The Upside of Vertical Machining Centers

The Upside of Vertical Machining Centers
SME Media February 2022
By Geoff Giordano

Vertical machining center suppliers are looking ahead to 2022 with optimism. They expect increased use of automation and increased awareness of the benefits of machining with more than three-axis equipment.

Getting to more sides of a workpiece in one or two setups is just part of the value proposition of VMCs, according to equipment makers. Automating with a robot in front of the machine, or adding a rotary axis, helps ensure productivity, while an understanding of machine kinematics—how the machine moves over time—is key to reproducibility.

A broad range of choices, from simpler three-axis machines to five-axis—both 3 plus 2 and, to a lesser extent, continuous versions—gives shops a wealth of opportunities to bring VMCs to bear on low- and high-volume runs. And opportunities for producing reshored parts offer yet another incentive.

VMC Business is Good

First of all, despite the uncertainty and muddled policy surrounding the COVID-19 pandemic as it drags into a third year of tumult, demand for VMCs is strong. However, supply is, unsurprisingly, a concern.

“The industry’s pretty hot,” asserted Jeff Wallace, general manager, national engineering for DMG Mori USA in Hoffman Estates, Ill. “We are selling everything that’s not screwed down. We’re selling stuff that is screwed down. The good problem is, we’re selling everything we have; the bad problem is that lead times of four to six weeks have extended to four to six months.”

VMCs are popular across multiple applications, Wallace said, even with “some low-volume production centers where we’re making some simplistic prismatic parts. Even the vertical three-axis machines are in high demand.”

Given workforce shortages that have only been exacerbated by the pandemic, automation of VMCs has become a chief concern.

“Frequently, we see with the verticals that we might retrofit a rotary axis so we can get to more than one side of the part. Customers are looking to automate as much as they can—even automate some of the three-axis vertical machining centers. Adding a rotary axis or even a dual rotary axis to be able to flip the part around and get to the other side so we don’t have to break it out of a vice and take it to another vice—whether in that machine or another machine—is very popular right now. Customers are looking at how they can optimize those VMCs and be able to get more productivity out of them.

“The nice thing about the VMCs is they’re relatively inexpensive and they’re easy to set up. You drop them on the floor, and most have a three-point leveling system. For a customer to get into a VMC, especially for short-run production, is very cost effective. The demand is high across the board for almost all our products—and it’s good for the industry. We’re not the only ones; all the other builders are seeing similar conditions. The pie is pretty big, and I’m glad the industry is healthy.”

Using its ROI calculator, DMG Mori helps illustrate how its VMCs can help shops improve their bottom line—particularly “with all the reshoring going on. We’re seeing a lot of product come back in to the U.S.—low-cost, prismatic parts that we have shopped out across the sea in the past 20 years. Small to medium-size shops have become very efficient at making these commodity components—things a VMC is very well suited to do.

“The caveat there is the manpower and whether you want to automate: Is it sticking a simple robot in front of the machine or putting on the rotary axis? We’ve got an automation group internal to DMG Mori, and the cobots are starting to take off on these VMC platforms. We don’t even have to add something as simple as an air cylinder to the door; we’ll let the robot open the door.” By taking those steps, Wallace said, customers are seeing five percent to six percent production gains.

Multi-axis VMCs are taking greater hold in the U.S., he concluded—exploding, in fact, with DMG Mori seeing a tenfold increase in sales the past couple of years. Europe initially had the edge in adoption, he said, but “in typical American fashion, once we wake up, it’s like, ‘OK, get out of the way.’ America has woken up, again primarily driven by the workforce issues. As people don’t want to do the job or we can’t find talent, how do you minimize that interaction with the machine to make a part? That’s where the multiaxis shines. If I can prep my bar correctly, I may never have to touch that part again until it is complete.”

Facilitating automation is the company’s Celos human-machine interface control, which allows machine operators to quickly manipulate a range of robots to perform various tasks. “We’ve developed applications that, if you set a robot down in front of a machine, the operator does not have to be a robot programmer. There’s a drag-and-drop graphic user interface to help operators program. Our target is to get that technology into the hands of the people so they are not as wary of automation but comfortable with it.”

The VMC Advantage

Generally easier to install, VMCs “are usually up and running in a shorter period of time and offer less interruption in day-to-day business,” explained Mitsui Seiki COO Bill Malanche. “They are also typically smaller in size than many horizontals, reducing the overall use of valuable factory floor space. The design of our machines give shops and large factories more capability in a smaller platform. In our Vertex line of VMCs, the Y-axis offers a bigger stroke than the X-axis making the overall width of the machine smaller. Most VMCs are typically wider than they are deep.”

