Posts

The Advances of Multiaxis Machining

CNC Machine Growth

As the manufacturing industry has developed, so too have the capabilities of machining centers. CNC Machines are constantly being improved and optimized to better handle the requirements of new applications. Perhaps the most important way these machines have improved over time is in the multiple axes of direction they can move, as well as orientation. For instance, a traditional 3-axis machine allows for movement and cutting in three directions, while a 2.5-axis machine can move in three directions but only cut in two. The possible number of axes for a multiaxis machine varies from 4 to 9, depending on the situation. This is assuming that no additional sub-systems are installed to the setup that would provide additional movement. The configuration of a multiaxis machine is dependent on the customer’s operation and the machine manufacturer.

Multiaxis Machining

With this continuous innovation has come the popularity of multiaxis machines – or CNC machines that can perform more than three axes of movement (greater than just the three linear axes X, Y, and Z). Additional axes usually include three rotary axes, as well as movement abilities of the table holding the part or spindle in place. Machines today can move up to 9 axes of direction.

Multiaxis machines provide several major improvements over CNC machines that only support 3 axes of movement. These benefits include:

  • Increasing part accuracy/consistency by decreasing the number of manual adjustments that need to be made.
  • Reducing the amount of human labor needed as there are fewer manual operations to perform.
  • Improving surface finish as the tool can be moved tangentially across the part surface.
  • Allowing for highly complex parts to be made in a single setup, saving time and cost.

9-Axis Machine Centers

The basic 9-axis naming convention consists of three sets of three axes.

Set One

The first set is the X, Y, and Z linear axes, where the Z axis is in line with the machine’s spindle, and the X and Y axes are parallel to the surface of the table. This is based on a vertical machining center. For a horizontal machining center, the Z axis would be aligned with the spindle.

Set Two

The second set of axes is the A, B, and C rotary axes, which rotate around the X, Y, and Z axes, respectively. These axes allow for the spindle to be oriented at different angles and in different positions, which enables tools to create more features, thereby decreasing the number of tool changes and maximizing efficiency.

Set Three

The third set of axes is the U, V, and W axes, which are secondary linear axes that are parallel to the X, Y, and Z axes, respectively. While these axes are parallel to the X, Y, and Z axes, they are managed by separate commands. The U axis is common in a lathe machine. This axis allows the cutting tool to move perpendicular to the machine’s spindle, enabling the machined diameter to be adjusted during the machining process.

A Growing Industry

In summary, as the manufacturing industry has grown, so too have the abilities of CNC Machines. Today, tooling can move across nine different axes, allowing for the machining of more intricate, precise, and delicate parts. Additionally, this development has worked to improve shop efficiency by minimizing manual labor and creating a more perfect final product.

The Anatomy of an End Mill

End mills feature many different dimensions that can be listed in a tool description. It is important to understand how each dimension can impact tool selection, and how even small choices can make all the difference when the tool is in motion.

Flutes

Flutes are the easiest part of the end mill to recognize. These are the deep spiraled grooves in the tool that allow for chip formation and evacuation. Simply put, flutes are the part of the anatomy that allows the end mill to cut on its edge.

end mill flutes

One consideration that must be made during tool selection is flute count, something we have previously covered in depth. Generally, the lower the flute count, the larger the flute valley – the empty space between cutting edges. This void affects tool strength, but also allows for larger chips with heavier depths of cut, ideal for soft or gummy materials like aluminum. When machining harder materials such as steel, tool strength becomes a larger factor, and higher flute counts are often utilized.

Profile

The profile refers to the shape of the cutting end of the tool. It is typically one of three options: square, corner radius, and ball.

Square Profile

Square profile tooling features flutes with sharp corners that are squared off at a 90° angle.

Corner Radius

This type of tooling breaks up a sharp corner with a radius form. This rounding helps distribute cutting forces more evenly across the corner, helping to prevent wear or chipping while prolonging functional tool life. A tool with larger radii can also be referred to as “bull nose.”

