Automating Toolpath Optimization

Some would say that True Mark Engraving Co. of Cleveland, Ohio, goes a bit overboard with its tooling rituals, but according to owner and President Dave Timura, the shop’s meticulous methodology maintains process consistency and ensures no other engraving shop can compete with its quality. To ensure the working life of its cutters, True Mark relies on tooling from Rego-Fix (Indianapolis, Indiana), along with in-house cutting tool grinding and replacing machine tool spindles when they run out as little as 0.0001 inch.

True Mark machines and engraves dies for a wide variety of industries and applications, including valves, high-end fittings and bolt heads. It also produces hot stampers for marking plastic parts such as oven dials, inserted-type dies that mark date codes on products and dies for forging companies. Most of the engraving work involves dies that mark final products. These dies are typically made from tool steels such as D2 and M2, and many of them are tiny and intricate. In fact, some letters/characters are so small it is impossible to read them with the naked eye. Representative of its high-end work is one of the smallest die blanks True Mark produces. This die’s machined letters are no taller than 0.004 inch from top to bottom, while the largest characters on other projects can measure up to 1-inch tall. The engraving process also requires the use of tiny, single-flute, custom-made cutters that must work at zero runout when taking 0.001-inch depths of cut. The shop has several recurring projects, and turnaround times for jobs vary anywhere from two hours to a couple of weeks. Typical lot sizes range from one to six parts, but the shop can take on 300-piece jobs as well.

Mr. Timura says that when he took the helm at True Mark in 1999, business was basically stagnant in terms of new work, profit and any kind of equipment investments, so his first order of business was to improve the shop’s quality and shorten job turnaround times. Now, the company follows very specific procedures when it comes to toolholder usage.

It begins by assigning every one of its toolholders to a specific CNC milling machine. Each machine’s designated group of holders is stored in racks marked with numbers corresponding to that particular machine. Also, the shop’s individual collets each run in a designated holder. Collets do not move from one holder to another, nor do toolholders move from machine to machine. The holders are stored in the same positions, and they are loaded into spindles with brand names facing toward the front of the machine. Additionally, only certain machines run certain-size-diameter toolholders. For example, a machine will never run a 0.25-inch-diameter holder one day then a 0.5-inch-diameter holder the next. Plus, every holder must run through an ultrasonic cleaning system any time it is detached from the spindle or has a cutter removed from it. Machine tool spindle interfaces are thoroughly cleaned as well.

“I admit it. I’m funny about my tooling,” Mr. Timura says. “But in addition to my specific holder procedures, I use only Rego-Fix tooling in my CNC machines and have ever since we transitioned from manual pantograph-type engraving machines to our first of several CNC mills. Once we saw the benefits and how easy the system works, we were hooked.”

True Mark uses Rego-Fix ER collets and the powRgrip (PG) system, which includes holders and tool loading/clamping units. Unlike other clamping systems that use heat or hydraulics to expand the holder, the PG system is designed to use the mechanical properties of the toolholder material to generate high gripping force with runout smaller than 0.0001 inch. Each surface interface, from the toolholder to collet and collet to cutter, is key to a PG holder’s vibration damping and high-transferable-torque capabilities, even after 20,000 cutter exchange cycles.

True Mark’s machining processes typically require smaller-sized cutters, so the company primarily runs PG 10 holders for cutter diameters between 0.0787 and 0.2362 inch. The shop’s largest collets are 0.250 inch in diameter, and machine spindle interfaces vary from HSK 63F to ISO 20 and 30 tapers. The shop has two manual PG clamping units, and programmer/machinist Cassie gravity turning inserts Timura, Mr. Timura’s daughter-in-law, does most of the tool cleaning and tooling setups. However, any of the shop’s four employees can operate the Rego-Fix system when necessary.

Rego-Fix products make up approximately 95 percent of True Mark’s tooling, with the remaining 5 percent consisting of other types of tooling for the shop’s manual machines. Each CNC machine is assigned 15 to 20 Rego-Fix holders—either ER collets or PG holders or both.

“I’ve looked at heat-shrink, and, in my opinion, it takes way too long to load and unload cutters,” Mr. Timura says. “Plus, we need as much working life out of our holders as possible, and heat-shrink only lasts so long. We’ve had most of our Rego-Fix tooling for more than seven years and have yet to replace any of shoulder milling cutters the holders or collets due to wear. Even our very first Rego-Fix holder is still in use. There is a bit more cost involved with the tooling, but it’s a non-issue considering the performance, quality and longevity Rego-Fix brings to the table.”

Mr. Timura checks the shop’s CNC machine spindles dutifully, so he knows how each and every one of them is performing. He says it is typical for him to load a cutter in a factory-prebalanced Rego-Fix holder and get zero runout when checking with a 0.0001-inch-increment indicator. “It’s totally amazing,” he says. “And, if there is runout, I can confidently rule out the Rego-Fix tooling as the cause and go right to checking the spindle itself.”

