RC vs Pulse EDM
Choosing the right EDM machine for your needs
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You will notice that ArcForge offers two different EDM machine designs:
- The RC Power Supply – described in The EDM How-To Book
- The Pulse Power Supply – described in Build a Pulse EDM Machine: The Next Generation
So which one is right for you?
The Difference Between RC and Pulse EDM
The primary difference is how the spark is created and controlled.
RC (Resistor-Capacitor) EDM
An RC machine stores energy in a capacitor and then discharges that capacitor across the spark gap to remove metal.
It’s simple, proven, and surprisingly capable.
Pulse EDM
A pulse machine does not discharge a capacitor.
Instead, the spark is electronically controlled using a timer circuit and power MOSFETs to precisely regulate the discharge.
That added control changes performance — but also adds complexity.
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The RC EDM – Simple, Affordable, Proven
The RC circuit was one of the earliest EDM designs (originally developed and used commercially decades ago). It’s stood the test of time for a reason.
Advantages:
- Simple to build
- Easy to understand and troubleshoot
- Lower cost
- Very reliable
- Great for beginners
Tradeoff:
- Higher electrode wear compared to a pulse supply
- Less accurate work
- Rougher surface finishes
If your primary goal is to build a tap burner for removing broken taps and drills, electrode wear usually isn’t a major concern. For that purpose, the RC design is hard to beat.
But don’t underestimate the RC design. The EDM logo burned into the steel file (shown above) was done using an RC machine. It’s capable of far more than just removing broken tools.
If you want a practical, affordable, and satisfying build — the RC machine is an excellent choice.
The Pulse EDM – More Control, More Capability
The Pulse EDM takes things a step further.
Instead of dumping capacitor energy into the gap, it electronically controls the spark timing. This allows:
Advantages:
- Reduced electrode wear
- Faster cutting speeds (in most cases)
- Finer surface finishes
- Greater accuracy
- Better control in delicate or detailed work
Tradeoff:
- More complex electronics
- Higher build cost
- More involved setup
The advantages of the Pulse EDM makes it well suited for:
- Squaring inside corners in milled pockets
- Machining complex shapes
- Working with exotic or hardened materials
- Jewelry and fine detail work
In fact, Chapter 18 of Build a Pulse EDM Machine: The Next Generation is dedicated to jewelry manufacturing and advanced EDM tips. If that kind of precision work is your goal, the Pulse machine is likely the better fit.
The “Chuck E. Cheese” burn shown above is an example of the level of detail achievable with a pulse supply.
If you love to build and are looking for a different kind of project that offers a challenge of integrating electronics and mechanical systems, an EDM may just be the ticket. Not many shops can boast a true pulse EDM sitting on the workbench for peanuts on the dollar.
So… Which One Should You Choose?
Ask yourself one simple question:
What do I want this machine to do?
If you want:
- A capable tap burner
- A lower-cost project
- A simpler electronic build
- A reliable shop tool
→ Build the RC EDM
If you want:
- Better surface finish
- Lower electrode wear
- More precision
- A more advanced electronics project
→ Build the Pulse EDM
Purchase a Starter Kit!