Ball Profile

This type of tooling features flutes with no flat bottom, rounded off at the end creating a “ball nose” at the tip of the tool.

Cutter Diameter

The cutter diameter is often the first thing machinists look for when choosing a tool for their job. This dimension refers to the diameter of the theoretical circle formed by the cutting edges as the tool rotates.

cutter diameter

Shank Diameter

The shank diameter is the width of the shank – the non-cutting end of the tool that is held by the tool holder. This measurement is important to note when choosing a tool to ensure that the shank is the correct size for the holder being used. Shank diameters require tight tolerances and concentricity in order to fit properly into any holder.

Overall Length (OAL) & Length of Cut (LOC)

Overall length is easy to decipher, as it is simply the measurement between the two axial ends of the tool. This differs from the length of cut (LOC), which is a measurement of the functional cutting depth in the axial direction and does not include other parts of the tool, such as its shank.

Overall Reach/Length Below Shank (LBS)

An end mill’s overall reach, or length below shank (LBS), is a dimension that describes the necked length of reached tools. It is measured from the start of the necked portion to the bottom of the cutting end of the tool.  The neck relief allows space for chip evacuation and prevents the shank from rubbing in deep-pocket milling applications. This is illustrated in the photo below of a tool with a reduced neck.

end mill neck

Helix Angle

The helix angle of a tool is measured by the angle formed between the centerline of the tool and a straight line tangent along the cutting edge. A higher helix angle used for finishing (45°, for example) wraps around the tool faster and makes for a more aggressive cut. A lower helix angle (35°) wraps slower and would have a stronger cutting edge, optimized for the toughest roughing applications.

helix angle

A moderate helix angle of 40° would result in a tool able to perform basic roughing, slotting, and finishing operations with good results. Implementing a helix angle that varies slightly between flutes is a technique used to combat chatter in some high-performance tooling. A variable helix creates irregular timing between cuts, and can dampen reverberations that could otherwise lead to chatter.

Pitch

Pitch is the degree of radial separation between the cutting edges at a given point along the length of cut, most visible on the end of the end mill. Using a 4-flute tool with an even pitch as an example, each flute would be separated by 90°. Similar to a variable helix, variable pitch tools have non-constant flute spacing, which helps to break up harmonics and reduce chatter. The spacing can be minor but still able to achieve the desired effect. Using a 4-flute tool with variable pitch as an example, the flutes could be spaced at 90.5 degrees, 88.2 degrees, 90.3 degrees, and 91 degrees (totaling 360°).

variable pitch

3 Steps to Shutting Up Tool Chatter

Cutting tools undergo a great deal of force during the machining process, which cause vibrations – also known as chatter or harmonics. Avoiding these vibrations entirely is not possible, though minimizing them is pivotal for machining success. Vibrations become damaging when proper machining steps are not followed. This leads to strong, part-ruining chatter. In these situations, parts have what is known as “chatter marks,” or clear vibration marks along the surface of a part. Tools can experience an increased rate of wear due to excess vibration.

Tool Chatter can be kept at bay by following three simple, yet often overlooked steps:

1. Select the Right Tool for Your Job

It seems elementary, but selecting the best tool for your application can be confusing. With so many different geometric styles for tooling – overall length, length of cut, reach, number of flutes – it can sometimes be difficult to narrow down one specific tool for your job. Oftentimes, machinists opt for general purpose tooling that can perform a variety of operations, overlooking the option that’s optimized for one material and job.

Opting for Material Specific Tooling is helpful, as each material has different needs. For example, steels are machined differently than aluminum materials. Everything from the chip size, to chip evacuation, is different. Variable Helix or Variable Pitch designs help to minimize chatter by reducing harmonics, which are caused by the cutting edge having repeated contact with the workpiece. In order to reduce harmonics, the time intervals between flute contact with the workpiece are varied.

Overall length is another important factor to consider when deciding on a tool for your job. The more overhang, or length the tool hangs from the spindle, the less secure the spindle-to-tool connection is, and the more vibration. Ensuring that your tool is only as long as needed for your operation is important to minimizing chatter and harmonics. If machining deep within a part, opt for reached tooling or an extended reach tool holder to help solidify the connection.

