Tag Archive for: Chip Recutting

Optimize Roughing With Chipbreaker Tooling

Chipbreaker End Mills feature unique notch profiles, creating a serrated cutting edge. These dividers break otherwise long, stringy chips into small, easily-managed swarf that can be cleanly evacuated from the part. But why is a chipbreaker necessary for some jobs, and not others? How does the geometry of this unique tool impact its proper running parameters? In this post, we’ll answer these questions and others to discover the very real benefits of this unique cutting geometry.

up close image of chipbreaker end mill

How Chipbreaker Tooling Works

As a tool rotates and its cutting edge impacts a workpiece, material is sheared off from a part, creating chips. When that cutting process is interrupted, as is the case with breaks in the cutting portion of the tool, chips become smaller in length and are thus easier to evacuate. Because the chipbreakers are offset flute-to-flute, a proper, flat surface finish is achieved as each flute cleans up any excess material left behind from previously passed flutes.

Benefits of Chipbreaker Tooling

Machining Efficiency

When chips are removed from the part, they begin to pile in the machine. For extensive operations, where a great deal of material is hogged out, chip accumulation can very rapidly get in the way of the spindle or part. With larger chips, accumulation occurs much faster, leaving machinists to stop their machine regularly to remove the waste. As any machinist knows, a stopped machine equates to lost money.

small metal chips in cnc machine resulting from the use of a chipbreaker end mill

Prolonged Tool Life

Inefficient chip evacuation can lead to chip recutting, or when the the tool impacts and cuts chips left behind during the machining process. This adds stresses on the tool and accelerates rate of wear on the cutting edge. Chipbreaker tooling creates small chips that are easily evacuated from a part, thus minimizing the risk of recutting.

Accelerated Running Parameters

A Harvey Performance Company Application Engineer recently observed the power of a chipbreaker tool firsthand while visiting a customer’s shop in Minnesota. The customer was roughing a great amount of 4340 Steel. Running at the parameters below, the tool was able to run uninterrupted for two hours!

Helical Part No.33737
Material4340 Steel
ADOC2.545″
RDOC.125″
Speed2,800 RPM
Feed78 IPM
Material Removal Rate24.8 Cubic In/Min

 

Chipbreaker Product Offering

Chipbreaker geometry is well suited for materials that leave a long chip. Materials that produce a powdery chip, such as graphite, should not be machined with a chipbreaker tool, as chip evacuation would not be a concern. Helical Solutions’ line of chipbreaker tooling includes a 3-flute option for aluminum and non-ferrous materials, and its reduced neck counterpart. Additionally, Helical offers a 4-flute rougher with chipbreaker geometry for high-temp alloys and titanium. Harvey Tool’s expansive product offering includes a composite cutting end mill with chipbreaker geometry.

helical solutions 7 flute chipbreaker end mill cutting edges
Helical Solutions 7 Flute Chipbreaker

In Summary

Chipbreaker geometry, or grooves within the cutting face of the tool, break down chips into small, manageable pieces during the machining process. This geometry can boost shop efficiency by minimizing machine downtime to clear large chips from the machining center, improve tool life by minimizing cutting forces exerted on the tool during machining, and allow for more accelerated running parameters.

Tackling Titanium: A Guide to Machining Titanium and Its Alloys

In today’s manufacturing industry, titanium and its alloys have become staples in aerospace, medical, automotive, and firearm applications. This popular metal is resistant to rust and chemicals, is recyclable, and is extremely strong for its weight. However, there are several challenges that must be considered when machining titanium and selecting the appropriate tools and parameters for the job.

Titanium Varieties

Titanium is available in many varieties, including nearly 40 ASTM grades, as well as several additional alloys. Grades 1 through 4 are considered commercially pure titanium with varying requirements on ultimate tensile strength. Grade 5 (Ti6Al4V or Ti 6-4) is the most common combination, alloyed with 6 percent aluminum and 4 percent vanadium. Although titanium and its alloys are often grouped together, there are some key differences between them that must be noted before determining the ideal machining approach.

Titanium 6AL4V chips with helical hvti end mill

Helical Solutions’ HVTI End Mill is a great choice for high efficiency toolpaths in Titanium.

Titanium Concerns

Workholding

Although titanium may have more desirable material properties than your average steel, it also behaves more flexibly, and is often not as rigid as other metals. This requires a secure grip on titanium workpieces, and as rigid a machine setup as is possible. Other considerations include avoiding interrupted cuts, and keeping the tool in motion at all times of contact with the workpiece. Dwelling in a drilled hole or stopping a tool next to a profiled wall will cause the tool to rub – creating excess heat, work-hardening the material, and causing premature tool wear.

Heat Generation

Heat is a formidable enemy, and heat generation must be considered when selecting speeds and feeds. While commercially pure grades of titanium are softer and gummier than most of its alloys, the addition of alloying elements typically raises the hardness of titanium. This increases concerns regarding generated heat and tool wear. Maintaining a larger chipload and avoiding unnecessary rubbing aids with tool performance in the harder titanium alloys, and will minimize the amount of work hardening produced. Choosing a lower RPM, paired with a larger chipload, can provide a significant reduction in temperature when compared to higher speed options. Due to its low conduction properties, keeping temperatures to a minimum will put less stress on the tool and reduce wear. Using high-pressure coolant is also an effective method to reduce heat generation when machining titanium.

mitsubishi evo camshaft cutters machine from titanium with helical solutions end mill

These camshaft covers were custom made in titanium for Mitsubishi Evos.
Photo courtesy of @RebootEng (Instagram)

Galling and Built-Up Edge

The next hurdle to consider is that titanium has a strong tendency to adhere to a cutting tool, creating built up edge. This is a tricky issue which can be reduced by using copious amounts of high pressure coolant aimed directly at the cutting surface. The goal is to remove chips as soon as possible to prevent chip re-cutting, and keep the flutes clean and clear of debris. Galling is a big concern in the commercially pure grades of titanium due to their “gummy” nature. This can be addressed using the strategies mentioned previously, such as continuing feed at all times of workpiece contact, and using plenty of high-pressure coolant.

