Finishing graphite electrode with diamond coated ball end mill
Graphite electrodes can be machined using an end mill, but due to the extreme hardness of the material, the cutting tool wears quickly, making efficient machining challenging. To address this issue, Union Tool Co., Ltd. has partnered with Asahi Diamond Industrial Co., Ltd. to develop a diamond-coated end mill specifically for graphite electrode processing. This collaboration significantly improved the adhesion between the diamond coating and the carbide substrate. After conducting trial runs with several users, the product received positive feedback and is now available as a standard offering on the market.
(1) DCB/DCLB Series Products
The DCB series features diamond-coated ball-end mills with ball nose radii ranging from R0.5 to 6.0 mm, featuring two flutes and a 35° helix angle. The entire cutting edge is coated with a diamond layer. The DCLB series, on the other hand, offers eight specifications with ball nose radii from R0.5 to 2.0 mm, designed as long-neck tools. Due to the difficulty in achieving strong adhesion between the diamond coating and the carbide substrate, improper coating methods, surface activation, or cutting edge design can lead to coating delamination during machining. To prevent this, the development of the DCB/DCLB series focused on enhancing the bonding strength through optimized surface treatment and edge geometry. As a result, these tools deliver stable, efficient, and high-quality performance when machining graphite electrodes without any coating failure.
(2) Example of Graphite Machining
A comparison test was conducted between DCB diamond-coated ball-end mills (R3) and uncoated carbide end mills when milling a flat graphite plate. The cutting conditions were as follows: spindle speed of 20,000 rpm, feed rate of 2,000 mm/min, axial depth of cut (Ad) of 1 mm, and radial depth of cut (Rd.pf) of 1.5 mm. After machining 20 meters, the uncoated tool showed significant wear along the back face, with a noticeable step formed at the Ad position. In contrast, the diamond-coated tool exhibited only minor wear near the cutting edge, with no such steps observed. Scanning electron microscopy confirmed that the diamond coating remained intact, with vertical wear marks present but no peeling detected. The wear on the ball nose radius was plotted, showing that the uncoated tool had 30 μm of wear, while the diamond-coated one only showed 1–2 μm, demonstrating a 20-fold improvement in wear resistance.
The newly developed DCB/DCLB series not only excels in graphite machining but also performs well on high-silicon aluminum alloys.
Yanjie Diamond-Coated Ball End Mill
Shengjie Diamond-Coated Ball End Mill is a specialized tool used for graphite and electrode machining. It comes in two versions: the standard DA-SBM series and the extended blade DA-SBL series. The DA-SBM series covers diameters from Ø1 to Ø12, while the DA-SBL series ranges from Ø2 to Ø10. For the same diameter, the DA-SBL series is approximately 40–60 mm longer than the DA-SBM series.
[Image: Standard Series DA-SBM]
[Image: Standard Series DA-SBM]
[Image: Extended Edge Series DA-SBL]
Yujie Diamond-Coated Ball End Mill Features:
- Offers wear resistance comparable to single-crystal diamond.
- Utilizes a specially developed hard alloy material to enhance coating durability.
- Designed with optimal geometry for machining graphite and copper.
- Incorporates a neck structure to avoid interference.
Diamond-Coated Ball End Mill for Graphite Processing
Originating from Germany, the GVR model is made from advanced imported materials and is specifically designed for graphite machining. It is coated with diamond to increase hardness and durability, making it suitable for a wide range of applications and customer needs.
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