Mag offers an integrated contouring head for horizontal boring mills in 1,250 and 1,600 mm (49.1" and 63") table/pallet sizes and live-spindle horizontal machining centers in 800 to 1,600 mm (31.5" to 63") pallet size. The contouring head can produce bottle bores, valve seats, seal faces, phonographic sealing surfaces, O-ring grooves, straight/tapered threads, chamfers, external profiles and other features. It is designed for single-setup rough and finish machining for oil and Coated Inserts gas parts, or other large parts that combine bored, milled and turned features. The head is available with a Kennametal KM80 or Sandvik Coromant Capto C8 tool interface.
The contouring head has a standard tool interface and loads tools via the machine’s automatic toolchanger. An absolute positioning slide handles diameters ranging from 50 to 540 mm (2" to 21") with tools as long as 600 mm (24"). The contouring spindle’s U-axis slide stroke provides the ability to produce small- or large-diameter features without head changing or manual intervention for machining complex features in a single set up. The live boring spindle can use 50 taper tools as long as 750 mm (29.5"). An auto-coupler enables the use of feed-out tools such as programmable boring bars.
The head is designed as a drop-in Carbide Milling Inserts module that can be added during manufacture or later and removed for service without affecting the operation of the boring spindle, the company says. The contouring spindle for both boring mills and HMCs is located immediately above the machine’s main spindle but slightly offset in the Y and W/Z axes to avoid tool interference. Rated power is 56 kW/75 hp on boring mills, and 45 kW/60 hp on HMCs.
Though high-speed machining, be it milling or turning, is one of the hottest topics today, there are many ways to define what it means. Some say it's spindle speeds running over some specified minimum rpm. Others define it as high cutting speeds or feeds, or a combination of the two. Whatever the definition, obviously it's not just a matter of tooling up CNCs with the right cutting tools, then ramping them up, otherwise we'd have nothing to talk about.
We prefer to think in terms of productivity, so high-productivity machining (HPM) is a term we're suggesting for when you optimize both speeds and feeds up to a point of diminishing returns, whether or not those speeds and feeds meet someone else's definition of "high speed machining." The rationale is that higher output is only beneficial if the end result is good parts, minimum rework and near-zero scrap. You also want to be sure you don't get the output at the expense of early retirement of your expensive CNC center due to excessive wear and tear.
There are many factors to consider before you decide whether you are a candidate for HPM. A lot depends on your application, workpiece, material, depth of cut, workload, and so on. The main application areas for HPM today include injection and blow dies and molds, forging dies, prototyping dies and electrodes.
Users have reported successes using materials such as high-alloy tool steels, heat resistant superalloys, bimetal compositions, stainless steel alloys, aluminum, compact graphite iron and copper. Principal beneficiaries of HPM are the aerospace, automotive, electric/electronic and defense industries. As machine shops become more savvy and comfortable with HPM, applications will undoubtedly expand quickly. The purpose of this article is to sort out "friendly" conditions for HPM, then cover the prerequisites in milling tool selection to get maximum output from CNC machining centers.
What are the advantages of HPM?
When you review these benefits, you'll probably question why the HPM fever hasn't caught on over a larger cross-section of industries. To begin answering, consider the life of wheel bearings on a sports-coupe driven at city speeds. Then, compare that to the life of wheel bearings on the same car driven at 200 mph on a high-speed highway. Which will last longer? The analogy to HPM is clear, and the moral is that the advantages also bring disadvantages. So, a number of issues must be addressed. Here are some of them:
Here's what's required on the process side.
Contrary to popular belief, machine tool capabilities are not ahead of tooling where performance is concerned. Both solid and indexable tooling for HPM is already available today. However, it is a question of selecting the right holder, insert, and tool/machine interface. Here are some guidelines:
Sensitive applications, such as milling of thin-walled or hard metal workpieces, can greatly benefit from HPM. Reason is that tool/workpiece engagement time is shorter than with conventional milling, therefore cutting pressure and forces are much reduced (Figures 4 and 5). When feed rates are higher than the time it takes to propagate heat, there is less heat produced in the workpiece (Figure 6). Less heat, in turn, means lower risk of distortion. This is especially important when working with thin walls or hard metals.
