Wire EDM (Wire Electrode Machining), commonly referred to as WEDM, is a type of electrical discharge machining. It employs a continuously fed single-electrode wire—such as brass wire, galvanized wire, or copper wire—to generate pulsed electrical discharges between the workpiece and the electrode wire, thereby removing metal material through high-temperature sparks.

It differs from conventional CNC milling:

Milling relies on tool contact for cutting, while slow wire engraving utilizes electrical discharge machining for non-contact removal.

Therefore, slow wire walking is particularly suitable for processing:

Quenched steel, mold steel, stainless steel
hard metal
Copper, aluminum, titanium alloys
Precision stamping dies, drawing dies, and plastic die inserts
Fine grooves, narrow slots, irregular holes, complex two-dimensional contours
Small fillets, sharp corners, and thin-walled parts that are difficult to machine with conventional milling cutters

The internal corner radius of wire EDM is primarily limited by wire diameter, with common values ranging from 0.05 to 0.15 mm. Due to the absence of significant mechanical cutting forces, it is suitable for machining precision components prone to deformation; however, it can only process conductive materials and is not appropriate for large-scale rapid material removal or the fabrication of complete three-dimensional surfaces.

2. The difference between slow-walking threads and fast-walking threads

project	Slow Wire Movement	Fast Wire
wire electrode	Brass wire, galvanized wire, copper wire, etc.	Primarily made of tungsten wire
Winding Method	Unidirectional continuous wire feeding, single-use	Repetitive high-speed wire feeding with reusable molybdenum wire
working accuracy	Gao	secondary
surface quality	Okay, but the blade can be sharpened multiple times.	same as
prime cost	The cost of equipment and consumables is relatively high.	Lower cost
applicable scene	Precision molds, precision components, high-precision contours	Conventional molds, rough machining, cost-sensitive components
Processing Liquid	Primarily deionized water, with micro-processing also utilizing oil-based media.	Emulsion or working fluid
Typical Advantage	Precision, surface roughness, stability	Cost, Versatility

3. Workflow for Slow-Walking Wire

Slow wire drawing is typically processed according to the following procedure:

programming
Generate the machining path based on the CAD drawings, and set the compensation value, taper angle, tool repair frequency, and machining parameters.
Piercing the threaded hole
To cut an internal hole or close a contour, first create the cutting hole using a perforating machine or drilling tool.
Clamping and alignment
Install the workpiece on the workbench and align it with the reference edge, hole, or positioning surface.
automatic wire feed
Modern wire-cutting machines typically feature an automatic wire threading function, enabling re-threading after wire breakage and enhancing unmanned processing capabilities. Some Sodick wire-cutting models come standard with tension servos and automatic wire reconnect/threading units.
Coarse Cutting
The first cut primarily removes material at a faster speed, but the surface and dimensions are not yet in their final state.
Blade Refining / Precision Refining
The second, third, and fourth cuts progressively reduce the discharge energy to correct dimensions, improve perpendicularity, and reduce surface roughness.
Detection and Cleaning
Check dimensions, perpendicularity, taper, and surface roughness; make compensatory cuts if necessary.

4. Core Structure of Slow-Walking Wire

system	act on
CNC Control System	Control movement of X/Y/Z/U/V axes, compensation, tapering, and program execution
impulsing power source	The generation of high-frequency pulse discharge is the core factor affecting speed, accuracy, and surface quality.
wire-moving system	Control line speed, tension, wire feeding, wire retraction, and automatic threading
Working Fluid System	Deionized water filtration, cooling, chip removal, and stable discharge gap
Workbench and Body	Decision on rigidity, thermal stability, and positioning accuracy
Upper and lower guide wire nozzles	The position, verticality, and flushing status of the control line
U/V-axis system	For taper machining and machining of irregular shapes (up and down)
Measurement and Compensation System	Including grating scale, temperature compensation, automatic edge detection, and wire break detection