2. Ensure a Secure Connection

When it comes to secure tool holding approaches, both the tool shank and the collet are important. A loose tool, unsurprisingly, has more ability to move, or vibrate, during machining. With this in mind, Helical offers Shank Configurations to help the connection including the ToughGRIP Shank, which replaces a smooth, mirror-like surface with a rougher, coarser one for increased friction. Helical is also a licensee of the HAIMER Safe-Lock™, added grooves on the shank of a tool that work opposite of the spindle rotation, securely fastening the tool in place.

Machinists must also know the different types of collets available to them to identify if a better solution might be necessary. For example, Hydraulic Tool Holders or Shrink Fit Tool Holders promote a stronger connection than a Mechanical Spindle Tightening method.

For more information, see Key Tool Holding Considerations

3. Choose a Chatter Minimizing Strategy

How a tool is run can mean the difference between stellar job results and a ruined part. This includes both the parameters a tool is run at, as well as the direction by which it rotates – either a Conventional Milling or a Climb Milling technique.

Conventional Milling

In this method, the chip width starts from zero and increases gradually, causing more heat to diffuse into the workpiece. This can lead to work hardening, creating more headaches for a machinist.

tool chatter

Climb Milling

Most modern machine shops will use a climb milling technique, or when the chip width starts at its maximum and decreases during the cut. Climb Milling will offer a more consistent cut than traditional methods, and puts less stress on the tool. Think of it like weight lifting – doing the heavy lifting will be easiest at the beginning of your workout. Similarly, a cut in which the thickest chip is removed first helps the tool maintain its strength. Because the chip cutting process is more swift, vibrations are minimized.

decrease tool chatter

For more information, see Climb Milling Vs. Conventional Milling

In Conclusion

Vibrations are unavoidable during the machining process, but minimizing them can mean the difference between successful machining and scrapped parts. Following three simple rules can help to keep your chatter and harmonics under control, including: Selecting the right tool, ensuring a secure machine-tool connection, and using it in a climb milling strategy. Both Harvey Tool and Helical Solutions have tools that can help, including shank modifications and Variable Helix or Variable Pitch end mills.

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.

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.

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
Material 4340 Steel
ADOC 2.545″
RDOC .125″
Speed 2,800 RPM
Feed 78 IPM
Material Removal Rate 24.8 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.

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.

Introduction to High Efficiency Milling

The following is just one of several blog posts relevant to High Efficiency Milling. To achieve a full understanding of this popular machining method, view any of the additional HEM posts below!

High Speed Machining vs. HEM I How to Combat Chip Thinning I Diving into Depth of Cut I How to Avoid 4 Major Types of Tool Wear I Intro to Trochoidal Milling


High Efficiency Milling (HEM) is a strategy that is rapidly gaining popularity in the metalworking industry. Most CAM packages now offer modules to generate HEM toolpaths, each with their own proprietary name. In these packages, HEM can also be known as Dynamic Milling or High Efficiency Machining, among others. HEM can result in profound shop efficiency, extended tool life, greater performance, and cost savings. High performance end mills designed to achieve higher speeds and feeds will help machinists to reap the full benefits of this popular machining method.

High Efficiency Milling Defined

HEM is a milling technique for roughing that utilizes a lower Radial Depth of Cut (RDOC) and a higher Axial Depth of Cut (ADOC). This spreads wear evenly across the cutting edge, dissipates heat, and reduces the chance of tool failure.

This strategy differs from traditional or conventional milling, which typically calls for a higher RDOC and lower ADOC. Traditional milling causes heat concentrations in one small portion of the cutting tool, expediting the tool wear process. Further, while Traditional Milling call for more axial passes, HEM toolpaths use more passes radially.

For more information on optimizing Depth of Cut in relation to HEM, see Diving into Depth of Cut: Peripheral, Slotting & HEM Approaches.

