Zero-Flush EDM Sinking: When Electrode itself Becomes the Pump
Deep Cavity Die-Sinker EDM without Flushing
Evacuation of by-products has been one of the key challenges in die-sinker EDM since the technology was first introduced. During EDM sinking, several by-products are generated and must be removed from the machining gap:
solid chips (metal particles + soot)
and gases – pyrolysis products of the working fluid
(≈ 50% hydrogen, and also ≈ 40% ethylene and acetylene).
Traditionally, the products of EDM sinking process are removed by flushing of dielectric work fluid under pressure through a nozzle (or several jet nozzles), as well as through technological holes in the electrode or workpiece. This should be distinguished from simple dielectric washing of the workpiece surface. When washing the chips are washed off the outer surface of the workpiece, so that the chip particles do not again fall into the EDM processing zone.
Supply of a dielectric for evacuation of chips is called flushing, and if the flushing is applied under high pressure – forced flushing.
In many cases, it is too difficult to organize flushing, often it is impossible. The results of processing largely depend on the experience of the operator. When EDM debris (chips/swarf) is removed insufficiently or unevenly, secondary discharges occur through the unremoved particles of chips. In the worst cases, discharge nests form in places where chips accumulate. All this leads to increased and uneven wear of the electrode, the appearance of short circuits, arc discharges, build-ups on the electrode and workpiece, slagging and, as a result, to defects! Insufficient and uneven chip evacuation is one of the main causes of defects in die-sinker EDM, especially when machining deep, narrow cavities.
Sodick linear EDMs have come as a game changer: the incredible speed of flat linear motors (LM), high thrust, amazing dynamics and fantastic accuracy made it possible to machine without flushing.
Die-Sinking EDMing on a non-Sodick sinking EDM machine with conventional ball screw drives along the XYZ axes.
Die-sinking EDMing by a Sodick EDM with high-speed flat linear servo drives along XYZ:
In conventional die-sinker EDMs with ball-screw drives, process stability often depends heavily on effective flushing. In deep or geometrically complex cavities, incomplete debris evacuation can become a major source of secondary discharges, arcing, uneven electrode wear and machining DEFECTs! The arrangement and method of flushing in each case depends on the shape of the electrode, the depth and direction of machining and cannot be standardized.
Chip evacuation flaws lead to increased and uneven wear of the electrode, the occurrence of short circuits, arc discharges, build-up on the electrode and the part, and slagging.
AS A RESULT – DEFECTS!
Linear servo drives in Sodick EDMs with powerful flat linear motors move the electrode at speeds up to 600 mm/s and accelerations up to 2.0G!
Dynamically and quickly moving up and down, the electrode works like a pump piston, evacuating EDM chips incomparably more efficiently than dielectric flushing!
Instead of dielectric flushing, the pumping effect of fast electrode movements is used! In other words, only relaxation (up-down reciprocation) movements and oscillations of the electrode itself are sufficient to wash out the chips.
This greatly reduces dependence on operator experience, cavity complexity and machining depth, while improving process stability and reducing the risk of defects. EDMing without defects!
The high machining performance does not come simply from fast electrode motion, but from the ability to position the electrode rapidly and precisely within the optimum discharge gap.
Ball-Screw Drive EDM (non-Sodick) jump-down time. The efficiency (actual EDMing time) is no more than 50%.
Sodick linear EDM jump-down time. The efficiency (actual EDMing time) is more than 90%.
Flat linear servo drives:
thanks to ultra-fast relaxations (jumps) and amazing accuracy of electrode feeds with continuous maintenance of the gap within the optimal limits, the efficiency of the EDM process has doubled!!
The high metal removal rate comes not so much from the speed of movement as from the fantastic accuracy of Sodick linear servo drives. Linear motors, following the CNC commands, invariably and stably position the electrode so as to keep the constantly changing GAP between the electrode and the surface of the machined part OPTIMAL at any given moment. And incredibly accurately too. Optimal gap means optimal spark discharge conditions, hence maximum removal rate and the best quality!
The electric spark interelectrode gap in the process of electric spark processing continuously changes. To compensate for changes, the relative position of the electrode is continuously adjusted by SMC (Sodick Motion Control) system – up to 1000 times per second! As a result, at every moment during EDM sinking you invariably get maximum productivity with the best quality, which is simply unattainable on EDMs with ball screw drives.
Sodick is the world’s only manufacturer of Die-Sinker EDM machines
driven by FLAT LINEAR MOTORS.
Production of EDMs with Flat Linear Motors since 1998.