Using a phase-toughened ceramic grade, Greenleaf has developed a versatile ceramic cutting-tool material. Called XSYTIN^®-1, the tool material has helped one forging customer increase its material removal rate by 164%, improve tool life by 101% and achieve other benefits.

For decades, the machining and heat treating of their output have been major bottlenecks for forging shops worldwide. They have proven to be time-consuming and costly processes due to the time and machinery required to perform the operations. Indexable carbide has been the tool of choice for nearly a century. Advances in coatings and tooling geometries have improved the machining process over the years, accounting for a constant evolution with each generation being slightly better than the last. However, the limited speed capabilities of carbide have always shackled its ability to reach the next level in the machining process.

Competitive Environment

We can all relate to the global competitive environment in which we live. In the forging industry, it was not long ago that most forgings were sourced in the proximity (or at least in trucking distance) of the end user. 

Today, the world looks different. Competitors are not only in different countries; they may be on different continents. What do we need to do in order to stay competitive in this ever-evolving world economy? One thing is for certain – we cannot stay stagnant. We must constantly improve efficiency, improve quality and reduce costs. We need a revolution, not the small steps of evolution.

Changing the Rules

As the saying goes, “if you don’t like the game, change the rules.” This is exactly what a major forging supplier did. In an effort to increase throughput and eliminate the annealing process, their customer challenged Greenleaf to integrate a ceramic grade where carbide had once previously reigned. 

This ceramic grade needed to excel in the harsh environment of machining rough forgings while also being able to machine a wide variety of steels and stainless steels with hardnesses ranging from 130-433 BHN. These forgings present some of the most challenging environments for tooling, including heavy scale, uneven surfaces, greater cut depths and unstable parts. Sounds easy, right? Until recently, most cutting-tool suppliers would look at this challenge as something of a pipe dream. Although ceramics could succeed in some of the applications, the technology simply was not there to do it all. What was needed was not more evolution but a revolution.

Cutting-Tool Revolution

Our response to the challenge was XSYTIN^®-1, Greenleaf’s phase-toughened ceramic grade. A Greenleaf sales and service engineer worked directly with the customer to develop the process and start testing, keeping in mind that this was unchartered territory for any ceramic. That meant testing a variety of edge preps and insert geometries, as well as speeds and feeds, to determine what would give the customer the best performance.

XSYTIN^®-1 turned out to be a unique but ideal choice for this application due to the grade’s highly technical development in which natural grain growth is promoted, causing the material to be many times stronger than any other ceramic tool on the market. This inherent strength allows for the use of relatively small edge preps, resulting in a desirable chip formation; reduced forces; lower power consumption; higher chip load; and better surface finish. All of these factors have a positive impact on tool life.

Ceramic Versatility

For forge milling, it is crucial that one insert can be utilized for a multitude of materials. In this particular case, the forge supplier has a variety of steel and stainless products, making it impractical to utilize different insert grades. The traditional challenge with ceramics has always been the need to plasticize the material being machined. In essence, this raises the temperature in the cutting zone to the plasticization point, reducing the forces to which the micro-geometry is subjected. The temperature needed and the forces generated on the micro-geometry have traditionally been outside of the operating scope for ceramics in softer steel and stainless steel applications. The natural strength of our ceramic material opens opportunities to gain previously unachievable productivity in a variety of metals.

It is not only different materials that are now machinable with ceramics through XSYTIN^®-1, it is also the ability to machine those materials at a much greater range of speeds. What makes this cutting material revolutionary is not its ability to machine at higher speeds, which it can, but rather that it can be utilized at speeds that do not produce full plasticization in the cutting zone. This becomes important in applications where higher speeds may not be practical due to machine limitations or instabilities and where carbide previously has been the only viable choice but at drastically reduced speeds. 

Until now, there has been a speed gap between the highest achievable speed of carbide and the lowest possible speed of ceramic. With this phase-toughened ceramic, Greenleaf can now machine a variety of materials at speeds that are lower than previously possible but higher than those capable with carbide, closing the application gap of the past.

The results show a significant reduction in cycle time on several different machines and on a wide variety of materials and hardnesses. XSYTIN^®-1’s ability to maintain edge strength through this harsh environment was never thought possible with a ceramic. The increase in edge strength allowed for a considerably sharper edge than traditionally used with ceramics. The sharper edge dramatically reduced spindle load, which allowed the customer to achieve chip loads much higher than ever thought possible. XSYTIN^®-1’s ability to maintain edge strength eliminates finishing passes by achieving a superior finish over carbide on the last roughing pass.

Eliminating the Finishing Pass

The ability to eliminate the finishing passes is worth pondering. In these applications, we tend to use larger milling tools. The larger the tool, the more it will weigh and the more cumbersome it is to replace with a finishing cutter. Even more valuable than the elimination of the finishing passes may be the time saved due to the lack of need for a tool change, which reduces noncutting time significantly. From a financial perspective, machining is not very complex. When the machine is running, we have the ability to make money; when the machine is not running, we only have costs. Significant time and cost savings can be achieved.

Conclusions

For Greenleaf’s customer, XSYTIN^®-1 increased the metal removal rate by over 164%, increased tool life by an average of 101%, eliminated finish passes and reduced spindle load by an average of 24%. This allows the customer to significantly reduce cycle times and increase throughput. 

Co-author Jan Andersson is Greenleaf Corp.’s global director, tech team and marketing. He may be reached at 814-763-2915 or jandersson@greenleafcorporation.com. Co-author Travis Biggs is a district manager for Greenleaf Corp. He may be reached at 814-763-2915 or tbiggs@greenleafcorporation.com.