间——电极开始提起到电极再次开始下降,开始下一个焊接循环。
为了改善焊接接头的性能,有时需要将下列各项中的一个或多个加于基本循环:
(1)加大预压力以消除厚工件之间的间隙,使之紧密贴合。
(2)用预热脉冲提高金属的塑性,使工件易于紧密贴合、防止飞溅;凸焊时这样做可以使多个凸点在通电焊接前与平板均匀接触,以保证各点加热的一致。
机械使用编辑
点焊机使用方法:
1、焊接时应先调节电极杆的位置,使电极刚好压到焊件时,电极臂保持互相平行。
2、电流调节开关级数的选择可按焊件厚度与材质而选定。通电后电源指示灯应亮,电极压力大小可调整弹簧压力螺母,改变其压缩程度而获得。
3、在完成上述调整后,可先接通冷却水后再接通电源准备焊接。焊接过程的程序:焊件置于两电极之间,踩下脚踏板,并使上电极与焊件接触并加压,在继续压下脚踏板时,电源触头开关接通,于是变压器开始工作次级回路通电使焊件加热。当焊接一定时间后松开脚踏板时电极上升,借弹簧的拉力先切断电源而后恢复原状,单点焊接过程即告结束。
4、焊件准备及装配:钢焊件焊前须清除一切脏物、油污、氧化皮及铁锈,对热轧钢,最好把焊接处先经过酸洗、喷砂或用砂轮清除氧化皮。未经清理的焊件虽能进行点焊,但是严重地降低电极的使用寿命,同时降低点焊的生产效率和质量。对于有薄镀层的中低碳钢可以直接施焊。
另外,用户在使用时可参考下列工艺数据:
1、焊接时间:在焊接中低碳钢时,本焊机可利用强规范焊接法(瞬时通电)或弱规范焊接法(长时通电)。在大量生产时应采用强规范焊接法,它能提高生产效率,减少电能消耗及减轻工件变形。
2、焊接电流:焊接电流决定于焊件之大小、厚度及接触表面的情况。通常金属导电率越高,电极压力越大,焊接时间应越短。此时所需的电流密度也随之增大。
3、电极压力:电极对焊件施加压力的目的是为了减小焊点处的接触电阻,并保证焊点形成时所需要的压力。
安全编辑
1.现场使用的,应设有防雨、防潮、防晒的机棚,并应装设相应的消防器材。
2.焊接现场10m范围内,不得堆放油类、木材、氧气瓶、乙炔发生器等易燃、易爆物品。
3.焊接操作及配合人员必须按规定穿戴劳动防护用品。并必须采取防止触电、高空坠落、瓦斯中毒火灾等事故的安全措施。
4. 次级抽头联接铜板应压紧,接线柱应有垫圈。合闸前,应详细检查接线螺帽、螺栓及其他部件并确认完好齐全、无松动或损坏。接线柱处均有保护罩。
5.使用前,应检查并确认初、次级线接线正确,输入电压符合电焊机的铭牌规定,知道点焊机焊接电流的种类和适用范围。接通电源后,严禁接触初级线路的带电部分。初、次级接线处必须装有防护罩。
6.移动点焊机时,应切断电源,不得用拖拉电缆的方法移动焊机。当焊接中突然停电时,应立即切断电源。
7.焊接铜、铝、锌、锡、铅等有色金属时,必须在通风良好的地方进行,焊接人员应戴防毒面具或呼吸滤清器。
8.多台点焊机集中使用时,应分接在三相电源网络上,使三相负载平衡。多台焊机的接地装置,应分别由接地极处引接,不得串联。
9.严禁在运行中的压力管道、装有易燃易爆物的容器和受力构件上进行焊接。
10.焊接预热件时,应设挡板隔离预热焊件发出的辐射热。
安装维护编辑
焊机必须妥善接地后方可使用,以保障人身安全。焊机使用前要用500V兆欧表测试焊机高压侧与机壳之间绝缘电阻不低于2.5兆欧方可通电。检修时要先切断电源,方可开箱检查。焊机先通水后施焊,无水严禁工作。冷却水应保证在0.15--0.2MPa进水压力下供应5--30℃的工业用水。冬季焊机工作完毕后应用压缩空气将管路中的水吹净以免冻裂水管。
焊机引线不宜过细过长,焊接时的电压降不得大于初始电压的5%,初始电压不能偏离电源电压的±10%。焊机操作时应戴手套、围裙和防护眼镜,以免火星飞出烫伤。滑动部分应保持良好润滑,使用完后应清除金属溅沫。新焊机开始使用24小时后应将各部件螺丝紧固一次,尤其要注意铜软联和电极之间联接螺丝一定要紧固好,用完后应经常清除电极杆和电极臂之间的氧化物,以保证良好接触。
焊机使用时如发现交流接触器吸合不实,说明电网电压过低,用户应该首先解决电源问题,电源正常后方可使用。需要指出的是,新购买的焊机半个月内如出现主件质量问题,可以更换新的焊机或者更换主件。焊机主机部分保修一年,长期提供维修服务。一般情况下用户通知厂方后,根据路程远近三到七天内服务到位。由于用户原因而造成的焊机损坏不在保修范围内。易损件、消耗件不在保修范围内。
由于电极的接触面积决定着电流密度,电极材料的电阻率和导热性关系着热量的产生和散失,因此,电极的形状和材料对熔核的形成有显著影响。随着电极端头的变形和磨损,接触面积增大,焊点强度将降低。工件表面的氧化物、污垢、油和其他杂质增大了接触电阻。过厚的氧化物层甚至会使电流不能通过。局部的导通,由于电流密度过大,则会产生飞溅和表面烧损。氧化物层的存在还会影响各个焊点加热的不均匀性,引起焊接质量波动。因此彻底清理工件表面是保证获得优质接头的必要条件。
故障排除
1、踏下脚踏板焊机不工作,电源指示灯不亮:
a.检查电源电压是否正常;检查控制系统是否正常。
b.检查脚踏开关触点、交流接触器触点、分头换挡开关是否接触良好或烧损。
2、电源指示灯亮,工件压紧不焊接:
a.检查脚踏板行程是否到位,脚踏开关是否接触良好。
b.检查压力杆弹簧螺丝是否调整适当。
3、焊接时出现不应有的飞溅:
a.检查电极头是否氧化严重。
b.检查焊接工件是否严重锈蚀接触不良。
c.检查调节开关是否档位过高。
d.检查电极压力是否太小,焊接程序是否正确。
4、焊点压痕严重并有挤出物:
a.检查电流是否过大。
b.检查焊接工件是否有凹凸不平。
c.检查电极压力是否过大,电极头形状、截面是否合适。
5、焊接工件强度不足:
a.检查电极压力是否太小,检查电极杆是否紧固好。
b.检查焊接能量是否太小,焊接工件是否锈蚀严重,使焊点接触不良。
c.检查电极头和电极杆、电极杆和电极臂之间是否氧化物过多。
d.检查电极头截面是否因为磨损而增大造成焊接能量减小。
e.检查电极和铜软联和结合面是否严重氧化。
6、焊接时交流接触器响声异常:
a.检查交流接触器进线电压在焊接时是否低于自身释放电压300伏。
b.检查电源引线是否过细过长,造成线路压降太大。
c.检查网路电压是否太低,不能正常工作。
d.检查主变压器是否有短路,造成电流太大。
7、焊机出现过热现象:
