ECM machines are very well suited for polishing metals due to the excellent surface finish and fast stock removal rates. We have built machines capable of polishing parts that save a significant number of man hours over manual polishing systems. Applications include the inside of stainless BPE pipes or around hardened steel shanks.
The rapid removal rates and high accuracy of the PECM Systems ECM machines lend themselves to polishing machines in industries where surface finish is critical – i.e. industries where areas with product build up is undesirable. An ECM machine can achieve much faster and more consistent results than manual polishing. ECM can also improve the Cr/Fe ratio on stainless products. The machine shown right is the first of five polishing systems being supplied to one customer in 2006.
As with this polishing example, welding can produce areas where product or contamination can build up on a surface. Removing the excess weld with ECM is a fast way to blend the weld in to the surrounding parts. ECM removes the weld and simultaneously polishes the part and thus any areas for contamination to build up are removed. This can be improved further by integrating a scotch polishing stage into the process.
Internal tube machining
The inside of tubes can be particularly tricky to machine conventionally due to limitations with the bore of the tube and the ability to produce complex shapes on the walls of the tube without stressing the part or creating burrs. The rifling of tubes or barrels can be done without imparting any heat or stress into the component.
The technologies described above can be used together in one machine to give a uniform surface finish to the inside of complicated parts such as high performance exhaust manifolds. Any surface imperfections such as welds or discontinuities are blended together to create a single flowing surface for increased throughput of gases. We also have experience of polishing around corners/bends in long complex tubes. This technique can be refined further to produce mirror finish surfaces using a unique non acidic electro polishing process.
PECM Systems have produced machines with an oscillating electrode timed to pulse generation – ‘Impulse ECM’. This allows a high stock removal rate and simultaneous high definition surface finish. Impulse ECM machines with very small gaps, <25 micron for certain applications, this allows intricate levels of detail while still maintaining a high rate of stock removal and a submicron surface finish.
We have supplied machines for producing tips of tablet compression punches, where dimensional control is critical as it will affect ‘dosage’ and surface finish has to be sub micron to ensure no particles stick to the punch.
PECM Systems also has a customer producing forging punches with ECM. Fine detail that is very robust is critical here so ECM excels as no brittle recast layer occurs.
This mould was produced on an Impulse ECM machine in three minutes. The surface finish is a direct result of the process, there has been no remedial finishing.
pECM Systems design and build ECM machines to the customers’ unique specification. We can customise any part of the machine from the axis travel to the power supply to produce custom, complete turnkey packages.
The discs shown are 6” in diameter and made of Titanium, they were produced by one of two machines supplied to a leading American Aerospace manufacturer as a complete package including mass production electrolyte system complete with automatic temperature and pH control.
Forming of flexible parts
As machining a part with ECM does not involve any physical contact of the workpiece and the ‘cutting’ electrode, complex, flexible parts can be easily machined in exotic, hard to conventionally machine alloys. This is ideal for the aerospace industry.
Complex geometry machining
Intricate parts can be produced in a single pass. The electrode is designed with the aid of a computer package to predict the precise shape required for the finished component.
Some of the features we can produce:
• Power supplies up to 20,000 Amps that can be operated in constant current or constant voltage mode
• High Power Pulsing system
• Combined EDM and ECM high speed machining systems
• Digital multi-axis control
• Systems for machining exotic materials, e.g. Titanium
• Rotary tables with 20,000 Amps commutation
• Filtration systems for high volume production environments
• Temperature & pH controlled electrolyte systems
HPC BLADES AND VANES
pECM Systems have developed a technology together with our consultants, who are specialists in Compressor Blade manufacturing, to enable the rapid production of High Pressure Compressor blades and vanes by ECM. Traditionally blades of this type are produced by making an oversized forging and then finishing to the final dimensions normally by milling or traditional ECM. PECP (Precision Electro Chemical Polishing) removes the need for the final, most critical stage of the forging process and produces a polished blade to drawing dimensions. Typically the surface finish after the process is 16 µin or better, the airfoil tolerance band will be 0.1mm or better and the airfoil SPC – Cpk will be better than 1.33.
The benefits of PECP are:
• Minimal electrode development
• Leading & trailing edges machined directly to final drawing requirements
• Mechanical strength of final forging
• No extensive mass media processing to remove forging/milling defects or milling pattern
• No post production chemical milling to remove alpha case on Titanium alloys
• No thickness control of Nickel alloy final forging
• No manual twist and bow work as is usually done on final forgings
• Short cycle times compared to milling from oversize forging or barstock, or traditional ECM of oversize forging or barstock
The technology can be applied to dual/triple axis machines to allow the simultaneous machining of the convex and concave faces of the blade, and finishing of leading and trailing edges.
OTHER SYSTEMS ENGINEERED
Highly detailed information of machines we have produced cannot be made available at this time due to non-disclosure agreements that are in place with our customers. However we can give overviews of the uses that PECM Systems ECM machines have been applied to.
• High Capacity ECM for diaphragm production.
• Steerable ECM drill.
• ElectroChemical Grinding System for the machining of LP and HP honeycomb seals.
• Impulse ECM used for the production of high definition precision components.
• ECM/EDM Hybrid machine.
• Digital EDM Systems, manual and 4 axis CNC including automatic pallet changes.
• 6 Headed EDM machine for cooling holes in compressor blades.
• STEM drilling – simultaneous machining of multiple turbulated holes in large turbine blades.
• We have developed a machine capable of cutting and steering small bore holes up to 3m via ultrasonic sensors.