CN113618212A - Method for manufacturing spot welding machine by using microwave oven transformer - Google Patents

Abstract

The invention discloses a method for manufacturing a spot welder by using a microwave oven transformer, in particular to the technical field of spot welder manufacturing, which comprises the following steps: step one, cleaning a transformer: dismantling a high-voltage winding, a filament winding and a magnetic shunt iron core of a transformer of the microwave oven, cleaning residual insulating paper and insulating paint, measuring the insulation between a primary winding and the iron core, wherein the resistance is infinite, and measuring the resistance value of a primary coil; step two, winding a secondary coil: cutting to length of about 3m, 25mm²After being sleeved with the heat shrinkage pipe, the bare copper wire is blown to the heat shrinkage pipe by a hot air gun to shrink and tightly wrap the copper wire, and a double-wire parallel winding mode is adopted. The invention selects the case with proper volume, opens the hole, installs the power switch, the foot switch socket, the welding electrode leading-out terminal, the control panel potentiometer knob and the like, and assembles the main transformer, the control panel and other accessories into a wholeIn the casing, to accomplish the preparation of spot welder for the transformer in the microwave oven can continue to utilize, avoids causing the waste of resource.

Description

Method for manufacturing spot welding machine by using microwave oven transformer

Technical Field

The invention relates to the technical field of spot welding machine manufacturing, in particular to a method for manufacturing a spot welding machine by using a microwave oven transformer.

Background

The spot welder adopts the principle of double-sided double-point over-current welding, when in work, two electrodes pressurize a workpiece to enable two layers of metals to form a certain contact resistance under the pressure of the two electrodes, when welding current flows from one electrode to the other electrode, instant thermal welding is formed at the two contact resistance points, and the welding current instantly flows from the other electrode to the electrode along the two workpieces to form a loop, and the internal structure of the workpiece to be welded is not damaged. The spot welding process comprises the following steps: cleaning the surface of a weldment, accurately assembling, sending the weldment into a position between an upper electrode and a lower electrode, and applying pressure to ensure that the weldment is in good contact; electrifying to heat the contact surfaces of the two workpieces, and locally melting to form a nugget; maintaining the pressure after power failure, and cooling and solidifying the nugget under the pressure to form a welding spot; and removing the pressure and taking out the workpiece. The welding quality is greatly influenced by welding parameters such as welding current, electrode pressure, electrifying time, working surface size of the electrode and the like. The spot welding is high-current welding, 220V alternating current is converted into lower voltage by using a transformer, the high current generated at the moment of spot welding ablates a weldment to generate a nugget so as to achieve the purpose of welding, and the consumed power is high during welding.

The microwave oven is also a common electric appliance in daily life, and most people can directly discard some worn microwave ovens, but the transformer in the microwave oven can be continuously utilized after being modified, so that the waste of resources can be caused by directly discarding the microwave oven.

Disclosure of Invention

Therefore, the invention provides a method for manufacturing a spot welder by using a microwave oven transformer, which is characterized in that a shell with a proper size is selected, a hole is formed, a power switch, a foot switch socket, a welding electrode leading-out terminal, a control panel potentiometer knob and the like are installed, and a main transformer, a control panel and other accessories are assembled in the shell to complete the manufacture of the spot welder, so that the transformer in the microwave oven can be continuously utilized, the waste of resources is avoided, and the problem of resource waste caused by the fact that the microwave oven is directly discarded and is not modified in the prior art is solved.

In order to achieve the above object, the embodiments of the present invention provide the following technical solutions: a method for manufacturing a spot welder by using a transformer of a microwave oven comprises the following steps:

step one, cleaning a transformer: dismantling a high-voltage winding, a filament winding and a magnetic shunt iron core of a transformer of the microwave oven, cleaning residual insulating paper and insulating paint, measuring the insulation of a primary winding and the iron core, wherein the resistance is infinite, and the resistance value of the primary winding is measured and is 2 ohms;

step twoAnd winding a secondary coil: cutting to length of about 3m, 25mm²The bare copper wire is sleeved with a heat-shrinkable tube, blown to the heat-shrinkable tube by a hot air gun to shrink and tightly wrap the copper wire, and a double-wire parallel winding mode is adopted, wherein the secondary sectional area is 50mm ²4 circles are wound in a main transformer core window in a penetrating mode, meanwhile, redundant copper wires can be reserved as welding electrode leads, insulation between a primary side and a secondary side and insulation between a coil and an iron core are measured, and resistance is infinite;

