Monitoring vibrations in high-speed grinding and spindle operations is increasingly important in meeting the production goals of today’s CNC machine centers. Many operators interpret the sound from a spindle as a harbinger of potential problems, but sound is not always the best indicator. The damage has often already started if an operator hears sounds from a spindle. When that happens, tolerances are missed, tools wear out quicker, products get rejected, and spindle repairs are more expensive. Spindle operators are most effective when they detect and diagnose problems early.

Vibrations often start well before sounds. Outfitting your spindle with the proper equipment—vibration analysis tools and software—allows operators to detect spindle issues before they reach a critical stage.

The reality is that long before a spindle emits a problematic sound, there will be a vibration. Indeed, sound is a vibration that travels through the air as a wave (vibrations also travel through water and solid objects). At specific frequencies, those sounds are undetectable. The vibrations are not strong enough, or they make a sound that is not within the frequency detectable by most humans. However, monitoring your CNC spindles and high-speed grinding operations for vibrations allows you to detect and repair problems much earlier, saving time and money and maximizing your productivity. Fortunately, there has been much headway in the development of spindle vibration sensor technology.

Talk to the experts about spindle vibration. Call GMN USA today.

Today, operators of high-speed grinding machines encounter more exotic and much harder materials—400 stainless steel, Inconel, or titanium. Operators are also finding projects requiring much closer tolerances. Material removal rates, more intricate machining demands, and pressure for more productivity contribute to the challenge.

Spindle vibration is especially counterproductive when it comes to those close tolerance projects. It takes only a slight vibration to push a tool beyond acceptable limits, resulting in tool failure, scrapped parts, unplanned downtime for spindle rebalancing, and the list goes on.

There are two forms of vibration in high-speed grinding that have the potential to cause damage.

Force vibration refers to internal sources or problems within the spindle. This vibration comes from the eccentric mass of rotating parts. In short, something is out of alignment. Causes include wheel imbalances, friction, improper tool clamping issues, motor problems, worn or damaged bearings, and more. Force vibrations are present even when the spindle is not engaged with the work material.

Self-excited vibration occurs when the high-speed grinding tool comes into contact with the work material. It might have to do with the material, tool selection, or other external factors. A simple example of self-excited vibration is a change in the material being machined, such as grinding chrome down into steel. The tool encounters changes in material properties, altering cutting forces and can initiate oscillations in the grinding tool. Generally, operators and experts refer to self-excited vibration as cutting chatter.

Signs of undetected spindle vibrations can initially appear as imperfections in the finish of the machined product or tolerances that exceed the specifications. Operators might also notice overheating of the spindle, excessive tool wear, and irregular noises. If left unchecked, these problems will worsen, as will the bill for repairs.

Vibration analysis is an umbrella term for different methods of detecting excessive vibration in high-speed grinding. Operators rely on several different modes of vibration analysis.

This measures the vibrations at different places through spindle vibration sensors. Operators can look at the individual measurements to determine whether the problem can be traced back to a misaligned tool, a worn bearing, or overheating.

This records the condition of the spindle over a period of time. This helps operators determine if the vibration occurs during a specific action, such as when using a particular tool or drilling at a particular angle.

In this instance, spindle vibration sensors monitor the spindle, looking for signs of wear and other changes.

The vibration may produce noise that is inaudible to the human ear. Through frequency analysis, certain sounds and vibrations can be linked to specific issues. Some bearing fault frequencies, for instance, are well over the 20 kHz range that humans can hear.

The reality is that all movements vibrate, but there are natural vibrations and unnatural vibrations. Modal analysis establishes a baseline of the natural vibrations of the spindle which can help operators differentiate between vibrations that are expected and those that may be cause for concern.

Large machine shop operations often have the budget and resources to maintain a selection of spindles and spindle motors for different projects. In some high-speed grinding applications, the operator might choose a manual tool change spindle, knowing that automatic tool change spindles can sometimes face clamping or alignment issues under certain conditions. Regardless of spindle type, selecting a variable-frequency drive (VFD) is crucial. The VFD provides added torque at lower speeds, while also enhancing speed control and reducing vibration, making spindle operations smoother and more reliable.

There are also other advantages to VFDs, including reduced power usage on start-up, modifiable speeds, controlled stopping, and torque limit adjustability.

The Business Research Company projects that the CNC spindles and the high-speed grinding market will increase by a compounded annual growth rate of 5.1% through 2030. Factors influencing this expansion include the demand for spindles that can handle changing materials and applications and technology developments in the spindle industry, such as advanced vibration analysis capabilities. CNC operators with vibration-detecting capabilities will get enhanced production from their spindles at a greater level of quality because they can detect and address problems early on, avoiding rejected products and expensive spindle repairs. Their reputations will flourish because customers know they can rely on these CNC centers for the best high-speed grinding projects.

GMN developed the IDEA-4S Spindle Monitoring System to provide CNC operators with the most advanced spindle vibration analysis. The IDEA-4S (Integrated Data Evaluation and Acquisition for Spindles) uses compact spindle vibration sensors, along with a host of other spindle diagnostic tools, to collect and store data about the operation of your spindles and high-speed spindle projects. You can connect IDEA-4S to your internal computer network and your industrial Internet of Things (IIOT). The IDEA-4S, initially developed for GMN spindles, has since been improved and expanded to work on almost any brand of spindle.

GMN USA has been a trusted name in high-speed grinding and CNC spindle technology for nearly a century. With over 100 years of combined spindle experience, our team offers a range of innovative spindles, spindle accessories, expert repair services, spindle storage and more.

GMN USA is ready to meet your spindle repair and maintenance needs. Contact us today to get started.