New vertical machining strategies and technologies help reduce cycle time, increase metal removal rates, and maintain accuracy. There’s nothing quite like having “smart” vertical machining centers (VMCs) with the latest advanced CNCs. While higher speeds and feeds are important, equally vital are strategies such as producing small medical parts with a fine surface finish, or creating a boatload of chips when roughing out large aluminum workpieces for aerospace applications on high-rail gantry machines.
As in all machining operations, purchasing a vertical machining center is a balancing act, with the focus on matching machine choices with budget and product requirements. Accelerating setup, reducing cycle times and improving troubleshooting are key considerations when selecting the appropriate VMC. On the one hand, tooling and production choices are as varied as the requirements of job shops. On the other, higher-volume contract manufacturers have different needs. VMCs are generally a first choice for the former and, more recently, a good option for the latter thanks to greater automation and the ability to slide effortlessly into cellular configurations. How, you might ask, does VMC technology meet the requirements of such a varied cross-section of users in today’s demanding, competitive manufacturing industry? Here are some clues.
Analytics for Interpreting Data
Chiron America Inc. (Charlotte, NC) builds its Chiron brand machines for high-speed operations, Stama machines for more robust milling and heavier cutting, and its Scherer Feinbau line of multifunctional and flexible vertical pickup lathes for turning. Another company division provides turnkey engineering and automation.
Chiron’s VMCs include the FZ single-spindle series and the DZ double-spindle machines, offered in 08, 12, 15, 18, 24 mill models with single or twin spindles in three-axis and five-axis versions with linear drives in all axes. The Stama line includes three-axis and five-axis machines with single-spindle or dual-spindle versions, mill-turns, and long-bed, dual-column machines capable of doing Op 10 and Op 20 on their respective spindles.
“Industry 4.0 enables manufacturers to collect a lot of data for digitally enhanced machining. But collecting data isn’t enough,” Norm Holtzhauer, vice president-engineering for Chiron, said of the company’s analytics software, “We have introduced our Smartline system to give customers tools that enable them to interpret the data and keep it in-house for analysis. They can take it to the cloud later if they so desire.” SmartLine’s condition monitoring module runs off the same computer, checking sensor data to analyze performance for bearings, coolant levels and vibration. Although it has a dashboard display, the data can also be viewed on any connected digital device, such as a smartphone or tablet.
“Most customers who have seen it have liked it and bought it,” Holtzhauer added. “RemoteLine provides distance monitoring of machine tool performance and gives users a chance to initiate troubleshooting over the phone.”
For medical applications, Chiron offers three and five-axis machines with as many as 13 axes of motion with two turning spindles, tilting heads and traveling X, Y and Z axes, as well as milling and drilling spindles. Medical device manufacturers typically select a part and finish it complete. Automation includes a bar feeder on the front and a conveyor on the back. Chiron’s five-axis machines can be integrated with a Variocell automation system that includes a permanent, factory-mounted robot. Initial setup is required, while guarding is included for lights-out or untended machining over weekends. Variocell has a stacker with 25 trays for completed machine parts.
Complete Systems Standard
Doosan Machine Tools America (Pine Brook, NJ) offers vertical machining centers that are complete systems, according to Andy McNamara, director of sales. “We do not offer machines and expect our customers to have to select from a wide variety of options a la carte to achieve their machining requirements. We develop machine technology that improves cycle times by increasing rapid rates, feed rates, and acceleration rates, in a reduced footprint machine. Then we build that capability into the machines as standard,” McNamara said.
Doosan’s vertical machining center lineup includes the third-generation DNM 5700 models, the heavy-duty, box-way Mynx series, and the DMP 500 2SP dual-spindle extension of its DNM line. The DMP features two spindles and two toolchangers in about the same footprint as a single-spindle machine. It is well-suited for automotive production applications.
“One new innovation that was needed for dual-spindle vertical machining is the ability to adjust each spindle slightly with the W axis. This is so fixturing doesn’t have to be perfect from left to right, correcting a former frustration with dual-spindle models,” he explained. Also, a new version of the 15,000-rpm spindle coming from Doosan offers more than just high speed. It also has improved acceleration rates and software programming of high feed rates, while still maintaining accuracy, according to McNamara.
