Electro-discharge machining (EDM): In the EDM setup, is the tool connected as the cathode (negative terminal)?

Introduction / Context:
Electro-discharge machining removes material by a series of controlled electrical discharges (sparks) between a tool electrode and the workpiece in a dielectric fluid. Polarity choice influences tool wear and stability. This item tests the basic polarity convention used in die-sinking EDM.

Given Data / Assumptions:

• Conventional die-sinking EDM with hydrocarbon or deionized water dielectric.
• Workpiece is conductive and is connected to the positive terminal.
• Tool is typically copper/graphite connected to the negative terminal.

Concept / Approach:
In most die-sinking EDM applications, the tool is the cathode (negative), and the workpiece is the anode (positive). This polarity reduces tool erosion relative to workpiece removal and provides stable spark characteristics. Alternate polarities can be used for special purposes, but the usual practice is tool negative.

Step-by-Step Solution:

Verification / Alternative check:
EDM manuals and application notes consistently recommend tool negative for common die-sinking operations with steel workpieces to minimize electrode wear.

Why Other Options Are Wrong:
Wire EDM uses continuously fed wire and different power supplies, but the question targets the common die-sinking convention; dielectric choice does not reverse the basic rule in standard practice.

Common Pitfalls:
Assuming polarity is arbitrary; overlooking that changing polarity can intentionally increase tool wear for special burnishing or dressing operations but is not the default.

Final Answer:
Correct