Principle of Cold Welding Machine: Explained and Analyzed

Electro Spark Deposition (ESD) is the international term for the cold welding machine, which was developed by former Soviet experts through research on the circuit principles of Electro Discharge Machining.

Its main purpose is to coat mold/metal surfaces with high-hardness materials such as tungsten carbide to improve wear resistance, heat resistance, anti-sticking, and other properties.

Initially, the maximum coating thickness of the machine was only about 30μm, so it could not meet the repair needs.

After extensive research and development, its output power was improved, and the structure of the welding gun and the composition of the welding rod material were improved.

In response to the previous front-rear vibration electrode, a rotating electrode was used, and argon protection was used to prevent oxidation and nitriding of the molten metal, achieving continuous multi-layer repair welding, improving the repair welding thickness, and pushing it to the market as a mold/metal repair machine.

For injection molding manufacturers without mold manufacturing departments, if traditional welding methods are used to repair molds when burrs appear on the molded products, the molds will deform or even crack due to the heat generated.

If there is no equipment such as EDM or milling machines to cut the excess weld metal, only high repair costs can be paid to entrust the mold manufacturer for repairs. During the repair period, machine downtime will cause delivery delays.

On the contrary, if our company’s mold repair cold welding machine is used for repair, there will be no deformation, biting edge, and other defects, and the mold can be easily repaired.

The excess weld metal can be controlled to a few wires. There is no need for special precision machining machines, only small polishing machines, grinders, files, oilstones, and other tools for manual precision machining.

Injection molding manufacturers can easily repair the mold trimming surface where burrs appear on their own, which is both time-saving and economical.

Introduction to the self-made mold repair cold welding machine:

1. Working Principle:

The principle of the mold repair cold welding machine is to use a charged capacitor to discharge with a period of 10^-3 to 10^-1 seconds and an ultra-short time of 10^-6 to 10^-5 seconds.

The electrode material and the contact part of the mold will be heated to 8000-12000°C, and the plasma state molten metal will transition to the surface layer of the workpiece in a metallurgical way.

Figure 1 shows a schematic diagram and various characteristics of (welding, coating). Area A is the coating or weld layer that is welded to the surface of the workpiece.

Due to the alloying effect between it and the base material, it diffuses and infiltrates into the interior of the workpiece, forming a diffusion layer B and obtaining high-strength bonding.

2. Achieving Cold Welding (Low Heat Input):

Why can cold welding be achieved? As shown in Figure 2, the discharge time (Pt) is extremely short compared to the interval time (It) until the next discharge, and the machine has enough relative stop time.

The heat will diffuse through the mold base to the outside world, so there will be no accumulation of heat in the processed part of the mold.

Although the temperature rise of the mold almost stays at room temperature, due to the instantaneous melting, the temperature at the tip of the electrode can reach about 1000°C.

3. High Bonding Strength:

When using the mold repair cold welding machine for repair welding, since the heat input is low, why is the bonding strength still very high?

This is because the welding rod produces metal droplets instantaneously, transitions to the contact part of the base material metal, and at the same time, due to the high-temperature effect of the plasma arc, a strong diffusion layer like roots is formed in the deep surface (as shown by B in Figure 1). It shows high bondability and will not fall off.

Figure 3 is a schematic diagram of the processing principle:

4. Characteristics of the Mold Repair Cold Welding Machine:

Achieve true cold welding, and the workpiece does not need to be preheated or insulated during the repair process. There is no heat input during the instantaneous process of welding, so the workpiece will not deform, anneal, bite the edge, or have residual stress, and it will not change the metal structure status of the workpiece.

High bonding strength for repair welding. Since the welding rod is ionized by the arc instantaneously and transferred to the workpiece in contact with it, the bonding strength is high and will not fall off.

High repair accuracy. The coating thickness can range from a few micrometers to several millimeters, and only polishing is needed. It can also be machined by turning, milling, planing, grinding, electroplating, etc.

Multi-functional use. It can perform functions such as repair welding and surface strengthening.

High economic practicality. It can be repaired on-site online, improve production efficiency, save time and cost. It is also easy to use. Anyone can operate it after a short period of training.

Wide range of applicable substrates, including various types of mold steel, stainless steel, tool steel, cast iron, cast aluminum, aluminum alloy, copper alloy, nickel alloy, and all conductive conductors.

Good environmental performance, no noise, dust, waste liquid, strong light, or odor.

Even if the repaired weld layer is worn, it can be repaired multiple times in the same location.

By using inert gases such as argon for protection, high-quality weld layers can be obtained.

Since a rotating welding rod is used, there will be no sticking wire phenomenon. It is easy to operate and can obtain high-quality weld layers, and the excess weld metal can be controlled to a small amount, thus saving precision machining time.

The Principle of Spark Welding Repair Machine:

Our company’s spark welding repair machine adopts advanced German cold welding repair and strengthening technology. It uses high-frequency electric spark discharge principle to perform heat-free welding on the workpiece to repair surface defects and wear of metal workpieces, ensuring the integrity of the workpiece.

It can also use the strengthening function of the spark welding machine to carry out strengthening treatment on the workpiece, achieving wear resistance, heat resistance, corrosion resistance, etc.

After the metal workpiece is repaired by the spark welding repair machine, it will not deform, anneal, has high welding strength, and is wear-resistant. It can be tested by metallography, tensile strength, and hardness testing.

The metallurgical combination of the welding material and the substrate ensures the firmness of the welding. It makes up for the shortcomings of ordinary argon arc welding and electric welding.

The spark welding machine can be used for welding narrow parts, deep cavity parts, and extremely hard materials without cracks or sand holes, nor does it cause deformation or concave phenomenon around the weld pool of the workpiece.