step three, manufacturing a spot welding pen: selecting a copper pipe with the diameter of about 10cm and the diameter of 10mm, tightly pressing and fixing the clamp in the copper pipe by using a hydraulic clamp, fixing a secondary outgoing line of the main transformer by using the same method at the other end of the copper pipe to ensure good contact, and sleeving a heat-shrinkable tube or other heat-insulating materials outside the copper pipe;

step four, assembling: selecting a case with a proper size, opening a hole, installing a power switch, a foot switch socket, a welding electrode leading-out terminal, a control panel potentiometer knob and the like, assembling a main transformer, a control panel and other accessories into the case, and completing the manufacture;

step five, testing: when in spot welding, the temperature of a welding spot is very high, metal near the welding spot is oxidized, so that the strength and the material characteristics of the welding spot are influenced, the longer the spot welding time is, the more serious the oxidation is, so that the proper welding mode is the shortest time as possible under the heavy current, the spot welding time generally does not exceed 0.5 second, the current output capacity of a spot welding machine changed by a transformer of a microwave oven is limited, so that the maximum current is firstly set, and the shortest welding time under the maximum current is searched; if the secondary wire and the electrode wire of the transformer are thick, the secondary current is large, the current is adjusted around a welding spot during spot welding without obviously changing color, the spot welding voltage is not directly related to the spot welding effect, but the resistance in a spot welding secondary circuit influences the spot welding current, the resistance in the spot welding circuit comprises four parts, namely contact resistance of a contact part, a spot welding electrode, a lead wire of the electrode and resistance of a secondary winding, if the total resistance in the spot welding circuit is large, the secondary voltage needs to be improved in order to achieve ideal spot welding current, but the loss in the circuit can be increased, the phenomenon of obvious heating is shown, and the efficiency is reduced; if the resistance in the loop is small, the secondary can use lower voltage, so the heat generation is not obvious, the efficiency is higher, the ideal spot welding machine is that the secondary can output enough current under lower voltage, and the increase of the secondary voltage can bring about the disadvantage of serious heat generation of a welding wire and the secondary.

Further, the working principle of the control board used in the fourth step is as follows: D1-D4 form a bridge rectifier circuit, convert the power supply of the power transformer into the direct current of the fixed polarity, supply the poststage circuit work after the three-terminal regulated voltage U1 regulated voltage; the R1 and the D5 form a starting indicating circuit, the D5 adopts a green LED, and the LED shines when the power supply is switched on to indicate that the power supply is switched on; u2 and U3 form monostable flip-flops respectively, when a foot switch is not pressed down, an internal switch is disconnected, pins 2 and 6 of U2 are low potential, and pin 3 of U2 is high potential; pins 2 and 6 of the U3 are high potential, pin 3 of the U3 is low potential, the light-emitting tube D7 does not emit light, and the optocoupler U4 is not electrified; after the foot switch is stepped, the internal switch is switched on, C3 is rapidly charged through R2, when the voltage is charged to be more than 2/3Vcc, U2 is triggered, the 3 rd pin outputs a low-potential negative pulse, a sharp trigger pulse is formed through differentiation of C5 and is coupled to the 2 nd pin of U3 to trigger U3, the 7 th pin of U3 is conducted, C6 is rapidly discharged to the ground, meanwhile, the 3 rd pin of U3 outputs a high potential, D7 emits light, and the optical coupler U4 is powered; the negative pulse coupled by the C5 triggers the U3 to disappear rapidly, but the C6 is a low potential after being discharged rapidly, the transient stable state of the U3 can be maintained continuously, the 3 rd pin of the U3 is maintained at a high potential, at the moment, the power supply can charge the C6 through the R6 and the R7, when the voltage on the C6 is charged to 2/3Vcc, the U3 can be recovered to the original stable state, the 3 rd pin of the U3 is recovered to a low potential state, the D7 does not emit light any more, and the optocoupler U4 does not get power any more; the time length of the high-potential pulse output by the 3 rd pin in the U3 transient state is related to the charging time lengths of R6, R7 and C6, and the pulse width T is 1.1 (R6+ R7) C6; an LED inside the optocoupler U4 emits light after the front stage is electrified, the rear stage of the U4 is connected, a common phase-shifting voltage regulating circuit is formed by R10, R11, C8, R12 and D8, the conduction angle of a thyristor Q1 is controlled by adjusting the resistance value of a potentiometer R11, the size of spot welding current of a spot welding main transformer is controlled, namely the spot welding time is controlled by adjusting R6 to change the pulse width of the 3 rd pin of the U3, and the spot welding current is controlled by adjusting R11; no matter how long the pedal switch is stepped on, the 3 rd foot of the U2 outputs a negative pulse to trigger the U3 once, and even if the pedal switch is not released after being stepped on, the spot welding machine only performs spot welding once; r3 and C3 constitute the anti-shake circuit, prevent that foot switch from stepping down and triggering U3 because of the shake of switch contact many times and causing the mistake spot welding, the size of R3 and C3 numerical value influence the time interval of continuous spot welding, and the numerical value is bigger, and the time interval of continuous spot welding is longer.

