Quantum Improvements in Productivity, Capability

Modulation-Assisted Machining (MAM) forms an intermittent gap between the tool cutting edge and the workpiece that is increasing and changing machining cycles.

In the heart of the Midwest, a manufacturing start-up founded by a small group of engineers and entrepreneurs is commercializing a new manufacturing technology that, they believe, will have a revolutionary impact on machining. Their technology, known as Modulation-Assisted Machining (MAM), fundamentally changes the physics of the metalcutting process. By forming an intermittent gap between the cutting tool and the workpiece, this converts the otherwise continuous cutting processes - such as drilling, boring, grooving, trepanning and turning - into a series of discrete cutting events with controllable chip formation and improved effectiveness of machining fluids.

M4 Sciences first commercial product, the TriboMAM, addresses centerline drilling performance in compact and Swiss-type CNC lathes. The basic concept is that the TriboMAM superimposes a low frequency oscillation (up to 1,000 cycles per second) on the drill tool in the feed direction and fully disengages from cut several hundreds of times per second. The controlled oscillation with the TriboMAM drilling device enables MAM technology and allows the technology to be transferred to commercial applications.

"With MAM, there is no such thing as a stringy chip. Every chip is tiny and has the exact same shape as the chip before it and the chip after it. Not only is chip control dramatically improved, but each time the tool is disengaged from cut, the cutting edge is coated with fluid. With MAM, every chip is produced with a lubricated cutting tool," says Jeff Bougher, president of M4 Sciences.

While the concept of vibrating tools is nothing new, M4 Sciences' approach involves the application of low frequency oscillations that are in the audible range and with amplitudes on the order of 100&mirco;m. The company is loathe to use the word "vibrate" to describe the technology and describes the patent pending process as a smooth and controlled oscillation of the cutting edge.

"The tool oscillates smoothly, and the motion is controlled almost to nanometer resolution. The cutting is also smooth and always takes place on the cutting edge of the tool. Modulation introduces less vibration into the machine than the coolant pump, and much less than a live milling tool or an interrupted cut," Bougher explains.

This was not always the case. When MAM research began more than a decade ago at Purdue University, it involved a large converted vertical mill. The potential of the process has always been evident, with industriallyfunded research by companies including Ford Motor Company, Boeing, Caterpillar, Rolls Royce and Diamond Innovations. When James Mann, CEO M4 Sciences, left his role as VP of Engineering with an Indiana manufacturing company to pursue his PhD in engineering at Purdue, he recognized the potential of the technology, and simultaneously the limits inherent with the large and dedicated machine that served as the research platform at the University.

Based on his industry experience, Mann understood that manufacturers who produced components requiring precision drilled holes were under intense pressure to reduce product cost, improve quality and shorten delivery times. In many cases, components were drilled at reduced production rates, or with additional operations that increased production cost and imposed constraints on new product designs. He also knew that the problem was compounded by high performance materials that are extremely difficult to machine, including metal alloys such as titanium, tantalum, stainless steel and Inconel.

Mann approached the technology development by posing a direct method for controlling the motion of the cutting tool itself, thereby reducing the local mass and related intertia of moving machine elements. "By incorporating the MAM technology directly into a tool holder, it was possible to design MAM directly into a small tool holder that could enable the technology across a range of machining platforms," Mann explains. The result was the patent pending technology and invention, authored by Mann and his colleagues Dr. S. Chandrasekar and Dr. W. Dale Compton at Purdue University, which is now being commercialized by M4 Sciences.

MAM TECHNOLOGY

The piezo actuator based TriboMAM toolholder fits in your hand, weighs less than one pound, and is operated by an external digital controller that requires only four operating process variables (spindle speed, drill feedrate, number of drill flutes and drill diameter).

Another objective of M4 Sciences design was that the TriboMAM needed to be simple to install. Today, this has been accomplished with most installations requiring less than an hour to complete, with no modifications to the existing machine tool.

"The TriboMAM is really easy to install since it is basically just a powered toolholder. All you do is remove your existing toolholder and replace it with ours. The power cable needs to be routed to the controller, which can be placed onto or near the machine. At that point, you are pretty much ready to go," Bougher explains.

TriboMAM toolholder and the external controller

The results of MAM are compelling and the company has several case studies documented on their website.

In one case, a customer was drilling a 0.32mm diameter hole 2.5mm deep in 4140 steel. Given the very small diameter, only flood coolant was used and a drilling peck cycle was required. In addition, the customer changed this small drill every 250 parts, while the other process tooling was changed every 500 parts. After installing the TriboMAM, the peck cycle was removed, which cut the drilling cycle time in half and the tool life was more than doubled.

The new MAM process eliminated the mid-process tool change.

In another case, a customer was gun drilling a European chrome alloy, 16MnCrS5Pb, on a Swiss-type lathe.

In this well developed application, the customer was drilling a 3.2mm diameter hole 46mm deep using a single flute carbide gun drill running at 0.020mm/rev with high pressure through tool coolant. After installing the TriboMAM, feedrates were increase up to 0.075mm - almost a four time increase in drill feedrate. Even at these extreme conditions, the chips with MAM were significantly smaller and easier to eject from the hole than those at the base rate.

A look at stringy chips produced by traditional metalcutting techniques (left) compared to precisely-shaped chips produced using M4 Sciences' Modulation- Assisted Machining TriboMAM (right).

In yet another case, a baseline process for drilling a 3.2mm diameter centerline hole in a titanium allows orthopedic bone screw (Ti6Al4V) used a single flute gun drill at a feedrate of 0.016mm/rev. After application of MAM, a sustainable two-time increase in feedrate of 0.032mm/rev was achieved.

M4 Sciences
West Lafayette, IN
m4sciences.com