The spark welding machine uses argon gas protection, and the welded area will not oxidize or turn blue. Using a microscope to observe the operation, even small parts are clear at a glance.

After welding, the surface can be mirror-polished, suitable for welding and reinforcement repair of various materials.

The welding point of the spark welding machine can be adjusted from 0.2mm to 2.0mm, and it can weld metal sheets as thin as 0.2mm without breaking through the sheet, and the weld is even and beautiful.

The spark welding repair machine is an indispensable repair and reinforcement tool for all processing, manufacturing, maintenance, and surface treatment enterprises.

At the same time, the spark welding machine is also a good helper for individuals engaged in special repair industry to get rich quickly.

Disadvantages of Traditional Repair:

After traditional repair, the workpiece may deform, reduce in hardness, have sand holes, local annealing, cracking, pinholes, wear, scratches, bite edges or insufficient bonding strength, internal stress damage, and even scrap. The resulting losses in manpower, material resources, and financial resources cannot be calculated.

Characteristics of electric spark stack welding repair machine:

  1. No annealing and deformation of mold/workpiece: No preheating is required for the mold, and there is no heat input during the stack welding instantaneous process, so there is no deformation, undercut, residual stress, no local annealing, and no change in the organization of the mold or metal product.
  2. High welding strength: Fully penetrate into the surface of the mold material, producing strong bonding force.
  3. High repair accuracy: The stack welding thickness ranges from a few microns to several millimeters, and can be polished and repaired without color difference.
  4. Multi-functional: Can perform stack welding and surface strengthening functions.
  5. Environmental protection: No pollution during the working process.
  6. Easy to operate: Anyone can use it easily, and stack welding can be performed in difficult-to-weld areas. By adjusting the discharge power and frequency with the regulator, the required thickness and smoothness of stack welding and strengthening can be obtained.
  7. Economical and convenient: Immediate repair on site, improving production efficiency and saving costs.

Adaptation range of electric spark stack welding repair machine:

Punching dies, forging dies, injection molds, casting molds, die casting molds, metal products, machine parts, tools.

Materials applicable to electric spark stack welding repair machine:

Aluminum, aluminum alloy, copper, copper alloy, low carbon steel, medium carbon steel, die steel, carbon steel, stainless steel, full steel, semi-steel, cast steel, cast iron, cast aluminum, carbon tungsten gold, and all conductive conductors.

Defects that can be repaired by electric spark stack welding repair machine:

Pinholes, air holes, burrs, flash, bumps, scratches, broken corners, collapsed corners, sand holes, cracks, wear, inward, manufacturing errors, manufacturing defects, welding defects.

Defective parts that can be repaired by electric spark stack welding repair machine:

Corners, sharp edges, grooves, sidewalls, bottoms, deep cavities, planes, parting lines, on-site repair during production operations.

Specifications of electric spark stack welding repair machine:

Input voltage (V)220V single-phase 50Hz/60hz2220V single-phase 50Hz/60Hz
Maximum output power (W)18001800
Secondary output voltage (V)20-16020-160
Maximum capacitance of capacitor (uf)480560
Variable frequency range (discharge frequency/second)40-2100(HZ)40-2100(HZ)
Workpiece temperature during welding repair (℃)20-8520-85
Solder joint temperature (℃)8000-100003000-10000
Welding wire (mm)1.0-3.2.10-3.2
Dimensions (length * width * height)460*300*360465*315*385
Weight (net weight KG)2830
Main consumables.Protective lenses, welding wires, argon gas, electricity.       

Comparison of various repair methods:

Comparison of electric spark stack welding repair machine with other argon arc welding and laser welding.

ItemElectric spark surfacing repair machineArgon arc weldingLaser welding
1. Heat input to the moldlowVery highlow
2. Deformation and undercut of the moldnothinglargeSmall
3. Bond strength with base metalgoodgoodgood
4. Thickness that can be overlaid (mm)<3>1>0.3
5. Control of the thickness of overlay weldingVery easy.Very difficulthard
6. The difficulty of overlaying welding at edges and cornersVery easyeasilyVery easy
7. Filling of pinholeseasilyeasilyeasily
8. Surfacing welding of the bottom surface of the side wall of the pore grooveVery easyhardhard
9. Speed of overlay weldingfastVery fastfast
10. Fine processingMethodHand madeEIM – Mechanical ProcessingHand made
Required timeshortlongsecondary
11. Total time for surfacing+finishingfastlongsecondary
12. Dimensions of repairable moldsSmall LargeMedium to largeSmall
13. Dimensions of the welding machineSmall and medium-sizedmedium-sizedlarge
14. Can it be repaired on sitecanmust notmust not
15. Direction of overlay weldingBoth front and up and down options are availabledowndown
16. Necessity of mold preheating and insulationno needneedno need
17. Applicable MaterialsSteel, aluminum, copper alloys, etcSteel, aluminumSteel, aluminum
18. ConsumablesMetal barsWelding wireWelding wire
19. Protective gasargonargonargon
20. Can manual precision processing be carried outcanmust notcan
21. Can hard material coatings be appliedcanmust notmust not
22. Total cost required for welding repairLow costexpensivecommonly
23. PriceLowMediumhigh
24. Operator safetysecurityIntense ultraviolet radiationIrradiation

Application range of electric spark stack welding repair machine:

  • Large mechanical equipment
  • Cylinder body, seals
  • Cast iron parts, cast steel parts
  • Aluminum molds, aluminum alloy products
  • Steel molds and their products
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Founder of MachineMFG

As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.

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