Over his career, Malanche recalled, he installed dozens of vertical machines in companies across the U.S. and abroad. “To this day I will still occasionally meet a customer at a trade show who remembers me installing their machine, and says that they still have it, and it still holds a couple of tenths.”

Mitsui Seiki emphasizes jig bore-style machines designed to have ultra-high precision in a tight working envelope, he noted, making them ideal for high-dollar, low-volume production.

“We have one customer who is producing intricate aerospace components that require extremely tight tolerances,” Malanche explained. “The vertical machines they are using are producing a family of parts that are designed for not only production but ongoing field support. This environment means that the machines could be used for production parts purposes one day but can unexpectedly be forced to be swapped out to offset field support requirements.

“This customer has qualified machinists producing the parts, but the level of the work is not suited for just hitting ‘cycle start’; the workpieces have numerous integrated bores and process checks that need to be made as the parts are being produced.” That customer started with five Mitsui Seiki VMCs and now has 16 in its operation.

In cases where parts must come off machines for “in- process” CMM inspection to go from operation to operation, Malanche said, “we helped the customer semi-automate the processes, where they could arrange the machines with ‘zero point’ fixture base plates to allow the same parts to be transferred from machine to machine and to the CMM with minimal setup and verification turnaround.”

Sometimes, rather small optional improvements can be made to base line VMCs to help with automation. Items like tool probes and spindle probes can be used to accelerate changeovers, and incorporating highly repeatable zero point base plates can add versatility.

“But I think the biggest advantage comes in having machines that are equipped for five-axis machining,” Malanche asserted. “Even though adding a fifth axis to most VMCs is generally costly up front, the investment is worth it and sometimes paid back quickly with critical applications. The advent of equipping high-precision rotary five-axis tables built into the machine structure allows manufacturers the advantage of even more versatility in process flow.”

Mitsui Seiki has designed its VMC platforms to handle many unique manufacturing challenges, he continued. The company’s baseline five-axis Vertex series are offered in three sizes to handle parts from 500 mm to 1200 mm in diameter. “We have built them with adaptations aimed to address many manufacturing challenges and new methodologies. Our machines are not built on a common platform with just extended ballscrews for bigger strokes; these are built on individual iron castings designed for years of service and life. Our smallest version, the Vertex 550-5X with a 400mm rotary table, weighs 20,000 pounds, and the Vertex 100X is triple that amount. These are not ‘disposable’ VMC machines.”

Vertex machines are built with options such as direct drive-type rotary axis motors needed for improved contour control in the airfoil market, he added. “We have combination platform machines designed for multi-process capability such as additive/subtractive metal deposition, milling and grinding and the high-speed electro erosion process called Blue Arc, which is being licensed through General Electric.” With these options, users are cutting materials including ceramics, graphite, aluminum, titanium, Inconel and more.

This kind of flexibility is helping VMCs reassert their place in the market, where over the years the requirements of higher production, coupled with reduced labor capability, made way for HMCs to take over. “In what seemed a relatively short period of time, the need for VMCs took a back seat to HMCs with bigger tool changers, pallet changers and full-blown flexible manufacturing systems,” Malanche said. “Thirty years ago, most medium to semi-high production shops relied heavily on VMCs for numerous reasons, including setup timing, ease of access, ease of maintenance, availability of skilled workers and product mix. VMCs have regained new life in the high-precision parts making market.”

Machines In Motion

The critical concept of kinematics, or how a machine moves, is something YCM Technology USA in Carson, Calif., stresses with its built-in kinematics calibration for the North American market. Those packages—featuring touch probes and tool-length measurement and tooling balls—will be standard on YMC’s 3 plus 2 or continuous five-axis machines, said Brian Huff, business development manager for the Midwest.

As a machine performs its functions, accuracy can change, Huff noted, and “it’s common that an operator would think the machine’s not accurate or the pickup wasn’t accurate.” Addressing that requires defining centers of rotation for the fourth and fifth axis and being able to calibrate them. Historically, manufacturers might set the center of rotation as part of the machine installation, he said. “If the customer struggles with accuracy, it would require a service call, and they’re coming back in to redefine those centers of rotation—which can be costly. Things happen, machines move, the weight of the workpiece changes—and other dynamics are in play. Some manufacturers have more readily embraced the importance of kinematics calibration. Therefore, our interest is to make it easy for our users and operators; it’s not going to require a service call, and you have the machine at the highest level of accuracy.”

