Take the latest generation of face milling tools for example. Many of them feature pre-hardened cutter bodies that maximise tool life and performance, as well as make use of inserts with as many as 16 cutting edges to minimise cost per edge for a lower cost per part. Some companies have even placed high emphasis on creating the perfect fit between the insert and its corresponding pocket to maximise the effectiveness, performance and tool life of a cutter.
Before purchasing a face mill cutter that presents multiple cutting edges, however, it is important for manufacturers to closely review their cutting processes to determine the best insert grades and geometries, cutter pitches and lead angles for their applications. It is also a good idea for them to evaluate the real costs of their cutting tools.
A market on edge
As manufacturers strive to reduce the price of their products without sacrificing quality, inserts that provide as many cutting edges as possible are growing in popularity, especially in the general engineering and automotive industries.
While more traditional face mills typically use inserts with four edges, cutting tool companies are now adding more and more cutting edges to their inserts to create the best possible economy for their customers. In fact, some face mill inserts provide as many as 16 cutting edges – for example, the Double Octomill™ from Seco.
Seco is able to achieve 16 cutting edges because each pocket on the Double Octomill face milling cutter features a negative axial angle that allows for the use of double-sided inserts. The inserts themselves use a positive rake angle to minimise power consumption while achieving higher cutting speeds for a significant increase in productivity.
Additionally, as the popularity of multi-edged inserts continues to grow, cutting tool companies are making them as thick as possible to ensure high strength and process security with low risk of edge breakage.
Nowadays, companies also offer a wide variety of high-performance insert grades and geometries so the cutter can operate effectively in various materials and processes. Some of the more advanced grade coatings manipulate aluminium and oxygen at the atomic level, allowing the inserts to have unmatched toughness and abrasion resistance for a longer, more predictable tool life.
With respect to insert geometry, those with small wipers are ideal for roughing operations, while wider wiper edges can perform roughing and finishing in a single operation, producing superior surface finishes. In the case of the Double Octomill, Seco’s M14 geometry with a 0.45 mm wiper flat is ideal for roughing, while the M15 with a 2.11 mm wiper flat is more suitable for finishing operations. Then there is Seco’s M13, which has the same wiper flat as the M15 but has a more positive geometry, making it perfect for lighter cutting.
The perfect fit
When designing modern face mills that boost productivity and cut operating costs via multiple cutting edges, cutting tool companies are taking a close look at the relation between the physical shape of an insert and its corresponding pocket.
In fact, companies, including Seco, are going the extra mile and grinding location grooves on the inserts to ensure they precisely align between the edge and the seat of each cutter body pocket. This enables the cutter to achieve very tight tolerances because there is always the same distance between the edge and the support surface.
With its Double Octomill, Seco is taking the perfect fit even further as the only cutting tool company to develop insert pockets that incorporate a strong centre lock screw and grooves for axial and radial high speed steel (HSS) location pins. These pins increase tool life because the pockets do not wear out as fast when compared with a traditional face mill. Additionally, each pocket features a hard HV 700 coating that protects the tool from wear and prevents chips from welding onto the cutter.
The HSS location pin design also simplifies the mounting and indexing of the inserts, as well as ensures maximum stability during operation. With no axial adjustment required, users simply place the insert in the pocket. In fact, they will “feel a click” when the insert is in the right spot, so it is nearly impossible to mount it incorrectly. This is important because an incorrectly positioned insert will experience uneven wear, creating different loads on the other inserts and unequal cuts in the workpiece.
Cutting tool companies are also making their inserts easier to handle by numbering each edge. Users should index all of the inserts at the same time and in the chronological number order. One worn insert will put undue stress on the others, creating a negative chain reaction that impacts part quality. Furthermore, by using the same edge number in all of the pockets, users can achieve the best possible tool life.
Given the wide variety of machines and materials on the market today, it is important to have the right cutter pitch for a particular face milling operation. Therefore, many cutting tool companies offer several different pitch options for their cutters with multi-edged inserts so that users can achieve optimum productivity in their application.
