When manufacturing metal parts, problematic vibrations are common. They affect tool life and surface finish, adding significant time and cost to job completion. Typically, metal parts manufacturers deal with vibration by setting sub-optimal machine parameters, or they use expensive “de-vibe” tools to address such problems. These Tuned Mass Damper (TMD) cutting tools transmit vibration energy of cutting tools to an auxiliary mass damper in the tool body. This energy transfer reduces vibration energy generated by cutting processes.
Supporting elements are made of rubber seal rings whose cross sections can be changed or adjusted to affect tool stiffness, and by extension, tuning frequency. These tools, however, are expensive – typically 10x-100x the price of a conventional tool. Additionally, oil leakage limits TMDs’ product service life to 1 or 2 years, after which the tool needs to be refurbished or replaced. TMDs also need to be tuned at every work shift, prior to cutting new materials or being used under different cutting conditions (speeds, feeds, depth of cut) than the previous job required.
Vibration is most prominent when the overhang length to diameter (L/D) ratio of a tool is high, which is often required to reach into deep pockets, holes or other features of the part being machined. As the part rotates around the tool (turning or lathe operation) or the tool rotates around the part (milling or drilling operation), the resulting action is vibration that yields poor surface finish and requires secondary operations to meet specifications.
With increased pressure to meet productivity goals, having a vibration dampening tool holder that performs correctly without having to be tuned for every shift prior to cutting new materials can provide tangible benefits to metal parts manufacturers. This challenge is becoming more widespread with the increased use of additive manufacturing (3D printing) because the technology requires longer and more flexible tools than ever to reach into relatively complex parts and geometric features.
One such option is a self-tuning mass damper (STMD) that consists of a tungsten mass supported by polymer discs inside the holder. The discs extract vibration energy from the cutting tool body to minimize movement and neutralize vibration by connecting the machine tool motor and the cutting head.
As cutting forces are applied to the tool, vibration occurs naturally on a frequency band, and the stiffness of the STMD self-adjust to that frequency to maximize the mass dampening effect.
STMDs are elegant – ingenious and easy to use – and can improve surface finish, accelerate cycle time, decrease tooling costs and breakage (Total Cost of Ownership), reduce scrap rates and decrease energy consumption.
This plug-and-play solution is an economical alternative to other de-vibe tools, which can cost up to $10K per unit, and can help to reduce the number of damaged parts while improving surface quality and prolonging the life of cutting inserts to help minimize production costs.
By enabling the completion of jobs faster, and more efficiently and economically compared to other options, STMD tool holders, because of their improved feeds and speeds due to stability, eliminate the need for re-programming or re-engineering jobs to compensate for machine inefficiency.
STMDs can integrate seamlessly with processes using a variety of workflows and CAM software solutions because their elegance makes them easy to test and allows them to perform correctly the first time, which improves turnaround.
How STMDs Work
STMDs can be extremely useful for improving speeds and feeds because stabilized tooling yields better results than tooling with extra, unintended movement. Specifically, the tool holder absorbs vibration with a tungsten mass supported by polymer discs inside the STMD. Those polymer discs, made from a proprietary formulation, have a frequency-dependent stiffness which allows them to react and adjust to changes in vibration. Because of their stability, STMDs allow for longest and deepest depth of cut.
STMDs are excellent examples of physics and chemistry working together and solving the complex problem of controlling vibration frequency on cutting tools due to changes in cutting conditions such as tool wear, wearing joints and variation of work piece materials. For those reasons, other kinds of tool holders require optimized tuning to ensure their performance and operating in out-of-tuning condition could make the vibration problem worse instead of improving it.
As for STMDs’ self-tuning properties, they achieve them through the spring elements that adjust stiffness according to vibration frequency, overcoming the problem of frequency changes.
Because all machine tools are different (big, small, long, short, new, old), vibration makes the machine tool’s vibration frequency unpredictable, as various tools vibrate at multiple frequencies. Currently, mass dampers on cutting tools are difficult to use because they are tuned to specific frequencies, or they need frequent turning to ensure vibration dampening efficiency.
In contrast, STMDs contain polymer discs that change their stiffness according to vibration frequency. When frequency is high, stiffness is high, and vice versa. The discs enable the self-tuning function on mass dampers, adapting automatically to machine conditions.
If downtime or re-work because of tool wear, and frequent stopping of machines to re-set dampers are considerations, STMDs can be a sensible alternative to other vibration dampening technologies.
They can also be useful when tool overhang length is a factor because a single tool can handle short and long overhangs alike without requiring a tool change. The result is that jobs take less time and cost less to complete.
Using turning as an example, the tool may be set up for different lengths for machining different parts. The longer the overhang length, the lower the vibration frequency and vice versa. The tool will vibrate at different frequencies, depending upon overhang length, and STMDs over a wider frequency range correlated to L/D ratio.
Research has shown that STMDs can reduce cycle time by 30%, decrease tooling costs by 5%-10%, lower energy consumption by 2%-3% and reduce scrap by 1%-2%. Although some of those percentages are small, given the high volume of machining operations, even the smallest percentage reductions can result in substantial savings.
What’s more, cutting process parameters (speeds and feeds) are conservative, or limited, when the risk of unstable variation is a consideration. When using STMD technology, vibration is a non-issue.
Additionally, when high speed machining excites multiple frequency variations on cutting tools, STMDs adjust themselves to dampen high and low frequencies, so it becomes possible to cut successfully at high speed and feed rates.
Besides manufacturing useful products, we pride ourselves on the support we provide to programmers and manufacturing engineers.
In fact, responsiveness is one of the things that differentiates us from other providers of vibration dampening solutions. If you give us your machine type and machine setup details, we can assist you with using STMDs. In most cases, we will respond within 24 hours because we understand the importance of delivering product on-time, on-spec and on-budget.
By using our STMDs instead of alternative tool holders, you get a helpful partner instead of just another vendor.
The idea for MAQ STMD came from Qilin (pronounced CHILL-in) Fu, our CTO, when he was a doctoral student at KTH Royal Institute of Technology in Stockholm. He studied how vibration affected machining and realized there were opportunities for improvement.
A breakthrough occurred in 2015 when Qilin used existing polymers for accurately measuring a polymer’s frequency-dependent stiffness. He found that some polymers have a substantially increased stiffness when frequency increases.
Eventually, a research team that included Qilin determined that a group of polymers with a specific physical structure and chemistry would have the necessary frequency-dependent stiffness for mass damper applications.
As for the company name, MAQ, it comes from the first names of the three co-founders – Mihai Nicolscu, Amir Rashid and Quilin Fu.
How we came into existence is a prime example of how basic research in an academic lab can lead to a great business idea and a thriving business.
If you have vibration dampening challenges, tell us and we’ll put our expertise to work for you.