Introduction: In the numerical control machining (CNC) industry, the machining of larger workpieces requires the use of larger and heavier cutting tools. Cutting tools are mostly made using traditional powder metallurgy methods, but when it comes to larger, complex structure workpieces, their production costs will increase accordingly. In order to complicate the difficulty of forming large-size workpieces, manufacturers have turned their attention to additive manufacturing.
On April 16, 2022, Antarctic Bear learned that foreign manufacturer Star SU Neher Company used 3D printing technology to produce lightweight, multi-functional large tool parts, and improve tool life and performance.
As demand for large parts increases in end markets such as aerospace and automotive, so does the demand for large cutting tools. This is especially true for electric vehicles, whose stator housing may exceed 230 mm. But larger cutting tools mean an increase in weight, which can lead to a range of problems, including spindle damage, tools falling off the spindle and increased noise. To avoid these problems, manufacturers may have to invest in machine tools with specially designed spindle interfaces, and these concerns have also led the aerospace industry to develop guidelines to limit the weight of cutting tools.
StarSU Neher is using 3D printing technology to reduce the weight of some of these knives. Photo courtesy of Star SU Neher
In order to solve the problem of equipment fragility caused by the increase in tool weight, Star SU Neher has adopted another method: 3D printing cutting tools, not only to make large milling cutters meet the weight requirements, but also to ensure that their performance and life exceed more than those of traditional counterparts.
Production of tools in the CNC industry
Most 3D printing tools are monolithic designs (tool holders are integrated in the tool body for added rigidity) for reaming, circular inserts, milling, and face milling operations. Jamie Dunneback, sales manager for circular tools at Star SU, says these tools can become big and complex, come in different forms, and can process larger features. Christian Matheis, a tool designer at Neher Group, says adding honeycomb-like internal lattice structures can reduce the weight of these tools by 30 percent without affecting the torsional strength.
While the company 3D prints some standard tool bodies (such as the NEHMO Long Life Series, which can customize different edge geometries), 99% of 3D printing tools are customized. Matheis explains, "We design each tool according to the needs of the part. All 3D printing is done at Neher's factory in Germany, which uses the DMG MORI Lasertec 30 Dual Selective Laser Melting (SLM) system to produce tool parts made of titanium, aluminum, steel and stainless steel. “
△ 3D printing tools on selective laser melting (SLM) systems
The benefits of tool lightweighting
In addition to meeting the requirements of the aerospace industry, lightweighting also offers a range of benefits. First of all, they become easier to machine for machine tools. Dunneback explains: "It reduces preventive maintenance, especially on the spindle. In addition, lighter cutting tools are less likely to fall off the spindle, which is a big problem, especially for horizontal machining centers. They are also quieter, helping users meet OSAA noise requirements, and they can run on a wider range of machine tools. For example, a machine with an HSK 63 spindle interface cannot run heavy cutting tools that require an HSK 100 interface. However, a 3D printed version of the same tool may be light enough to fit the HSK 63 interface. ”
△ By adding an internal mesh structure to the tool body, tool designers can reduce weight by up to 30% while maintaining torsional strength.
Matheis said tests of the 3D printed NEHMO Long Life face milling tool also showed a 40 percent increase in tool life compared to conventionally produced tools. This is partly because 3D printing allows manufacturers to be able to add optimized coolant channels to cutting tools. Traditionally, the coolant channels in cutting tools are drilled, which limits their design and therefore their effectiveness. 3D printed tools can be added to the channel to deliver coolant to the cutting edge more efficiently. Matheis says the improved coolant flow can increase metal removal rates by 30 percent, and it can help users achieve minimal lubrication (MQL).
3D printing tools also have a better balance, which further extends the life of the tool. According to Matheis, this is partly due to the accuracy of the 3D printing process and the possibility of adding a passive attenuator.
In addition, 3D printing enables tool designers to add functionality that helps with chip evacuation. Matheis says an internal coolant channel flushes chips through the tool and out of the work area. The inclusion of chip guides in the tool design can further aid chip evacuation.
In addition to lightweighting, 3D printing enables tool designers to add optimized channels that directly control the flow of coolant to the cutting edge. This, according to the company, could increase tool life by 40 percent and metal removal by 30 percent, while helping users implement the lightest amount of lubrication
Due to the one-off of parts, 3D printing is well suited for custom tools. According to Matheis, 3D printing isn't necessarily faster than traditional machining (a large tool body that occupies the entire printing bed takes about 24 hours to produce, while several smaller tool bodies can also be printed in one batch), but it does reduce the number of machines and processes required. While the traditional machining of the tool body requires milling and turning, the post-processing of the 3D printing tool body is usually limited to brazing the PCD tip into the tool body and laserting or erosion of the cutting edge.
Dunneback said that the brazed inserts of 3D printing tools, like traditional machining tools, can be repaired multiple times. Moreover, even tools printed in Germany can be repaired at the company's factory in North America. "We have a factory in Farmington Hill, Michigan, where we can quickly repair or change knives," he said. “