Mold Shop Finds Tool Performance Outweighs Price
The RoboGrind CNC tool production center from Excalibur Tool has six CNC machine axes and an integrated Fanuc five-axis industrial robot. The center is designed to produce high-quality cutting tools from solid carbide or HSS, minimizing labor through the use of unattended, “lights out” manufacturing. The center can operate autonomously for as long as 12 hours. The Fanuc LR Mate industrial robot is integrated to the center, so even double-ended tools can be produced automatically with no end chipping, cemented carbide inserts the company says. Having six CNC axes allows the center deep hole drilling inserts to produce end mills, step tools, brazed tools and other special tools in one clamping. An optional telephone dialer can issue an alert to a cellular or home phone when the center needs the tool pallet reloaded, or in the event of a machine fault.
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New Cutting Tool Material For Steel Turning
The Tradesman Machinist variable-speed bench grinder from Cuttermasters produces features typically made with traditional tool and cutter grinders. It is designed to take the place of larger and more expensive tool grinding machines. The grinder, which uses precision-plated superabrasive wheels, can cut off carbide end mills and drills, produce Weldon flats on end-mill shanks, and grind neck reductions on end mills.
The machine’s DC grinding system operates with no loss of torque at speeds ranging from 400 to 4,000 rpm, and the lower rpm prevents heat stress fast feed milling inserts without the use of coolant when cutting off or grinding large neck reductions or producing large flats on carbide tools, the Carbide Drilling Inserts company says.
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Top Ten Tips For Tooling Productivity
I define a CNC machine tool’s accuracy as how precisely its axes can follow intended paths to commanded endpoints while under load. I define its repeatability as how precisely it can duplicate commanded motions (again, under load) during multiple cycles throughout the day.
These are definitions for dynamic accuracy and repeatability. They likely vary from your machine builder’s specifications. Builder specifications commonly Surface Milling Inserts indicate static accuracy and repeatability; that is, the machine is not in cycle performing machining operations when related measurements are taken.
In fairness to machine builders, dynamic accuracy and repeatability vary with the amount of stress exerted on machine components. The greater the stress, the more difficult it is to maintain accuracy and repeatability. This makes it impossible for machine builders to provide, much less guarantee, dynamic accuracy and repeatability specifications. There are simply too many variables.
That said, machine builders should be able to establish whether their machine can achieve accuracy/repeatability requirements for your particular application. They should be willing to guarantee as much if you ask them to do so prior to purchasing a new machine tool.
Certain accuracy-related factors are beyond a CNC user’s control once a machine is installed. These include:
• It must be able to perform the most powerful machining operations in your application without excessive deflection of its support components.
• Linear scales directly monitor the position of the moving component for an axis. Unlike rotary encoders, they are not highly dependent upon the integrity of axis system components (way systems, ballscrews and couplers).
Other accuracy-related factors are the responsibility of the machine user. These include:
• Machine builders initially calibrate pitch error and backlash compensations, but if accuracy is to be maintained, end users must repeat these calibrations at regular intervals during a machine’s life.
• Machine tools must be placed in a stable working environment that minimizes ambient temperature and humidity variations.
Ensuring that a machine installation can provide adequate dynamic accuracy for your application—and keeping it properly maintained—is but half the issue of producing consistent, acceptable components. You must also confirm that the machine can accurately repeat from the first workpiece to the last—hour after hour, day after day—even as machine components warm up after idle periods.
An important repeatability-related issue linked to machine design is thermal variation of moving components. Primary concerns are the machine’s spindle and way systems because they have the biggest impact on machined surfaces. As these components warm, they grow. As they cool, they shrink. This makes it difficult—maybe impossible—to hold size on critical, tight-tolerance surfaces during the machine warm-up period.
Machine builders go to great lengths to minimize thermal changes in machine components (cooling the spindle and/or way systems, for instance). Additionally, they incorporate design methods that minimize the repeatability impact of thermal variation. With CNC turning centers, for example, the headstock may be perpendicular to the bed. As it warms, only the height of the cutting tool’s edge changes. This minimizes the amount of machined diameter variation from part to part as the machine warms up.
When purchasing any new CNC machine, you should understand how the builder deals with thermal variation. More importantly, you must confirm that machined-surface variations caused by thermal growth during warm-up will not exceed tolerances. Otherwise, you could be in for a productivity-wasting surprise when you discover that your new machine must run for a warm-up period before it can be used in production.
Some of the most severe repeatability issues have nothing to do with machine design. Instead, they are influenced by the machine’s application. Variations of any kind—during a production run or from one time a job is run to the next—can impact repeatability. Things that change from cycle to cycle will cause the need for a time-consuming adjustment. If the variation is great enough, it could result in scrap.
Examples of variations during a production run include:
• Tool wear. As cutting edges wear, machined surfaces will vary. External surfaces grow while internal surfaces shrink.
• Dull tool replacement. When dull cutting tools are replaced, extreme caution is required to ensure that cutting edge(s) do not vary from their predetermined position(s).
From one time a job is run to the next include:
• Workholding setup. Many factors affect workpiece stability (placement/alignment of the workholding device, clamp location and force applied, and program zero assignment, for instance).
• Cutting tool Carbide Turning Inserts assembly, measurement and offset entry. Component and assembly variations result in rigidity variations that can lead to machining issues.
• Machine condition. Variations caused by mishaps and the neglect of preventive maintenance can result in sizing problems with jobs that have run successfully in the past.
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NC processing technology
Developed in conjunction with major aircraft builders, Cutting Carbide Inserts Emuge’s Alu-Jet-Cut solid carbide end mills are designed for rapid, large-volume aluminum machining in mold and die, aerospace, automotive and machine tool manufacturing applications. The company says the tools are particularly useful for machining monolithic airframe structural components, which often require removal of as much as 95 percent of the weight of a solid block of material.
The end mills are capable of cutting speeds in excess of 3,000 sfm. A tough, wear-resistant carbide substrate helps resist vibrations that could otherwise lead to premature chipping of cutting edges at high cutting speeds, the company says. Additionally, a chip conveyor (chip breaker) provides control over chip shape and directional flow to increase chip evacuation capacity. This enables stable operations with full radial engagement (slot milling) at 1 × D depth of cut to achieve material removal rates in excess of 650 cubic inches per minute.
According to the company, the tools undergo a specialized grind/polish process that provides a high-quality surface within the flutes to reduce the tendency Carbide Drilling Inserts for aluminum build-up or “cold welding” along the cutting edges. This surface, combined with the cutter’s shear velocity, reduces heat transfer from chip to tool, the company says.
The end mills also feature progressive flute spacing to reduce vibration at high cutting speeds. For increased process safety and reliability, the tools undergo a special surface treatment that roughens the shanks, yet allows them to maintain a narrow h5 tolerance.
The tools are offered in various corner radii, roughing and finishing designs. Roughing cutters are available with three flutes and finishing cutters with three or four flutes. All tools feature coolant-through capability and are well-suited for machining with minimum-quantity lubrication (MQL), the company says.?
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Emuge Micro End Mills and Chucks Tackle High Precision Tasks
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 Tungsten Carbide Inserts 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 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.
Cemented Carbide InsertRego-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 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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