In applications where a machine has high-power capabilities, a close pitch cutter is the best option. This is especially true when processing cast iron because shorter chips are involved and a close pitch removes more material per minute. However, a close pitch cutter paired with a weak machine often results in unwanted vibrations. Normal and coarse pitches use fewer teeth/inserts in the cutter so they require less torque, making them better solutions for machines with limited power capabilities.
The Double Octomill, for example, is available in three different pitch versions. On the normal and normal+ versions, the insert locks into place via a centre lock mounting with a strong screw. The close pitch version offers wedge mounting using a new, stronger and self-orientating wedge.
Face milling is one of the most common forms of milling, and manufacturers can perform the process using a variety of different tools. For example, there are 45-degree cutters that reduce vibrations on long overhangs, shoulder cutters for thin-walled components, and round insert cutters that have the strongest cutting edges.
Cutters with a 45-degree angle, such as the Double Octomill, tend to be the most popular because the smaller the angle the better the relation between the different directions of the cutting forces, which go straight up into the spindle. The 45-degree angle also produces a chip thinning effect that promoted increased productivity. At this angle, however, if the workpiece is fixtured in such a way that the cutter has to mill close to a wall, there will be a portion of the workpiece left uncut as the cutter cannot go any further. Cutters with a 90-degree lead angle tend to bend and create vibrations when milling a straight wall on the side of a workpiece because most of the forces are in the radial direction.
Given all of the different cutter options, manufacturers need to determine which one brings the most benefit to their operations because one user may want to reduce cutting forces, where another is more concerned about properly ending a cut.
Paying the price
Cutter cost, tool life and productivity-enhancing features are critical things to consider before purchasing a face mill. After all, cutting tools have a strong impact on cost per part. For example, while a high-performance cutter with multiple insert edges may cost more up front, it can save users in the long run through increased tool life, lower cost per edge and an overall lower cost per part. However, not every application benefits from this type of cutter.
In order to purchase the right cutter for their exact needs, manufacturers must weigh the different options available to them, considering variables such as workpiece material and hardness, application type, cost per insert, cost of edges in the cut per load, number of indexes needed to complete a job, cutter style, coating types, cutting diameters and speeds, and much more.
Because there are so many variables to consider, manufacturers should also evaluate the cutting tool company selling a particular cutter and see what level of customer support it provides. After all, application support can be a major source of improved productivity, but it is one manufacturers often overlook. In recent years, the relationship dynamics between manufacturers and cutting tool companies have changed and grown into partnerships, where both parties work together for mutual support, problem solving and developing total manufacturing solutions.
Utilising a cutting tool company’s in-depth knowledge of manufacturing technology as a resource allows customers to keep abreast of the latest advancements in manufacturing, as well as understand how those innovations play into process optimisation. The end result is that they continue to increase their competitive advantages and differentiate themselves as a technology leader in the increasingly challenging global market.
The manufacturing world is continuously evolving, which requires machine shops to constantly re-evaluate their machining processes to ensure they are getting the best possible quality, efficiency, productivity and economy from their cutting tools. As a result, cutting tool companies are doing more to develop new solutions that keep their customers on “the cutting edge,” while also saving them money.
Among those solutions is a new generation of face milling cutters with unbeatable low cost per edge for achieving a lower cost per component. But because so many different options come with these modern face mill cutters, it is important for manufacturers to work closely with their cutting tool suppliers to ensure they get the best cutter for their unique needs.
Christer Jönsson, Corporate Product Manager Milling, Seco Tools
Seco Tools is a leading manufacturer of high performance metal cutting tools. Seco’s product range includes a complete programme of tools and inserts for turning, milling, drilling, reaming and boring as well as complementary tool holding systems. With more than 25,000 standard products, Seco is a complete solutions provider for the metal cutting industry and equips machine tools from the spindle down to the cutting edge.
The company is headquartered in Fagersta, Sweden and represented in more than 50 countries worldwide with 40 subsidiaries, distributors and channel partners.