How often should VMCs be calibrated? It could be once a week, once a month, or even daily depending on the application, Huff advised.

“We tell our customers that if you have work that’s more critical and you notice more deviation, run the kinematics program. If you’re running close-tolerance work, run the kinematics; run it before the job, run it daily to be sure. If you’re seeing 0.0005″ deviation over the course of a week, maybe run it weekly.” That translates to 0.0127 mm.

Ideally, Huff would like to “make kinematics a normal conversation” and try to help bridge the gap between the companies that define centers of rotation at installation and those that think that kinematics calibration should be easily accessible and quickly executed. “It’s becoming a way of life for all the manufacturers.”

Another way YCM addresses accuracy is through its partnership with Kessler, whose spindles and heads are appearing on YCM vertical machines to address clamping force for the A and C or B and C axes and maintain rigidity at the tip of the cutting tool. “Our standard spindle on our double column five-axis die-mold machine peaks out at 54 hp,” Huff said, or 40.2 kW. “It’s an HSK 100, with 16,000 RPM, that produces full horsepower at 2,500 RPM. High rigidity, torque, RPM and horsepower makes for a really versatile spindle and head configuration. Our aerospace version goes up to 18,000 RPM, with an HSK 63 spindle producing 94 hp [70 kW], targeted for aluminum machining.” Furthermore, the partnership with Kessler gives YCM a Midwest resource for spindle repair.

YCM Technology is putting particular emphasis on its five-axis machines. While 3 plus 2 configurations are more popular, demand for full five axis is growing, Huff noted. He, too, sees requests for automation increase.

“We’re consistently seeing requests for automation as part of the machine package. It’s not just palletization; we are seeing more acceptance of and interest for pick-and-place automation. It’s a natural fit with five-axis because in many cases you are able, within one or two setups, to machine the entire workpiece complete. Workholding of parts in this case is critical and that you don’t have any interference of fixtures or clamps in the way of the cutter. If you can hold a workpiece from the bottom side and allow five sides to be accessible, that’s ideal. For workholding from the bottom, there are manufacturers that have designed systems that do a great job; we are currently working with companies that offer these types of solutions. Also, we offer palletized automation packages with the YCM machines and are further developing collaborative and pick-and-place automation packages.”

Aiming for High Production

Over the past two to three years, most VMC rollouts by Chiron have been robust, high-volume production platforms designed to meet the machining demands of large automotive and aerospace components, said Business Development Manager Simon Knecht of Chiron America in Charlotte, N.C.

“With these machining centers successfully established and widely available to our North American customers, we’re further strengthening our product portfolio on the opposite end of the manufacturing spectrum: high-precision, micro-machined components,” Knecht said.

This year, Chiron is launching its Micro5 machining center, developed in Switzerland and designed for small workpieces—in the realm of 50×50×50 mm—he said. “The speed and dynamics of this machining concept are designed to support customers with increased productivity. Along with the benchmarks of high speed and minimal moving mass, the machine is a modular platform and can be equipped with integrated automation. Additionally, the Micro5 was engineered for flexible scalability, which gives manufacturers the ability to create seamless production lines with multiple machines.”

VMCs generally are based on a modular concept, he explained; it is common practice to change from fourth- to fifth-axis layout. “Many times, our customers have changed the machine configuration to a different table setting utilizing fourth or fifth axis on the table.”

Like other suppliers, Chiron America is addressing the operator skills gap. Smart automation “is one part of a solution that ensures throughput during planned production hours,” Knecht said. “Automation technologies, especially robots, usually have a high technical availability and run with high reliability. With processes and cells designed for smaller batches, our automation solutions are even capable of changing fixtures in the machine. As opposed to a manual setup, which can often take more than an hour to change the fixtures, automating the VMC with a zero clamping system improves throughput and gets the machine back to what it is designed for: Machining. Our machining table axis configurations are designed to accommodate these clamping methods.”

Trends like the shift toward e-mobility and pandemic-stressed supply chains are demanding more flexibility from equipment—making setup-reducing VMC a critical tool. “The ability to quickly change to a different workpiece on a machine drives the approach to reduce the number of setups and finishing as many operations as possible within the same machine,” Knecht said. Chiron’s integrated workpiece changing enabled part loading and unloading while their five-axis VMCs are running.

Leveraging this flexibility and utilizing a VMC for many different workpieces “will lead to tangible benefits in terms of ROI,” Knecht concluded. “Too many times I have seen dedicated machinery and equipment that sits still following the loss of a job or project, while the manufacturer is unable to utilize the machine to its fullest.”