How to Mitigate Chatter to Boost Machining Rates

Every machinist knows about milling tool chatter. How it sounds. What it does to surface finish. How it diminishes tool life. When it happens, the first reaction is to turn down the feed rate. While that usually works, there is often a much better solution where the milling process stabilizes at significantly higher machining rates.

How do you find that “sweet spot” of cutting parameters that delivers the best machining process? Historically, it was a matter of trial and error. Now it can be done in a matter of minutes with technology that can analyze the vibration signature of any machine-tooling combination and decipher optimal machining parameters. With this approach, you can improve machining efficiency several times over while achieving exceptionally high-quality output.

Though machining vibration analysis technology has been proven for over 20 years, it has only recently become broadly accessible to any shop via the MSC MillMax® Service from MSC Industrial Supply. With it, an MSC Metalworking Specialist will come to your shop and test specific combinations of tool, toolholder, and machine to quickly determine the right feeds and speeds to drive that tool to maximum effect. With this method, an MSC Metalworking Specialist can quickly help any shop achieve its objectives of shorter cycle times, better surface finishes and accuracy, or longer tool life.

How the MillMax Service Works

The test to identify optimal process parameters for a machine tool system is quick and relatively simple. A small sensor is placed on the end of a cutting tool on the milling machine. When the tool is tapped with an instrument hammer the force of the impact and the tool’s vibration frequency response are recorded and fed into software that automatically analyzes the data and determines the vibration signature of that specific combination of tool, toolholder and machine.

The MSC MillMax software includes a dashboard with an interactive speedometer, along with a picture of the tool and corresponding sliders that allow the user to experiment with the axial and radial depth of cut in search of the best possible material removal rate.  Whenever the engagement is altered, the dashboard automatically adjusts to find the relative speed zones where chatter will not occur.

This test is typically performed for the shop by an MSC Metalworking Specialist. Once the measurements are complete the dashboard is literally generated in seconds. The Metalworking Specialist can then help guide the user to the most optimal process parameters based on the goal(s) of reducing cycle time, raising quality or extending tool life.
 

One of the great aspects of this process is that it does not require a shop to tie up a machine for an extended period of time. When a test is requested, the Specialist will reach out to collect information about the application, the machine, and the cutting tool before (or sometimes after) the test in order to optimize time on site and limit the disruption on the shop floor to a minimum. The test is typically performed in 15 minutes or less.
 

The Results

A great many of MillMax tests have been conducted in the field across a variety of industries and have delivered astonishing results. For example:

• In a key application, Aerospace manufacturer Ascentec Engineering increased metal removal rate (MRR) by 300% and reduced cycle time by 80%, for a 410% gain in productivity.
• Job shop and forge tooling maker Gemini Precision Machining improved MRR by 30% while achieving a 30% increase in tool life.
• Air compressor manufacturer VMAC Global Technology increased speed by 18% and feedrate by 122% to achieve a 121% increase in MRR. That change reclaimed 183 machine hours per year and enabled a 9% increase in capacity.

There are many such examples across a wide range of industries and applications including aerospace, automotive, medical, defense and a variety of job shops. Overall average gains run as high as:

• 200% increase in feed rates
• 300% increase in metal removal rates
• 50% decrease in cycle times
• 100 hours of annual capacity gained per successful test.
   

Where to Use MillMax

It is important to understand that the MillMax test must be conducted on a specific combination of machine, toolholder and tool. Given that, it’s not practical or even desirable to test every tool combination in the bin. The key is to select applications that deliver the best return.

If you get an order for 10 parts and may never see it again, process optimization is not the issue. But for longer runs and repeating jobs, the time invested in process optimization can pay for itself many times over. The best applications for MillMax are heavy or long roughing cycles and long finishing cycles where improving a single tool’s efficiency can have a major impact on total cycle time. It’s particularly well suited for tools with high length-to-width ratios.

An effective strategy some shops apply is to select a limited common set of tools, say, for roughing, which many shops do anyway. With just a few tap tests you can generate a comprehensive set of dashboards to cover most if not all of a shop’s roughing toolpaths. Even if this prevents using an optimal tool for a given application, the benefits in overall improved metal removal rates are far worth the occasional compromise.
 

Your Metalworking Expert

While MillMax is an extraordinary tool for vibration detection and analysis, MSC emphasizes that it is their Metalworking Specialists applying the tool that enables shops to achieve their total improvement objectives. That can involve much more than performing a tap test. According to MSC Metalworking Specialist, Matt Hagopian, “For some customers it’s just a matter of adjusting feeds and speeds. But in other cases we can work on improving radial and axial cutter engagement, finding a better combination of tool and toolholder for the application, and even assist with things like coolants, workholding applications, and programming strategy.”

If all of this sounds expensive, it’s not. MSC most often provides these services for free to their regular customers. With MSC’s growing field support team now approaching 150 Metalworking Specialists located throughout the U.S., that service can now be found somewhere near you.

Please visit the MSC website for more information on MSC MillMax® Service or to request a tap test.