High Efficiency Milling

Built-In CAM Applications

Machining technology has been advancing with the development of faster, more powerful machines. In order to keep up, many CAM applications have developed built-in features for HEM toolpaths, including Trochoidal Milling, a method of machining used to create a slot wider than the cutting tool’s cutting diameter.

HEM is largely based on the theory surrounding Radial Chip Thinning, or the phenomenon that occurs with varying RDOC, and relates to the chip thickness and feed per tooth. HEM adjusts parameters to maintain a constant load on the tool through the entire roughing operation, resulting in more aggressive material removal rates (MRR). In this way, HEM differs from other high performance toolpaths, which involve different methods for achieving significant MRR.

Virtually any CNC machine can perform HEM – the key is a fast CNC controller. When converting from a regular program to HEM, about 20 lines of HEM code will be written for every line of regular code. A fast processor is needed to look ahead for the code, and keep up with the operation. In addition, advanced CAM software that intelligently manages tool load by adjusting the IPT and RDOC is also needed.

HEM Case Studies

The following example shows the result a machinist had when using a Helical Solutions HEV-5 tool to perform an HEM operation in 17-4PH stainless steel. While performing HEM, this ½” diameter, 5-flute end mill engaged the part just 12% radially, but 100% axially. This machinist was able to reduce tool wear and was able to complete 40 parts with a single tool, versus only 15 with a traditional roughing toolpath.

The effect of HEM on a roughing application can also be seen in the case study below. While machining 6061 aluminum with Helical’s H45AL-C-3, a 1/2″, 3-flute rougher, this machinist was able to finish a part in 3 minutes, versus 11 minutes with a traditional roughing toolpath. One tool was able to make 900 parts with HEM, a boost of more than 150% over the traditional method.

Importance of Tooling to HEM

Generally speaking, HEM is a matter of running the tool – not the tool itself. Virtually every tool can perform HEM, but using tooling built to withstand the rigors of HEM will result in greater success. While you can run a marathon in any type of shoes, you’d likely get the best results and performance from running shoes.

HEM is often regarded as a machining method for larger diameter tooling because of the aggressive MRR of the operation and the fragility of tooling under 1/8” in size. However, miniature tooling can be used to achieve HEM, too.

Using miniature tooling for HEM can create additional challenges that must be understood prior to beginning your operation.

Best Tools for HEM:

  • High flute count for increased MRR.
  • Large core diameter for added strength.
  • Tool coating optimized for the workpiece material for increased lubricity.
  • Variable Pitch/Variable Helix design for reduced harmonics.

Key Takeaways

HEM is a machining operation which continues to grow in popularity in shops worldwide. A milling technique for roughing that utilizes a lower RDOC and higher ADOC than traditional milling, HEM distributes wear evenly across the cutting edge of a tool, reducing heat concentrations and slowing the rate of tool wear. This is especially true in tooling best suited to promote the benefits of HEM.

Most Common Methods of Tool Entry

Tool entry is pivotal to machining success, as it’s one of the most punishing operations for a cutter. Entering a part in a way that’s not ideal for the tool or operation could lead to a damaged part or exhausted shop resources. Below, we’ll explore the most common part entry methods, as well as tips for how to perform them successfully.


Pre-Drilled Hole

Pre-drilling a hole to full pocket depth (and 5-10% larger than the end mill diameter) is the safest practice of dropping your end mill into a pocket. This method ensures the least amount of end work abuse and premature tool wear.

tool entry predrill

 


Helical Interpolation

Helical Interpolation is a very common and safe practice of tool entry with ferrous materials. Employing corner radius end mills during this operation will decrease tool wear and lessen corner breakdown. With this method, use a programmed helix diameter of greater than 110-120% of the cutter diameter.

helical interpolation

 


Ramping-In

This type of operation can be very successful, but institutes many different torsional forces the cutter must withstand. A strong core is key for this method, as is room for proper chip evacuation. Using tools with a corner radius, which strengthen its cutting portion, will help.

ramping

Suggested Starting Ramp Angles:

Hard/Ferrous Materials: 1°-3°

Soft/Non-Ferrous Materials: 3°-10°

For more information on this popular tool entry method, see Ramping to Success.


