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The benefits of high-feed milling can significantly outweigh the potential challenges. The process offers amazing productivity, nearly triple the metal removal rate of conventional methods, and increases tool life. However, there are several things you must know in order to make high-feed milling successfully work for you.

1. Machine Tools
   Rigid, highly capable machine tools are a must because the cutters run at high feeds, which require the machine and the control to keep up with these demands. New equipment is a lot more advantageous when dealing with high-feed milling technology. It’s possible to apply new high-feed mills on older machines, but the process works best with large cutters because the feeds and speeds are not as accelerated.
   
   2. Inserts
   Trigon-style inserts provide the lowest possible lead angle over round or square inserts. Low lead angles produce a much thinner chip, which in turn, requires higher feedrates to maintain proper chip thickness for the insert geometry. The lower lead angle also directs the cutting forces in the axial direction, pushing up into the spindle, which is more stable and easier on the machine. Higher lead angles create thicker chips requiring less adjustment in feedrate. They also produce more radial force causing vibration and stress on the spindle bearings.
   
   3. Insert Grade
   Make sure you have the right insert grade for your job because you don’t want your tool to fail prematurely, especially if you’re performing a lights-out operation. Choosing the correct insert grade for the type of material you are machining can increase tool predictability, resulting in fewer tool changes, less rejects and less reworking.
   
   4. Machining Application
   Not every machining method is created equal. While high-feed mills with long overhangs are great, for high-speed options for milling processes, you need to remember you can’t run them as fast as you would tools with shorter overhangs without adding specialized vibration dampening toolholders or reducing cutting speed. When a tool with long overhang operates faster than it should, you can experience increased vibrations, causing insert chipping and premature insert failure.
   
   5. Programming
   Optimize the cutter path through proper programming, so you don’t put any unrealistic demands on the cutting tool. For example, when you are in a mold and come to a corner, changing directions without using a smooth transition is very hard on a tool because it creates a large angle of engagement. A good rule of thumb is to program an arc that is 50 percent larger than the cutter diameter. If using a 2.0” cutter, program a 3” diameter arc. Programming an arc in pocket corners reduces the angle of engagement and avoids overloading the cutter. Machine tools can also have problems in this area because several calculations are involved in generating an arc. If the machine tool can’t properly calculate the arc, the toolpath can become erratic.
   
   6. Engaged Tools
   Keep your high-feed mills as engaged as possible across the full diameter or less than half the insert width. One of the reasons these mills work so well is because their cutting forces are directed at the machine spindle in the axial direction to create balance. If you use the same cutter and only engage it 50 or 60 percent of the diameter, you will experience push and increased vibrations because the cut is unbalanced.

(Source: 6 Ways to Optimize High-Feed Milling)

When selecting the appropriate tool for any roughing applications, consider these key factors.

On old, large, robust machines that are more than 10 years old, standard 90-degree, square shoulder cutting tools often achieve the best metal removal rate (MRR). These cutting tools can handle a heavy depth of cut (DOC) and do not require the high feed rates of some newer cutting tools. Tougher grades of carbide are required, as they provide good resistance to the shock and lack of rigidity that is common in older machines.

New, large, robust machines that are fewer than 10 years old typically achieve optimum MRR with high-feed or button milling tools that are designed to run at higher feed rates with lower DOC than 90-degree cutting tools. High-feed and button milling tools require a machine and control that can quickly process programming information, as well as axis motors capable of smoothly executing rapid changes in direction. A button cutter supports a heavier DOC range, while a high-feed system uses fast feed rates better. A large, powerful, rigid machine is better off with a high-feed cutting tool system, as it can handle heavier DOC than a smaller cutting tool solution. Tools with mid-hardness grades of carbide work well here, as the newer machine’s rigidity often provides more uniform tool pressure, which makes it possible to run a longer-lasting, harder grade of carbide for more extended periods of time before indexing is required.

Old, small, light-duty machines that are more than 10 years old lack rigidity and processing speed. For these machines, button cutters with small diameters of 2 inches or less are often the optimal choice. Button cutters are capable of higher feed rates, but they do not require higher feed rates to succeed. Choose a DOC that the machine handles well and as much feed rate as the machine and control can accept without losing accuracy or repeatability. Tough-grade carbide inserts may help overcome any lingering rigidity issues.

New, small, light-duty machines that are fewer than 10 years old are common in mold and die work. The most affordable are 40-taper machines, and while generally not well suited to heavy cuts, modern machines are capable of feed rates that go well into the range of hundreds of inches per minute. Therefore, high-feed cutting tools are the best choice most of the time, as they operate at a light DOC and feed rates of 200–300 ipm. This helps increase metal removal rates and lengthen tool life. A controlled, rigid cut on a newer machine should support a mid-hardness, high-performance grade of carbide and yield greater tool life (or number of minutes in the cut) before indexing.

(Source: Taking the Guesswork out of Cutting Tool Selection)

The lead angle of your cutter has a dramatic effect on not only the chip that you generate, but also the cutting forces in both the axial and the radial directions. All of this can affect your overall productivity. There are many milling lead angle concepts on the market today and each is designed to perform a specific task.

