KEVOS® MAKEOS · Manufacturing

Wire EDM Cut Plan (Kerf, Wire Offset and Corner Radius, Cutting and Skim Time, Wire Use, Tension, Cost)

For a wire EDM profile, how wide is the cut, what is the smallest inside corner the wire can make, how long will the main cut and skims take, how much wire is used, is the wire tension safe, and what does the part cost?

Plan for a wire EDM profile cut: the kerf and wire offset from the wire diameter and spark gap, the smallest inside corner radius the last pass can leave against the drawing, the main-cut feed from the area cutting rate for the thickness, the main-cut, skim and start-hole times, the wire run off the spool and its mass and cost, the wire's breaking load from its tensile strength and the tension setting as a share of it, and the machine and wire cost per part.

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How this tool works

Inputs, units and where to find them

InputUnitTypical source
Cut
Profile length cutmmLength of the profile the wire travels on the main cut.
Workpiece thicknessmmThickness of the work the wire cuts through.
Smallest inside corner radius on the drawingmmSmallest inside corner radius the drawing allows on the cut profile.
Start holesNumber of start holes the wire must be threaded through.
Time per start hole, drilled and threadedminTime to EDM-drill one start hole and thread the wire through it.
Wire and settings
Wire diametermmDiameter of the electrode wire.
Spark gap on each side, main cutmmGap between the wire and the cut wall on each side during the main cut, from the machine's settings.
Spark gap on each side, last passmmGap on each side on the last skim pass (the main cut if there are no skims).
Main-cut area cutting ratemm²/minRate at which the main cut sweeps area through the work (feed × thickness), from the machine maker's tables for the wire and material.
Skim passesNumber of trim passes after the main cut to improve accuracy and finish.
Skim pass speedmm/minFeed along the profile on each skim pass.
Wire run speedm/minSpeed at which wire is fed off the spool through the cut.
Wire tensile strengthMPaTensile strength of the wire, from the wire maker.
Wire tension settingNTension the machine applies to the wire.
Largest tension as a share of the breaking loadLargest share of the breaking load you allow the tension to reach.
Wire densityg/cm³Density of the wire material.
Cost
Wire priceA$/kgPrice of the wire per kilogram.
Machine rateA$/hCharge-out rate for the wire EDM machine.

What each input means

Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.

Cut

What this means: Profile length cut
Illustration: Profile length cutA bar with a dimension line and arrows from one end to the other, marking the length Profile length cut.LExample: 240 mmProfile length cut
What it is
The length of the profile the wire travels along on the main cut.
Units and format
Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000000 mm. Required: the tool does not calculate until every input is valid.
Example
The form opens with 240 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Cutting time, wire used and cost rise in proportion.
Get it right
Take it from the CAM path or the CAD outline, including lead-in and lead-out.
What this means: Workpiece thickness
Illustration: Workpiece thicknessThe cross-section of a plate or wall with a dimension across its thickness, marking Workpiece thickness.tsection through the materialExample: 30 mmWorkpiece thickness
What it is
The thickness of the workpiece the wire cuts through.
Units and format
Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
Example
The form opens with 30 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
The main-cut feed falls in proportion, so time rises with thickness.
Get it right
Use the full height of the work at the cut, including any stacked plates.
What this means: Smallest inside corner radius on the drawing
Illustration: Smallest inside corner radius on the drawingA circle with a line from its centre to its edge, marking the radius Smallest inside corner radius on the drawing; the radius is half the diameter.rcentre to edge= half the diameterExample: 0.2 mmSmallest inside corner radius on the drawing
What it is
The smallest inside corner radius the drawing allows on the cut profile.
Units and format
Enter a number in mm: millimetres. The form accepts 0 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
Example
The form opens with 0.2 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Only moves the corner pass line.
Get it right
Check the drawing notes; sharp inside corners are not possible with a round wire.
What this means: Start holes
Illustration: Start holesA row of identical items being counted; Start holes is how many there are.nExample: 1Start holes
What it is
The number of start holes the wire must be threaded through before cutting closed profiles.
Units and format
Enter a plain number with no unit. The form accepts 0 to 1000. Use a whole number. Required: the tool does not calculate until every input is valid.
Example
The form opens with 1 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Each hole adds its drilling and threading time.
Get it right
Count one for each separate opening; open profiles cut from the edge need none.
What this means: Time per start hole, drilled and threaded
Illustration: Time per start hole, drilled and threadedA timeline from a start mark to an end mark; Time per start hole, drilled and threaded is the time between them.startendthExample: 4 minTime per start hole, drilled and threaded
What it is
The time to EDM-drill one start hole and thread the wire through it.
Units and format
Enter a number in min: minutes. The form accepts 0 min to 1000 min. Required: the tool does not calculate until every input is valid.
Example
The form opens with 4 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Adds directly to the time per part.
Get it right
Use your shop's time for the hole size and work thickness.