The engraving process uses the very tip of the cutters, and any surface imperfection or off-center split in a cutter’s geometry worsens at the tip. Therefore, any flaw in the toolholder or the machine tool’s spindle will significantly shorten the cutters’ working lives and ruin an entire engraving job. That’s why True Mark grinds its own solid-carbide, single-edge cutters for engraving die blanks. According to Mr. Timura, the shop sees better performance with the cutters it makes itself. While they may look like a simple 45-degree cutter with a split, the finish and size of the tool points are different than those of off-the-shelf cutters. The shop makes its cutters from 12-foot barstock, which a local grinding shop cuts it to individual tool lengths, and roughs in the general shapes and splits of each tool. True Mark finishes the split and grinds the critical angle of the tool’s cutting edge. For the final step, the company manually polishes each tool to remove any grind lines or waviness, and ensure splits are precisely centered.

Depending on workpiece material and character size, cutter life can range from several hours to mere minutes, with total machining times also varying, the company says. To determine cutter life, the shop examines each finished part under a microscope. This visual information, along with past experience, establishes a reference point for how long cutters will last when processing particular materials and character sizes. With some parts, however, cutter wear is highly visible without a microscope.

The tools at True Mark typically operate at speeds of 25,000 or 30,000 rpm, with some running as fast as 40,000 rpm. Roughing and finishing cutter geometries differ from one another, and most jobs can be completed using a total of four or five cutters.

Some may call the steps it takes extreme, but by grinding its own cutters, following a specific tooling methodology and using Rego-Fix toolholders, True Mark is able to ensure continuous machining precision.

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Xometry Launches E Commerce Website for Tools, Supplies

Exsys Tool Inc. has opened a larger, all-inclusive facility in Monterrey, Mexico. The new facility of Exsys Mexico S. de R.L. de C.V combines a previous sales office and off-site warehouse and repair facility under one roof. The facility will serve as a hub for meeting the growing demands of manufacturers throughout the country and will provide them with modular toolholding systems.

The facility’s location enables the company to work more closely with customers and major machine tool OEMs in Mexico. Exsys’ intention is that customers may benefit from enhanced sales, service and applications support. The facility will also provide those repair services that were previously TCGT Insert exported to the United States or Europe, and with its warehouse space, the company will boost its Mexico WNMG Insert inventory of most frequently ordered products to expedite delivery times to customers.

Cesar Vela, general manager, will manage the new facility.

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Next ACE Machine Tool Training Hub Planned for North Carolina

Shops can benefit in a number of ways by broaching on a CNC lathe. Locking a lathe’s spindle and driving a broaching tool in and out of a workpiece to create keyways and slots increases the number of operations that can be performed in a single chucking on a single machine. This improves feature-to-feature accuracy, reduces the amount of time for handling and setup, and eliminates the need for specialized broaching equipment.

Tools with brazed or replaceable carbide inserts are commonly used for such broaching operations. The latter version offers an advantage in that the insert—not the entire tool—can be replaced after it becomes worn. That way, the tool body can remain installed in the lathe’s turret during insert replacement, making it unnecessary to re-zero the tool after a new insert is installed.

Razorform Tools (Playa Del Rey, California) has a new twist on the replaceable insert concept for broaching tools. Its Razorform tool system is said to be the industry’s first indexable-insert-style broaching tool, providing two cutting edges per High Feed Milling Insert TiN-coated, micro-grain carbide insert. Once one insert edge becomes worn, a machine operator removes two screws securing the sizeable insert to the tool body and flips the insert around to the present the second cutting edge. This design not only decreases tooling cost, but also increases tool life and performance, the company says.

The size and proprietary geometry of the Razorform insert, in addition to the support provided by the tool body, offer stability during the cut to reduce chatter. The force of each longitudinal cut is directed through the middle of the insert and the heat-treated, 4140-steel tool body, which also contributes to overall system rigidity. The inserts are currently available in sizes to create slots from 1/8 to 5/16 inch wide. Custom widths are also available.

The company recommends using Cutting Carbide Inserts coolant during broaching operations primarily to wash chips out of the slot during machining. A typical depth of cut is 0.0015 inch per pass, but smaller depths may be necessary when broaching extremely hard materials.

One early adopter of this broaching tool system for CNC lathes is Baldor Electric, located in Fort Smith, Arkansas. The manufacturer of electric motors had been using brazed-insert tools to machine keyways in 4140 steel workpieces. The company was able to machine 20 to 30 parts per brazed insert. The tool would then have to be removed from the machine and re-sharpened. Now, using the Razorform tool, it is possible to machine 100 parts per insert cutting edge and then index the insert to machine another 100 parts. Because the tool body remains installed in the machine during insert change, the company claims to save 10 to 15 minutes of downtime because it isn’t necessary for an operator to re-zero the tool.

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CNC Grinder Series Supports High Production

M4 Sciences offers its next-generation TriboMAM drilling system based on modulation-assisted Cutting Carbide Inserts machining (MAM) technology. The system is APKT Insert said to enable drilling as much as five times faster than conventional approaches in diameters ranging from 0.2 to 12.0 mm, as well as to provide improved surface finishes. The unit can be integrated into existing machines and processes, and installs in less than one hour, the company says.