a.检查电极座与机体之间绝缘电阻是否不良,造成局部短路。
b.检查进水压力、水流量、供水温度是否合适,检查水路系统是否有污物堵塞,造成因为冷却不好使电极臂、电极杆、电极头过热。
c.检查铜软联和电极臂,电极杆和电极头接触面是否氧化严重,造成接触电阻增加发热严重。
d.检查电极头截面是否因磨损增加过多,使焊机过载而发热。
e.检查焊接厚度、负载持续率是否超标,使焊机过载而发热 [1] 
优缺点
电阻焊具有下列优点:
1、熔核形成时,始终被塑性环包围,熔化金属与空气隔绝,冶金过程简单。
2、加热时间短、热量集中,故热影响区小,变形与应力也小,通常在焊后不必安排矫正和热处理工序。
3、不需要焊条、焊丝等填充金属,以及氧、乙炔、氩等焊接材料,焊接成本低。
4、操作简单,易于实现机械化和自动化,改善了劳动条件。
5、生产率高,且无噪声及有害气体,在大批量生产中,可以和其它制造工序一起编到组装线上,但闪光对焊因有火花喷溅,需要隔离。
电阻焊具有下列缺点:
1、缺乏可靠的无损检测方法,焊接质量只能靠工艺试样和焊件的破坏性试验来检查,以及靠各种监控技术来保证。

2、点、缝焊的搭接接头不仅增加了构件的重量,且因在两板间熔核周围形成夹角,致使接头的抗拉强度和疲劳强度均较低。

The spot welding machine is divided into universal type (general type) and special type according to the purpose; according to the number of welding points welded at the same time, there are single-point type, double-point type, multi-point type; according to the conductive mode, there are single-side, Double-sided; according to the transmission method of the pressurizing mechanism, there are foot type, motor-cam type, pneumatic type, hydraulic type, compound type (pneumatic hydraulic combined type); according to the characteristics of operation, there are non-automatic and automated; according to The installation method is divided into fixed, mobiles or portable (hanging type); according to the moving direction of the movable electrode (usually the upper electrode) of the welding machine, there are vertical stroke (the electrode moves linearly) and circular stroke; According to the power supply method, there are industrial frequency welding machine (using 50 Hz AC power supply), pulse welding machine (DC pulse welding machine, energy storage welding machine, etc.), frequency conversion welding machine (such as low frequency welding machine).
When the workpiece and electrode are fixed, the resistance of the workpiece depends on its resistivity. Therefore, the resistivity is an important property of the material to be welded. The metal with high resistivity has poor conductivity (such as stainless steel) and the metal with low resistivity has good conductivity (Such as aluminum alloy). Therefore, when spot welding stainless steel, it is easy to generate heat and difficult to dissipate heat. When spot welding aluminum alloy, it is difficult to generate heat and easy to dissipate heat. When spot welding, the former can use a smaller current (thousands of amperes), while the latter must use a large current (several Million amps). The resistivity depends not only on the type of metal, but also on the heat treatment state, processing method and temperature of the metal.