Arcing

This method of tool entry is similar to ramping in both method and benefit. However, while ramping enters the part from the top, arcing does so from the side. The end mill follows a curved tool path, or arc, when milling, this gradually increasing the load on the tool as it enters the part. Additionally, the load put on the tool decreases as it exits the part, helping to avoid shock loading and tool breakage.


Straight Plunge

This is a common, yet often problematic method of entering a part. A straight plunge into a part can easily lead to tool breakage. If opting for this machining method, however, certain criteria must be met for best chances of machining success. The tool must be center cutting, as end milling incorporates a flat entry point making chip evacuation extremely difficult. Drill bits are intended for straight plunging, however, and should be used for this type of operation.

tool entry

 


Straight Tool Entry

Straight entry into the part takes a toll on the cutter, as does a straight plunge. Until the cutter is fully engaged, the feed rate upon entry is recommended to be reduced by at least 50% during this operation.

tool entry

 


Roll-In Tool Entry

Rolling into the cut ensures a cutter to work its way to full engagement and naturally acquire proper chip thickness. The feed rate in this scenario should be reduced by 50%.

tool entry

 

Ball Nose Milling Strategy Guide

Ball Nose Milling Without a Tilt Angle

Ball nose end mills are ideal for machining 3-dimensional contour shapes typically found in the mold and die industry, the manufacturing of turbine blades, and fulfilling general part radius requirements. To properly employ a ball nose end mill (with no tilt angle) and gain the optimal tool life and part finish, follow the 2-step process below (see Figure 1).

ball nose

Step One: Calculate Your Effective Cutting Diameter

A ball nose end mill’s Effective Cutting Diameter (Deff) differs from its actual cutting diameter when utilizing an Axial Depth of Cut (ADOC) that is less than the full radius of the ball. Calculating the effective cutting diameter can be done using the chart below that represents some common tool diameters and ADOC combinations or by using the traditional calculation (see Figure 2).

ball nose

ball nose

Step Two: Calculate Your Compensated Speed

Given the new effective cutting diameter a “Compensated Speed” will need to be calculated. If you are using less than the cutter diameter, then its likely your RPM’s will need to be adjusted upward (see Figure 3).

ball nose

KEY
ADOC = Axial Depth of Cut
D = Cutting Diameter
Deff = Effective Cutting Diameter
R = Tool Radius (Dia./2)
RDOC = Radial Depth of Cut
SFM = Surface Feet per Minute
Sc = Compensated Speed


Ball Nose Milling With a Tilt Angle

If possible, it is highly recommended to use ball nose end mills on an incline (ß) to avoid a “0” SFM condition at the center of the tool, thus increasing tool life and part finish (Figure 4). For ball nose optimization (and in addition to tilting the tool), it is highly recommended to feed the tool in the direction of the incline and utilize a climb milling technique.

ball nose

To properly employ a ball nose end mill with a tool angle and gain the most optimal tool life and part finish, follow the 2-step process below.

Step One: Calculate Your Effective Cutting Diameter

The chart below that represents some common effective cutting diameters and ADOCs at a 15º tilt angle. Otherwise, the traditional calculation below may be used (see Figure 5).

ball nose

ball nose

Step Two: Calculate Your Compensated Speed

Given the new effective cutting diameter a compensated speed will need to be calculated. If you are using less than the cutter diameter, then its likely your RPM’s will need to be adjusted upward (see Figure 6).

ball nose

KEY
Deff = Effective Cutting Diameter
SFM = Mfg Recommended Surface Feet per Minute
Sc = Compensated Speed

6 Uses of Double Angle Shank Cutters

A Double Angle Shank Cutter is often referred to as the “Swiss Army Knife of Machining” due to its extreme versatility. This singular tool can be used for chamfering, back chamfering, V-groove milling, deburring, and countersinking. Below, we’ll learn the nuances of each operation, and why a Double Angle Shank Cutter might is an excellent tool to have on hand in any machine shop.


