With graphite, the magic words are high speed. High speed machining centers with 30,000- to 60,000-rpm spindles are capable of accelerated feeds that serve to reduce cycle times and improve surface finish, as well as edge quality.

The motors required to run these spindles are smaller and lighter and this results in lower cutting forces and reduced tool breakage. This is particularly critical because many electrodes are intricate and the production of them involves small, fragile micro tooling.

  Spindle
The smaller the tools, the higher the spindle speed needed to efficiently machine quality parts and avoid tool breakage. High frequency spindles with speed ranges up to 60,000 rpm are ideal for milling, drilling and engraving graphite electrodes using micro tools. High speed machining technology uses high rpm rates, taking a smaller stepover, but with significantly increased feedrates.

  Move your hand through the flame of a burning candle. If you move too slowly, there’s enough time for the flame to cause damage. But if you sweep your hand swiftly through the flame, there’s insufficient time for the fire to damage your skin. The same principle applies to high speed machining with micro tooling. Move fast, and there’s insufficient time for heat to feed back into the part and cause issues.

 Using small micro tools for graphite or virtually any other material simply isn’t as easy as finding an adapter to hold a tiny tool in a 40-taper spindle on a conventional CNC machine. Because that spindle was designed for large tools like a three-inch fly cutter intended to hog out deep cuts in dense substrates. As such, it has so much torque and force that it just breaks small tools, which is both inefficient and very costly over the long haul.

  The only option an operator has in this situation is to slow the rpm and feedrates down to a crawl, and this isn’t efficient either because it results in unacceptable cycle times. A vivid, and perhaps comical, analogy is the Hemi-powered pick up truck versus the sportscar. The reality is that you wouldn’t compare the two or even consider racing them against on another. Why? Because the truck was designed with the power and force to haul or tow enormous mass, while the sports car was designed for speed and maneuverability.

  In essence, conventional CNC manufacturers who tout the ability to run micro tools are like an auto manufacturer putting a spoiler and racing stripes on a clunky SUV and claiming that it now possesses the same qualities as a Porsche. Well, just like you can’t put a spoiler and racing stripes on an SUV and expect it to perform like a sports car, you can’t retrofit a high speed spindle onto a clunky conventional machine and expect it to efficiently accomplish high speed machining with micro tooling.

 Geometry
Just like conventional CNCs can’t be retrofitted to efficiently run microtools, conventional tooling geometry (for larger tools) can’t just be scaled down for micro tooling. The geometry of the tooling used to mill electrodes plays a key role in both quality and efficiency. Scaling down the tool geometry of larger diameter tools to a smaller format yields unacceptable feedrates and unsatisfactory finishes.

  Tooling requirements change when tool diameter is decreased and spindle speed is increased. Conventional tooling using inserts is not appropriate for micro tooling applications. This is primarily due to the high rpm rates rather than the tool diameter.

 Tool Wear
Increased rpm rates require properly balanced tools with significantly increased chip room to assure proper chip removal. While geometry can assist in both quality and efficiency when milling graphite, tool wear is still a concern due to the inherently abrasive nature of this material. Specialty tool coatings can be a weapon in battling excessive wear.

 Some coatings to consider are diamond coating, titanium aluminum nitride coating (TiAIN), which is often used for applications in steel and, finally, aluminum chromium nitride coating (AlCrN)—generally used for applications in very hard aluminum (such as cast aluminum or sand cast aluminum), but which has shown effectiveness with other abrasive substrates like fiberglass. 

About First-rate Mold Solution Co., Ltd.
First-rate Mold Solution Co., Ltd. in China, provide industry design,mold design,mold manufacturing,molding analysis,project management service.

 About www.firstratemold.com
our website has a lot of professional knowledges in mold industry in blog and news, also we are interested in CAD/CAM/CAE, such as AUTOCAD,UGNX, PRO/E,CATIA, CIMATRON, SOLIDWORKS, MOLDFLOW and so on,we welcome professional engineer,mold maker and someone who are interested in injection molding,plastic product,injection mold and mold industry to our section of blog and news,we would like to share with them