In order to ensure the nugget size and the strength of the welding spot, the welding time and welding current can complement each other within a certain range. In order to obtain a certain strength of the solder joint, a large current and a short time (strong conditions, also known as hard codes), or a small current and a long time (weak conditions, also known as soft codes) can be used. The choice of hard or soft specifications depends on the performance, thickness and power of the welding machine used. There are upper and lower limits for the current and time required for metals of different properties and thicknesses, which shall prevail when used.
The electrode pressure has a significant effect on the total resistance R between the two electrodes. With the increase of the electrode pressure, R decreases significantly, but the increase in welding current is not large, and it cannot affect the reduction in heat production caused by the decrease in R. Therefore, the strength of the solder joint always decreases as the welding pressure increases. The solution is to increase the welding current while increasing the welding pressure.

classification
The spot welding machine can be divided into universal (universal, special) spot welding machines according to the purpose;
According to the number of welding points welded simultaneously, it is divided into: single point type, double point type, multi point type;
According to the conductive method, it is divided into: single-sided and double-sided;
According to the transmission method of the pressurizing mechanism, it is divided into: foot pedal, motor-cam type, pneumatic type, hydraulic type, compound type (pneumatic hydraulic type);
According to the characteristics of operation: non-automated and automated;
According to the installation method, it is divided into: fixed, mobiles or portable (hanging) spot welding machine;
According to the moving direction of the movable electrode (usually the upper electrode) of the welding machine, it is divided into: vertical stroke (the electrode moves linearly) and circular stroke.
How it works
The process of spot welding is to turn on the cooling water; clean the surface of the weldment, after the assembly is accurate, send it between the upper and lower electrodes, and apply pressure to make the contact good; energization makes the contact surface of the two workpieces heated and partially melted to form Nugget; maintain pressure after power off, so that the nugget cools and solidifies under pressure to form a solder joint; remove the pressure and take out the workpiece. Spot welding process parameters such as welding current, electrode pressure, energizing time, and electrode working surface size have a significant impact on welding quality.