Wire and settings

What this means: Wire diameter
Illustration: Wire diameterA circle with a line straight through its centre from edge to edge, marking the diameter Wire diameter.dmeasured acrossthe centreExample: 0.25 mmWire diameter
What it is
The diameter of the electrode wire.
Units and format
Enter a number in mm: millimetres. The form accepts 0.01 mm to 1 mm. Required: the tool does not calculate until every input is valid.
Example
The form opens with 0.25 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Sets the kerf, the smallest corner and the wire strength.
Get it right
The handbook gives 0.05 to 0.30 mm; finer wire makes smaller corners but cuts slower and is weaker.
What this means: Spark gap on each side, main cut
Illustration: Spark gap on each side, main cutTwo parts separated by a small gap with a dimension across the gap, marking Spark gap on each side, main cut.gExample: 0.03 mmSpark gap on each side, main cut
What it is
The spark gap between the wire and the cut wall on each side during the main cut.
Units and format
Enter a number in mm: millimetres. The form accepts 0 mm to 1 mm. Required: the tool does not calculate until every input is valid.
Example
The form opens with 0.03 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
A larger gap widens the kerf and the wire offset.
Get it right
Take it from the machine's technology tables for the wire and material.
What this means: Spark gap on each side, last pass
Illustration: Spark gap on each side, last passTwo parts separated by a small gap with a dimension across the gap, marking Spark gap on each side, last pass.gfExample: 0.01 mmSpark gap on each side, last pass
What it is
The spark gap on each side on the last skim pass, which sets the finished size and the smallest inside corner.
Units and format
Enter a number in mm: millimetres. The form accepts 0 mm to 1 mm. Required: the tool does not calculate until every input is valid.
Example
The form opens with 0.01 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
A smaller gap allows a tighter inside corner.
Get it right
Take it from the tables for the last skim setting; it is smaller than the main-cut gap.
What this means: Main-cut area cutting rate
Illustration: Main-cut area cutting rateItems moving past a point on a conveyor; Main-cut area cutting rate is how many pass in each unit of time.count pointArExample: 120 mm²/minMain-cut area cutting rate
What it is
The area the main cut sweeps through the work per minute: feed along the profile times the thickness.
Units and format
Enter a number in mm²/min: mm²/min. The form accepts 0.000001 mm²/min to 100000 mm²/min. Required: the tool does not calculate until every input is valid.
Example
The form opens with 120 mm²/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
The main-cut feed and time change in proportion.
Get it right
Take it from the machine maker's tables for the wire and work material.
What this means: Skim passes
Illustration: Skim passesA row of identical items being counted; Skim passes is how many there are.nsExample: 2Skim passes
What it is
The number of trim passes run along the profile after the main cut to improve size and finish.
Units and format
Enter a plain number with no unit. The form accepts 0 to 20. Use a whole number. Required: the tool does not calculate until every input is valid.
Example
The form opens with 2 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Each pass adds its skim time and wire.
Get it right
Use as many as the drawing's tolerance and finish need; each one costs time.
What this means: Skim pass speed
Illustration: Skim pass speedA cutting tool moving along a turning workpiece; Skim pass speed is how far the tool advances for each revolution or tooth.vsadvance perrev or toothExample: 12 mm/minSkim pass speed
What it is
The feed along the profile on each skim pass.
Units and format
Enter a number in mm/min: millimetres per minute. The form accepts 0.000001 mm/min to 10000 mm/min. Required: the tool does not calculate until every input is valid.
Example
The form opens with 12 mm/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Skim time falls in proportion as the speed rises.
Get it right
Take it from the machine's tables for the skim setting.
What this means: Wire run speed
Illustration: Wire run speedA marker moving along a track; Wire run speed is the distance it covers per unit of time.vwdistance ÷ timeExample: 8 m/minWire run speed
What it is
The speed at which new wire is fed off the spool through the cut.
Units and format
Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 100 m/min. Required: the tool does not calculate until every input is valid.
Example
The form opens with 8 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Wire used and wire cost rise in proportion.
Get it right
Read it from the machine's cutting condition.
What this means: Wire tensile strength
Illustration: Wire tensile strengthA test bar pulled from both ends: stress Wire tensile strength is the force carried by each square millimetre of its cross-section.Rmstress = force ÷ areaExample: 900 MPaWire tensile strength
What it is
The tensile strength of the wire, which sets the load at which it breaks.
Units and format
Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 5000 MPa. Required: the tool does not calculate until every input is valid.
Example
The form opens with 900 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
A stronger wire takes more tension at the same share.
Get it right
The handbook gives 345 to 1,000 MPa for brass wire; use the wire maker's figure.
What this means: Wire tension setting
Illustration: Wire tension settingA block with an arrow pushing on it; the arrow is the force Wire tension setting.TExample: 15 NWire tension setting
What it is
The tension the machine applies to the wire to keep it straight in the cut.
Units and format
Enter a number in N: newtons. The form accepts 0.000001 N to 1000 N. Required: the tool does not calculate until every input is valid.
Example
The form opens with 15 N as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Raises the share of the breaking load the wire carries.
Get it right
Read it from the machine's cutting condition.
What this means: Largest tension as a share of the breaking load
Illustration: Largest tension as a share of the breaking loadTwo wheels of different sizes linked together; Largest tension as a share of the breaking load compares one with the other.umaxExample: 0.5Largest tension as a share of the breaking lo…
What it is
The largest share of the wire's breaking load you allow the tension to reach, leaving margin for spark heating.
Units and format
Enter a plain number with no unit. The form accepts 0.01 to 1. Required: the tool does not calculate until every input is valid.
Example
The form opens with 0.5 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Only moves the tension pass line.
Get it right
Base it on the wire maker's guidance and your record of breakages.
What this means: Wire density
Illustration: Wire densityA cube of material: density Wire density is its mass divided by the volume it fills.massvolumeρExample: 8.5 g/cm³Wire density
What it is
The density of the wire material, used to turn the wire length used into a mass.
Units and format
Enter a number in g/cm³: grams per cubic centimetre (1 g/cm³ = 1000 kg/m³). The form accepts 1 g/cm³ to 25 g/cm³. Required: the tool does not calculate until every input is valid.
Example
The form opens with 8.5 g/cm³ as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Wire mass and cost rise in proportion.
Get it right
About 8.5 g/cm³ for yellow brass wire.

