Manufacturers are always under pressure to produce more units in less time—that’s true whether you’re an OEM, a Tier-1 supplier or a local job shop. Even when the battle to boost productivity is hard-fought, victory usually comes a percentage point at a time. The reasons boil down to basic physics.
You can improve your speed and feed rates, tweak your workholding or use more durable, longer-lasting tools, but the gains you’ll see from doing so will be incremental at best. That’s not to say these things aren’t worth doing—even incremental gains in efficiency for an order of half a million parts can yield a huge return on investment.
Automation can tip the scales further in your favor, but the gains are still limited by your production processes. Automated loading and unloading of machines will almost certainly increase overall efficiency, but you’re still bound by the minimum cycle times for each operation.
Ideally, you would compress multiple operations into one, but that typically demands a major overhaul to your production line or, at the very least, a new hybrid machine.
Fortunately, when it comes to turning operations, there’s another option.
What is rollFEED Turning?
Turning is one of the oldest manufacturing operations as well as one of the most common. You can make a lot of end-use parts on an inverted vertical lathe, but for applications requiring a particularly high surface finish—such as gears, shafts and crankshafts—manufacturers have had to resort to grinding. In some cases, skiving can be sufficient, but the problem with this approach is that you can’t use it for facing.
Enter rollFEED turning, a new technology developed to produce high surface quality and reduce overall turning cycle time. It’s based on a special insert for machines with live tooling which adds a third axis that moves simultaneously with the X- and Z-axes. As a result, the cutting tool can be “rolled” across the surface of the part, so the point of contact moves progressively along the tool.
“One of my colleagues actually had this idea while he was working on his thesis, “said Philipp Ruckwied, manager of cutting technology at EMAG. “He didn’t go further with it at the time, but then Vandurit came to us two years ago with the same idea, as well as the capability to produce inserts and tool holders. We made the first cuts with Vandurit on our machines and developed the system together.”
Although rollFEED turning is only available on EMAG machines, it’s worth noting that it can be retrofitted to existing EMAG turning centers, depending on the size of the work envelope.
“The latest modular EMAG machines can all be retrofitted for rollFEED turning,” said Ruckwied. “You need live tooling, but it’s also possible to add that as well.” In addition, EMAG can provide specialists with expertise in rollFEED turning to help new users get acclimated to the process.
Advantages of rollFEED Turning
One of the biggest advantages of rollFEED turning is that enables larger working radii, which yield a better surface finish. “It just mathematics: the surface quality will be much better if you have a big radius on the cutting edge,” said Ruckwied. Does that mean you can forgo grinding entirely with rollFEED turning?
“Normally, skiving is the answer if you don’t want to do a grinding operation but still want to achieve high surface quality in a turning operation,” said Ruckwied. “It’s possible to get a similar finish with rollFEED turning, but it’s easier with skiving because that uses a straight cutting edge. The curved cutting edge makes machining more difficult, but the tolerances are also a bit more open.”
Because rollFEED turning introduces an additional axis, it requires more than conventional G-code programming. “We have a simple subroutine which takes all the parametric inputs from the CNC program, like a turning operation, and in the background this cycle translates it to get all the axis controls and change the outputs to get the operation running perfectly,” said Ruckwied.
EMAG worked with Open Mind to develop the CAM software for rollFEED turning, based on the latter company’s hyperMILL technology.
Of course, you can still do conventional turning with a rollFEED-enabled machine—you can even do it with the rollFEED insert. “It’s just a matter of tool holding position,” said Ruckwied, “so you don’t need a tool change. You can dedicate a machine to rollFEED if that’s your best option, but we designed and developed it to be used on a standard turning machine with live tooling.”
In addition to offering better surface quality, rollFEED turning can also provide a significant boost to machining efficiency. According to Ruckwied, rollFEED turning is up to 80 percent faster than conventional turning. “If you don’t need the high surface quality, you can just run the system faster, because you have this big radius on the curved cutting edge,” he said.
As a result of the 3-axis motion, rollFEED turning can also increase production efficiency by way of reduced wear on consumables. “The wear on the inserts is much lower than conventional turning,” said Ruckwied, “because the contact point on the inserts is moving during the B-axis motion, the contact point is very small and fast moving. So, the wear is on the complete cutting action, not just the insert radius.”
rollFEED Turning Applications and Inserts
Although the gains in machining efficiency will likely make rollFEED turning appealing to anyone looking to produce more parts in less time (i.e., anyone in manufacturing), the process was designed with some specific applications in mind.
“You can machine cast iron and hardened parts with relaxed surface requirements at a very fast feed rate; we speed it up to three or four times faster,” said Ruckwied. “It depends on the surface requirements, but for roughing operations, you can use the big radius on the insert to get the surface machined very fast.”
At present, rollFEED turning technology is exclusively offered by EMAG and Vandurit, which applies to the inserts as well. “The inserts can only be ordered from Vandurit or EMAG,” said Ruckwied. “There are two standard inserts, with different carbide and coatings. For inner diameter machining, you typically need a special insert. Today, the ID tool design takes a few weeks, plus the time it takes to manufacture the inserts and the toolholders.”
Fortunately, the rollFEED turning process makes the cost-per-consumable lower than grinding. “The cost per part is much lower compared to grinding,” said Ruckwied. “Plus, when you run the process that fast, together with the low wear on inserts, we’ve done as many as 3,000 parts with one insert.”
Saving Time and Money with rollFEED Turning
For applications with special surface finish requirements, grinding may be the only option. However, if you can achieve the surface finish you need using rollFEED turning, the reduction in capital investment costs can be significant. “From that standpoint—your average lathe vs. your average grinder—it’s about 50 percent of the capital costs,” said Ruckwied. “So, the overall capital investment is significantly less.”
Moreover, additional savings can be found in the coolant filtration system, since rollFEED turning has significantly lower requirements for coolant filtration compared to grinding. “The overall cost of that filtration system is much lower,” said Ruckwied. “There’s also an efficiency gain vs. grinding, from the reduced cycle time. If you’re in a high-volume environment, that means not only a cost savings per unit, but also fewer units required to produce that half a million parts per year.”
EMAG will be demonstrating rollFEED tuning and more during the company’s Technology Day on June 6 and 7. Follow techdays.emag.com to learn more.
EMAG has sponsored this post. All opinions are mine. --Ian Wright