The spot welding machine uses the high temperature arc generated by the positive and negative poles during an instant short circuit to melt the welded material between the electrodes to achieve the purpose of combining them. The structure of the spot welding machine is very simple. To put it bluntly, it is a high-power transformer that turns 220V AC into a low voltage, high-current power supply, which can be DC or AC. The welding transformer has its own characteristics, that is, it has the characteristics of a sharp drop in voltage.
After the electrode is ignited, the voltage drops, the adjustment of the working voltage of the welding machine, in addition to the primary 220/380 voltage conversion, the secondary coil also has a tap to change the voltage, and there is also an iron core to adjust the adjustable iron core. The welding machine is generally a high-power transformer, which is made using the principle of inductance. The inductance will produce a huge voltage change when it is turned on and off. The high voltage arc generated by the positive and negative poles during an instantaneous short circuit is used to melt the solder on the electrode. To achieve the purpose of combining them.
Spot welding is a resistance welding method in which a weldment is assembled with joints, pressed between two electrodes, and the base metal is melted by resistance heat to form a welding spot. Spot welding is more used for the connection of thin plates, such as aircraft skins, fire pipes of aircraft engines, car cabin shells, etc. The welding transformer of the spot welding machine is a spot welding appliance, and its secondary has only one loop. The upper and lower electrodes and electrode arms are used to conduct welding current and transmit power. The cooling water path passes through transformers, electrodes and other parts to avoid heating and welding. The cooling water should be passed before the power switch is turned on. The quality of the electrode directly affects the welding process, welding quality and productivity. Electrode materials are commonly made of copper, cadmium bronze, chrome bronze, etc .; electrode shapes are diverse, mainly determined by the shape of the weldment. When installing the electrode, pay attention to keeping the upper and lower electrode surfaces parallel; the electrode plane should be kept clean, and usually trimmed with emery cloth or file. Welding cycle The welding cycle of spot welding and projection welding consists of four basic stages (spot welding process):
(1) Pre-compression stage-the electrode is lowered to the stage where the current is turned on, to ensure that the electrode is pressed against the workpiece, so that there is proper pressure between the workpieces.
(2) Welding time-Welding current passes through the workpiece and generates heat to form a nugget.
(3) Maintenance time—cut off the welding current, and the electrode pressure continues to be maintained until the nugget solidifies to a sufficient strength.
(4) Rest time-the electrode starts to lift up and the electrode starts to fall again, and the next welding cycle begins.
In order to improve the performance of welded joints, it is sometimes necessary to add one or more of the following to the basic cycle:
(1) Increase the preload to eliminate gaps between thick workpieces and make them fit snugly.
(2) Use preheating pulse to improve the plasticity of the metal, make the workpiece easy to fit tightly, and prevent spatter; doing this during convex welding can make multiple bumps evenly contact with the flat plate before welding to ensure the uniform heating of each point.
Mechanical use edit
How to use spot welding machine:
1. The position of the electrode rod should be adjusted during welding so that the electrode arms remain parallel to each other when the electrode is just pressed against the weldment.
2. The selection of current adjustment switch stages can be selected according to the thickness and material of the weldment. After power on, the power indicator light should be on, and the electrode pressure can be adjusted by adjusting the spring pressure nut and changing its compression degree.
3. After completing the above adjustments, you can turn on the cooling water first and then turn on the power to prepare for welding. Procedure of the welding process: the weldment is placed between the two electrodes, the foot pedal is pressed, and the upper electrode is brought into contact with the weldment and pressurized. When the foot pedal is continuously pressed, the power contact switch is turned on, and the transformer starts to work The circuit is energized to heat the weldment. When the foot pedal is released after welding for a certain period of time, the electrode rises. The power of the spring is first cut off and then restored to the original state. The single-point welding process is ended.
4. Weldment preparation and assembly: Steel weldments must be cleaned of all dirt, oil, scale and rust before welding. For hot-rolled steel, it is best to pick the welded area first by pickling, sandblasting or using a grinding wheel to remove scale. Although uncleaned weldments can be spot welded, the service life of the electrode is severely reduced, and the production efficiency and quality of spot welds are also reduced. For medium and low carbon steels with thin coatings can be directly welded.
