Get the most out of long turning operations

Robots can be applied to VTLs to perform certain tasks like managing automatic tool changers and attachments on the machine. DiPaolo

Machine shops often define large parts differently. For one shop, a 35-in.-dia. component can be huge and well outside of their comfort zone. For another, a 60-in.-dia. part may be quite small in comparison to a 30-ft.-dia., 200-ton part that it has worked on in the past. Regardless of the part size, large parts can be challenging to produce, oftentimes taking hours or days to complete a single operation. When it comes to turning operations on large parts, vertical turning lathes (VTLs) offer some advantages. One of the biggest is that gravity is this machine’s friend. The workpiece is vertically configured and gravity helps hold it in place. In most cases, this setup helps reinforce workholding and process stability, especially as most of the workpiece load is being directed down into the machine base and foundation.

The extremely large, heavy, and sometimes awkwardly shaped components are not only expensive by nature of the workpiece size, they also are expensive to produce due to the extensive amount of time required to move them from one operation to the next. Here are a few tips and tricks to help shops get the most out of a VTL for large part production.

Limit Material Handling

"It’s much more costly to move large parts than small parts around the shop," said Vince D’Alessio, president, Elliott Matsuura Canada, Oakville, Ont. "In doing so, shops should look at equipment that can better handle parts and limit machine downtime."

Examining the entire process for inefficiencies and areas of opportunity can help make the production of large parts better. Standard machining best practices for small parts often can be adapted for large part turning. Shops should think through its process and determine the most effective way to process a part and how it can take advantage of machine features.

"For example, some machine shops can get clever with workholding that will enable it to hold the part on the machine in such a way that it can perform turning on the OD and ID as well as facing, and even turning features on the bottom or hard-to-reach areas of the part," said Nelson Martins, president, DiPaolo Machine Tools, Mississauga, Ont. "This will go a long way towards reducing inefficient non-cutting time."

Another way to limit the downtime associated with material handling is by effectively using machine uptime. Instead of having an operator just sitting and watching the machine, with the right equipment and accessories, he can be setting up the next part or taking a finished part off a pallet.

"With these large components, cleaning the table and setting up another part can take sometimes upwards of a day’s work," said Martins. "That’s a lot of downtime. Having an operator prep for a pallet switch and set everything up in advance can ensure that the machine is up and running again as quickly as possible."

Explore Supplemental Operations

There has been a big shift in machine tool capabilities, large and small, towards done-in-one. Having the ability to put the part on one machine and perform numerous operations can help reduce material handling and increase machine uptime. This is now being adopted on many large VTLs.

"Does the part require milling or grinding in addition to turning operations, or does it require machining on different faces?" asked D’Alessio. "If the answer is yes, then it’s important to determine if the machine can handle the supplemental operations. There is a real push, not only with small parts, but to make large parts completely on one machine. Not all component features will lend themselves to this, but examining the features will give shops a better indication if this is possible."

Today’s VTLs have the capability to integrate numerous operations in addition to turning. A VTL with an added Y-axis can enable milling operations. According to D’Alessio, many of these large parts require grinding, and VTLs can be set up to perform these operations by adding a special attachment. Beyond the common applications, a VTL can be equipped to perform drilling, coping, and even gear cutting using a special head attachment.

Having the ability to put the part on one machine and perform numerous operations can help reduce material handling and increase machine uptime. This is now being adopted on many large VTLs. Elliott Matsuura

"In some cases, a large gear can take a whole shift to set up," said Martins. "If you have to take that extremely large workpiece off the VTL and move it to a gear cutter, you lose upwards of a whole shift. That’s a lot of inefficient time. Having the capability to perform that operation on the lathe is just one way to save a substantial amount of time, and time savings inevitably helps a shop make more money."

Add Automation and Advanced Features

For the most part, large VTLs cannot be run automatically, according to D’Alessio, but instead need to be attended in large part by an operator. However, there are some areas where automation or accessories can be added to limit human intervention.

"Automation can be used to change out tools on the machine so it can be done quickly and efficiently," said D’Alessio. "Certain accessories also can help shops make a complete part in as few operations as possible. For example, a tool changer for both turning and milling tools or an X-axis linear scale to hold size are important. High-pressure coolant is necessary for efficient cutting of the tools, especially because the tools are in the cut for a significant amount of time."

