Titanium Milling Capabilities Drive
Productivity at Davis Tool

“I remember 15 years ago when every shop wanted to claim they were doing machining titanium --it was a big deal,” says Kevin Brown, program manager of Davis Tool in Hillsboro, Ore. “Today, many are cutting it, but most are relying on outdated technology that’s too slow for time-sensitive and tight-margin jobs. . In aerospace precision machining, slow is not an option.”

Geared-head spindles have been historically used to provide the torque required for titanium milling. Today, some manufacturers are discovering that machining centers with high-torque integral drive spindles are now used for machining titanium with better results. These improvements have led shops like Davis Tool to make the switch, allowing for more flexible and efficient aerospace precision machining.

New Technology for Machining Titanium, Tested

“I’ve been around machine tools for many years, even working as a machine distributor for a major Japanese machine tool manufacturer, so I didn’t just assume the claim that an integral drive spindle can perform in high-torque situations was legitimate,” says Brown. “And because most of our parts are sensitive, non-disclosure aerospace components, we weren’t comfortable sending out samples for a machine manufacturer to test, so we did our own testing to see if this new technology could outperform our current geared-head machines.”

Davis Tool used computer modeling and statistical analysis to compare performance curves of their current geared-head machines versus newer integral drive spindles to determine estimated cut times and the potential efficiency a pallet handling system could provide for their setup. The tests yielded positive results when cutting on a modern machining center with a high-torque integral drive spindle, demonstrating improved acceleration and deceleration rates, increased flexibility, and higher potential tooling speeds due to the 8,000-rpm spindle. Additionally, improved cycle time efficiency in titanium milling resulted from the inclusion of a pallet handling system.

"Testing proved that Makino's M-package high-torque integral drive spindle would be able to out-perform geared-head machines, sometimes by a significant margin," comments Brown. "In fact, we found no performance or efficiency downsides to making the switch. For a shop used to machining titanium with geared-head spindles, that was a surprise."

Two New Machines in a Cell

After testing, Davis Tool purchased two Makino a82Ms and a Makino Machining Complex (MMC2), replacing five geared-head spindle machines. The a82M included a high-torque spindle package designed to handle the demands of titanium milling and other difficult-to-machine materials. This two-machine cell was dedicated to precision machining of complex titanium aerospace components.

Makino’s a82M horizontal machining centers feature 8,000-rpm, 50-hp spindles with 744 foot-pounds (1,009 Nm) of torque and a 43.2-by-32.3-by-40.1-inch work zone. Each of Davis Tool’s a82Ms has a 300-tool magazine.

"Many in our shop refused to believe that two machines could out-perform the five geared-head machines," comments Brown. "We proved that a significantly more efficient machine, combined with an automated pallet handling system like the MMC, eliminates a great deal of wasted time in all areas. The Makinos would have been much faster than our geared-head machines even as stand-alones, but throwing an MMC into the mix added a whole new level of efficiency, eliminating substantial periods of out-of-cut time in our precision aerospace machining."

Since installation, the company has reported higher metal removal rates, increased accuracies, greater throughput, and reduced setup times, with an overall cycle time reduction of 25-50% in titanium milling projects previously run on geared-head spindles

"The metal removal rates of our titanium milling applications are through the roof," says Brown. "In one part we took an 800-pound titanium block and machined it down to 90 pounds in four operations. Total machining time was 100 hours in the a82Ms, when it was over 200 hours in the geared-head spindles. No matter what part we're cutting, we're going faster and more efficiently. We've also saved floor space and increased tool life, all while increasing accuracy."

The new a82M cell takes up half the floor space of the five previous machines, allowing Davis Tool to fit a Makino MCB1310 and pallet handling system into the newly freed space. Achieving twice the metal-removal rate, the shop is spending half the money per cubic inch of metal removed. In addition, parts produced on the a82Ms are holding true position tolerances to 0.003 inches, dimensional tolerances down to 0.0006 inches, and milling surface finishes as fine as 32 micro-inches. These tolerances were unobtainable on their old geared-head machines.

The Move to Automation

Davis Tool has been growing since its inception in 1981 in Ron Davis’ garage, and has grown to $30 million a year, employing over 200 and running three shifts a day.

Davis Tool’s first Makino was purchased in 1987. Their list of Makinos ranges from new to some older workhorses, including two MC1516s, two A55Es in a cell that often machines aluminum, two MCB1310s, and most recently the pair of a82Ms in a cell.

“We know that our competitors are constantly improving, and to stay a leader we must do the same,” says Ron Davis Jr., executive manager. “We invest in new technologies because it makes our shop more productive than others, and because, in the long run, it makes us more efficient and more profitable.”

Included in those technologies is automation. Davis has several automation cells, including three Makino pallet handling systems.

“The programmers and operators have become skilled in automation techniques, customizing the perfect schedule for our job shop environment,” says Davis.

“We realized that running smaller combined quantities in a high-mix, low-volume job shop allowed enough flexibility and throughput to get jobs done quickly. Results were good enough for us to justify three flexible manufacturing systems purchases.”“Before we added the cells, our machines faced a lot of downtime,” says Brown. “After a machine produced a test piece, it sat idle for two or three days sometimes. It was a waste of setup time to set up a machine and take it down only to set it back up again. Since our automated cells can retain multiple setups, the downtime has been significantly reduced. Each new cell is more productive than the machines they replaced and often provides us increased capacity.”

New Opportunities

Before the a82M cell, the shop’s bottleneck was typically the geared-head machines. The new bottleneck is material.

“We’ve gone from a situation where we can’t move the parts through the shop fast enough to waiting on material,” says Brown. “It’s out of our hands, but our production is running at such a pace now that our suppliers can’t keep up with us.”

Having extra bandwidth to produce has opened up Davis Tool’s ability to take on other parts—parts they may have turned away in the past, in fear they’d lose money on the job or not be able to keep the tight schedule required to fulfill the contract.

"It's very hard when you're a shop owner who can't take a job because you're unsure if you can handle it," says Davis. "It's always difficult to guarantee tight delivery times when working with outdated technology. Now that we have a titanium milling cell cranking out parts quickly and a flexible setup that allows us to always be cutting, we're taking on the jobs we hesitated on in the past."

Because the pallet handling system doesn’t have to wait for setup or programming, Davis Tool can always be cutting. The process does not stop when setup or testing is required. In addition, metal-removal rates have increased so dramatically that they’re able to promise jobs with tight lead-times.

"It's always our goal to improve on our process. Adding high torque integral drive spindles in an automated titanium cell is just another example of this," comments Brown. "From here, we're looking at the possibility of adding third and fourth machines to our titanium milling cell and additional pallets. We're running at 95 percent spindle utilization on the cell. If there is a problem, it's that we don't have more a82Ms."