In addition, users can refer to the following process data when using:
1. Welding time: When welding medium and low carbon steel, this welding machine can use the strong specification welding method (instantaneous power-on) or the weak specification welding method (long-term power-on). The strong standard welding method should be used in mass production, which can improve production efficiency, reduce power consumption and reduce workpiece deformation.
2. Welding current: The welding current depends on the size, thickness and contact surface of the weldment. Generally, the higher the metal conductivity, the greater the electrode pressure, and the shorter the welding time. The current density required at this time also increases.
3. Electrode pressure: The purpose of the electrode to apply pressure to the weldment is to reduce the contact resistance at the welding point and ensure the pressure required when the welding point is formed.
Security editor
1. For the on-site use, there should be a rainproof, moisture-proof and sun-proof shed, and corresponding fire-fighting equipment should be installed.
2. Within 10m of the welding site, flammable and explosive materials such as oil, wood, oxygen cylinder, and acetylene generator shall not be stacked.
3. Welding operations and cooperating personnel must wear labor protection equipment as required. Safety measures must be taken to prevent accidents such as electric shock, falling from high altitude, and gas poisoning.
4. The copper plate connected to the secondary tap should be tight, and the terminal should have a gasket. Before closing, the wiring nuts, bolts and other parts should be checked in detail and confirmed to be intact and complete, without looseness or damage. There are protective covers at the terminals.
5. Before use, you should check and confirm that the wiring of the primary and secondary wires is correct, the input voltage meets the nameplate requirements of the electric welding machine, and know the type and applicable range of the welding current of the spot welding machine. After connecting the power supply, it is strictly forbidden to touch the live part of the primary line. The primary and secondary wiring must be equipped with protective covers.
6. When moving the spot welding machine, the power supply should be cut off, and the welding machine should not be moved by pulling the cable. When there is a sudden power failure during welding, the power should be cut off immediately.
7. When welding non-ferrous metals such as copper, aluminum, zinc, tin, lead, etc., it must be done in a well-ventilated place, and the welding personnel should wear gas masks or breathing filters.
8. When multiple spot welders are used together, they should be tapped on the three-phase power network to balance the three-phase load. The grounding devices of multiple welding machines shall be connected by the grounding poles respectively, and shall not be connected in series.
9. It is strictly forbidden to weld on the pressure pipes in operation, containers with flammable and explosive materials and stressed components.
10. When welding preheated parts, baffles should be set up to isolate the radiant heat from the preheated welded parts.
Installation and maintenance
The welding machine must be properly grounded before use to ensure personal safety. Before using the welding machine, use a 500V megohmmeter to test that the insulation resistance between the high-voltage side of the welding machine and the casing is not less than 2.5 megohms before it can be powered. The power supply must be cut off during inspection before unpacking and checking. Welding machine is first to pass water and then welding, work is strictly prohibited without water. The cooling water should be guaranteed to supply industrial water at 5--30 ° C at an inlet pressure of 0.15-0.2MPa. After the welding machine is completed in winter, compressed air is used to blow the water in the pipeline to avoid freezing and cracking of the water pipe.
The welding machine leads should not be too thin or too long, the voltage drop during welding should not be greater than 5% of the initial voltage, and the initial voltage should not deviate from ± 10% of the power supply voltage. Gloves, aprons and protective glasses should be worn when the welding machine is in operation to avoid flying sparks from the sparks. The sliding part should be kept well lubricated, and metal splash should be removed after use. After using the new welding machine for 24 hours, the screws of each part should be tightened once, especially pay attention to the connection screws between the copper flexible joint and the electrode. To ensure good contact.
When the welding machine is used, if the AC contactor is found to be inadequate, it means that the grid voltage is too low. The user should first solve the power supply problem and use it after the power supply is normal. It should be pointed out that if the quality problem of the main parts occurs within half a month of the newly purchased welding machine, the new welding machine or the main parts can be replaced. The main part of the welding machine is guaranteed for one year and provides long-term maintenance services. Under normal circumstances, after the user informs the factory, the service is in place within three to seven days according to the distance. Damage to the welding machine due to user reasons is not covered by the warranty. The wearing parts and consumables are not covered by the warranty.
