Precise electrochemical machining (pECM/PECM) is an advanced metal working technique that offers a solution for products that are difficult or impossible to produce through conventional techniques. PECM can be used to process virtually all metals and alloys.

Watch this video to learn more about the pECM technology and its benefits over the conventional metal working techniques.

 

/// Precise Electrochemical Machining (PECM)

Precise Electrochemical Machining, abbreviated as PECM or pECM, is an advanced metal-working technique which can machine products that are difficult or impossible to design through conventional machining. It is an extremely accurate technique, capable of machining any electrically conductive work piece due to the fact that the technology is based on electrolysis (i.e., chemical change, especially decomposition, produced in an electrolyte by an electric current). Among its wide material application capabilities are even improved and tough to machine metal alloys irrespective of their hardness, strength or thermal properties.

During the process the metal work piece is dissolved (Machining) locally through electricity (Electro) and chemistry (Chemical) until it reaches the required complex 3D end shape.

The ECM process

Cathode Anode Anode

The cathode (electrode) does not touch the anode (workpiece). The product is not cut, but dissolved

/// The process in detail

During the pECM process metal is dissolved from a workpiece with direct current at a controlled rate in an electrolytic cell. The workpiece serves as the anode and is separated by a gap (which can be as small as 10 µm) from the tool, which serves as the cathode. Therefore, the work piece and the work tool do not touch in any moment. The electrolyte, usually a salt solution in water, is pumped under pressure through the inter-electrode gap, thus flushing away metal dissolved from the workpiece. As the electrode tool moves towards the work piece to maintain a constant gap, the workpiece is machined into the complementary shape of the tool.

PECM resembles electroplating in reverse: instead of adding material, pECM removes it. The technique can also be described as the opposite of electrochemical or galvanic coating or deposition process. Due to the non-contact principle of the process, no mechanical or thermal stress is exercised on the work piece.

Material removal rate (MRR) is an important characteristic in evaluating the efficiency of the non-traditional machining processeses. In pECM, material removal takes place due to the atomic dissolution of the work material. In addition, unlike the previous generations of pECM machines, the current pECM technique benefits from pulsating power supply and a vibrating axis. This concept enables processing even products with a minimum process-gap of just a few micrometers, as well as shaping complex forms both internally and externally.

  1. PECM consists of four assemblies: Mechanical, Process water, Control, and Power, represented by the following modules:

  2. Tool feed system
  3. Electrolyte filtration and supply system
  4. Control system
  5. Power supply
 

 

Graph A. PECM process cycle: Mechanical vibration axis pathway

Schematic of vibration and puls

This is a schematic representation of the sinus-like vibration and electric pulses which dissolve the material. The mechanical vibration, with a stroke of 400 µm, provides both a rinse cycle and a process cycle with adjustable pulse frequency of 0,5 ms to 5 ms. In addition, it is also possible to conduct investigations and/or production using the older DC method (with continuous current). This can be especially beneficial for applications where machining speed is given priority over the level of accuracy.

 

Graph B. PECM process cycle: Cathode – Anode interaction

Schematic of an ECM set-up

Above a schematic representation is shown illustrating the electrode with a vibrating axis (adjustable frequency of 20-50 Hz) and the work piece with the copied shape of the electrode. The process fluid (electrolyte) is used as a conductive medium and transfer medium of reaction products, the latter consisting of metal ions, metal hydroxides, metal oxides, gas and heat.

/// PECM advantages

PECM has numerous advantages over the conventional machining working techniques, which can be summarized in the following four groups:

  1. MACHINING ACCURACY
  2. SUPERIOR PROCESS STABILITY
  3. CAPABLE OF CREATING MICROSTRUCTURES
  4. FRAGILE & THIN SECTIONS CAN BE SAFELY MACHINED
  1. DESIGN FREEDOM
  2. FULL-FORM SHAPING (INCL. 3-D PRODUCTS) IN A SINGLE STEP
  3. GENERATING COMPLEX SHAPES AND CONTOURS
  4. SUITABLE FOR MACHINING HARD-TO-REACH LOCATIONS
  1. SURFACE INTEGRITY
  2. EXCELLENT SURFACE FINISH WITH 'NO' BURR CREATION
  3. HARDLY ANY TOOL WEAR
  4. NO MECHANICAL OR THERMAL LOAD ON THE WORKPIECE
  1. PROCESS INNOVATION
  2. THE MATERIAL IS DISSOLVED AND NOT CUT
  3. MACHINING OF NEW EXOTIC METAL ALLOYS
  4. EXTREMELY SUITABLE FOR HIGH-VOLUME PRODUCTION