A square shoulder cutter produces the majority of its cutting forces in the radial direction, making this design best suited for not only a square shoulder, but machining components where vibration could be an issue.

With the square shoulder cutter, you get no chip-thinning effect. The programmed feed rate per tooth is exactly equal to the actual chip thickness. This makes a square shoulder milling cutter a smart choice for components with thin surfaces, in cases where you have unstable fixturing; machines having weaker spindles; and, of course, when you need to produce a 90-degree shoulder.

Of note, the 90-degree lead angle is commonly used in face milling. It can easily perform the task, but it’s not commonly the most productive or cost-effective choice. A cutter with a 45-degree lead angle should be your first choice for face milling.

An important rule to remember is that as the lead angle of your cutter decreases, so does the chip thickness. Due to this, you have the opportunity to increase your feed rate to compensate. This makes the 45-degree lead angle cutter a smart choice for general-purpose face milling operations, reducing vibration on long overhangs and machining short chipping materials—such as grey cast iron.

Today, many companies are using a strategy employing light cutting depths at very high feed rates. Using a very small lead angle—such as 10 degrees—should be your first choice in machining with low depths of cut.

(Source: How to Optimize Moldmaking Milling Operations)

Mold builders encounter many challenges when deep-hole drilling, including hole straightness, poor cutting tool life and excessive time spent in the hole. Troubleshooting these challenges requires a look at correct coolant flow, pressure and chip evacuation but begins with understanding the limitations of the cutting tools, toolholders and machines.

Time—whether spent in the hole, changing out drills or completing the job—significantly impacts holemaking in moldmaking. Specifically, increasing speeds and feeds influence the time spent machining. Often, shops are using outdated cutting tools simply because they are the tools they are comfortable with, and they are the supply on hand.

Whether you are using twist drills or refurbished indexable carbide drills, the extra time you spend resharpening and setting up the tooling often counteracts any added benefit you may have gained with low-cost tooling. So, to improve cost per hole and throughput, keep up with new cutting tool innovations.

(Source: How to Overcome Deep-Hole Drilling Obstacles in Mold Machining)

Depending on the specific application of the customer, it will be possible to find the perfect toolholding system as the different systems offer different technical features and advantages. We will concentrate on the following four kinds of toolholders: (1) hydraulic toolholders, (2) toolholders for polygonal clamping, (3) universal toolholders and (4) heat shrinking holders.

Hydraulic Toolholders

Special toolholding solutions are applied for particular customer solutions. There is one toolholder that can be applied for most of the applications—a hydraulic toolholder.

A hydraulic toolholder uses a different way of clamping the cutting tool compared to systems of conventional toolholders. Introduction of force is done via a screw (with a screw, a piston and sealing). By actuating (turning) the screw, an even hydraulic pressure is generated inside the toolholder. This pressure is transmitted via a steel expansion sleeve, which clamps the tool.

With this clamping system, best run-out accuracy and a repeatability of less than 0.003 mm (0.00012”) are achieved. As the cutting tool is held in a hydraulic chamber, the toolholder offers superior damping effects, due to the oil in the holder. The user gets a higher surface quality of the workpiece and higher up-times of the toolholder as small eruptions of material, as a result of vibrations of the cutter, are avoided.

These toolholders are not only maintenance-free and resistant against dirt, but they also are easy to use and offer a safe clamping of the cutting tool.

Toolholders for Polygonal Clamping

The polygonal clamping system is one of those highly engineered devices that is surprisingly simple: a ground polygon-shaped bore rigidly clamps a cutting tool in three places.

For high-speed applications, polygonal clamping is a great solution since the clamping of the tool shank is done by the elastic deformation of the holder. The main advantage of these toolholders is its extremely slim design.

There are two versions available on the market to cover different applications. A slim version of the toolholder, which stands out with its extremely slim design of the tool shank and its long reach of the tool. It is even possible to use shorter cutting tools with this holder, which in return, results in lower costs for the user. The rigid version of the toolholder has a bigger, and therefore, stiffer body of the holder and offers better qualities with regard to radial force compensation. Both versions can be used with long extensions, which make them even more flexible for difficult machining tasks.

Clamping of the tool or an extension is done within the elastic range of the material of the tool shank. Therefore, there are no restrictions with regard to the lifetime of the tool. Changing a tool can be done within seconds by using an external clamping device. This device does not need any external power source and therefore can be used anywhere. This fact makes polygonal clamping systems very interesting for applications that require a frequent tool change.

Universal Toolholder

The third toolholding system to be discussed are universal toolholders. With two choices available—one for light-duty applications and one for medium- to heavy-duty applications—users have the possibility to gain the very important advantage of vibration damping for improved tool life and workpiece surface finish at a price point competitive with most high-end colleted toolholder systems.