The drilling system features a new micro-controller that is half the size of the previous generation, as well as process-level feedback capabilities such as real-time diagnostics and process stability monitoring. The micro-controller monitors the drilling process to increase reliability of CNC machines in applications for the medical, automotive, hydraulic and energy manufacturing sectors.

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New Seal Design Protects Machine Tools Spindles

Thread milling is becoming more popular for a few reasons, says Jamie Rosenberger,? threading tool product manager for Allied Machine and Engineering, manufacturer of holemaking and finishing tools. For one, she says, most new CNC machine tools now offer helical interpolation as a standard feature. (This simultaneous XYZ motion of a spinning thread mill into a part’s hole is required to enable the tool, which has a body diameter that is only a fraction of the hole diameter, to cut the threads.) Therefore, new machinists and programmers who have “cut their teeth” on this type of newer machine tool technology seemingly are more open to considering thread milling as a viable alternative to traditional tapping operations.

In addition, Ms. Rosenberger says thread milling is particularly well-suited WCMT Insert for challenging, expensive materials, such as tool steel, stainless steel and high-temperature alloys. In fact, Allied Machine and Engineering’s new AccuThread T3 line of thread mills was designed specifically for these applications.

She explains that during tapping operations, the tap is completely engaged with the workpiece, which results in a good bit of heat generation because the tap’s cutting edges do not get a chance to cool down and coolant has a tough time reaching them. This is particularly problematic when tapping high-temperature alloys, commonly used for aerospace and oil/gas applications, because those materials resist heat rather than absorb it. As a result, all the heat generated during tapping is directed into the tap. This, combined with the high tool pressure resulting from multiple teeth being engaged with the material, can cause the tap to wear prematurely or even break off in the hole. The latter scenario might require time-consuming rework or cause the workpiece to be scrapped, which can be costly given that threading is typically one of the final machining operations performed on a part. These considerations are what make thread milling more attractive to some shops, especially those threading expensive workpiece materials, even though thread mills are more expensive than taps.

That said, it also can be challenging to machine threads in high-temperature and hardened materials using conventional thread-milling tools that machine a complete thread in one 360-degree helical movement (for example, a thread mill that has a sufficient number of cutting edges to mill the entire thread profile into a 0.75-inch-deep hole in one helical rotation). The high cutting pressure generated because all cutting edges are simultaneously engaged with the material can cause tool deflection and poor thread finish.  

Conversely, Allied Machine and Engineering’s AccuThread T3 solid carbide thread mill with proprietary, multi-layer AM210 PVD coating cuts essentially one thread at a time in a continuous helical motion into a hole, which minimizes tool pressure and the risk of deflection. Although these tools have three teeth, the first performs the bulk of the thread-cutting action and the other two essentially clean the threads it creates. Therefore, there is little cutting pressure on the tool, so deflection typically is not problematic. In addition, during thread milling, the cutting edges have a chance to cool, because they are not constantly in the cut and it is easier for flood coolant to reach them.

What is also advantageous about the AccuThread T3 is that the tool is spun counterclockwise to enable it to perform climb milling as it is moved helically in a clockwise motion down into a hole when creating a right-handed thread. With climb milling, a tool’s cutting edge creates a “thick-to-thin” chip. That is, it forms the thickest part of the chip when it engages with the material and creates the thinner portion of the chip when it exits the cut. This generates less deflection than conventional milling (in which the tool effectively rubs on the material as it engages to create a “thin-to-thick” chip) and results in more effective chip evacuation to minimize chip re-cutting.

Given the benefits that thread milling offers, Ms. Rosenberger says Allied Machine and Engineering still gets questions about how best to leverage this technology. Here, she provides a few tips for shops that are considering thread milling:

• As opposed to tapping, thread milling can provide better hole quality while minimizing the risk of scrapping parts, which is especially important when parts are large and expensive. However, it is not the best threading solution for all applications. Tapping is still typically preferred when producing threads that have length-to-diameter ratios of more than 3:1.

• Think of thread milling like most other machining practices. The more stock to be removed or the more challenging the material, the more passes that may be required. For example, coarse thread pitches might require multiple passes. 

• Climb milling is always preferred to conventional milling due to reduced tool deflection and less generated heat.

• Always use cutter compensation when thread milling. This enables you to control the precise diameter of the thread without risking scrapping the part due to creating a thread diameter that is too large.

• Always use rigid toolholders. During cutting, thread mills experience radial side pressure and should be securely clamped in toolholders such as power milling chucks, hydraulic chucks, shrink-fit holders or end-mill holders. ER collets should not be used for thread milling.

• Don’t spend time writing your own thread-milling routines. Many software packages are available from thread-mill manufacturers, such as Allied Machine and Engineering’s InstaCode, to save you time by providing the code TNMG Insert to you.

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