The purpose of this tutorial is to learn how to use periodic motions with replicated geometries.

The scenario considered is a bucket conveyor experiencing surges of material from inconsistent loading.

You will learn how to:

And you will use these features:

The geometries in this tutorial are composed of:

The first item will be created from a Rocky conveyor template.

The remaining components will be imported as .stl files, all of which can be found in the tutorial directory.

To get started with this tutorial, do the following:

For the Geometries step, we will import the following 6 geometry files in .stl format:

We will also add a default Feed Conveyor, and then create two separate Inlets (from two different Surfaces) from which to release the regular and surge material, respectively.

Now that all of the geometries are included in your project, you can visualize them in a 3D View window.

Turning the geometry for a single bucket into a full, 20-bucket conveyor involves the following steps:

For the Motion Frames step, we will accomplish the first two steps above by creating a single frame with four separate motions, as explained below.

The complex bucket motion can be defined on a single frame using four separate motions:

The fourth motion brings the bucket back to the starting point, so to keep the bucket moving, the entire, four-part motion set must be repeated.

In Rocky, this motion repetition is done via Periodic Motions.

The four separate motions within the frame will be defined using the bucket velocity and belt length.

Using this information, we can then determine that one full revolution takes 8.98148 s.

When Enable Periodic Motion is turned on for a frame, the full list of motions contained within that frame will be repeated as soon as the Periodic Motion Period completes.

The total time between the earliest motion's Start Time (in our case, 0 s) and the latest motion's Stop Time (in our case, 8.98148 s) is saved within Rocky as the periodic motion period.

As we want the motion to repeat as soon as the last motion finishes, we will set the Periodic Motion Period as equal to the motion total time.

The full list of motions contained within the frame will be repeated until it reaches the Periodic Stop Time.

Now that you understand more about periodic motions, you can create the single motion frame that will contain the four separate bucket motions.

The completed Motion Frame setup should now look similar to the image below.

For this tutorial, since the geometry has a motion with displacement assigned, the movement can be previewed using the Motion Preview window.

Later in Part B of this tutorial we will analyze two buckets separately using moving cubes.

Follow the steps in the table below to create the second Motion Frame.

For this tutorial, the Replicate Geometry option will be activated for the Bucket geometry, which will create copies of the geometry (and its assigned motions) at specified intervals along the motion's path.

The results are shown below.

As seen in the Motion Preview (and/or 3D View) window, the single bucket has now been replicated into 20 buckets evenly spaced along the path of the bucket motion.

For the Materials step, default values will be used for all three default materials.

We will slightly modify the friction values for the Materials Interactions step.

And for the Particles step, we will create a new sphere-shaped particle group in a range of sizes with some added rolling resistance.

For the Inlets and Outlets step, we will create two particle inlets: one to provide a consistent feed for the conveyor and another to provide additional surges of material through the inlet.

For the second inlet, we want the material surge to be represented by 5-second bursts of material that appear every 5 seconds, starting 5 seconds into the simulation (as shown).

To replicate the material surge, we will set this second Particle Inlet to have a Periodic injection, which will enable particles to be released from the Entry Point in bursts.

These bursts are defined via the following parameters:

Rocky calculates the particle mass released in each periodic burst by equally dividing the total particle mass by the total number of bursts during the simulation.

With a 3D View window opened, your Data panel and Workspace should look similar to the below image.

The Simulation Summary screen appears, then processing begins.

This completes Part A of this tutorial, in which Rocky was used to set up and process a simulation of a Bucket Conveyor.

During this tutorial, it was possible to:

What's Next?

The purpose of this tutorial is to analyze the results from the Bucket Conveyor simulation we processed in Part A.

You will learn how to:

And you will use these features:

Now that our project has finished processing, we can begin analyzing the results.

Let's start by viewing the contributions from each separate inlet.

Each inlet's contribution is represented by a separate color.

Another way to evaluate the effect of the surges is to plot the particles count.

The resulting plot shows a steeper curve whenever the mass flow is increased from a surge.

We can also filter the particles by the Particle Boundary property and plot the Particles Count for each Inlet separately.

First we will isolate the particles that result from the Regular Feed.

The resulting plot shows two more curves:

Next, let's evaluate the draw efficiency.

This can be done by using two moving cubes (each one for a bucket) and a Time Plot to analyze the carried Particle Mass for each bucket.

We will use the motion frames we created in Part A to describe the cubes motion.

This results in two cubes encompassing two buckets (as shown).

Due to the assigned motion frames, the cubes will accompany the buckets for the whole simulation (check this on Motion Preview and by multi-selecting both cubes with the Bucket wall visible).

Now that we have the Cube selections, we can use it to create a Time Plot showing the Sum of Particle Mass for the two buckets.

The resulting plot represents the Particle Mass in each Cube region.

Note that when crossing the Hopper (at 13.3 s for example), the cubes encompass particles that are not necessarily being carried by the buckets, and it causes peaks on the plot.

The relevant values are the ones that keep constant for more than a second in the plot, when all the particles inside the cube are being carried by the bucket (15 s). (Compare the images shown.)

The particle mass carried by the buckets varies between 2.6 kg (at the beginning, with few particles on the Hopper) and 16 kg.

Another analysis we can do with this project involves using the Particles Trajectory User Process, which displays the path particles take by translating their movements into 3D curves.

To visualize the trajectory of the particles, do the following:

This completes Part B of this tutorial, in which Rocky was used to analyze the results from a Bucket Conveyor simulation.

During this tutorial, it was possible to:

What's Next?