Milling Beautiful Copper Electrodes without Burrs

AE-LNBD-N carbide end mill demonstrates superior durability, precision, and excellent surface finish in copper electrode application

Peng Li | OSG Shanghai

Copper electrode is commonly used for the manufacturing of plastic molds. In recent times, the design of the final plastic product is becoming more complicated and smaller in size. As the molds are becoming “higher precision” and “higher quality,” a demand for the copper electrodes used for die-sinking EDM to become “higher precision” and “higher quality” has also increased.

“High precision” and “high quality” in copper electrodes mean high shape accuracy, little dimensional changes even after long hours of processing, excellent machined surface roughness, and being burr-free. To meet the needs of today’s electrode machining, OSG has developed the AE-LNBD-N DLC coated carbide end mill, which is uniquely engineered for copper electrode applications.

Recently, a manufacturer located in Dongguan, Guangdong Province, China whose name cannot be disclosed due to confidentiality reasons, was seeking for productivity improvement in its copper electrode production for LED lamp molds. Founded in 2021, this company specializes in the production and sales of parts for electronics, semiconductors, mold and die, and general mechanical equipment. This newly established company currently employs approximately 50 staff and has a production space of 1,000-square-meter.

Each year, this customer manufactures 1,000 to 2,500 pieces of different types of copper electrodes. They have been machining electrodes made of chrome copper for LED lamp molds since the company’s founding. The parts are machined using a vertical machining center with a BT30 spindle heat shrinkable toolholder. The dimensional tolerance required by the customer was +/- 0.01. The finish should be less than Ra 0.8, and the copper electrodes should not have obvious tool marks and burrs when visually inspected.

An electrode made of chrome copper.

This manufacturer initially used a competitor R0.1 and R0.2 carbide end mill with coating for the processing. At an axial depth of cut of 0.015 mm and a pick feed of 0.015 mm, the competitor end mill was used at a cutting speed of 25,000 min-1 and a feed rate of 250 mm/min. The competitor end mill had a tendency to stick to the chips and the tool would wear out after four hours of milling. Additionally, tool marks and burrs were clearly visible on the machined surface. Moreover, when machining larger sized copper electrodes, a single tool was insufficient to complete the entire machining. Thus, the customer’s programmer needed to edit multiple machining programs, which increased the time required for repeated confirmation and the risk of operational errors. Due to the undesirable surface finish and poor tool life, the existing tool could not meet the customer’s requirements.

In search of application improvement, the customer consulted with a tooling distributor, who introduced OSG to provide technical support. Once in contact, applications engineer Peng Li from the OSG Shanghai office immediately followed up by visiting the customer’s production plant. Upon a detail evaluation of the application, Li recommended OSG’s R0.1 x 0.5 x 4 AE-LNBD-N carbide end mill (EDP# 3056376) for a test trial.

The AE-LNBD-N is a 2-flute long neck carbide end mill designed for high-precision finishing of copper electrodes.

OSG’s AE-LNBD-N is a 2-flute long neck carbide end mill designed for high-precision finishing of copper electrodes. Its unique ball specifications include an optimal cutting edge shape with excellent sharpness, high quality primary relief surface, and superior ball R precision that ensures a stable radius accuracy – all of which contribute to allowing high quality milling of copper electrodes without burrs. The AE-LNBD-N is coated with OSG’s DLC-IGUSS, a thick film type coating that suppresses wear on the cutting edge and achieves both high tool durability and good machining accuracy.

At an axial depth of cut of 0.015 mm and a pick feed of 0.015 mm, the AE-LNBD-N was used at a cutting speed of 17.6 m/min (28,000 min-1), a feed rate of 300 mm/min (0.005 mm/t), and averaged 30 hours in tool life. Although OSG’s AE-LNBD-N is nearly twice the cost of the competitor tool, it demonstrated 20 percent greater efficiency and 7.5 times the durability.

Left: The cutting edge of the AE-LNBD-N after 30 hours of milling. The AE-LNBD-N exhibited minimal wear and can continue to be used for further machining. Right: The cutting edge of the competitor end mill after four hours of milling. The competitor end mill exhibited significant wear and has reached the end of its tool life.

After the first cutting test, the customer performed further stability verification on the AE-LNBD-N by testing it on several other machining centers for processing purple copper and chrome copper materials. The results were consistent and highly satisfactory to the customer, where the AE-LNBD-N demonstrated superior durability, precision, and excellent surface finish even after long hours of processing.

For more information on the AE-LNBD-N DLC coated carbide end mill for copper electrodes and OSG Shanghai