Further, the transformer of the microwave oven selected in the step one is designed according to the overpower under the low temporary load rate, the primary coil is thick in wire diameter, the instantaneous power is large, and the requirement of spot welding in daily use is met.

Furthermore, in the process of manufacturing the secondary coil in the second step, redundant bare copper wires need to be led to the welding electrode as outgoing wires after the winding is finished, and the length of the bare copper wires is shortened as much as possible under the condition that the using length is met so as to reduce the line loss.

Further, the spot welding pen in the third step selects an aluminum oxide copper electrode with the diameter of 3mm, a corresponding pure copper fixture is adopted, the aluminum oxide copper electrode is fixed in the copper pipe through a hydraulic tool, and the secondary outgoing line is fixed at the other end of the copper pipe in the same way.

The invention has the following advantages:

1. the invention removes the transformer in the microwave oven, removes the secondary coil (high-voltage side) on the transformer, rewinds and retains the primary coil (220V side), removes the magnetic shunt iron core, and insulates to meet the spot welding requirement in daily use, thereby realizing the recycling of the transformer in the microwave oven, avoiding the waste of resources, considering the factors of material selection, the number of wires which can be contained in the window area of the transformer iron core, and the like, the output voltage of the secondary coil is properly selected about 4V when the nickel sheet of the battery is spot-welded, the instantaneous current can exceed 1000A when the spot welding is carried out, so 3m 25mm is selected²The bare copper wire sleeve heat-shrinkable tube is manufactured, and the secondary side of the transformer adopts a double-wire parallel winding mode during rewinding, namely the section area of the secondary side is 50mm²4 turns are wound, and redundant bare copper wires are led to a welding electrode as leading-out wires after the winding is finished, so that the requirement is metThe length of the cable can be shortened as much as possible to reduce the line loss under the condition of using the length;

2. the invention realizes the control of the welding time and the current by adding the control circuit, so as to prevent the occurrence of the phenomenon that the manual control cannot ensure the precision and the welding electrode is easy to cause electric arc to burn through the weldment when being separated from the weldment, thereby improving the accuracy of the invention in the spot welding.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.

The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the effects and the achievable by the present invention, should still fall within the range that the technical contents disclosed in the present invention can cover.

FIG. 1 is a circuit diagram of a control board according to the present invention;

fig. 2 is a schematic structural diagram of a manufactured transformer provided by the present invention.

Detailed Description

The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to the accompanying fig. 1 and 2 of the specification, the method for manufacturing a spot welder using a transformer of a microwave oven of the embodiment includes the steps of:

step one, cleaning a transformer: dismantling a high-voltage winding, a filament winding and a magnetic shunt iron core of a transformer of the microwave oven, cleaning residual insulating paper and insulating paint, measuring the insulation of a primary winding and the iron core, wherein the resistance is infinite, and the resistance value of the primary winding is measured and is 2 ohms;

the transformer is originally designed as a step-up transformer, a secondary coil positioned on a high-voltage side needs to be removed and then wound again, the primary coil positioned on a 220V side is reserved, and a magnetic shunt iron core needs to be removed and insulation is well made;

