ANCA's New EDG With ANCA Motion SparX Erosion Generator Decreases Cycle Time For PCD Tools By 50%

How the fox outsmarted the hare: using intelligence to outperform brute force.

When ANCA teamed up with Precorp (now part of the Sandvik-Coromant group) to create the ANCA EDG (Electro Discharge Grinding) machine in 2011, the mission was clear. Both companies wanted to create a high-performance Rotary Electro Discharge Machining (EDM) platform that was not only able to produce best-in-class tool geometries but also have market leading cycle times.

It was the brainchild of Pat Boland, ANCA Founder and Managing Director, who realised quickly that to outperform the incumbent competition, brains were needed over brawn. “The erosion process is simple in its complexity. The basis of the process uses positive and negative electrodes with electrolyte to create sparks along a material. ANCA has a 45-year history in making the world’s best carbide and HSS tools and we wanted to use that skill set in PCD tooling,” said Pat.

The main drivers behind the ANCA EDG machines were that it needed to be simple enough for all types of brazed shear-fluted tools to be easily created, but complex enough to enable the creation of the infinite variety of helical solid-tipped, veined and chevron tools. Pat adds: “We realised early on that with the complexity of tool geometry we wanted to allow our customers to create, the 5-axis interpolation while maintaining the precise erosion gap distance was going to be a challenge.”

This is when Boland, a Master of Electrical Engineering from the University of Melbourne, knocked on the door of RMIT University Melbourne, and was introduced to Electrical Engineering PhD candidate, now Dr, Kotler Tee. Dr. Tee came with glowing recommendations and was quickly employed by ANCA to head up the creation and deployment of the EDG erosion process. Working side-by-side, Boland and Tee formulated ideas and set to work on creating arguably the most technically advanced erosion process in the market today.

Step 1: Maintain the optimum spark erosion gap with IAC
The first task they tackled was maintaining the optimum spark erosion gap for both simple 2D and complex 3D path interpolations. “During the erosion process, maintaining the optimum spark erosion gap is fundamental to the process working with high efficacy. This is very simple for rotary 2D path interpolation. However, when 3D path interpolation involves 4 or 5 axes moving simultaneously; surface area, volume and path changes become a challenge,” said Dr. Tee. “From our testing, we knew that the standard was to simply sets the machine feedrate to the lowest allowable to maintain a useable spark gap distance; however, this leads to a lot of ‘air-time’ and drastically lowers feedrates.” To allow the feedrate to remain high and maintain the optimum spark erosion gap, the idea of Intelligent Adaptative Control (IAC) was born.

Intelligent Adaptive Control (IAC) is an in-time, servo-controlled feature that automatically monitors and controls the erosion gap distance, in-process. Utilising the EtherCAT functionality of the ANCA Motion AMD5x control system, IAC synchronises the machine moves with the generator performance. IAC adjusts and maintains the optimum spark gap distance which is very important when eroding 3D geometries such as PCD flutes and gashes on drills and endmills. With geometry changing in up to 5-axes at once, IAC automatically adjusts the gap distance and machine feedrate to optimise the erosion speed and surface finish. This involves not only speeding up feedrates when erosion is along linear paths but also slowing down feedrates when path changes occurs.

“Twists and turns along the erosion path leads to scenarios where the electrode wheel is likely to come into close contact with the tool or comes off the tool. This can lead to optimal, bad and missed sparks along the trajectory,” added Dr. Tee. IAC automatically accounts for this and maintains the fastest possible feedrate along the length of any changeable path. This automatically results in an overall increase in feedrates, minimum thermal damage, superior surface finish, increased MRR and decreased cycle time.

An added benefit of IAC is the ease in which PCD and carbide micro-tools can be manufactured. As IAC maintains the optimal distance, the chance of wheel collisions and hence tool breakage is very low. This is critical when eroding tools under 0.5mm.

Step 2: Optimise the erosion process with ASC
The next challenge was creation of optimum sparking to facilitate the erosion process. The current, voltage, duration, time-off and therefore intensity of sparks changes based on the material that is being eroded. That is, PCD will require certain parameters as opposed to carbide (HM) and High-Speed Steel (HSS). The challenge is that PCD wafers are generally 0.6mm PCD with a 1mm carbide backing. Sintered PCD, as with the Precorp-Sandvik “veined” process, chevron tools and solid-tipped tools, are formed onto carbide backing also. When aggressively eroding, such as roughing operations, the copper electrode wheel erodes along the PCD-carbide border. Erosion parameters optimised for PCD can inadvertently over-erode the carbide backing. This in turn leads to over-erosion at the PCD-carbide border, named an “undercut” as it selectively erodes the carbide under the PCD. Additionally, it can lead to “cobalt leeching” which is when the PCD binder, cobalt, is preferentially eroded away leaving exposed PCD gains.