1. Thread Milling

Both in purpose and look, a Double Angle Shank Cutter is very similar to that of a single-form thread mill. Single-form thread mills are more versatile than multi-form thread mills, as they are not locked into a fixed pitch. Double Angle Shank Cutters that have a 60° angle can create internal and external 60° Unified National (UN) and metric threads. Double Angle Shank Cutters with a 55° angle can be used to thread 55° British Standard Pipe Threads (BSPT). To determine the thread sizes that various Double Angle Shank Cutters can produce, it’s helpful to consult thread fit charts, which pair appropriate cutter diameters to the thread size needed.


2. Chamfering

Depending on the requirements of your chamfering operation, and the angle of the chamfer you’re creating on your part, a Double Angle Shank Cutter might be appropriate. The angle of the top or bottom of the cutting face of the tool (called out below in as a B1 dimension), will determine the angle of your part’s chamfer. The area marked in red in Figures 2 and 3 below indicate the cutting portion for your chamfering and back chamfering (leaving a chamfer on the bottom of a part) operation.

For more information on the angles of Double Angle Shank Cutters, view Harvey Tool’s helpful guide: “Angles Untangled.”


3. Back Chamfering

Consider a through-hole that has a burr or tear-out caused from drilling the back of a workpiece. Reorienting the workpiece and relocating the hole is time-consuming, and it may be difficult to accurately finish the hole. In a case like this, back chamfering the burred hole without changing the setup is a preferred method. Put simply, the ability to accurately chamfer not only the top – but also the bottom of a part without needing to refasten the workpiece in your machine will save valuable time and money.

For best results when chamfering with Double Angle Shank Cutters, use a stepping over technique with diminishing passes as the radial engagement increases. This strategy helps to manage the amount of contact along the angle and can significantly avoid tool deflection.


4. Machining V-Grooves

A Double Angle Shank Cutter is commonly applied for machining V-groove profiles because of its cutting head, which is perpendicular to the tool centerline. This provides effective cutting action, even at a low spindle speed. A low tip speed can lead to issues with other tools, such as Chamfer Cutters, where the pointed profile is on-center of the tool.


5. Deburring

The task of hand-deburring parts can be tiresome for you, and cost inefficient for your shop. It can also lead to inaccuracies in parts that require precise dimensions. Double Angle Shank Cutters can be used to debur a part right in your CNC machine. By doing so, the process of finishing a part is made simple, fast, and accurate. Of course, ensuring proper clearance prior to machining the bottom of a machined hole is pivotal.

Other useful and versatile tools to have on-hand for quick CNC deburring include deburring end mills, back deburring mills, undercutting end mills, and chamfer cutters.


6. Countersinking

Countersinking a part  is done so a screw, nail, or bolt is able to sit flush with the part surface. Using specialty profile tooling can help enlarge the rim of a drilled hole and bevel the sides for a screw to sit accurately. A Double Angle Shank Cutter can also perform this operation by using the bottom portion of its cutting face.


Because of its ability to perform six different operations, Double Angle Shank Cutters are an ideal tool to keep in your tool carousel. In a bind, these tool forms can mill threads, chamfer, back chamfer, machine v-grooves, deburr in your CNC machine, and countersink. This versatility makes it a machining favorite and can offer shops boosted productivity by eliminating the need to flip parts, deburr by hand, or carry multiple tool forms.

For more on Harvey Tool Double Angle Shank Cutters, Click Here.

Corner Engagement: How to Machine Corners

Corner Engagement

During the milling process, and especially during corner engagement, tools undergo significant variations in cutting forces. One common and difficult situation is when a cutting tool experiences an “inside corner” condition. This is where the tool’s engagement angle significantly increases, potentially resulting in poor performance.

