A beginner's guide to Sinker EDM Machine
Sinker EDM Machine is a machine that forms a cavity by sparking a shaped electrode into the workpiece under dielectric fluid. It is used for blind cavities, sharp corners, deep ribs and textured mould surfaces. 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, oil and gas is used as the example: materials that work harden and still have to be certified.
In plain terms
Sinker EDM Machine is a machine that forms a cavity by sparking a shaped electrode into the workpiece under dielectric fluid. If you have not met the term before, the useful way to think about it is this: it is chosen when a part needs blind cavities, sharp corners, deep ribs and textured mould surfaces.
The terms you will hear
- Work tank – 800 x 600 x 400 mm.
- Electrode material – graphite or copper.
- Surface finish – Ra 0.4 to 3.2 µm.
What it costs and how long it takes
Electrode count and electrode machining, not the sparking itself, and a realistic cycle is 4 to 20 hours for a mould cavity. Those two numbers, not the headline hourly rate, decide the price of the part.
What to ask a supplier
- What tolerance will you hold in production, not just on the first part?
- What does the dimensional report cover, and which standard is it written to?
- What happens to the fixtures and programmes if we reorder in a year?
Applications
Sinker EDM Machine is used for blind cavities, sharp corners, deep ribs and textured mould surfaces, and in practice it appears most often in injection mould cavities, forging dies, turbine blade root forms, deep ribbed housings.
How it fits into a machining route
Sinker 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: electrode count and electrode machining, not the sparking itself. 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.
CMM for position, comparator for the profile 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 Sinker EDM Machine?
±0.01 mm is realistic in production. Tightening it beyond the functional requirement increases cost without improving the part.
Which material is usually used?
H13 tool steel is the usual choice, supplied against in-house approval with dimensional reports.
How is the result verified?
CMM for position, comparator for the profile, with the results recorded so a repeat order can be compared with the first.
What is the most common mistake?
The recast layer left in place on a part that will see fatigue loading.
How long does it take and what does it cost?
A realistic cycle is 4 to 20 hours for a mould cavity, and the cost driver is electrode count and electrode machining, not the sparking itself.
Related capability
If you are specifying Sinker 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 Sinker EDM Machine in the encyclopedia: Horizontal Machining Centre, 5-Axis Machining Centre, Wire EDM. Reading them together gives a fuller picture of how the process, the material and the measurement affect each other.