Since the contact area of the electrode determines the current density, the resistivity and thermal conductivity of the electrode material are related to the generation and loss of heat. Therefore, the shape and material of the electrode have a significant effect on the formation of the nugget. As the electrode tip deforms and wears, the contact area increases and the strength of the solder joint will decrease. Oxides, dirt, oil and other impurities on the surface of the workpiece increase the contact resistance. An oxide layer that is too thick can even prevent current from passing through. Local conduction, due to excessive current density, will produce splashes and surface burns. The existence of the oxide layer will also affect the unevenness of heating of each solder joint, causing welding quality fluctuations. Therefore, thoroughly cleaning the surface of the workpiece is a necessary condition to ensure that high-quality joints are obtained.
Troubleshooting
1. The welding machine does not work when the pedal is depressed, and the power indicator does not light:
a. Check whether the power supply voltage is normal; check whether the control system is normal.
b. Check whether the contact of the foot switch, the contact of the AC contactor and the split shift switch are in good contact or burned.
2. The power indicator light is on, the workpiece is not compressed and welded:
a. Check if the foot pedal travel is in place and the foot switch is in good contact.
b. Check whether the pressure rod spring screw is adjusted properly.
3. Unexpected spatter during welding:
a. Check whether the electrode head is seriously oxidized.
b. Check whether the welding workpiece is badly corroded and has poor contact.
c. Check whether the adjustment switch is too high.
d. Check whether the electrode pressure is too low and the welding procedure is correct.
4. The welding spot has serious indentation and extrudates:
a. Check if the current is too large.
b. Check whether the welding workpiece is uneven.
c. Check whether the electrode pressure is too large and the shape and cross section of the electrode head are appropriate.
5. Insufficient strength of welding workpiece:
a. Check whether the electrode pressure is too low, and check whether the electrode rod is tight.
b. Check whether the welding energy is too small, whether the welding workpiece is severely corroded, so that the welding point is poorly contacted.
c. Check if there is too much oxide between the electrode tip and electrode rod, electrode rod and electrode arm.
d. Check whether the cross section of the electrode head is increased due to wear and the welding energy is reduced.
e. Check whether the electrode and copper soft-coupling and bonding surface are severely oxidized.
6. Abnormal noise of AC contactor during welding:
a. Check whether the incoming voltage of the AC contactor is 300V lower than the self-release voltage during welding.
b. Check whether the power lead is too thin and too long, causing the line voltage drop too large.
c. Check if the network voltage is too low to work properly.
d. Check whether the main transformer has a short circuit, causing too much current.
7. Welding machine overheating phenomenon:
a. Check whether the insulation resistance between the electrode holder and the body is bad, causing a local short circuit.
b. Check whether the inlet water pressure, water flow rate, and water supply temperature are appropriate, and check whether the waterway system is blocked by dirt, causing the electrode arm, electrode rod, and electrode head to overheat due to poor cooling.
c. Check if the copper flexible coupling and electrode arm, electrode rod and electrode tip contact surface are seriously oxidized, causing contact resistance to increase and generate heat.
d. Check if the electrode head section is excessively worn due to wear, which overloads the welder and generates heat.
e. Check whether the welding thickness and load continuity rate exceed the standard, causing the welder to overload and heat up [1]
Pros and cons
Resistance welding has the following advantages:
1. When the nugget is formed, it is always surrounded by a plastic ring, the molten metal is isolated from the air, and the metallurgical process is simple.
2. The heating time is short and the heat is concentrated, so the heat affected zone is small, and the deformation and stress are also small. It is usually not necessary to arrange correction and heat treatment processes after welding.
3. No filler metals such as welding rods and welding wires, and welding materials such as oxygen, acetylene, argon, etc. are needed, and the welding cost is low.
4. Simple operation, easy to realize mechanization and automation, and improve working conditions.
5. High productivity, no noise and harmful gas. In mass production, it can be assembled on the assembly line together with other manufacturing processes, but flash butt welding needs to be isolated due to sparks and splashes.
Resistance welding has the following disadvantages:
1. Lack of reliable non-destructive testing methods, welding quality can only be checked by destructive testing of process samples and weldments, and by various monitoring techniques.
2. The lap joints of spot and seam welds not only increase the weight of the component, but also form an angle around the nugget between the two plates, resulting in a lower tensile strength and fatigue strength of the joint.

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