Machining this difficult area with the wrong approach may result in:

  • Chatter – visible in “poor” corner finish
  • Deflection – detected by unwanted “measured” wall taper
  • Strange cutting sound – tool squawking or chirping in the corners
  • Tool breakage/failure or chipping

Least Effective Approach (Figure 1)

Generating an inside part radius that matches the radius of the tool at a 90° direction range is not a desirable approach to machining a corner. In this approach, the tool experiences extra material to cut (dark gray), an increased engagement angle, and a direction change. As a result, issues including chatter, tool deflection/ breakage, and poor surface finish may occur.

Feed rate may need to be lessened depending on the “tool radius-to-part radius ratio.”

corner engagement

More Effective Approach (Figure 2)

Generating an inside part radius that matches the radius of the tool with a sweeping direction change is a more desirable approach. The smaller radial depths of cut (RDOC) in this example help to manage the angle of engagement, but at the final pass, the tool will still experience a very high engagement angle.  Common results of this approach will be chatter, tool deflection/breakage and poor surface finish.

Feed rate may need to be reduced by 30-50% depending on the “tool radius-to-part radius ratio.”

corner engagement

Most Effective Approach (Figure 3)

Generating an inside part radius with a smaller tool and a sweeping action creates a much more desirable machining approach. The manageable RDOC and smaller tool diameter allow for management of the tool engagement angle, higher feed rates and better surface finishes. As the cutter reaches full radial depth, its engagement angle will increase, but the feed reduction should be much less than in the previous approaches.

Feed rate may need to be heightened depending on the “tool-to-part ratio.” Utilize tools that are smaller than the corner you are machining.

corner engagement

Ramping to Success

Poor tool life and premature tool failure are concerns in every machining application. Something as simple as tool path selection – and how a tool first enters a part – can make all the difference. Tool entry has a great deal of influence on its overall success, as it’s one of the most punishing operations for a cutter. Ramping into a part, via a circular or linear toolpath, is one of the most popular and oftentimes the most successful methods (Figure 1). Below, learn what ramping is, its benefits, and in which situations it can be used.

ramping

What is Ramping?

Ramping refers to simultaneous radial and axial motion of a cutting tool, making an angular tool path. Oftentimes, this method is used to approach a part when there is a need to create closed forms such as pockets, cavities, engravings, and holes. In doing so, the need to plunge with an end mill or drill to create a starting point is eliminated. Ramping is particularly important in micromachining where even the slightest imbalance in cutting forces can cause tool failure.

There are two types of ramping toolpaths: Linear and Circular (Figure 2 ).

ramping

Linear Ramping involves moving a cutting tool along two axes (the z-axis and one of the x, y axes). This method has significant more radial engagement with complementary increased cutting forces distributed across only two axes.

Circular Ramping (Helical Interpolation) has a spiral motion of the cutting tool that engages all three axes (x, y, and z axes). This method typically has less radial engagement on the cutting tool, with the cutting forces distributed across the three different axes. This is the recommended method, as it ensures the longest tool life.

Suggested Starting Ramp Angles:

Soft/Non-Ferrous Materials: 3° – 10°

Hard/Ferrous Materials 1° – 3°

Benefits of Ramping

When a tool enters the part via a Ramping method, it gradually increases in depth, preventing any shock loading on end mills. This reduces costs resulting from unnecessary tool breakage. Ramping produces smaller chips when compared to plunging, which makes chip evacuation faster and easier. As a result, cycle time can be decreased by running the end mill at faster parameters. Ramping also creates an extra space in the tool changer that would otherwise be occupied by a drill purposed with machining a starter hole.

Arcing

Similar to ramping in both method and benefit, arcing is another technique of approaching a workpiece (See Figure 3).

While ramping enters the part from the top, arcing enters from the side. The end mill follows a curved tool path (or arc) when milling, thus gradually increasing the load on the tool as the tool enters the part, as well as gradually decreasing the load as the tool exits the part. In this way, shock loading and possible tool breakage are avoided.

For more information on ramping, arcing, and other tool entry methods, please see Helical Solutions’ “Types of Tool Entry.”