How to use the Resolator

The basic general procedure is to simply mount the Resolator onto a structure, then set sensors/instruments and finally control the Resolator to sweep through different frequency ranges to stimulate local resonances. Depending on the technique, the use of sensors/instruments/strobes etc. can then be used to check and prove resonant conditions.

Mounting

The use of the Resolator is very straightforward and quite simple. Start by determining what machine and/or surrounding structure such as bases, beams, pipes etc. that you determine to test for resonance. Remember that the stimulation force from the unbalanced CAM inside the Resolator will shake in a 360 degree direction but only in that one plane. In other words, it can shake both horizontally and vertically but not axially. Keep this in mind when you decide where you will mount the Resolator. While it will shake in every combination of horizontal and vertical direction, to check all directions, you might consider mounting the Resolator 90 degrees and run the test again to get that third dimension.

Once the direction of the test is determined, locate a place to mount the Resolator tightly to a structure. Since there are infinite ways and places to mount such a device, we have included some mounting structures to help with the most common mounts. One can simply use a C clamp to hold down the base, or bolt on an included channel for a better fit on round parts such as motors, rolls, rotors and pipes. To hold it tight in situations where the part cannot be simply clamped, we have included chain that can be wrapped around a part and then screwed tight for a good, firm connection. We encourage you to also design your own mounting brackets to accommodate your very particular situations and share them with Update so that we can help others with an ever expanding range of mounting techniques.

Remember that while any temporary clamping can loosen during the shaking that occurs in use, the Resolator has its rotational element contained completely enclosed for safety. If it falls off to the floor, it will simply just shake there until you turn it off and mount it again more tightly.

Modifying the Stimulus source

Once properly mounted, the Resolator will provide a powerful 360 degree force to stimulate resonant frequencies. However, all conditions are different and therefore the strength and distance of the stimulation form the source will vary. For example, the amount of unbalance of the CAM will suffice for most machine tests, but you may wish to have a stronger force when testing extra large structures.

To increase the amount of stimulus strength, simply add more weight. This is done by removing the clear protective cover and adding washers and holding nut to the CAM. Adding this additional weight is good for use with larger structures and lower frequencies. However, one must remember that measuring resonance can be accomplished with quite sensitive instruments and often with very little stimulus, especially if looking at phase.

The key determining factors in just how much weight is needed relates not only to the size and mass of the part under test, but also its composition and how it is held. If something is made of “tight, hard, stiff” material such as metal, and held very tightly, then the resonance curve can be more narrow in frequency but more easily excitable in amplitude. In other words, a high Quality (Q) resonant zone part.

On the other hand, one can imagine a large but soft material, like foam, which would have a “dampened” or low Q resonance. The frequency plot would then look like it was “squashed down” with lower amplitudes over a much wider frequency range. In the end, you will mostly likely find that the machinery world has lots of stiff, high Q resonances and although large, they can be tested for resonance with a lot less weight than initially thought. Therefore, add additional weight only when really needed.

Another factor that can affect the performance of the stimulation provided by the Resolator is how the unit is coupled to the part it is mounted on. If the unit is strapped down with a strap that is not tight and/or stretchable, there will be some absorption of the energy into the coupling system rather than transferring it all into the part(s) you wish to measure. We have found that using a chain and screw tightening system to be more effective at more tightly coupling the Resolator to a given mounting point than using, for example, a nylon cable. Again, all situations will be different and therefore it is important to be thoughtful as well as creative in your use of the flexible tool.

Resonance test configurations

Once the Resolator is securely and tightly mounted, the control box can be used to sweep through various frequencies. The control box has a simple on/off switch and Coarse and Fine speed control dials. The detected speed or stimulation frequency is displayed on the easy to read LED display. To best test a given frequency range, we suggest a very slow sweep through that frequency range so that if a part starts to experience going into a resonant condition, it has a little time “to get going” before sweeping past the resonant frequency zone. Running through the first multiples of running speed (1x, 2x, 3x etc.) of close by machinery will stimulate resonances in surrounding parts and/or structures that could be also causing problems under normal running conditions.

Additional instrumentation

There are several different ways to use additional instrumentation to test and prove resonant conditions. These can include something as simple as holding a coin in your hand and hand feeling higher and lower vibration levels on various parts as the Resolator is being swept or simply staying at a suspected resonance frequency. On the other end of the spectrum, the Resolator can be used as a stimulation source for testing structures using multiple sensors and sophisticated software such as Operational Deflection Shape (ODS) and some Modal techniques.

The simplest test would be to use a basic vibration PEN. Sweep the Resolator around machine running speeds and quickly check for unusually high amplitudes with the PEN. Then run the Resolator to the suspected resonance frequency and use the PEN to take a series of equally space readings along a line, such as along a pipe or base. By simply plotting the amplitudes on a graph and connecting the dots, you will draw a visual representation of the vibration modal shape of that given part, in that given direction. Comparing the plotted curve to classic 1st, 2nd, 3rd etc. resonance plots, one will quickly and easily see if the part is in fact resonant and where to place the mitigating parts (like braces, clamps, weights etc.).

If you have an instrument with a FFT display available, you can use the following procedure. First, set the display to peak hold (one that will only keep the highest detected amplitude for a given frequency). Then place the pickup on a suspected resonant part. Start the Resolator at its slowest speed and very slowly (and as evenly as you can) sweep to higher and higher speeds. When finished, you will see a frequency plot that will show the characteristic higher amplitudes when various resonances are found.

(Hint: when approaching key frequency ranges such as machine 1x, 2x, 3x, RPM x # blades etc., use the fine speed adjustment to more slowly enter and exit the operating speed range. If your instrument requires you to manually change the time duration of each reading cycle, adjust the time so that the resolution will be increased as you change the change of sweep rate with the fine control. This will help increase the resolution and sometimes more clearly define the resonant frequency zone)

The effect of resonance on phase is one of the strongest indicators that a resonant ( vs. just higher amplitudes) condition actually exists. This is because that the detected phase of a vibrating part will shift a full 180 degrees as it is stimulated throughout the resonant zone frequencies. Therefore, the use of a strobe light triggered from an accelerometer is one of the best ways to determine, and prove resonance.

The procedure is to place the accelerometer on the suspected resonant part and then set the strobe to trigger from the accelerometer. Then shine the strobe light onto the Resolator’s unbalance CAM (seen through the clear protective cover) and note its angular position. Then slowly perform the frequency sweep procedure, watching the position of the CAM. When the part to which the accelerometer is mounted experiences a true resonance, you will see the CAM angular position sweep 180 degrees. Note the frequency reading at the beginning and end of the resonance zone to define the actual full range of that specific resonance situation.

Present users are finding new uses for the Resolator all the time. Whether it is used for checking for resonances in machine tools before the first cut on a new setup, or determining if resonance problems will occur when proposed new speeds are actually used when contemplating a line speed up, the Resolator will help define this ever present, confusing and important natural phenomenon.