Can dry milling also be extended to HPM? For the most part, the same benefits obtainable from turning off the cutting fluid in conventional milling Machining Carbide Inserts applications also apply to HPM. In general, when milling, cutting fluid can do more harm than good, because it increases the thermal shock on cutting edges. To a large degree, most of the cutting fluid converts to steam anyway when it hits the hot cutting zone, so the cooling benefit is lost. Eliminating liquid coolant can boost tool life 25 to 50 percent in many cases and save about 15 to 20 percent in coolant and disposal costs.
However, there are a few exceptions to the cutting fluid "rule" for HPM. Dry machining is not recommended in these situations:
In instances when it is necessary to apply copious amounts of cutting fluid, select a cemented carbide insert with a tough substrate and multilayer coatings. The preferred alternative to liquid coolant is compressed air and oil mist under high pressure Carbide Turning Inserts as the second choice. With cermet, ceramic or cubic boron nitride inserts, coolant should not be considered an option at all.
The key to optimizing capacity lies in keeping big-ticket machinery working, in cutting at optimum rates for the material and, above all, in minimizing idle machine time. It is best to look at the total productivity picture to see the value of optimizing speeds, as well as feeds, without losing part quality or incurring rework or scrap.
Tooling is not an obstacle for those who want to implement high-productivity machining. Rather, users have to apply different tool selection criteria and machining techniques than with conventional milling. Any of today's machining centers will perform as well as its tooling allows. And you can control which tooling goes on that machine.
About the authors. Andy Pitsker is Product Manager Tooling Systems and Steve Piscopo is Product Manager Milling Tools with Sandvik Coromant in Fair Lawn, New Jersey. They can be reached at (201) 794-5000, fax (201) 794-5217.
With a good application and when properly applied, a tool life management system can dramatically increase the output from a CNC machine tool. But I’ve seen quite a bit of misapplication and confusion when it comes to how and where to use these tools. Although it is a short explanation, this column should help you assess the appropriateness of applying a tool life management system to your applications and get you off on the right foot.
When considering whether this Carbide Drilling Inserts system is right for your applications, remember that the ultimate goal of any tool life management system is to keep all tool maintenance offline. Tool maintenance includes any task done to keep tools cutting on size (measuring workpieces and sizing tools) as well as any task performed when tools get dull (tool/insert replacement, remeasuring program zero, trial machining, and more). By doing tool maintenance offline, I mean the task must be done in conjunction with the production run, while the machine is in cycle.
If this can be achieved, tool maintenance being done during a production run will have no effect on cycle time. We define cycle time as the total time it takes to complete a production run divided by the number of usable parts that have been produced. Think about it: In most applications, tool maintenance can Shoulder Milling Inserts add a lot of time to a production run. Many CNCs (especially turning centers) must be down while dull cutting tools are replaced. If you can keep tool maintenance from affecting production run time, jobs will be completed faster and cycle times will be reduced.
How close you can come to achieving this goal depends on many factors. Unless the tool life management system can be applied to several consecutive jobs, the production run must be long enough to require dull tool replacement. For most companies that have small lots to run, this system may not be advantageous.
Also, to move machine maintenance offline, the machine must be designed in such a way that tools can be safely removed and replaced during tool maintenance while the machine is running. If they cannot, you may only be postponing the inevitable.
Consider, for example, a typical CNC turning center that has a 12-station turret. Perhaps a long-running job requires four tools, so there is ample space in the turret to duplicate the tools that wear out the quickest (such as roughing tools). So you double tool the roughing tools in the turret and program the tool life management system to switch to the new roughing tool when the first one gets dull. All you’re really doing is prolonging the time between tool maintenance. Eventually all tools will be dull, and the machine will have to be down during tool maintenance. Though your operator can probably replace all of the tools at one time more quickly than replacing them one at a time, you’re not moving tool maintenance offline.
When the tool life management system detects one or more dull tools, it will alert the operator. The operator will check to see which tools are dull and will note their related station numbers. At the toolchanger magazine, there will be a special switch. When the switch is placed on “manual,” the machine will not allow a tool change, and it will keep track of the current magazine status. The operator can manually rotate the magazine to remove or replace tools. When finished, the operator will place the switch back to “auto,” and the magazine will rotate to its original position.
