Looking at the challenges in the metal processing industry from the perspective of tool development

In recent years, the metal processing industry has developed rapidly, and its power comes from many aspects. Factors such as economic globalization, intensified market competition, use of difficult-to-process materials, and awareness of environmental issues. As a result, the end-users of the tools demand continuous improvement from the tool manufacturers. The general trend in the metalworking industry is to develop more advanced processing techniques. Although most of the epoch-making inventions in the history of tool development come from specialized scientific research institutions, it is the vast number of tool manufacturers who directly face specific machining challenges. Because tool manufacturers are on the front lines of developing new tool materials, tool structures and machining methods.

Processing challenges of new materials

Powder metal parts are an economical alternative. Parts made using powder metal technology have many unique advantages. Powder metal technology enables complex parts to be machined near final size and contours, significantly increasing machining efficiency. Usually all that is required is a finishing operation. In addition, powder metal technology intentionally leaves residual porosity within the part, which is beneficial for properties such as self-lubrication, weight reduction, and sound dampening. Certain complex parts that are difficult or impossible to manufacture using traditional casting processes can easily be produced using powder metal techniques. In conclusion, powder metal technology offers an economical method for producing parts. So, what are the challenges of machining powder metals?

The processing difficulty of powder metal materials is often underestimated. Because powder metal materials tend to contain hard particles in a soft, sometimes porous structure, processors are often misled by material hardness values. The particle hardness is as high as HRC70, while the macroscopic hardness is as low as HRC10. Hard particles and porosity can cause microscopic fatigue on the cutting edge of the tool. The cutting edge of the tool appears to travel from particle to particle and hole to hole as it cuts in and out. Repeated small impacts cause small cracks on the cutting edge. These fatigue cracks grow and eventually lead to chipping of the cutting edge. The chipping is so subtle that it looks like normal wear and tear. The common deviation between particle hardness and macrohardness means that machining powder metal parts is often like machining a grinding wheel.

The unique properties and machining characteristics of powder metal parts mean that high CBN content for increased wear resistance and fine particle size for improved cutting edge toughness are essential requirements for machining. CBN200 inserts are made of extremely fine-grained material with a high content of CBN, which just meets these requirements. There is also a unique metal binder that makes CBN200 an ideal machining solution. Its excellent wear resistance and toughness are ideal for *minimizing processing costs.

By matching the chamfers, widths and cutting edge grinds, we have strengthened the cutting edge and thus increased tool life, improved surface finish and machining tolerances, enabling customers to achieve higher productivity and reliability. This cutting edge design is especially useful for difficult-to-machine powder metal materials.

The valve seat on the cylinder head of the automobile engine is a typical powder metal part. The tool life of the PCBN machining tool for the finishing of the valve seat hole is 5000 pieces, while the life of the carbide tool machining is 300 pieces. The life of the two is different. ten times. The replacement of carbide tools by superhard tool materials such as PCBN has become a trend in more and more applications.

Challenges of chip breaking in difficult-to-machine materials

Titanium alloys are notoriously poor conductors of heat, which means that high temperatures remain at the cutting point, leading to alloying tendencies such as welding, bonding and diffusion, which can quickly damage the cutting edge. The cutting properties of titanium alloys produce a thin, high-velocity chip that is difficult to break into manageable chips. Often, this chip will deflect conventional cooling delivery systems, starve the cutting point of coolant, and damage the part. Using conventional tools with large positive rake angles and sharp cutting edges can minimize these effects*, but the resulting long chips are difficult to control.

Seco developed the Jetstream tool in response to the aerospace industry's need for improved cutting performance in titanium alloys. It is a revolutionary new solution to the age-old problem of precisely delivering coolant to the cutting zone.

The working principle of the Jetstream tool is to direct the concentrated high-pressure jet of coolant at high speed to the best position close to the cutting edge. This jet of coolant lifts chips off the rake face, improves chip control and tool life, and can increase the cutting parameters applied, and not just for aerospace materials. Jetstream tools have proven effective with almost all material groups and have a wide choice of coolant pressures.

Efficient heat dissipation from the cutting zone is one of the most critical factors affecting tool performance. The benefits of using coolant to dissipate heat are clear, and until now coolant was simply used to flush the area. For the coolant to be truly effective, it should be able to quickly remove heat from the cutting zone, and directional coolant flow to get the coolant precisely where it is needed is much more effective.

In order for the insert to work effectively, both the workpiece and the insert need to reach a certain temperature level. If there is too much heat, the tool life will be shortened; if there is not enough heat, the chips will not form properly. As the chip forms, the heat it contains needs to be removed. The inability to remove heat quickly results in a ductile chip that is flexible and cannot be broken, and its own constant curling makes it very inconvenient for the operator to handle.

Jetstream tools are very effective at removing heat from the cutting zone, allowing the chip to cool rapidly and harden to make it brittle. The resulting chips are easily broken and can be removed from the cutting zone.

