**1 Two Main Methods for Precision EDM Grinding of Shaft Parts**
The block electrode radial feed EDM grinding method, also known as the forming block reverse copying or inverse copying method, is one of the primary techniques used in precision EDM grinding of fine shaft parts. This method utilizes a block electrode with a surface shape that matches the micro-axis busbar. During the process, the forming surface is radially servo-fed against the axis of the rotating fine shaft (see Figure 1). The wire electrode EDM method, developed by Professor Masawachi Takahisa from Tokyo University in 1984, is another widely used technique. It involves a wire electrode moving along a guide fixed on a numerical control table, with the NC system controlling the relative motion path of the tangent point of the guide. The wire electrode is then servo-fed radially and axially against the rotating fine shaft (see Figure 2).
When comparing the two methods, the block electrode method offers a much faster erosion rate—about five times or more—due to the larger discharge processing area. However, this method suffers from frequent interruptions because the tool electrode's wear cannot be compensated quickly, requiring constant monitoring and adjustment. This makes automation difficult and limits the number of manual interventions. As a result, it is challenging to maintain consistent shape and dimensional accuracy, especially during multi-piece machining.
In contrast, the wire electrode method allows continuous roughing and finishing processes without interruption. The energy loss of the wire electrode is continuously compensated through its movement, making the tool wear negligible. The precision of the workpiece is ensured by the numerical control system’s motion accuracy. Additionally, the wire electrode is a single-use component, which increases processing costs due to the need for a precise wire-moving mechanism. The block electrode, on the other hand, can be repaired and reused after wear, offering better cost efficiency in some applications.
**2 Block Electrode Tangential Feeding EDM Grinding Method**
To address the limitations of the above two methods, a new block electrode EDM technique was introduced—the tangential feeding method. This approach enables automatic compensation for electrode wear. As shown in Figure 3, the upper surface of the horizontally placed tool electrode serves as the main working surface. The distance between this surface and the workpiece axis is set to the desired processing radius. The tool electrode is then servo-fed horizontally. As the electrode wears during the machining process, the tangential feed automatically compensates for the loss until the target radius is achieved.
This method ensures that the workpiece can eventually be removed from an un-worn or minimally worn portion of the tool electrode, allowing for consistent shape and dimensional accuracy. The length of the electrode directly affects the number of workpieces that can be processed in a batch. For example, using a copper block electrode to machine a 0.6 mm diameter shaft from a 5 mm diameter bar, with a medium current setting, the measured electrode wear rate is about 1.75%. After machining eight pieces, the worn area on the electrode’s top surface measures approximately 4 mm in length and 2 mm in depth, forming a right-angled triangular depletion zone.
If the electrode is 80 mm long, it can process up to 160 workpieces before needing replacement. In comparison, the radial feed method would only allow 10 workpieces per electrode. The tangential feed method works like a "mold," where the shape of the workpiece depends mainly on the tool electrode’s surface, while the size depends on the offset position and the discharge gap. This provides strong controllability and high consistency in shape and size.
**3 Characteristics of the Block Electrode Tangential Feed Precision EDM Method**
One of the key advantages of the tangential feed method is its automatic electrode wear compensation. Unlike the radial feed method, it doesn’t require special mechanisms for electrode compensation, making it ideal for batch processing. A single electrode can process multiple workpieces at once, ensuring good consistency in shape and size. The material utilization rate is higher than both the radial feed and wire electrode methods, as the electrode is fully utilized before being reprocessed.
The method also improves automation. Once the electrode is adjusted, the workpiece is automatically machined to the desired size, reducing manual intervention. With proper programming, coarse, medium, and fine machining can be completed in a single pass. The pulse equivalent of the tangential feed is smaller, which enhances the stability of the servo feed, particularly in delicate EDM operations. Although this reduces the retreat speed and may cause challenges in arc suppression, the overall process is more stable and efficient.
Compared to the radial feed method, the tangential feed method increases productivity by 20–30% due to reduced manual intervention. While the manufacturing, positioning, and adjustment of the tool electrode require higher precision, experimental results have confirmed the feasibility of this method. The processed workpieces exhibit excellent consistency in shape and size, proving that the tangential feed method is a reliable and efficient alternative for precision EDM grinding of fine shaft parts.
Titanium Disc
Here you can find the related products in Titanium Disc, we are professional manufacturer of Titanium Forged Disc, Titanium Alloy Round Discs, Pure Titanium Disc, Grade 2 Titanium Disc. We focused on international export product development, production and sales.
Shaanxi Lasting titanium Industry Co.,Ltd is a professional manufacturer & exporter for titanium materials in China more than 30 years' successful experience. We offer the largest selection of Titanium Powder, Titanium Ingots, Titanium forgings, Titanium Bars, Titanium Sheets/Plates, Titanium tube/pipes, Titanium fittings and other Titanium Products in a wide range of sizes grades and specifications. There are more than 3000mt all kinds of Titanium and Titanium alloys materials have been exported from us every year.
Why Choose Lasting Titanium?
-Provide Titanium and Titanium Alloy products Since 1990.
-Titanium Exports hold the record of Top 3 in China for 15 Consecutive Years.
-Titanium Products have been Exported to more than 60 Countries and Regions.
-Supply the best quality products at a reasonable price.
-Provide very fast delivery and excellent customer service.
-Our Certificates: ISO9001, AS9100, AS9120 and PED.
Titanium Disc, Titanium Forged Disc, Titanium Alloy Round Discs, Pure Titanium Disc, Grade 2 Titanium Disc
SHAANXI LASTING TITANIUM INDUSTRY CO., LTD. , https://www.lastingti.com