Stroke, Frequency and Force: The Keys to Vibratory Compaction

David Strong

One of the more common applications for industrial vibration is to settle or compact a wide variety of products.  This ranges from foundry sand around a core to powdered metal, beer bottle caps, individual sugar packets, ceramic mixes to concrete blends used in ATM wall enclosures.  This compaction process can be accomplished on any one of a number of vibratory equipment products including vibratory joggers (VJ), vibratory packers (VP) either pneumatic or electric powered, flat deck tables (FA), grid tables (GT) where the vibrating table is integrated with a roller section or the vibratory belt table (BT).  Regardless of the equipment used we start by understanding the material and working with a few basic parameters to accomplish the task.

The most critical parameters in any compaction problem are frequency of vibration and the amount of force applied, these two drive the third parameter, stroke or displacement.  As a rule of thumb, heavier materials respond best to high frequency vibration and the resulting smaller stroke that high frequency vibrators produce.  Lighter material or discrete parts often compact best with lower frequency vibration and the larger stroke they produce.   Typically we would start testing a product at a given frequency based on bulk density and adjust the force to load (g’s) ratio to get the best compaction results.  With the wide range of vibrators at our disposal we can choose from air cushioned pneumatic vibrators (VMSAC), rotary electric (RE) vibrators from 900 rpm to 3600 rpm or even electro-magnetic (CM) vibrators that best suit the frequency and force requirements.

Testing any product typically involves getting a representative sample from the customer, reviewing its individual properties and selecting a frequency of vibration.  As an example, we might look at a heavy, fine particle material.  Conventional wisdom would point us towards higher frequency vibration, typically 1800 to 3600 vibrations per minute (VPM) and low g’s, 2 to 2.5.  Material is loaded into a graduated cylinder and volume is recorded before and after vibrating the material.  During the short period of vibration we can observe the material as it is being compacted.  Incorrect choices of frequency or g’s will result in aeration of the product which can be readily observed.  The goal of the testing process is to arrive that the optimum combination of frequency and force where the product settles quickly and completely.  Little is gained by introducing too much energy, or high g’s, into the product, at worst the product fluidizes and doesn’t compact or the customer wastes money on over sized vibrators.

Once we’d determined the best frequency of the vibration and the level of force required for the job, the real fun starts!  Depending on the customers manufacturing process, we can select and recommend the appropriate piece of equipment to accomplish the task.  If the plant set up uses gravity or power roller sections, perhaps the recommendation might be for a vibratory grid table (GT).  Cleveland Vibrator can design a grid table deck that interfaces with the roller section.  When the product is in place, the grid table is elevated “through” the roller section, lifting the product off the rollers, vibrating it and then lowering it back in place.  Once that cycle is completed the compacted material can be moved onto the next step in the manufacturing process.  Smaller “stand alone” applications may best be suited for a vibratory packer utilizing a low cost, dependable air cushioned pneumatic piston vibrator producing the necessary force and frequency to accomplish the task.

Going back to my “one size fits none” theory, Cleveland Vibrator has many options for your product compaction solutions.  It all starts with your goal for your process.  From there our sales, engineering and manufacturing team works together to provide you with the best solution for your unique challenge.  Give us an opportunity to review and discuss your application and propose a solution, that’s what it’s all about!


Leave a Reply

Your email address will not be published. Please enter your name, email and a comment.