5. Common Technical Parameters Table for Slow-Walking Wires

5.1 Equipment Capability Parameters

Parameter Item	Common range/Typical values	Reference for high-precision or high-end models	explain
Processing axis count	X/Y/Z + U/V, commonly features 5-axis control	High-end devices can handle complex slopes and irregular shapes with varying dimensions.	X/Y controls the contour of the control plane, while U/V controls the offset of the upper guidewire nozzle
X/Y route or distance of travel	Approximately 300×200 mm to 1300×1000 mm	Mainframe computers can exceed 1300×1000 mm.	In the Makino wire-cutting series, the compact models measure approximately 370×270 mm, while the larger models reach up to 1310×1010 mm.
X-axis stroke / Machining height	Common: 150–500 mm	Some mainframes are even higher.	The GF CUT F documentation states that its manufacturing process covers components with heights ranging from less than 1 mm to 350 mm.
Maximum workpiece weight	300–3000 kg is common	The mainframe can reach a weight of up to 6,000 kg.	According to Makino's specifications for its large-scale wire-cutting machines, the maximum workpiece weight is 3,000 kg for the U86 model and 6,000 kg for the U1310 model
Electrode wire diameter	0.10 / 0.15 / 0.20 / 0.25 / 0.30 mm Common	Microfabrication allows the use of finer filaments.	The GF data list a wire diameter range of 0.10–0.30 mm; Makino also offers a wire-cutting series designed for micro加工 and high-precision applications.
Electrode wire material	Brass wire, galvanized wire, copper wire, specially coated wire	For micro加工, tungsten wire or specialized fine wire can be used.	Different filament materials affect speed, surface quality, and material costs.
work material	Conductive materials such as steel, cemented carbide, copper, aluminum, titanium, PCD, and graphite	High-hardness materials offer significant advantages.	The GF profile lists materials such as steel, cemented carbide, copper, aluminum, titanium, PCD, and graphite.
surface roughness Ra	The initial rough cut has an average roughness (Ra) of 2.0–3.2 μm; multiple sharpening operations reduce the Ra to approximately 0.1–0.8 μm.	High-end precision finishing can achieve Ra 0.15 μm or better.	The GF CUT F documentation states that its digital generator achieves surface quality as low as Ra 0.15 μm.
working accuracy	Common range: ±0.005–±0.01 mm	High precision achievable at the ±0.002–±0.003 mm level	It is significantly influenced by the machine tool, temperature, material thickness, and tool sharpening frequency.
Pitch/ Hole spacing accuracy	Common value: approximately ±0.005 mm	High-end devices can achieve an accuracy below ±0.003 mm.	The GF data indicates that the average pitch deviation across the entire working area is below ±2.5 μm.
Tapering machining	Common values: ±3°, ±15°, ±30°	Some models can accommodate a larger size.	The GF TAPER-EXPERT documentation specifies that it can be machined with a taper ranging from 0° to 30°.
Minimum interior angle R	Typically, it ranges from approximately R0.05 to R0.15 mm.	Depends on wire diameter and discharge gap	The thinner the wire, the smaller the theoretical internal angle, but the processing efficiency and stability decrease.
automatic wire feed	Commonly found in mid-to-high-end devices	Supports automatic re-stranding of broken wires	This is crucial for continuous processing and unmanned nighttime operations.
fluid	Primarily deionized water	Micro-fine precision machining also employs oil-based media.	Oil-based media are commonly used in applications requiring fine precision and extremely high surface quality. According to Makino's documentation, horizontal cutting with oil-based media is suitable for small-scale electronics, medical applications, and microfabrication.

5.2 Process Setting Parameters

process parameters	Common Setting Direction	Impact on processing
Wire diameter	0.10–0.30 mm is commonly used, while 0.20/0.25 mm is the most frequent.	A larger wire diameter results in better stability and speed; a smaller wire diameter reduces the internal angle but decreases efficiency.
line tension	Fine wires exhibit low tension, while thick wires exhibit high tension.	Insufficient tension will affect the verticality and straightness; excessively high tension may lead to wire breakage.
Wooling speed	Automatically match based on wire diameter, material, and thickness	Affects chip removal, wire consumption, and discharge stability
discharging gap	Typically automatically controlled by the machine tool technology library	Affects size compensation, surface quality, and stability
pulse length Ton	The rough cut is larger, and the finish cut is smaller.	The higher the removal rate, the greater the effect; however, the surface roughness deteriorates.
Pulse interval Toff	Appropriately increase when using thick materials and experiencing poor chip removal.	An excessively small gap may lead to short circuits or wire breakage; an excessively large gap reduces efficiency.
peak point current	The rough cut is higher, and the finish cut is lower.	The higher the current, the faster the cutting speed; however, the heat effect and surface roughness increase accordingly.
Servo voltage	Control the gap between the electrode wire and the workpiece	Affects short-circuit rate, stability, and dimensional consistency
Flushing Pressure	Coarse cutting and thick materials generally yield higher results.	Excellent flushing performance, effective chip removal, with superior speed and stability.
Hydroelectric conductivity	Controlled by the deionized water system	Unstable electrical conductivity can affect the discharge state.
Number of blade cuts	Common: 1 rough cut + 1 to 4 finishing cuts	The more cuts are made, the better the dimensions and surface quality, but the processing time increases.
Offset Amount	Set according to wire diameter, discharge gap, and tool repair amount	Directly affects the final size
Taper Compensation	Controlled by the U/V axis and the positions of the upper and lower guidewire nozzles	For die blanking clearance, ejection slope, and upper/lower irregular contour profiles