step two, winding a secondary coil: cutting to length of about 3m, 25mm²The bare copper wire is sleeved with a heat-shrinkable tube, blown to the heat-shrinkable tube by a hot air gun to shrink and tightly wrap the copper wire, and a double-wire parallel winding mode is adopted, wherein the secondary sectional area is 50mm²4 circles are wound in a main transformer core window in a penetrating mode, meanwhile, redundant copper wires can be reserved as welding electrode leads, insulation between a primary side and a secondary side and insulation between a coil and an iron core are measured, and resistance is infinite; in the process of manufacturing the secondary coil, redundant bare copper wires are required to be used as outgoing lines to be led to a welding electrode after the winding is finished, and the length of the outgoing lines is shortened as much as possible under the condition that the using length is met so as to reduce the line loss;

step three, manufacturing a spot welding pen: selecting a copper pipe with the diameter of about 10cm and the diameter of 10mm, tightly pressing and fixing the clamp in the copper pipe by using a hydraulic clamp, fixing a secondary outgoing line of the main transformer by using the same method at the other end of the copper pipe to ensure good contact, and sleeving a heat-shrinkable tube or other heat-insulating materials outside the copper pipe; the spot welding pen selects an aluminum oxide copper electrode with the diameter of 3mm, a corresponding pure copper fixture is adopted, the aluminum oxide copper electrode is fixed in a copper pipe by a hydraulic tool, and a secondary outgoing line is fixed at the other end of the copper pipe by the same method;

step four, assembling: selecting a case with a proper size, opening a hole, installing a power switch, a foot switch socket, a welding electrode leading-out terminal, a control panel potentiometer knob and the like, assembling a main transformer, a control panel and other accessories into the case, and completing the manufacture;

wherein, referring to the attached figure 1 of the specification, the working principle of the control panel is as follows: D1-D4 form a bridge rectifier circuit, convert the power supply of the power transformer into the direct current of the fixed polarity, supply the poststage circuit work after the three-terminal regulated voltage U1 regulated voltage; the R1 and the D5 form a starting indicating circuit, the D5 adopts a green LED, and the LED shines when the power supply is switched on to indicate that the power supply is switched on; u2 and U3 form monostable flip-flops respectively, when a foot switch is not pressed down, an internal switch is disconnected, pins 2 and 6 of U2 are low potential, and pin 3 of U2 is high potential; pins 2 and 6 of the U3 are high potential, pin 3 of the U3 is low potential, the light-emitting tube D7 does not emit light, and the optocoupler U4 is not electrified; after the foot switch is stepped, the internal switch is switched on, C3 is rapidly charged through R2, when the voltage is charged to be more than 2/3Vcc, U2 is triggered, the 3 rd pin outputs a low-potential negative pulse, a sharp trigger pulse is formed through differentiation of C5 and is coupled to the 2 nd pin of U3 to trigger U3, the 7 th pin of U3 is conducted, C6 is rapidly discharged to the ground, meanwhile, the 3 rd pin of U3 outputs a high potential, D7 emits light, and the optical coupler U4 is powered; the negative pulse coupled by the C5 triggers the U3 to disappear rapidly, but the C6 is a low potential after being discharged rapidly, the transient stable state of the U3 can be maintained continuously, the 3 rd pin of the U3 is maintained at a high potential, at the moment, the power supply can charge the C6 through the R6 and the R7, when the voltage on the C6 is charged to 2/3Vcc, the U3 can be recovered to the original stable state, the 3 rd pin of the U3 is recovered to a low potential state, the D7 does not emit light any more, and the optocoupler U4 does not get power any more; the time length of the high-potential pulse output by the 3 rd pin in the U3 transient state is related to the charging time lengths of R6, R7 and C6, and the pulse width T is 1.1 (R6+ R7) C6; an LED inside the optocoupler U4 emits light after the front stage is electrified, the rear stage of the U4 is connected, a common phase-shifting voltage regulating circuit is formed by R10, R11, C8, R12 and D8, the conduction angle of a thyristor Q1 is controlled by adjusting the resistance value of a potentiometer R11, the size of spot welding current of a spot welding main transformer is controlled, namely the spot welding time is controlled by adjusting R6 to change the pulse width of the 3 rd pin of the U3, and the spot welding current is controlled by adjusting R11; no matter how long the pedal switch is stepped on, the 3 rd foot of the U2 outputs a negative pulse to trigger the U3 once, and even if the pedal switch is not released after being stepped on, the spot welding machine only performs spot welding once; the R3 and the C3 form an anti-shake circuit, so that error spot welding caused by shaking of a switch contact to trigger the U3 for multiple times when the foot switch is stepped on is prevented, the time interval of continuous spot welding is influenced by the magnitude of the numerical values of the R3 and the C3, and the larger the numerical value is, the longer the time interval of continuous spot welding is;