“Our machine condition selection feature allows the user to machine as fast and as accurately as they want,” he said. “If you want to rough out a part very fast and you are less concerned about accuracy, you can select an R1 level condition, which prioritizes speed over accuracy. To show the versatility of this function, the user could rough with an R1, semi-finish with R5 and finish with an R9-10 when ultimate accuracy is required.”
According to McNamara, Doosan’s 15,000-rpm spindle allows users to better utilize small tools, and the ompany supplies larger tool magazines that help match tools with spindle rpm choices. The company has also developed an “Easy Operations” software package for the machines’ FANUC controls. This simplifies CNC functions so that users need only hit a single button, for example, to change a tool, position a table, or perform other functions reducing setup time and the potential for human error. In addition to its standard pallet changers, Doosan developed the DooCell, a small robotic cell that can be connected with two machines: two DNMs or a DNM and a Lynx, for example. Parts are loaded and unloaded by a robot from sliding drawers.
Thermal Control for Die/Mold
Michael Cope, product specialist at Hurco Companies Inc. (Indianapolis, IN), sings the praises of the high-speed programming coupled with higher spindle speeds and more accurate cutting of Hurco’s CNC. This allows molds to be finished in much less time than in the past. For example, Cope stated, Hurco’s UltiMotion motion control technology produces finer surface finishes and shorter and smoother overall machine cycles.
Niche customers for Hurco tend to be high-mix, low-volume moldmakers and job shops for prototyping and other projects. According to Cope, Hurco’s BX40i line of double-column, bridge-style machines will be extended with two planned new models: the BXi 50 and 60. “The BXi series is characterized by thermal stability,” he said. “Coupled with an 18,000-rpm motorized spindle, the series is especially well-suited for die/mold applications.” Cope noted that the BX40i is a bridge-style machine that moves the column over the table with rigid dual-contact HSK toolholders that help reduce machine heat growth. The spindle described above delivers 47 hp (35 kW). There is also a dedicated five-axis trunnion-style version, the BX40Ui.
Hurco’s WinMax control offers conversational shop-floor programming as well as G code and NC programming. Conversational high-speed toolpath routines for pocketing, in a feature called AdaptiPath, allow users to benefit from the same type of roughing algorithms offered by CAD/CAM programs. Pockets are roughed out in a fraction of the time of normal pocketing routines, according to Cope. “AdaptiPath allows the programmer to easily control the amount of material the tool will engage, even in corners,” he said. “This type of toolpath control allows for deeper cuts and faster speeds when pocketing and also offers a rest machining process prior to finishing the pocket.”
Variety of VMC Controls
If manufacturers need specific CNCs to be built into vertical machining centers, Lagun Engineering Co. (Harbor City, CA) offers various choices. “If a factory has standardized on a particular brand—FANUC, Siemens, Heidenhain or any other control—we can customize the machine and will build it with that CNC,” said James Garvey, head of maintenance and Western sales manager.
“We offer a variety of sizes from our 16 × 16 × 16″ [406 × 406 × 406 mm] studio mill all the way up to larger 84 × 120″ [2.13 × 3.05 m], as well as large heavy bed mills. The most popular machine platform is the 48 × 24″ [1.22 × 0.6 m]. It’s important for us to be able to customize with CNCs. Many companies standardize their CNC controls. That makes it easy to move from machine to machine and learn a new machine with a minimum of training. Maintenance departments become familiar with spare parts and can often troubleshoot control problems,” Garvey explained.
Lagun builds vertical machining centers for the aerospace and oil and gas sectors, as well as for moldmaking and general engineering. It also caters to more extreme applications, such as explosion-proof munitions factories and shipbuilding. “Our electrics are UL-inspected and approved, and automation includes pallet changers, rotary tables and FANUC robots,” Garvey continued. “Our big strength is that we listen to what the customer wants and make the changes to the machine. In fact, we converted our vertical machining center platform to vertical grinding centers for a long-time customer.”
Few Lagun VMCs are to be found in the used machine market. “They last too long,” Garvey claimed. “We use the best materials, castings, ballscrews, rotary tables and spindles, even the best bolts. Our machines are reliable to such an extent that we don’t need large [numbers of] service personnel. We train our customers in using the CNC properly and using correct maintenance procedures to keep the machine up and running.”
Small Footprint VMCs
Elsewhere, for those concerned with fixe-axis precision machining in small-footprint platforms, Mazak Corp. (Florence, KY) said it has the solution: the UD 400/5X model. For applications ranging from medical instruments to die and mold components, it has a rigid base and double-column symmetrical construction.
