Tracing disturbance from its source through the machine before selecting a mount pad coupling or bumper

A packaging machine developed a sharp buzz after its cycle rate increased. The first proposal was to install softer feet. A measurement showed that the dominant vibration came from a reciprocating head, crossed the frame through a bracket and excited a guarding panel. Softer feet would have changed the machine's motion without treating the loud panel.

Noise reduction in automation works best when the disturbance path is known. Rubber can isolate a source, dissipate part of the energy, interrupt a structure-borne path or soften an impact. Those are different jobs and often require different geometry.

Begin at the Excitation

Servo acceleration, gear mesh, pump pulsation, imbalance, valve switching and end-stop impact produce different frequency content. A mount selected from machine mass alone may isolate one band and amplify another near resonance. Record operating speed, transient events and the directions of the forces.

The machine structure also changes the result. A flexible panel can radiate sound even when the source movement is small. A rigid connection can bypass a soft isolator. Hoses, cable trays, anchors and safety guards need to be included in a machine vibration control review.

Isolation Depends on the Frequency Ratio

Rubber vibration mounts deflect under static load and create a supported natural frequency. Useful isolation generally begins only when forcing frequency is sufficiently above that natural frequency. A very stiff mount may transmit disturbance, while an excessively soft one may allow unacceptable travel or instability.

The mount therefore needs load per position, center of gravity, disturbing frequency, available deflection and motion limits. Unequal loads can leave one mount lightly compressed and another overloaded. The selected hardness is only one input; shape factor and loaded area also affect stiffness.

Damping Controls the Crossing

During start-up and shutdown, a machine may pass through resonance. Elastomer damping components convert part of cyclic strain energy into heat and can limit the peak. More damping is not always the same as more isolation at normal speed, so the transient and steady-state requirements should be separated.

Temperature, frequency, strain amplitude and compound formulation change dynamic stiffness and damping. Data measured on a small laboratory specimen at one frequency cannot be copied directly to a large bonded mount working near a hot motor.

Impact Needs Travel and Progressive Stiffness

A bumper used at the end of a cylinder stroke must absorb energy within available travel. If it bottoms against metal, the peak force returns. Conical, hollow or ribbed forms can create progressive stiffness, but repeated high-frequency impact also generates heat and fatigue at the root of the geometry.

Industrial vibration isolation near a stop should be evaluated with the real moving mass and velocity. Static compression alone does not show rebound, heat build-up or the effect of a misaligned strike. A retained bumper may be safer than a loose pad when fragments could enter the equipment.

A‍‌‍‍‌ Real World Wind Turbine Example

Parker's literature on wind-energy features center-bonded mounts that serve to isolate vibration, to control shock and to minimize structural noise. It also gives a description of the elastomeric drive-train coupling's that are used to reduce torsional vibration, misalignment allowance, and gear and bearing protection.

This publication does not feature one wind turbine vibration spectrum before and after, thereby, this piece is only showing an established application and not a customer with quantified results. The crucial design tip is that mounts and couplings are positioned differently along the path.

Parker's engineering guide does also highlight the same point. It defines isolation as the act of shielding the equipment against vibration or shock. It describes that rubber-to-metal mounts are applied based on load, frequency, bearing a load in a certain direction, and environmental conditions.

Weigh Your Instruments the Vibration Source, the Intermediate Path and the Vibration Sink

In the beginning place the sensors at all the places of interest - the origin of vibration, across the coupling and on the target structure. Capture the running condition and the revolutions per minute when plotting traces. One single vibration level value overall may hide a narrow peak which results in noise or a short impact which destroys the sensor.

ISO 20816-1 generally outlines the measuring and evaluation of vibration on entire machines. The ISO document lists the 2016 version as published and under revision. It is not the all-encompassing acceptance limit for every automatic machine; the machine maker is expected to specify the relevant places, the machines running states and the acceptance limits.

Component Qualification Test

Run candidate rubber vibration mounts through temperature cycles representative or expose them to oils, coolants and cleaning compounds which can change stiffening or adhesion. Test the static settlement, the speed-dependent transmissibility and the motion of emergency停车.

On elastomer damping parts heat build-up, cracks, edge of bonding, and permanent deformation shall be inspected after the required number of cycle. Afterwards the same acoustic or vibration testing should be done with a working program identical to the one for the reference. A subjective perception of being quieter is quite helpful but, definitely, it should not be considered an alternative to measurable evidence.

We may, for example, have a balanced source, a stiffer panel, a changed bracket, and a tuned elastomer combined to get the best machine vibration control. Nevertheless the rubber element should be attributed solely for the part of the improvement shown through the controlled experiment.

Vibration isolation at industrial level also needs a commissioning review. A tightened hose, a grounding strap, or safety cable can constitute a rigid alternate parallel route around the base isolator. Examine the final machine when anchored to check that the prototype frame and the production utility connections are transmitting different forces.

You should re-measure once the machine has a reasonable running-in time and at the temperature. At the moment that you are getting ready to operate, the stiffness of the rubber changes with machine temperature, and fasteners can loosen. The records of a qualified machine should include sensor position, operating recipe, load, floor condition so that the maintenance crew of the future will replicate the condition that is the baseline.

In order to get a Yida overview of how to reduce noise in automation, please give: machine weight, mount coordinates, direction of force, running-speed interval, impact energy, temperature, fluids, and travel of course. With such data, the designers and compounders of rubber can create the geometry and compound that match the disturbance pattern that you measured, thereby, not just go after the softer ‍‌‍‍‌one.