These toolholders clamp tools using expansion technology similar to hydraulic toolholders, only the expansion is achieved via mechanical means instead of through a hydraulic fluid medium. This results in a toolholder system that provides the user with vibration damping and high runout accuracy—less than 0.005mm measured at the face of the toolholder

Additional features of universal toolholders—when compared to colleted-style toolholder systems—are the ability to tighten the toolholders to a hard stop (no torque wrenches are required); a tight and secure clamping of the entire shank of the round tool (collets clamp more tightly near the nose of the toolholder and less tightly at the bottom of the clamping bore); flexible clamping through the use of standard intermediate sleeves; and, very accurate axial length adjustment through the use of an internal length adjustment screw.

Heat Shrinking Technology

The fourth toolholding system to note is heat shrinking technology (see Figure 4). This technology is based on heating up and cooling down a toolholder through induction technology.

An induction coil—with some units using a high frequency coil—heats up the toolholder precisely at the area where the tool has to be inserted. After inserting the cutting tool, you need to cool the toolholder, which can be done via a cooling jacket. Cooling down the toolholder will cause the holder to shrink around the cutting tool shank. In this way, the cutting tool is clamped and offers a force conclusive grip, which allows high torques.

The result of the shrinking process is an almost homogeneous tool with many advantages. Main benefits of the heat shrinking technology include high run-out accuracy of less than 0.003 mm, high transmissible torques and a relatively slim toolholder design. If it comes to vibration dampening, hydraulic toolholders or polygonal toolholders offer better qualities than heat shrinking toolholders.

(Source: How to Choose the Right Toolholder)

CAM software, as it relates to tool life, does two things: it controls the tool motion and the entry and exit of the workpiece material. The traditional way of driving machines using older algorithms have been superseded by newer tool motion using advanced algorithms—a technique that removes large amounts of material quickly using a dynamic milling motion that constantly adjusts the toolpath, ensuring the most efficient cut possible. It allows use of the entire flute length of the cutting tool, often eliminating multiple depth cuts. Large, aggressive cuts are followed by fast, smaller up-cuts. A single toolpath can cut material in two directions: on step-downs (-Z) and step-ups (+Z), which removes the maximum amount of material with the minimum of step-downs, significantly reducing cycle times and leaves the part closer to near net shape for subsequent finishing operations. Likewise new finishing techniques blend two efficient cutting techniques in a single toolpath. This toolpath evaluates the model and smoothly switches between constant Z cutting and constant scallop machining. The result is a finer finish, less work, and less tool wear. Other new dynamic milling techniques help promote tool efficiency during cleanup routines. Another uses high-speed contouring to remove material along walls. It supports multi-passes and can include finishing passes where it determines there is more stock to remove. Newer CAM software seems to truly “understand” where the stock is and the best way to remove it to avoid cutting tool abuse. How you enter and exit material has a profound effect on tool life. Using the older toolpaths, machinists would often come straight into the material. That entry has tremendous impact on the tool and shortens its life. That shock causes micro fissures and cracks. The best practice now is to come in with an arc motion. It’s a gentler way of initiating the approach and cut. Turning operations also have new toolpaths that are helping users get the most out of their turning/grooving tools. There are gains in efficiency and surface finish, and the user also attains the benefit of completing an area using only one tool versus two or three tools. (Source: How to Lengthen Tool Life with CAM Software Moves)

The first step to finding a toolholder that suits your specific needs is a careful evaluation of the machining environment. Shops dealing with the upper limits of accuracy requirements will most likely focus on hydraulic, shrink-fit and collet systems. Far more common are those that need to hold tolerances in the 0.0005" to 0.001" range. For these manufacturers, the precision, repeatability and versatility of ER collets make them an extremely wise choice. Though visual evaluation is helpful in discerning good systems from bad, it is only the first step in successful evaluation. Flaws in the manufacturing process often result in the production of systems that are superficially sound but unable to withstand the rigors of the machining processes. These defects frequently result in breakdowns and increased costs for mold shops that thought they were getting a good deal. Though many red flags exist to help buyers avoid flawed products, there are really only two guaranteed proofs of an ER collet’s quality: repeatability and time. (Source: Selecting the Best Toolholding Solution for Your Shop)

When considering all of the technologies being put to use on a daily basis for the machining of dies and molds, the cutting tool is one of the least expensive, but most highly scrutinized purchases that a company makes. As employees, we need to learn the basics of justifying an investment to an owner or someone responsible for purchasing. As owners, we need to look at the entire picture—there’s more to determining the value of a cutting tool (or any technology) than simply considering its price, and that the right question is not, “What is the price”, it’s how much can I make by implementing this technology? Cutting tool investments can provide companies a return of investment very quickly. The implementation of new cutting tool technology also will result in tool cost savings. Cutting tool manufacturers that implement the latest technologies in the development of their cutting tools are able to provide more economical solutions by creating stronger cutting tools and inserts. Much of these advancements are made possible by utilizing the latest pressing techniques (pressing of the carbide insert), enabling the creation of stronger tools and inserts that have more cutting edges, making better use of the carbide. The introduction of a new cutting tool technology doesn’t need to be complicated, and companies will usually benefit immediately when making the upgrade. It’s as simple as developing a working relationship/partnership with those specializing in cutting tools who are exposed to a great number of applications and can be a valuable resource for keeping up to date with newly released technology. (Source: Determining the Value Of Your Cutting Tool)