An integral 45,000-rpm HSK-E40 spindle producing 8.5 hp (13.4 kW) has temperature-controlled cooling oil circulating throughout the spindle housing to enable long periods of high-speed operation. Ballscrew core cooling further controls temperature, while 16 sensors detect any other heat emperature changes.
A UD 400/5X tilt/rotary table accommodates workpieces as heavy as 264.55 lb (120 kg) and as large as 15.75″ (400 mm) in diameter and 11.81″ (300 mm) in height, with simultaneous five-axis capability. The table’s B and C axes both utilize direct-drive motors that eliminate vibration and heat buildup while enabling a 60-rpm traverse rate in the B axis and 150 rpm in C. The X, Y and Z-axis travels are 15.75, 21.65 and 13.78″ (400, 550 and 350 mm), respectively.
The UD-400/5X also has scale feedback on all linear and rotary axes and linear guides for smooth movement. Optional features like being able to control the tool nose or the cutting point enable greater optimization and accuracy, while a 40-tool magazine helps parts to be machined in one fixturing. Mazak pairs the UD-400/5X with its Mazatrol SmoothX CNC control, especially for machining dies and molds. Smooth Technology functions in the control include variable acceleration control (VAC) to allow operators to utilize the high-speed linear axes when possible. Seamless Corner Control (SCC) helps optimize acceleration and deceleration around corners, and active vibration control (AVC) minimizes vibration at the program level. These control features all combine to cut cycle time and produce more accurate parts.
Spindle Power Promotes High Metal Removal Rates
What’s a good way to boost metal removal? According to two spindle builders, if a shop matches a high-speed spindle to the task at hand, it can increase metal removal rates (MRR) dramatically.
Fischer USA Inc. (Racine, WI) is focused on developing the highest speed and highest power spindles. One development resulted in an HSK 63, 230-mm diameter, 125-kW, 30,000-rpm spindle that’s being used for high-MRR machining in a monolithic aluminum airframe. That same spindle technology was used by Swedish machine builder Modig to reach record-breaking MRR in 7075 stainless, with a 295-hp (220-kW) spindle achieving removal of 1000 cm3/min and chip volume of 52.3 gal (198 L), according to Doug Kranz, vice president of sales and marketing for Fischer USA.
Kranz stated that Fischer’s new-generation Compact Shaft Cooling (CSC) system provides a thermally stable spindle system. A cooled tool interface and minimum axial shift of the spindle shaft produces high-precision cutting. “The CSC spindle achieves a stable temperature behavior substantially faster than conventional spindles,” improving cutting operations and extending machine life, said Kranz. Since the temperature variation due to speed change is mostly compensated, the spindle can produce better results with reduced rejects, he explained. “For the highest precision machining, we focus on tool center repeatability. Cooling the shaft on the last critical 4″ [101.6 mm] from the shaft face to the tool tip overcomes the limitations of mechanical compensation of the tool.”
When added to conventional milling machines and machining centers, the HES Series of vertical machine spindles from NSK America Corp. (Hoffman Estates, IL) give shops the ability to do high-speed machining, small diameter drilling, and milling with improved surface finishes compared to standard, lower speed OEM spindles, acdelivers up to 50,000 rpm for larger diameter (1/4” max) applications and interfaces with BT, NT, CAT, ST, R8 and HSK shanks. The HES810 spindle focuses on micro-machining with smaller shanks (4 mm max) and allows existing equipment to continuously machine up to 80,000 rpm in nano-machining and optical machining in a variety of materials including carbon composites. NSK America offers the HES-810 motor/spindles in BT, NT, CAT, HSK and ST shanks.The HES810 spindle focuses on micro-machining with smaller shanks (4 mm max) and allows existing equipment to continuously machine up to 80,000 rpm in nano-machining and optical machining in a variety of materials including carbon composites. NSK America offers the HES-810 motor/spindles in BT, NT, CAT, HSK and ST shanks.
In a recent application, the HES510 provided appropriate torque, maintained rpm, and reduced cycle time by 93% (from 5-1/2 hours to 22 minutes) compared to the spindle speeder it replaced for heatsink manufacturer Dau Thermal Solutions, according to NSK America. The company’s high-speed spindles are integrated motor/spindles that use their own motor for spindle rotation. There are no gears that generate heat, vibration, and thermal growth, all of which are detrimental to precision high-speed machining.