Friday, July 31, 2015

Passive-Aggressive Tooling Approach to Vibration Damping

By Mike Smith, Product Manager – Reaming, Boring and EPB

Steadyline Turning Bars
Long tooling overhangs while machining difficult-to-access part features, such as deep cavities, create perfect conditions for high levels of vibration that are extremely detrimental to cutting operations. Fortunately, vibration-damping milling holders and turning bars for long-reach applications negate the effects of vibration and allow for higher metal-removal rates, increased productivity, improved surface finishes and longer tool and spindle lives. 

Today’s tooling systems can be passive, aggressive or a combination of both when it comes to dealing with vibration. Passive tooling controls vibration via their material make up, while active ones use some type of moving mechanism typically housed in internal cavities.

Tooling that combines the two methods – “passive-dynamic” – uses, for instance, systems that are passive until a first hint of vibration activates them. At that moment, a damper mechanism counter-vibrates against the vibration. The damper is at the same frequency as the holder itself and that kills the vibrations entering it.

The key to passive-dynamic tooling is to actually put enough load on the toolholder to trigger the damper into action. Typically in long-reach operations, machinists tend to run slow to limit vibration, but doing so may fail to activate the damper.

Vibration-damping tooling, such as Seco’s Steadyline, actually needs to run hard. Substantial feeds and depths of cut will ensure optimum tool performance and the best possible workpiece surface finishes, along with increased productivity. 

One of the greatest advantages of the Steadyline milling and turning systems is the flexibility they offer. Steadyline Combimaster, for instance, is a two-piece milling system with a wide range of shank types, lengths and interchangeable cutter heads. This makes for a wide range of applications such as square shoulder milling, end milling, copy milling, face milling, plunge milling and disc milling.

For turning, Steadyline turning bars feature Seco’s GL turning heads that make it possible to perform rotating and static operations with the same bar. Once the bar is set, a shop can mount heads without having to reset the system, requiring only the use of a spanner wrench to loosen and tighten the heads. Available in 6xD, 8xD and 10xD lengths and with a broad selection of turning heads, these turning bars handle a variety of operations, including roughing, finishing, boring, threading and grooving.

Because of the rigidity and anti-vibration properties of the Steadyline turning bars, they handle very high machining parameters. This makes it possible to leave them in the turning machine’s turret and use the tools for short work as well to eliminate the need for multiple tools. 

For large holes, shops can circular interpolate at high feedrates to rough machine with the Steadyline, then finish cut with a finish boring head or reamer. The Steadyline bar also accommodates twin boring heads for staggered boring. This provides a much more stable setup as compared with a modular system constructed of separate pieces.

Seco offers several tips to get the most benefits from its Steadyline tooling. One recommendation is to cut off portions at the end of a toolbar for an optimized fit into a turning machine’s turret block. In fact, Seco puts lines on the Steadyline turning bar to indicate where it can be cut.

However, care should be taken when clamping the bar in a vise for cutting. The damper is in the front of the hollow tube, and the vise pressure could crush it internally if the bar is clamped on the wrong portion. Also, soft jaws should be used for best results. 

Another tip is to pay attention to temperature fluctuations. Rubber O-rings surround the damper, so excessive heat or cold could cause the rings to become too soft or hard. This doesn’t permanently change how the damper operates, but the rings need to get back to the right consistency prior to tool use.

While some milling operations run dry, too much heat affects how the Steadyline milling holder operates, so coolant should be applied. And if the holder has been sitting in cold conditions for several days or weeks, there should be a warm up period prior to using it to allow the damper to “unfreeze.”

Another tip is to store the holder in a vertical position, as opposed to on its side. When stored lying down, the damper might get stuck and require some effort to free it.

Steadyline tooling benefits aerospace, heavy equipment, moldmaking and automotive applications, along with many others, where long-reach operations are needed. In addition, Steadyline tooling is well suited for where there are issues with fixturing being in the way or when machining tough materials prone to extensive vibration, even without a long-reach situation.

Download the Steadyline turning and milling brochure. 

About the Author
Mike is Seco's product manager for reaming and EPB tool holders, which includes EPB’s line of rough and finishing boring heads. In his spare time, Mike enjoys spending time with his wife and two daughters as well as running when he gets a chance. 

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