Titanium Solutions

While the primary concerns when machining titanium and its alloys may shift, the methods for mitigating them remain somewhat constant. The main ideas are to avoid galling, heat generation, work hardening, and workpiece or tool deflection. Use a lot of coolant at high pressure, keep speeds down and feeds up, keep the tool in motion when in contact with the workpiece, and use as rigid of a setup as possible.

In addition, selecting a proper tool coating can help make your job a successful one. With the high heat being generated during titanium machining operations, having a coating that can adequately deal with the temperature is key to maintaining performance through an operation. The proper coating will also help to avoid galling and evacuate chips effectively. Coatings such as Harvey Tool’s Aluminum Titanium Nitride (AlTiN Nano) produce an oxide layer at high temperatures, and will increase lubricity of the tool.

Tooling Solutions

Helical Solutions offers the HVTI-6 line of tooling optimized for High Efficiency Milling (HEM) in Titanium and its alloys. Helical’s HVTI-6 features its Aplus coating which offers added lubricity and high temperature resistance for improved tool life and faster speeds and feeds.

As titanium and its many alloys continue to grow in use across various industries, more machinists will be tasked with cutting this difficult material. However, heat management and appropriate chip evacuation, when paired with the correct coating, will enable a successful run.

machining titanium

Climb Milling vs. Conventional Milling

There are two distinct ways to cut materials when CNC milling: Conventional Milling (Up) and Climb Milling (Down). The difference between these two techniques is the relationship of the rotation of the cutter to the direction of feed. In Conventional Milling, the cutter rotates against the direction of the feed. During Climb Milling, the cutter rotates with the feed.

Conventional Milling is the traditional approach when cutting because the backlash, or the play between the lead screw and the nut in the machine table, is eliminated as seen in Figure 1 below. Recently, however, Climb Milling has been recognized as the preferred way to approach a workpiece since most machines today compensate for backlash or have a backlash eliminator.

infographic showcasing conventional milling with backlash elimination


Key Conventional and Climb Milling Properties:

Conventional Milling (Figure 2)

As previously stated, traditionally conventional milling has been the common choice for most machinists. This is where the cutting edge of the tool is actually rotating away from the direction of the feed. An example of this is seen in Figure 2 below. Until recently, this has been the common choice due to backlash however, the rise of climb milling has caused machinists or machines to adapt and compensate for this issue.

That is not to say there aren’t benefits to climb milling. For example, this strategy offers a machinist more control and less vibration than its climb milling counterpart. Similarly, for materials that traditionally chatter or tear, conventional milling would be the proper strategy to choose. On the other hand, here are some reasons why it might be most beneficial to adopt a climb milling strategy:

  • Chip width starts from zero and increases which causes more heat to diffuse into the workpiece and produces work hardening
  • Tool rubs more at the beginning of the cut causing faster tool wear and decreases tool life
  • Chips are carried upward by the tooth and fall in front of cutter creating a marred finish and re-cutting of chips
  • Upwards forces created in horizontal milling* tend to lift the workpiece, more intricate and expansive work holdings are needed to lessen the lift created*

infographic of conventional milling and its feed and rotation paths

Climb Milling (Figure 3)

As machinists are always trying to find ways to increase efficiency and tool life, climb milling has gotten a lot of recent traction in the space. Less heat is generated within the tool, and friction is more easily mitigated. These two alone lead to longer tool life, allowing for more parts completed per tool, lowering a shops bottom line. Also, climb milling can lead to a better surface finish due to how the chips are formed at the cutting edge.

With more modern machines now compensating for backlash or utilize backlash eliminators, it has become a much easier strategy to adopt within shops. While we went over some reasons why climb milling is not an effective strategy above, here are some reasons why a machinist may want to explore climb milling:

  • Chip width starts from maximum and decreases so heat generated will more likely transfer to the chip
  • Creates cleaner shear plane which causes the tool to rub less and increases tool life
  • Chips are removed behind the cutter which reduces the chance of chip recutting
  • Downwards forces in horizontal milling is created that helps hold the workpiece down, less complex work holdings are need when coupled with these forces
  • Horizontal milling is when the center line of the tool is parallel to the work piece

infographic of climb milling and its rotation and feed comparisons


When to Choose Conventional or Climb Milling

Climb Milling is generally the best way to machine parts today since it reduces the load from the cutting edge, leaves a better surface finish, and improves tool life. During Conventional Milling, the cutter tends to dig into the workpiece and may cause the part to be cut out of tolerance.

However, though Climb Milling is often the current preferred way to machine parts, there are times when Conventional Milling is the necessary milling style. One such example is if your machine does not counteract backlash. In this case, Conventional Milling should be implemented. Without accounting for backlash, breakage can occur due to the forces within the machine during tool engagement.

In addition, conventional milling should also be utilized on casting, forgings or when the part is case hardened. This is due to the cut beginning under the surface of the material, where it will gradually build a chip. Climb milling into these materials will see maximum chip thickness on engagement, which could lead to premature failure of the cutting edge due to the forces generated.