In wire EDM, most cutting is straight through, and with a correctly mixed dielectric fluid and good flushing from the nozzle, a finished part usually drops away on its own. With large workpieces, however, the falling part can hit and snap the molybdenum wire — one of the most common losses in everyday machining. Knowing how to control the drop prevents most of this damage.
1. Six ways to keep the part from dropping
- Hold it with magnets: once the cut is past halfway, press strong magnets onto the workpiece; when it is most of the way through, add several more over the already-cut area. Note that many metals are not magnetic.
- Clamp or tie it: secure the cut section with a suitable clamp (such as a G-clamp), cable ties, tape or adhesive wrap.
- Leave an allowance in the program: stop the program with a small amount of stock left and support the part from below — for example, leave 0.2mm and run a D offset back to zero.
- Pause and pack the kerf with wire: near the end of the cut, pause the machine and push spare molybdenum wire into the kerf (the more the better) to cushion the drop.
- Knock off oversized parts: leave about 0.25mm and knock the part free with a hammer — any burr left on large round or square parts can be filed off.
- Choose the lead-in direction: program the lead-in toward the L3 direction; experience shows this reduces wire breakage.
2. Night shifts and special cases
Unattended operation makes drop prevention more important. With water-based dielectrics there is no shortcut — it comes down to careful handling:
- Stop the program about 0.5mm before the end, leave 0.5mm of stock, pause before the final break, then magnet the part so it cannot fall.
- Do not try “turn off the flush or reduce the flow” as a workaround — intermittent flushing damages the wire badly.
- Oil-based dielectrics turn dirty and lose efficiency in hot weather; the contaminants that stick to dropped parts also degrade the discharge itself.
3. Quick reference
| Method | Best for | Key action |
|---|---|---|
| Magnets | Workpieces that hold magnetism | Add strong magnets once past halfway |
| Clamps / ties | Small or irregular parts | G-clamps, cable ties, tape |
| Programmed allowance | General use | Leave 0.2–0.5mm of stock |
| Pack the kerf with wire | End of cut | Push spare wire into the kerf as a buffer |
| Knock off | Oversized parts | Leave 0.25mm, knock free with a hammer |
| Lead-in direction | Programming stage | Lead in toward L3 |
Summary. Drop prevention comes down to two ideas: stop the part from falling freely, or cushion the impact when it does. Matching the method to the part size, material and shift pattern, with good programming habits, cuts the losses caused by broken wire.
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