6. Common Machining Accuracy References

Processing Requirements	Recommended Process	Approximate Effect
General Profile Cutting	1 rough cut	Fast speed, generally smooth surface
Typical mold component	1 rough + 1 refined	The size remains relatively stable, with significant improvement in surface quality.
Precision Die	1 rough + 2 finish / 3 finish	The accuracy, perpendicularity, and surface quality are satisfactory.
High-precision insert	1 rough + 3 finish / 4 finish	The surface is fine with stable dimensions, but the cost is high.
Small rounded corner / Micro-slot	Fine thread + Multiple blade adjustments	Can process small R and small grooves, but with relatively low efficiency.
Thick plate cutting	Optimize flushing + Reduce speed	Focus on controlling wire breakage, slope, and chip removal.

7. Advantages of slow-winding wire

High precision

Suitable for mold parts, precision punches, dies, inserts, etc.

Can process high-hardness materials

It can also be processed after quenching, unlike milling cutters which wear out more easily.

No significant cutting force

Suitable for thin-walled parts, slender components, and parts prone to deformation.

Highly capable of complex contour processing

Irregular holes, fine grooves, narrow seams, internal corners, and small fillets all offer significant advantages.

Good surface quality

Repeated blade adjustments yield excellent surface roughness. According to the GF documentation, its wire-cutting system achieves surface quality as low as Ra 0.15 μm through precise control of each spark energy.

8. Limitations of slow-winding wire

Only conductive materials can be processed.

Non-conductive materials such as plastic, ceramic, and glass cannot be directly processed using conventional slow-wire cutting methods.

It must be able to thread through silk.

When creating a cutting hole or sealing contour, a threaded hole must be prepared first.

The processing speed is slower than milling.

Especially when working with thick materials, multiple tool adjustments, or high precision requirements, the processing time increases significantly.

The cost of consumables is relatively high.

The slow-wire electrode is typically single-use, while the water filter, resin, conductive blocks, and wire guide nozzle are also consumables.

A sharp corner is not necessarily an absolute sharp corner.

The minimum internal angle is determined by the wire diameter and the discharge gap; a theoretically ideal zero-radius sharp corner cannot be achieved.

9. When selecting a model or obtaining a quote, focus on these parameters.

When reviewing slow-winding equipment or external processing quotes, it is recommended to focus on the following key points:

Maximum processing stroke and workpiece weight
Whether the workpiece can be properly placed and supported.
Maximum processing thickness
Thick layers significantly affect speed, perpendicularity, and wire breakage risk.
achievable tolerance
It must be clarified in advance whether the tolerance is ±0.01 mm, ±0.005 mm, or ±0.002 mm.
Surface roughness requirements
The prices and delivery times for Ra 1.6, Ra 0.8, Ra 0.4, and Ra 0.2 vary significantly.
Number of blade cuts
The quotation must clearly specify whether it applies as a "one-size-fits-all" approach or follows the "1 rough, 2 finishing/1 rough, 3 finishing" sequence.
Cable diameter requirement
Small R and small grooves require fine wires, which are slower and more expensive to process.
Is there a taper or an asymmetrical shape?
When performing taper machining, verify the angle, height, and accuracy.
Cut hole position
The inner hole component must have a thread passage hole; the hole diameter and position also affect the machining process.
Materials and heat treatment conditions
The processing conditions for quenched steel, cemented carbide, titanium alloy, and aluminum alloy differ.
Batch processing and unmanned machining capabilities
Automatic thread feeding, thread breakage followed by re-feeding, and processing fluid management can affect the continuous nighttime processing capability.

In one sentence:

Slow wire cutting is a high-precision, low-cutting-force machining method suitable for hard conductive materials and complex profiles; its core principle lies not in "fast cutting," but in "accurate, fine, and stable cutting."

Fast, Medium, and Slow Wire Cutting: Key Differences

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Fast, Medium, and Slow Wire Cutting: Key Differences

How can you accelerate the delivery of your CNC machining project?

Fast, Medium, and Slow Wire Cutting: Key Differences

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