Graphite has become particularly important as a raw material for the production of electrodes. It is impossible to imagine tool and mold making without graphite electrodes. Graphite is also used successfully in mechanical and systems engineering as well as in medical technology and hydrogen technology.
Milling graphite in the best possible way
Hufschmied has developed the Graphite-Line GRAFTOR® tools especially for machining graphite materials and green ceramics. The patented cutting geometry of these tools lets you produce graphite electrodes with significantly fewer tools and in half the time. In addition, the Graftor® tools from Hufschmied are up to approximately three times superior to commercially available standard geometries in terms of tool life.
The full potential of this high-performance tool becomes apparent when the available cutting edge length is fully utilized. This produces metal removal rates that are more than double those of other double-edged tools currently available on the market. You get the finished electrode in half the machining time. In addition, the gradations from roughing to pre-finishing to finishing the electrode can be much coarser, making it easy to save a few passes. For example, a typical sequence is to first use a 12mm cutter for roughing, then a 6mm cutter for pre-finishing, and finally a 2mm tool for finishing. With Garftor® tools, it is possible to go directly from 12mm to 2mm diameter, or the complete machining can be done right away with the 2mm tool.
Even delicate geometries can be produced with very high feed rates, since the alternation between roughing and finishing cutting means that almost no cutting pressure is built up. Conversely, this means that high height PINS or narrow webs can be produced without special programming techniques and with normal working feeds. In addition, the electrodes become much more dimensionally accurate and precise, as with other types of tools.
Starting in 2021, the newly developed Graftor mini tools will transfer the concept of Graftor tools described above to the MICRO range from diameter 0.5mm. Thanks to the nanocrystalline diamond coatings DIP® and DIP®3S developed in our research for highest surface qualities, graphite or ceramic dust adhesions to the surface structure of the diamond coating are a thing of the past. Due to the nanocrystalline layer structure, a significantly higher diamond content of more than 95% is incorporated in the diamond layer. As a result, significantly longer tool life can be achieved with thinner coatings and even very fine structures can be machined more easily and WITHOUT feed adjustment, as less cutting pressure is built up due to the significantly lower cutting edge rounding.
The Graftor® tools, like all HIGH Performance tools from Hufschmied, are gauge block marked for tool and die making. Gauge block marking means that each tool is labeled with its pitch diameter and pitch radius measured on the envelope at the head. With gauge block marking, the high accuracy requirements of automated production systems that operate 24/7 can be easily satisfied. The measuring accuracies and tolerances used for the respective tools of the Grafit-Line, as well as the GRAFTOR®, can be found on the corresponding store page with descriptions of the quality line.
For highly efficient graphite machining, Hufschmied has developed a Time Saving Concept with two variants.
Time Saving Concept 1
Time Saving Concept 1 uses the Graftor® – a tool that can be used as both a roughing and finishing tool. The Graftor® geometry can reduce the machining time of a graphite electrode by up to 50 percent.
In addition, a large number of different tools can be replaced by a single tool. This saves storage space in the machine. Since fewer different tool dimensions have to be taken into account in the manufacture of the electrode, the programming effort is also significantly reduced, usually by a ratio of 3 to 1.
Graftor® tools can also be used with all graphite grades available on the market, from ultra-fine-grained graphites with an average grain size of 0.5 µm to finishing and roughing graphites between 3 and 8 µm, as well as coarse-grained graphite grades above 10µm. The same also applies to slate or mica graphites, where the straight alternating cutting geometry produces significantly better cutting edges than tools that work in only one preferred direction.
Time Saving Concept 2
For older machines or for applications where the highest surface qualities up to mirror-like graphite surfaces are required, e.g. for glass molds, there is the Time Saving Concept 2, in which two different tools are used for roughing and finishing: a graphite roughing cutter with WD toothing 107GR-WD and the Piranha finishing cutter with three cutting edges 63CWI and 63CWIR for the highest surface qualities.
In Time Saving Concept 2, up to 30 percent of the machining time can be saved. This is due to the significantly increased in-feeds of the graphite roughing cutters and the higher feed rates of the Piranha finishing cutters.
107GR- Graphite roughing cutters
The service life of these tools for graphite machining is also significantly increased compared to other suppliers thanks to our patented DIP® diamond coating. Due to the special WD toothing with double lateral relief, very high cutting depths can be achieved. The material removed is atomized into the finest and smallest possible particles by the rasping effect, so that on the one hand the extraction of these particles can be carried out as quickly and easily as possible and on the other hand the danger of coarse particles being hurled onto already finished graphite electrode geometry elements is avoided.
Again, the nanocrystalline diamond coatings DIP® and DIP®3S, developed in our research, stand for highest surface qualities. Due to the nanocrystalline layer structure, a significantly higher diamond content of more than 95% is incorporated in the diamond layer. As a result, significantly longer tool lives can be achieved with thinner coatings and even very fine structures can be finished more easily and WITHOUT feed adjustment, since less cutting pressure is built up due to the significantly lower cutting edge rounding.
For extreme surface quality, we also have the option of applying the DIP® NANO2 coating to the Piranha finishing tools. The surface roughness of this coating is well below 0.02µm, making it particularly suitable for applications where transparent component surfaces must be achieved, such as glass molds.
Piranha finishing cutters : 63CWI/63CWIR
Thanks to their unequal pitch, these Piranha finishing cutters significantly reduce vibration. As a result, surface finishes are significantly improved, and high pins and narrow ridges are not induced to vibrate during machining and are therefore not torn off by these resonant vibrations.
Graphite Mini Milling Tools HM915 / HM905
For small and fine geometries, Hufschmied offers mini milling tools from a cutting edge diameter of 0.2 mm in various projection lengths. These tools are available from stock in many different increments of working depths L3 from 3xD1 up to 30xD1. This allows you to handle all possible 3- and 5-axis applications without any problem, even with the finest microstructures.
The DIP® nanocrystalline diamond coating helps due to its low surface roughness and the small cutting edge radius that these tools are virtually OUTPERFORMER in machining speed and at the same time in service life compared to other MINI milling tools available on the market.
Just like the Piranha finishing cutters, the MIN milling tools of the Grafit-Line are also manufactured on high-precision grinding machines in and are 100% final measured on Zoller measuring machines to ensure the highest accuracies in the finishing operations. Highest efficiency at lowest manufacturing costs per component in graphite electrode production is called Grafit-Line by Hufschmied.