As you may have guessed, you probably won’t be able to achieve the goal of moving all tool maintenance offline with your existing equipment. Machine functions that contribute to tool life management may have to be factory installed. However, I’m amazed at the number of companies that have perfect applications for a tool life management system but do not even consider one during the purchase of a new machine. Indeed, incorporating the benefits of moving tool maintenance offline in a machine’s justification may make the difference when it comes to being able to justify a new machine purchase.
Also, machine tool builders are getting very good at helping users move tool maintenance offline. Take advantage of this expertise when you purchase your next machine. At the very least, let the builder help you determine whether or not you have an appropriate application for a tool life management system.
The reCool system from Rego-Fix is an alternative to through-coolant-dedicated live tooling heads that enables standard external-coolant live tooling heads to be quickly and easily equipped on turning machine turrets with through-coolant capability. According to the company, the system offers the same benefits as through-the-tool coolant delivery, such as longer tool life, more efficient chip control, reduced heat generation and shorter cycle times. The system accommodates collet sizes ranging from ER 16 to ER 4Lathe Carbide Inserts 0 and is capable of handling cutting speeds ranging to 6,000 rpm while delivering coolant pressures as high as 300 psi. It retrofits onto existing straight and angled live tooling heads with ER outputs.
The reCool system consists of four components: a special clamping nut with outer ring, a coolant pipe, a straight fitting and an elbow fitting. The four kit connectors thread onto most common types of live heads with straight thread holes, and a range of High Feed Milling Insertadapters are available. Through its clamping nut, the system induces a tooling head’s external coolant supply into the collet holder cavity and prevents coolant from seeping back into the internal component of the live tooling head. Coolant serves as a seal and bearing, reducing friction and dissipating heat.
Whipple Superchargers’ more advanced rotor machining process means its power adders have become more potent.
Founded by former race crew chief and car owner Art Whipple in 1987, this Fresno, California, company manufactures twin-screw superchargers for automotive and marine racers and anyone else looking to improve their engine’s performance. As one of a few different types of “power adders,” as they are commonly referred to (turbochargers and nitrous oxide are others), superchargers introduce additional air into an engine beyond what the engine can pull on its own. The more air that can be delivered into the engine, the more fuel that can be proportionally added. That means the engine’s displacement becomes “bigger” than it physically is, producing more horsepower.
The accurate, non-contact meshing of two helical rotors inside a casing is the key for proper function of twin-screw superchargers. With the Whipple design, the male rotor has three helical lobes and the female has four, explains Supercharger Designer Garrett Bright. These rotate counter to each other and extremely closely. As the lobes of each move past air inlet ports, the air becomes trapped between the rotors and casing. Rotor rotation progressively reduces the space the air occupies, compressing it. Compression continues until the inner-lobe RCMX Insert space becomes exposed to an outlet port, through which the air is discharged higher than atmospheric pressure into the intake manifold that sits atop the engine.
Supercharger efficiency depends on how effective sealing is between the mating rotors and the casing. Until recently, Whipple had solely used rotors manufactured and supplied by a European company. It still uses those supplied rotors for some of its supercharger models. However, Whipple has since started to design and machine its own rotors in house, and the machining process it has developed produces more cylindrical and accurate rotors than those its supplier provides. In fact, more precise machining means new supercharger designs are 5% more efficient than those using the supplied rotors.
Getting to this more accurate machining process took time. But with DCMT Insert the help of advanced measurement, machine tool, workholding and tooling technology (and guidance from the companies that make that equipment), Whipple has established a means for not only accurately machining its rotors, but also minimizing changeover times and upping cutting aggressiveness to reduce cycle times.
