Insights
October 5, 2025 · 3 min read · Materials
Dissimilar Thinking • Episode 3
Inside the Arc
The Physics of Metal Fusion in Milliseconds
📚 Catching up? Episode 1: Breaking the Rules • Episode 2: Material Compatibility Matrix
Let's talk about what happens in the fastest part of your manufacturing process...
You know those high-speed camera videos where they capture a bullet piercing an apple, or a water balloon exploding? The ones that slow down a fraction of a second into thousands of frames, revealing physics you never knew was happening?
That's what we're about to do with percussion welding.
In Episodes 1 and 2, we told you percussion welding completes in milliseconds. We showed you it can join dissimilar metals that traditional welding can't touch. We gave you the parameters and compatibility matrices.
But we haven't answered the fundamental question that every engineer eventually asks:
"Okay, but how does it actually work?
What's happening at the atomic level?"
Great question. Strap in—we're about to slow down those milliseconds into four distinct phases and explain the physics behind each one.
Chapter 01 / 08
The Four Phases of Percussion Welding
Every percussion weld follows the same four-phase sequence. Let's break it down:
1. The parts are loaded to a pre-defined gap. 2. A capacitor-discharge arc melts the surfaces. 3. The molten surfaces are thrust together. 4. The joint is bonded within milliseconds, with no filler, flux or solder.
Chapter 02 / 08
Phase 1: Gap and Charge
This is the "calm before the storm" phase. The two materials are positioned at a pre-defined gap, close together but not touching.
Electrical Engineering
While the materials wait in their micro-gap, the percussion welder's capacitor bank is charging up. Think of it like cocking a spring-loaded trap—you're storing energy that will be released in one explosive burst.
Energy Storage Formula
E = ½CV²
Where:
- E = Stored energy (joules)
- C = Capacitance (farads)
- V = Voltage (volts)
Engineer's Note: The capacitor bank size (those "Cap: 1, 2, or 3" settings from Episode 2) directly affects the energy reservoir.
Want to see it on your parts?
Send samples and we'll run test welds before you commit.
Chapter 03 / 08
Phase 2: Arc Formation
This is where the magic happens. The moment you hit that initiation switch, the stored energy discharges across the micro-gap, creating an electrical arc.
What Is a Plasma Arc?
When voltage is applied across the gap, the air ionizes. Electrons are stripped from atoms, creating a soup of ions and free electrons—that's plasma, the fourth state of matter.
Chapter 04 / 08
Phase 3: Impact and Fusion
The actual "percussion" in percussion welding
While the arc is still active, the solenoid actuator fires. This is where the name "percussion welding" comes from—the parts don't drift together gently, they are thrust together with a controlled force.
The Mechanics of Impact
The Model 808 Percussion Welder Actuator
This is the mechanical heart of the system. It's a solenoid specifically engineered for percussion welding with:
- Low mass moving parts — Allows for rapid acceleration
- Precise force control — Delivers consistent impact energy
- Repeatable performance — Critical for production consistency
The "Velocity" setting you choose (remember those values from your parameter table?) directly controls how fast the actuator moves—which determines impact force and gap-closing speed.
What Happens When Molten Surfaces Collide
This is where percussion welding becomes fundamentally different from every other joining process. You're not melting materials together (TIG/MIG), you're not flowing molten material into a joint (soldering/brazing), and you're not using friction to generate heat (friction welding).
The molten surfaces are thrust together and bond into one joint.
Chapter 05 / 08
Phase 4: Cooling
After the molten surfaces are thrust together, the joint cools and the bond solidifies within milliseconds.
Want to see it on your parts?
Send samples and we'll run test welds before you commit.
Chapter 06 / 08
Summary of the Physics
A stored charge discharges across a pre-defined gap as an arc, the surfaces melt, the molten surfaces are thrust together, and the joint bonds within milliseconds. There is no filler, flux or solder, and the heat-affected zone is minimal.
Chapter 07 / 08
Test Your Materials
Understanding the physics is step one. Seeing it work on your actual materials is step two.
We'll run live welds on your materials—no charge, no obligation.
Chapter 08 / 08
Coming Up in Dissimilar Thinking
🏭
Episode #4: Application Engineering
Application notes for medical, aerospace, automotive, battery and electronics uses.
🔬
Episode #5: Process Optimization
Advanced parameter tuning, production troubleshooting, quality control strategies, and getting from prototype to high-volume manufacturing.
Previous Episode
← Episode 2: The Material Compatibility Matrix
Coming Soon
Episode 4: Application Engineering →
About Percussion Welder
Led by Collin Eidsness, our team designs, manufactures, and supports percussion welding systems.
Part of: Dissimilar Metal Joining
More on dissimilar metal joining
Dissimilar Metals Guide →FAQ
What is percussion welding?
A heat-plus-impact process for joining metals.
An electric arc supplies the heat, then a rapid mechanical movement forces the two materials together, forming a full metallic bond with no filler.
Do I need filler metal, solder or flux?
No. There's no filler, solder or flux, and no electrodes to wear out.
That means cleaner joints, less waste, and no consumables to buy.
How do I know if my materials can be welded?
Start with the Parameter Finder or the weld schedules table.
If your pair isn't listed, tell us your weld challenge. We'll reply with a straight answer about whether percussion welding is a fit, and how.
Still have a question? Tell us your weld challenge and an engineer will reply.
Start here
Share what you're joining and what's going wrong. We'll tell you straight whether percussion welding is a fit.
Prefer to talk? Book a demo or call 303-536-7838