This is akin to digging under the foundations of a paved pathway. If you dig too much material away from under the path, eventually the path will collapse in. Machine testing showed that the undercut and cobalt leeching during heavy roughing lead to a brittle border along the cutting edge and premature tooling wear. To avoid this happening and to optimise the erosion process, Adaptive Spark Control (ASC) was created.

ASC uses the ultra-fast EtherCAT servo system along with DSP (Digital Signal Processors) and FPGA (Field Programmable Gate Arrays) on the generator itself. The EDG erosion generator is able to monitor and process every spark, in real time. The waveform of each spark is automatically monitored and categorized based on material being eroded, erosion gap distance and other factors essential to optimal erosion process. The generator can then dynamically adapt the energy level of each-and-every spark (current, voltage, duration and time-off) to suit the material being eroded.

ASC optimises the erosion process leading to less cobalt leaching and a reduction in undercut at the PCD-carbide border. This leads to a stronger cutting edge and a finished tool that is less prone to chipping. This helps achieve longer tool life, less tool wear and lower tooling costs. Testing on tooling suited to the machining of CFRP (Carbon Fibre Reinforced Plastic) showed a tool life increase of up to 60%.

These intelligent erosion controls are now protected by Patents awarded to ANCA.

Step 3: Boost the power electronics with ANCA Motion SparX Erosion Generator
The last piece of the puzzle was optimising the electronics to enable even higher and more aggressive erosion all-the-while maintaining very high surface finish results. For this, ANCA leant on the expertise from their sister company, ANCA Motion. Richard Colin, Senior Electrical Engineer, was given the task of creating the industry leading erosion generator based on the AMD5x Servo platform. Richard was adept at high frequency, high power electronics, having previously desiged Ground Power Units (GPUs) for the aviation industry prior to working at ANCA Motion (To this day, Richard can be seen living in his Pratt and Whitney leather jacket). “I jumped at the chance. I had been waiting for the opportunity to work with the latest best-in-class semiconductor power electronics for wide-bandgap switching speeds.”

When compared to equivalent componentry, the mega-amp per pulse technology enables ANCA customers to broaden the power range they can access and utilise. The ANCA Motion SparX Erosion Generator exhibits superior performance over the range of Extra-Heavy Roughing to Ultra-Fine Finishing operations, utilising Pico-pulse technology for high energy-density ablation. This enables vastly superior controllability, providing customers with optimised feedrates, superior surface quality and drastically reduced cycle times. This pulse precision allows erosion that ranges from ultra-low energy pulses for exceptional ultra-fine finishing, through to high energy pulses for fast material removal.

In the PCD erosion process, cycle time is directly related to the Material Removal Rate (MRR). The ANCA Motion SparX Erosion Generator delivers unrivalled increases in MRR utilizing the new Extra-Heavy Roughing, Super Fine Finishing and Ultra-Fine Finishing operations. What this equates to is an unsurpassed increase in MRR and a 50% decrease in cycle time compared to competitor machines - arguably the fastest cycle times in the market. Additionally, erosion surface quality also sees an improvement across all power modes. Polished surface finishes of Ra < 0.1µm and Rz < 0.5µm can be easily achieved using the newly release “Ultra-Fine Finishing” process with Pico-pulse technology. These operations enable the production of superior cutting edges necessary for the most demanding of cutting tool applications.

Combining intelligence in a domain once dominated by brute force electronics, not only gives ANCA customers an edge over the competition but enables a smarter approach to tool making. “The difference between our approach and the approach of our competitors is that ANCA focusses on what our customers want to achieve with their erosion process. They strongly told us that they wanted a process optimised for helical and round PCD tooling. We worked closely with ANCA Motion to design our erosion generator to suit not only shear tooling but the infinite array of highly complex geometries, rather than re-using generator technology originally created for Wire Electro Discharge Machining (Wire-EDM). Our approach turned the industry on its head. We let the geometries dictate the process, not the process dictate the geometries available.”

“We used intelligence to outperform brute force, like the fox outsmarting the hare,” quipped Dr. Tee.