Emak Electrochemical Treatment Machine: How It Removes Metal

• 1
  Key takeaways
• 2
  What an Emak electrochemical treatment machine actually does
• 3
  Parameters that decide stock removal and finish
• 4
  Surface finish and edge quality you can plan around
• 5
  When an Emak electrochemical treatment machine is the wrong call
• 6
  How the process fits alongside CNC machining
• 7
  Choosing between electrochemical removal, EDM, and milling

An Emak electrochemical treatment machine removes metal by controlled electrolysis. The workpiece is the anode, the shaped tool is the cathode, and a conductive salt solution flows through the gap between them. Apply direct current and the anode surface gives up metal ions into the electrolyte. No cutter touches the part, so there is no mechanical load, no chatter, and no work-hardened layer at the cut face.

The tool is usually a copper or brass electrode shaped as the negative of the feature you want. It advances toward the workpiece at a feed rate that matches how fast the anode dissolves. When those two rates match, the gap holds steady and the electrode profile copies itself into the part. That is the whole trick: keep the gap constant and the geometry reproduces.

Because material leaves as ions rather than chips, the process ignores hardness. A 60 HRC tool steel and a soft copper blank dissolve on the same curve if their electrochemical properties are similar. That is why this method shows up in die and mold work, where a hardened cavity still needs an accurate, low-roughness finish after the last heat treat cycle.

The electrolyte does two jobs. It carries current between the electrodes and it flushes the dissolved metal and hydrogen bubbles out of the gap. If the flow stalls, conductivity drops, bubbles collect, and the surface turns uneven. Flow rate and pressure are process parameters, not plumbing details.

Four variables do most of the work: gap size, current density, electrolyte conductivity, and flow rate. Gap size usually sits between 0.1 mm and 0.5 mm. A tighter gap improves profile accuracy but leaves less room for flushing, so the risk of shorting rises. A wider gap is more forgiving but blurs the copied shape at the edges.

Current density drives removal rate. Higher current dissolves metal faster and raises the risk of pitting and stray attack on surfaces that should stay untouched. Low current gives a smoother surface but takes longer and can let the passive film on stainless steel slow the reaction unevenly.

Electrolyte choice depends on the alloy. Sodium nitrate and sodium chloride solutions are common for steel and nickel alloys. Chloride solutions cut faster but tend to be more aggressive on masked areas. Nitrate solutions are gentler and hold a better finish on stainless and heat-resistant alloys.

Temperature and concentration drift over a long run. If the tank warms several degrees, conductivity climbs and the gap closes on its own. Machines that hold tolerance over hours control electrolyte temperature in a loop rather than topping up the tank and hoping.

A well-controlled process leaves no recast layer, no micro-cracks, and no heat-affected zone. That matters for parts that see fatigue cycles or that go straight into a vacuum chamber. Laser and EDM both leave a recast or white layer that has to be etched or polished away. Electrochemical removal skips that step.

Typical as-produced roughness lands in the Ra 0.2–0.8 μm band on a controlled machine, which is finer than most milling operations reach without a finishing pass. On the same part, conventional CNC milling at GreatLight holds Ra 0.8–1.6 μm, so the electrochemical route is one finishing stage ahead.

Edge condition is the trade-off. Because dissolution follows the current field, corners round slightly. A sharp external edge is difficult, and a sharp internal corner is more difficult still, since current density falls into the corner and removal slows there. Radius the corners in the design if you can.

Deburring is effectively free. The same field that dissolves the surface rounds over burrs and feather edges. For cross-drilled holes in hydraulic bodies, that saves a manual operation and removes the risk of a burr left inside a passage.

Skip it for simple prismatic parts. If a three-axis mill can cut the feature in one setup, the tooling cost of a shaped electrode will never pay back. Electrode fabrication is the main fixed cost, and it only amortizes across a run or across a feature that is genuinely hard to reach.

Skip it for deep blind pockets with tight internal radii. Flushing gets difficult as depth grows, and the electrolyte cannot clear the dissolved sludge. You end up with a tapered wall and a rough floor. Sinking EDM handles that geometry with less fuss in most shops.

Skip it when the part is non-conductive. Plastics, ceramics, and anodized surfaces do not dissolve. The process also needs the workpiece to be electrically continuous, so a masked or coated blank has to be stripped at the contact points.

Corner rounding is the other reason to pass. If the drawing calls for a true 90° internal corner or a knife edge, the process will not hold it. Redesign the corner with a radius, or route the part to milling instead.

Most parts do not use one process end to end. A hydraulic manifold gets its bores and faces milled on a five-axis center, then the cross-drilled intersections go through electrochemical deburring because a cutter cannot reach inside the passage. The two operations solve different problems.

The same pattern holds for hardened tooling. Rough the cavity before heat treat, harden it, then finish the cavity electrochemically. You avoid cutting a 60 HRC surface and you avoid the recast layer that EDM would leave. The electrode does the finish work in one pass.

GreatLight runs 127 high-precision CNC machines, including 16 simultaneous 5-axis centers and 16 mill-turn centers, across three plants and 7,600 m². Electrochemical steps sit at the end of the routing as a finishing or deburring operation, after the geometry is already established.

Inspection does not change. Parts are checked 100% before shipment, with raw material checks, in-process monitoring, and final inspection. Surface roughness and corner radii are measured at the features the process was brought in for, not only at the datums.