Wire EDM Machine inspection and measurement methods
Wire EDM Machine is a machine that cuts conductive material with a travelling brass wire in deionised water, by spark erosion. It is used for internal profiles, sharp internal corners and hardened parts that cannot be milled. This entry explains what it is, what the numbers on a data sheet mean, and what to put on a drawing.
It is written from the point of view of the buyer and the drawing office: the values that are realistic in production, the ones that cost money, and the way the result is verified. Where an industry sets the requirement, robotics is used as the example: repeatability across a family of near identical parts.
How it is measured
Optical comparator for the profile, CMM for position. The equipment is calibrated, the uncertainty is recorded, and the part is at room temperature before the first point is taken.
| Specification | Typical value |
|---|---|
| Characteristic | Method |
| Size | gauge or CMM, to the drawing tolerance |
| Geometry | CMM evaluated against the datum frame |
| Surface | Ra 0.4 µm with one skim pass, Ra 0.2 µm with three |
| Material | in-house approval with dimensional reports |
| Tolerance | ±0.005 mm |
What the report contains
- Every feature called up on the drawing, with a measured value rather than a tick.
- The datum order used, so the report can be reproduced.
- The certificate reference for the material and the calibration dates for the equipment.
Common sources of dispute
Most disagreements are about method, not about the part: a warm part, a burr left on, or a datum taken in a different order. Design a start hole or allow a start from outside the profile
Applications
Wire EDM Machine is used for internal profiles, sharp internal corners and hardened parts that cannot be milled, and in practice it appears most often in tool and die work, hardened punch and die sets, prototype gears, medical cutting instruments.
How it fits into a machining route
Wire EDM Machine is one station in a route rather than the whole of it. The part arrives with the previous operation finished and leaves with the features it is responsible for completed, so the datum and the clamping method are agreed before the first part rather than discovered on it.The route is fixed before the first part is cut, and it is the route rather than the individual setting that holds the result: cutting time, which is why roughing and skimming are split. Where a drawing calls for something the route cannot hold economically, that is raised at quotation rather than after the parts are made.
Standards, documentation and what is issued
The documentation requirement is in-house approval with dimensional reports. Material is supplied against a certificate where the application calls for it, inspection results are recorded with the job, and the records are kept so that a repeat order can be compared with the first instead of being measured from scratch.
Optical comparator for the profile, CMM for position is the verification step. Where a customer format or a standard report is required, it is agreed before the batch starts, because a report written after the event is a report nobody can use.
Frequently asked questions
What tolerance should be specified for Wire EDM Machine?
±0.005 mm is realistic in production. Tightening it beyond the functional requirement increases cost without improving the part.
Which material is usually used?
D2 tool steel is the usual choice, supplied against in-house approval with dimensional reports.
How is the result verified?
Optical comparator for the profile, CMM for position, with the results recorded so a repeat order can be compared with the first.
What is the most common mistake?
Start holes omitted from the drawing, with no way to thread the wire.
How long does it take and what does it cost?
A realistic cycle is 1 to 8 hours depending on height and finish, and the cost driver is cutting time, which is why roughing and skimming are split.
Related capability
If you are specifying Wire EDM Machine on a drawing and want a second opinion on the route, send the model and the quantity. The first response is a manufacturability review with the likely risk points and a quotation, so the decision can be made on facts rather than on a price alone.
Machining, inspection and documentation are handled in one place, which is why the dimensional report and the material certificate arrive with the parts rather than after them.
Related entries
These entries sit next to Wire EDM Machine in the encyclopedia: Swiss-Type Lathe, Turn-Mill Centre, Thread Milling. Reading them together gives a fuller picture of how the process, the material and the measurement affect each other.
