Gunning for deep holes

Guns aren’t the only metal products that require holes with high depth-to-diameter ratios. So the latest generation of UNE series gundrilling machines also can help manufacturers in the automotive, medical, energy, defense and aerospace industries hit production targets.

Made by Unisig in Menomonee Falls, Wisconsin, UNE series machines are billed as a good fit for high-volume/low-mix or low-volume/high-mix manufacturing environments. With five models built from two frame sizes, the UNE series can drill hole diameters from 1.4 mm to 40 mm (0.06" to 1.57") and depths up to 3,000 mm (118"). Two single-spindle models offer maximum hole diameters of 25 mm (0.98") and 40 mm while the three two-spindle models in the series can drill holes up to 12 mm (0.47"), 20 mm (0.79") and 32 mm (1.26") in diameter.

The single main-spindle servomotor delivers enough horsepower for two-spindle machines. When powered in single-spindle mode, however, Unisig points out that these machines can produce larger-diameter holes, allowing shops to add business without adding a machine.

For higher precision, all UNE bases are optimized using finite element analysis and machined on five sides in a single setup. At customer sites, no underlying foundation work is required, which simplifies installation.

Working with a machining center, lathe or Swiss-style machine, UNE series gundrilling machines produce holes with high depth-to-diameter ratios. Image courtesy of Unisig

“The stiffness of the bed is such that (the machines) don’t take any strength from the foundation,” said CEO Anthony Fettig.

For efficient part processing, the compact machines can fit in close to an existing machining center, lathe or Swiss-style machine. Their size also saves valuable floor space and makes it easier to relocate them if necessary.

To simplify integration into a manufacturing cell, all UNE models are robot-ready. The robot-ready package usually includes Ethernet communication capability that allows messages to be passed back and forth between the machine and robot. The package also contains an automatic door that opens in response to a signal from a robot.

Even in manufacturing settings without a robot, the automatic door can be beneficial. For one thing, Fettig said, the automation eliminates the task of opening and closing a machine door, which fatigues operators who do it hundreds of times a day.

Additionally, a possibly surprising advantage of an automatic door is that it can give a big boost to throughput.

In Unisig’s production division, “we had a (long) history of running the same job over and over with manual operation,” Fettig said. “But when we put in the automatic door, we saw a 17% jump in productivity.”

That was because at the end of a cycle, there had been a delay in opening the door when operators responded to a light signal. However, the opening of the automatic door triggered prompt action by operators.

“The automatic door (opening) is a physical thing happening that operators notice,” Fettig said.

Something that sets apart UNE series machines from many others is a programmable coolant delivery system. Unlike pressure-based coolant delivery, this flow-based system is designed to provide the right amount of coolant to the cutting edge of a tool.

“We learned that the pressure of the coolant is secondary in importance because it’s the flow of the coolant that carries chips away, not the pressure,” Fettig said.

Consider an application in which shop personnel need to deliver a lot of coolant to a cutting tool, so they set the coolant pressure to 1,000 psi. But he said they actually have no idea how much flow will be going through the drill.

“If it’s clogged with chips or if the hole in the end is too small or any number of other things, they might only be getting a very small amount of flow through the drill,” Fettig said. In that case, “they’re going to break that drill.”

On the other hand, the UNE’s programmable system ensures that enough energy is put into the process to produce the necessary coolant flow.

“We might say that for a (certain) size drill we want 3 gallons a minute through that tool to carry the chips away — and we don’t care if it takes 200 psi or 2,000 psi to get that flow through the drill,” Fettig said.

Many manufacturers either avoid parts that require gundrilled holes or attempt to produce them with machining centers, which he said harms the production process.

“So we see our machines as a perfect complement to production cells and also as a way to add a (special) capability to your shop,” Fettig said.