Cost

What this means: Wire price
Illustration: Wire priceA stack of coins and a note representing the money amount Wire price.$Example: 25 A$/kgWire price
What it is
The price of the electrode wire per kilogram.
Units and format
Enter a number in A$/kg: A$/kg. The form accepts 0 A$/kg to 10000 A$/kg. Required: the tool does not calculate until every input is valid.
Example
The form opens with 25 A$/kg as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
Wire cost rises in proportion.
Get it right
Use your current supplier price for this wire grade and diameter.
What this means: Machine rate
Illustration: Machine rateA stack of coins and a note representing the money amount Machine rate.$Example: 80 A$/hMachine rate
What it is
The hourly charge-out rate for the wire EDM machine.
Units and format
Enter a number in A$/h: A$/h. The form accepts 0 A$/h to 100000 A$/h. Required: the tool does not calculate until every input is valid.
Example
The form opens with 80 A$/h as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Effect on the result
The machine cost rises in proportion.
Get it right
Use your shop's costing rate, which may be lower for unattended running.

Method and formulas

  1. Kerf = wire diameter + 2 × spark gap; wire offset = wire diameter ÷ 2 + gap.
  2. Smallest inside corner = wire diameter ÷ 2 + the last-pass gap, against the drawing's smallest radius.
  3. Main-cut feed = area rate ÷ thickness; main-cut time = length ÷ feed; skim time = passes × length ÷ skim speed.
  4. Wire used = run speed × cutting time; mass = density × π d² ÷ 4 × length.
  5. Breaking load = tensile strength × π d² ÷ 4; tension share = tension ÷ breaking load.
  6. Cost = total time × machine rate + wire mass × wire price.
  7. Example: a 0.31 mm kerf at 4 mm/min; the cut takes 104 min and 333.79 g of wire, about A$147.01 a part.

Limitations

  • Area cutting rates, gaps and skim speeds come from your machine's tables for the wire and material; this plan does not predict them.
  • Taper cuts, part supports and wire breakages are not included.
  • Example values are illustrations. Replace them with values for your actual task.

Typical uses

  • Check that the wire can make the drawing's inside corners
  • Estimate wire EDM time and cost for a die or part
  • Check the wire tension against the wire's strength

Who it is for

  • Toolmakers
  • Wire EDM operators
  • Estimators

What you get

  • Kerf, wire offset and smallest inside corner
  • Main-cut feed, cut, skim and start-hole times
  • Wire used, its mass and cost
  • Wire breaking load and tension share
  • Cost per part

Interpreting the result

  • Wire EDM time is set by the area swept, so time grows with thickness at the same profile length.
  • Skims improve accuracy and finish but at much lower speed; specify only as many as the drawing needs.

References

  • Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1394–1403. Topic reference; no source tables or recommended settings are reproduced.

Learn the Concepts Behind This Tool

These KEVOS® Library readings explain the method this tool uses, with worked examples.

KEVOS® tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.

Open the Wire EDM Cut Plan (Kerf, Wire Offset and Corner Radius, Cutting and Skim Time, Wire Use, Tension, Cost) calculator

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