Mr. Bright says Whipple was spurred to machine its own rotors after seeing the results from precise measurements of its supplier’s rotors taken on its Zeiss Accura coordinate measuring machine (CMM). This CMM features a rotary table as well as Zeiss’ Vast scanning technology and Gear Pro option in its Calypso measuring software. Mr. Bright says this software is particularly effective for measuring mating rotors because he can assign specific control points on the male and female rotor helical profiles where they meet to determine the clearance between the two at those points. Mr. Bright determined that the profile for each rotor should be ±63 microns with the goal of achieving a clearance of approximately 125 microns. The company wasn’t getting that from its rotor vendor.
Whipple’s rotor-machining process using form tools is similar to that of its supplier’s, but with modifications to increase rigidity. The machine Whipple purchased in October 2016 is a Mazak Integrex e-420H-S II turn-mill with B-axis milling head. Cylindrical 6061 aluminum rotor blanks are first center-drilled longitudinally on another machine to enable a steel shaft to be pressed into them. As an operator loads a blank into the Integrex, the machine’s main spindle and then subspindle clamp on the shaft’s protruding journals. Next, the machine’s B axis is drastically tilted to orient a custom form tool that matches the desired flute profile when at that angle (see this story’s opening photo). Finally, the spinning form tool is moved along the Z axis as the rotor is slowly rotated to create each flute in multiple passes. “At this point, what we have here is a high-end, two-axis lathe,” Mr. Bright quips.
Initially, Whipple used extended-length, pull-back-style ER collets to clamp on the shaft journals. The extended length was required to position the blanks away from the subspindle to provide sufficient clearance for the B-axis spindle to tilt as far over the subspindle’s chuck as necessary. However, the pull-back functionality of those collets made loading rotor blanks time-consuming and challenging. Collet tightening (resulting in pullback) put excessive load on the main spindle, meaning the W-axis subspindle had to be trammed-in to help dial-out the load. Otherwise, chatter or poor surface finishes could result. As a result, operators such as Chris Jensen would continually clamp and reclamp until most of the load was eliminated. This typically took 10 minutes. Plus, Whipple was constantly replacing collets due to the wear they experienced being tightened and loosened so many times.
At the advice of Kellen Bush, Mazak’s application engineer who worked with Whipple on this project, the company contacted Hainbuch to devise an alternative workholding approach. Hainbuch Sales Manager Tom Chambers explains that the company’s custom workholding solution not only provides the extended reach required to enable the machine’s B axis to tilt to the requisite angle without interference, but it also offers higher rigidity while simplifying changeovers. This is possible largely because dead-length collets are used instead of pull-back types. Mr. Chambers says dead-length collets “clamp in space,” meaning the rotor blanks will not move when the collets are clamped. As a result, no additional load that would have to be dialed-out is applied to the main spindle. Changeovers now take only 2 minutes.
The Kyocera Unimerco form tools Whipple uses to machine its rotors (as does Whipple’s European supplier) actually are not commonly used for cutting metal. Anders Varga, sales manager for Kyocera Unimerco, says this type of tool is typically used for cutting wood, composites and other fibrous materials. This is primarily due to the amount of pressure that would be exerted on the tool as a result of the high contact area between a metal workpiece and long insert cutting edges. That these tools can be used in this rotor-machining application speaks to the rigidity of the machine with Capto spindle interface and its custom workholding.
Using form tools that match the rotors’ helical flute profile (profiles Mr. Bright has refined) eliminates polishing that might be required if multiple end mills were used to carve the flutes. The rotors are machined so their lobes are as big as possible, but slightly undersized to allow for a subsequent proprietary coating. Whipple typically keeps two roughing tools and three finishing tools on hand for both male and female rotors. The tools use uncoated, micro-grain carbide inserts. The inserts for the roughing tools are attached to the tool bodies via screws; finishing tools are brazed to them.
Not only is Whipple’s machining process achieving the 125-micron clearance goal between mating rotors, but end-to-end rotor cylindricity is more consistent. Mr. Bright says that with the original workholding approach, the difference in cylindricity of one end of a rotor compared to the other might be as high as 10 microns. Now, that has been reduced to 1 micron. Rotor cycle times are a tad faster, too. Cycle times for a male rotor is 14 minutes and a female rotor takes 20 minutes. But for Whipple, this is gravy. Its primary goals were to achieve higher rotor machining precision and speeding changeovers, both of which it has realized.