With Jetstream tools, Seco understands the importance of the idea of delivering coolant directly to the tool/workpiece interface. It uses* a small amount of coolant, which provides effective cooling and also makes the chips brittle enough to break more easily, allowing for increased cutting speeds and longer tool life (due to reduced work hardening and groove wear). Not to mention the elimination of downtime and part damage associated with tangled long chips.

In Seco's experiments, a common tool produced Ti6Al4V parts at a cutting speed of 40m/min, a feed of 0.25mm/rev, and a depth of cut of 2mm, with a machining cycle of 5min. With the Jetstream tool, the cutting speed can be increased to 80m/min, the machining cycle can be shortened to 3min, and the productivity can be increased by 40%.

Process efficiency challenges

Times are changing, and the ever-increasing competition for efficiency demands more and more efficient processing methods. High-feed milling is key to keeping the company at the forefront.

High feed milling is actually a roughing method developed for high metal removal rates to increase productivity and save machining time. Combine a shallow depth of cut (not more than 2mm) with a large cutting arc radius or a small entering angle to direct the cutting force toward the axial machine spindle.

This milling method can achieve machining speeds that are three times faster than conventional methods. Instead of cutting with a greater depth of cut (which will shorten tool life), it does it in the opposite direction. It pairs a shallow depth of cut with a high feed per tooth to protect the tool. And get a higher metal removal rate than normal machining.

This approach has many advantages. For example, cutting forces are directed at the machine spindle in the axial direction; vibration is reduced and thus tool life is increased; high feed milling (HFM) methods utilize smaller entering angles; radial cutting forces* are minimized while axial cutting forces* Maximize; reduce the risk of vibration and obtain stable machining; this method even increases cutting parameters when machining with large overhangs.

Machining with a smaller depth of cut and faster feed per tooth can remove over 1000cm3 of workpiece material per minute. In fact, sometimes the feed rate can be increased up to 10 times the normal value. And even though it's a rough machining method, a shape close to the finished product can still be obtained. This allows the user to skip the semi-finishing and go directly to the final finishing. Possibility to produce more parts per machine.

The HFM method is very effective for cavity milling, especially mold machining. In addition to pocket milling, it can also be used for machining methods such as face milling, helical interpolation milling and plunge milling. The HFM method has been adopted in more machining fields, and tool manufacturers are also exploring ways to improve machining economics. In addition to the common triangular inserts, square inserts with 4 cutting edges have also been used in high-feed milling cutters.

Process Economics Challenge

Shoulder milling has a large share in the milling sector. Regardless of the machining difficulties, users want an economical tooling solution that increases productivity while reducing cost per piece. Multi-edge tools already exist, but users are still looking for tools that offer* a low cost per edge.

The economy of shoulder milling is also reflected in the following aspects. The user wanted to achieve a true 90° straight wall the first time, without having to resort to another expensive and time-consuming milling operation. Some multi-blade tools are noisy and vibrate violently, so the effect of surface roughness is not ideal. Low-noise, low-vibration milling tools are required, and tight tolerance inserts (peripheral ground) and insert seats must be used. Customers need high-precision tools to achieve the best quality surface roughness. Reducing the inventory of different tools can help increase profits. The customer required a shoulder mill that could be used for many different operations, including face milling. In fact, customers want a reliable, cost-effective, recommended solution for common machining.

Seco Tools' Square-6 product is a unique shoulder mill with a triangular insert. The Turbo whirling cutter with 2 cutting edges per insert is a common type of shoulder milling cutter. It cuts lightly and has high machining efficiency. The fly in the ointment is that the insert has a low number of effective cutting edges and lacks an advantage when it comes to economy. Square-6 has 6 cutting edges, so the cost per cutting edge is low and very economical. The axial rake angle of the insert seat is negative, but the positive cutting edge on the insert guarantees a positive cutting rake angle, thus ensuring high performance. Square-6 is available with 3 different insert geometries and 3 different pitches, which allows it to provide the same high performance in a wide range of materials, machining and operating conditions. The 90° entering angle ensures that a true 90° square shoulder can be obtained in one pass, saving production time. Coated cutter bodies provide longer tool life. Pre-hardened cutter bodies and peripherally ground inserts provide better accuracy, higher reliability, and improved precision and tolerances on machined parts.

The triangular-shaped shoulder mill insert has 6 cutting edges, which increases the manufacturing difficulty of the cutter body. Common Turbo whirl inserts and square inserts are single-sided inserts with 2 and 4 cutting edges, respectively. The blade of Square-6 is double-sided, which puts forward higher requirements for the design and manufacture of the blade seat on the blade holder. But with the advancement of manufacturing technology, its processing has not become a problem. Therefore, with the continuous advancement of manufacturing technology, economical products like Square-6 will continue to appear.