step five, testing: when in spot welding, the temperature of a welding spot is very high, metal near the welding spot is oxidized, so that the strength and the material characteristics of the welding spot are influenced, the longer the spot welding time is, the more serious the oxidation is, so that the proper welding mode is the shortest time as possible under the heavy current, the spot welding time generally does not exceed 0.5 second, the current output capacity of a spot welding machine changed by a transformer of a microwave oven is limited, so that the maximum current is firstly set, and the shortest welding time under the maximum current is searched; if the secondary wire and the electrode wire of the transformer are thick, the secondary current is large, the current is adjusted around a welding spot during spot welding without obviously changing color, the spot welding voltage is not directly related to the spot welding effect, but the resistance in a spot welding secondary circuit influences the spot welding current, the resistance in the spot welding circuit comprises four parts, namely contact resistance of a contact part, a spot welding electrode, a lead wire of the electrode and resistance of a secondary winding, if the total resistance in the spot welding circuit is large, the secondary voltage needs to be improved in order to achieve ideal spot welding current, but the loss in the circuit can be increased, the phenomenon of obvious heating is shown, and the efficiency is reduced; if the resistance in the loop is small, the secondary can use lower voltage, so the heat generation is not obvious, the efficiency is higher, the ideal spot welding machine is that the secondary can output enough current under lower voltage, and the increase of the secondary voltage can bring about the disadvantage of serious heat generation of a welding wire and the secondary.

Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims (5)

1. A method for manufacturing a spot welder by using a transformer of a microwave oven is characterized by comprising the following steps: the method comprises the following steps:

step one, cleaning a transformer: dismantling a high-voltage winding, a filament winding and a magnetic shunt iron core of a transformer of the microwave oven, cleaning residual insulating paper and insulating paint, measuring the insulation of a primary winding and the iron core, wherein the resistance is infinite, and the resistance value of the primary winding is measured and is 2 ohms;

step two, winding a secondary coil: cutting to length of about 3m, 25mm²The bare copper wire is sleeved with a heat-shrinkable tube, blown to the heat-shrinkable tube by a hot air gun to shrink and tightly wrap the copper wire, and a double-wire parallel winding mode is adopted, wherein the secondary sectional area is 50mm²4 circles are wound in a main transformer core window in a penetrating mode, meanwhile, redundant copper wires can be reserved as welding electrode leads, insulation between a primary side and a secondary side and insulation between a coil and an iron core are measured, and resistance is infinite;

step three, manufacturing a spot welding pen: selecting a copper pipe with the diameter of about 10cm and the diameter of 10mm, tightly pressing and fixing the clamp in the copper pipe by using a hydraulic clamp, fixing a secondary outgoing line of the main transformer by using the same method at the other end of the copper pipe to ensure good contact, and sleeving a heat-shrinkable tube or other heat-insulating materials outside the copper pipe;

step four, assembling: selecting a case with a proper size, opening a hole, installing a power switch, a foot switch socket, a welding electrode leading-out terminal, a control panel potentiometer knob and the like, assembling a main transformer, a control panel and other accessories into the case, and completing the manufacture;

step five, testing: when in spot welding, the temperature of a welding spot is very high, metal near the welding spot is oxidized, so that the strength and the material characteristics of the welding spot are influenced, the longer the spot welding time is, the more serious the oxidation is, so that the proper welding mode is the shortest time as possible under the heavy current, the spot welding time generally does not exceed 0.5 second, the current output capacity of a spot welding machine changed by a transformer of a microwave oven is limited, so that the maximum current is firstly set, and the shortest welding time under the maximum current is searched; if the secondary wire and the electrode wire of the transformer are thick, the secondary current is large, the current is adjusted around a welding spot during spot welding without obviously changing color, the spot welding voltage is not directly related to the spot welding effect, but the resistance in a spot welding secondary circuit influences the spot welding current, the resistance in the spot welding circuit comprises four parts, namely contact resistance of a contact part, a spot welding electrode, a lead wire of the electrode and resistance of a secondary winding, if the total resistance in the spot welding circuit is large, the secondary voltage needs to be improved in order to achieve ideal spot welding current, but the loss in the circuit can be increased, the phenomenon of obvious heating is shown, and the efficiency is reduced; if the resistance in the loop is small, the secondary can use lower voltage, so the heat generation is not obvious, the efficiency is higher, the ideal spot welding machine is that the secondary can output enough current under lower voltage, and the increase of the secondary voltage can bring about the disadvantage of serious heat generation of a welding wire and the secondary.