Beyond this, robots also can be applied to VTLs to perform certain tasks. For example, robots make sense for managing automatic tool changers and attachments on the machine.

"We recently installed a VTL that had two robots integrated into it," said Martins. "One of the robots managed the automatic tool changer and is capable of handling different size attachments and tapers. The robot does a better job at managing the variety of tools while automating the whole process, but this machine had a second robot integrated into it for doing an in-process operation to make it more of a lights-out manufacturing experience, as the robot can perform various operations. The machine runs 24 hours per day, but it’s not necessarily attended for all of those 24 hours."

Automation is a great way to maximize machine uptime, and while robots are not always a good option for these large machines, there are instances where they make sense. Shops shouldn’t limit their capabilities because adding a robot to a large VTL isn’t usually done outside of high-production environments. There are many ways to take advantage of automated operations on a machine that produces one part every three to four days, shops just need to be open to exploring them.

Optimize the Process

Beyond automation features, measurement and inspection are especially important to ensure the features on these large, expensive workpieces are performed correctly and the part doesn’t need to be reworked, or worse, scrapped.

"Making large parts on a VTL is one thing, but inspecting them is a whole other side of the process that requires attention," said D’Alessio. "Using proper probing technologies on the machine to ensure that the feature and sizes needed are correct before taking the workpiece off is so important. The last thing any shop wants to do is have to take a large part back to the machine and set it up again to be redone, wast-ing a significant amount of time. Probing and other measuring devices can enhance the productivity on the machine."

Process probing or in-process gauging are extremely common on small machines, but can and should be applied to large part turning. While it certainly has been adopted slowly by manufacturers using VTLs, the most efficient shops are using it.

"When the tool is in the cut for as long as it is, process monitoring of tool wear in the machine can help shops better manage issues," said Martins. "Systems like these allow shops to collect data and information about the lifetime of an insert in a specific process at certain speeds and feeds. Having that information can signal when a tool needs to be changed out and avoid tool failure, getting the machine back up and running with limited downtime.

With the right equipment, like additional pallets and accessories, an operator can be setting up the next part or taking a finished part off one pallet while the machine is running a different component on another pallet. DiPaolo

Having the ability to put the part on one machine and perform numerous operations can help reduce material handling and increase machine uptime.

Productivity levels, overall equipment effectiveness (OEE), and the effective machine usage aren’t always the first things shops think about when turning large parts on a VTL. There is this notion that these applications don’t lend themselves well to productivity gains, but process optimization through data collection and in-process inspection can help shops make better parts more efficiently.

"Shops really have to rethink their approach to large part turning to take advantage of what’s out there," said Martins. "Strategies that work for small parts also can work for large parts as well, and that’s a hard thing for many shops to get behind. At the end of the day, if the shop is cutting the OD of one part for 8 hours or the OD for 800 parts for 8 hours, it is still cutting for 8 hours. And the data and information coming out of that can help drive decision making."

Develop Skills and Training

There is a lot of upfront cost and investment when it comes to large part turning, specifically for shops looking to take advantage of the latest features and technology. Having a deep understanding of applications will help shops better navigate process planning. Having operators that are open to new technologies and interested in learning new skills is necessary.

"However, right now the challenge for people making large parts is finding the skilled workers that know how to work with these large VTLs," said D’Alessio. "There are a lot of people that work in shops that are very comfortable with making parts that maybe fit in the palm of your hand. But when shops start getting into these huge components, they may have the equipment, but it is difficult to not only find workers with the necessary experience, but also retain workers for these types of machines."

No shop wants to have an inexperienced operator take on a project with the challenges associated with large part turning. The cost of the workpiece alone can put pressure on the operator to get it right the first time.

"Operator experience becomes even more crucial as you get into larger parts," said Martins. "A good machinist can make good parts on a bad machine. A bad machinist tends to make bad parts on good machines. That experience is really important, but machinists are creatures of habit. Sometimes they are their own obstacles to learning and implementing new technology, especially if it’s something they’ve been doing for a long time."

Fostering an environment where learning and adaptability are key will help operators push their own boundaries when it comes to adopting new technology and upgrading skill sets. This, along with really understanding machine features and accessories, will make large part turning on VTLs much more efficient.

Elliott Matsuura Canada, www.elliottmachinery.com