2. The method of manufacturing a spot welder using a microwave oven transformer according to claim 1, wherein: the working principle of the control board used in the fourth step is as follows: D1-D4 form a bridge rectifier circuit, convert the power supply of the power transformer into the direct current of the fixed polarity, supply the poststage circuit work after the three-terminal regulated voltage U1 regulated voltage; the R1 and the D5 form a starting indicating circuit, the D5 adopts a green LED, and the LED shines when the power supply is switched on to indicate that the power supply is switched on; u2 and U3 form monostable flip-flops respectively, when a foot switch is not pressed down, an internal switch is disconnected, pins 2 and 6 of U2 are low potential, and pin 3 of U2 is high potential; pins 2 and 6 of the U3 are high potential, pin 3 of the U3 is low potential, the light-emitting tube D7 does not emit light, and the optocoupler U4 is not electrified; after the foot switch is stepped, the internal switch is switched on, C3 is rapidly charged through R2, when the voltage is charged to be more than 2/3Vcc, U2 is triggered, the 3 rd pin outputs a low-potential negative pulse, a sharp trigger pulse is formed through differentiation of C5 and is coupled to the 2 nd pin of U3 to trigger U3, the 7 th pin of U3 is conducted, C6 is rapidly discharged to the ground, meanwhile, the 3 rd pin of U3 outputs a high potential, D7 emits light, and the optical coupler U4 is powered; the negative pulse coupled by the C5 triggers the U3 to disappear rapidly, but the C6 is a low potential after being discharged rapidly, the transient stable state of the U3 can be maintained continuously, the 3 rd pin of the U3 is maintained at a high potential, at the moment, the power supply can charge the C6 through the R6 and the R7, when the voltage on the C6 is charged to 2/3Vcc, the U3 can be recovered to the original stable state, the 3 rd pin of the U3 is recovered to a low potential state, the D7 does not emit light any more, and the optocoupler U4 does not get power any more; the time length of the high-potential pulse output by the 3 rd pin in the U3 transient state is related to the charging time lengths of R6, R7 and C6, and the pulse width T is 1.1 (R6+ R7) C6; an LED inside the optocoupler U4 emits light after the front stage is electrified, the rear stage of the U4 is connected, a common phase-shifting voltage regulating circuit is formed by R10, R11, C8, R12 and D8, the conduction angle of a thyristor Q1 is controlled by adjusting the resistance value of a potentiometer R11, the size of spot welding current of a spot welding main transformer is controlled, namely the spot welding time is controlled by adjusting R6 to change the pulse width of the 3 rd pin of the U3, and the spot welding current is controlled by adjusting R11; no matter how long the pedal switch is stepped on, the 3 rd foot of the U2 outputs a negative pulse to trigger the U3 once, and even if the pedal switch is not released after being stepped on, the spot welding machine only performs spot welding once; r3 and C3 constitute the anti-shake circuit, prevent that foot switch from stepping down and triggering U3 because of the shake of switch contact many times and causing the mistake spot welding, the size of R3 and C3 numerical value influence the time interval of continuous spot welding, and the numerical value is bigger, and the time interval of continuous spot welding is longer.

3. The method of manufacturing a spot welder using a microwave oven transformer according to claim 1, wherein: the transformer of the microwave oven selected in the step one is designed according to the overpower under the low temporary load rate, the primary coil is thick in wire diameter, the instantaneous power is large, and the requirement of spot welding in daily use is met.

4. The method of manufacturing a spot welder using a microwave oven transformer according to claim 1, wherein: and in the second step, the redundant bare copper wires are required to be used as outgoing wires to be led to the welding electrodes after the winding is finished in the process of manufacturing the secondary coil, and the consumption of the wires is reduced by shortening as much as possible under the condition of meeting the use length.

5. The method of manufacturing a spot welder using a microwave oven transformer according to claim 1, wherein: and the spot welding pen in the third step selects an aluminum oxide copper electrode with the diameter of 3mm, adopts a corresponding pure copper fixture, is fixed in the copper pipe by a hydraulic tool, and fixes the secondary outgoing line at the other end of the copper pipe by the same method.

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