SolidWorks Motion – Trace path and convert to SolidWorks Curve, a hidden gem.

The other week I took my daughter to the science museum, my favorite educational distraction.  While we were exploring the exhibits we came across a pendulum drawing machine (Harmonograph) that makes cool pictures.  We whipped out a few before moving onto the Bernouli Ball (I’ll have to get back to that as that’s something SolidWorks Flow Simulation can do).  Here’s a picture just like the drawings we made now hanging on my refrigerator.

The next week I was discussing SolidWorks motion with a prospect and how it allows you to simulate complex motions and the Harmonograph came into my head (can you imagine a more complex motion than the above image?).  So I made a first example, really simple, two pendulums, probably took all of 5 mins to create.

In motion I added gravity and clicked run, although I left out the details that connect the pendulums to the drawing pen I was able to see the drawing was working by tracing a point on one pendulum with respect to the other pendulum.  See how the curve moves with the pendulum on the left while tracing the path of the pendulum on the right.

After determining the system was working as expected (crawl, walk, run) I added a simple drawing mechanism.  To reduce the modeling effort I replaced the wires linking the pendulum to the drawing mechanism with 2 simple equations.  Now the system was quite recognizable, even to my 3 year old.

From there I had to try another version of the drawing machine I’ve seen with rotation (loved my spiralgraph so much I wore the teeth off). 

Of course there’s a point beyond Motion’s ability to simulate these really cool drawing machines.  I’ve created a few cams over the years using this functionality.  Basically what we do is simulate the desired linear motion, then trace that with respect to some rotating object and SolidWorks motion with automatically draw out the required cam for your system.  From there you can make that trace become a curve in SolidWorks, simply extrude, rinse and repeat.  So if you’ve ever needed a complex path created by the motion of objects in your design SolidWorks Motion is the tool for you.

Tim Newton

Symmetry Solutions Inc

When setting up a model in static simulations, I often run through the bolt/pin process to create connections that will transfer loads to joining bodies, defining the connection by selecting the appropriate geometry on the holes we are using for the pin/bolt and running the simulation.  But what happens when we want to analyze the actual connection itself to verify if the bolt/pin is going to withstand the stress generated by the model conditions?  How can we determine whether or not the designed geometry of the bolt, its material, grade and preload will pass or fail?  SolidWorks has a very useful tool for defining a pin/bolt check plot to look at just this.

By looking at the axial, bending and shear forces acting on each bolt/pin within the assembly defined through the simulation study, SolidWorks compares this with other parameters (strength and area) to calculate axial, bending and shear load ratios to equate a combined ratio.

The inverse of this sum is then used against the defined factor of safety in the bolt/pin definition to give a pass/fail output.

To take a look at how this tool can be used to determine model geometry and the required bolt, material and grade to use, I have set up a simple assembly with two configurations; 8 mm and 10 mm diameter bolt studies to analyze.

In this particular model, I have multiple bodies being bolted together in series; this must be defined in the advanced option in the bolt property manager.  Select the advanced option located in the lower portion of the property manager and select the cylindrical wall of the body/bodies that are in series of the connection (figure 2).

In the words of SolidWorks, “Sensors monitor selected properties of parts and assemblies and alert you when values deviate from the limits you specify.”  They come in handy when creating optimization studies.  (Check out this week’s blog.)

To create a sensor, right click the “Sensors” folder in the feature manager tree.  Then, select “Add Sensor”

Next, select your sensor type.

Simulation Data: Monitors simulation results like stress and displacement

Mass Properties: Monitors things like mass, volume and surface area

Dimension: Monitors any dimension you select

Interference Detection: This option is only available for assemblies.  It will warn you if any parts (of your choosing) interfere with one another.

Proximity: This option is also only available for assemblies.  It is similar to interference detection.  It will warn you if your parts cross a line.

Motion Data: This option is only available with the motion add in turned on.  It will monitor existing result information from a motion study.

Within these options there is much to explore.  Happy hunting!

I once wrote an optimization program which found the best fillet size, thickness and angle of a two dimensional cantilever beam with a given load. It took three days to write. What I’m about to show you took me 30 minutes. It makes use of real geometry and doesn’t require programing! Enter simulation automation…

Let’s consider a scenario. You work for an amusement park ride manufacturer. Your company has begun to streamline their design process. (Good idea if you ask me.) The company would like your team to design components which will be interchangeable (like Erector Set parts). The designer you work with calls himself an artist. He wears leather pants. His ideas are nutty. It’s up to you to make real decisions. He comes to you with the part seen below and says, with a blank stare, “To date, this is my best work. Try not to taint it.”

The company will be making thousands of these parts which will be made from cast carbon steel. It is designed to hold pipes and should carry at least 3000 lbs.

Decision: you decide that the part should have a safety factor of two. (The stress should not be higher than 120 MPa.) This means that the part should be able to hold at least 6000 lbs. without failing.

You setup an initial study to benchmark the current design.

You might not know this, but SolidWorks includes FEA tools with every package it sells. Chances are you probably don’t use these tools. You might think they’re too complex. Or, maybe, you’re on the other side of the fence and think these Xpress tools are too limited. Let me show you why you should be using these tools all the time.

To illustrate my point, let’s use a simple example of a link as seen in the picture above. Is it going to be strong enough? Wait, strong enough for what? What material should it be made of? Shouldn’t I know these things before I begin a simulation?
The answer is no! None of that matters. Actually, these are the wrong questions.
Don’t get me wrong. Down the road, these things will matter. But for right now, we shouldn’t be too concerned with these questions. Instead, let’s look at this in a different way. So, what are the right questions?
Answer: How can we make this part stronger?
When you boil static simulation down, the only two variables to play with are geometry and material. Since we aren’t concerning ourselves with material, let’s see how we can make changes to the geometry to improve upon what we have.
First, let’s create a simulation to get a baseline stress result. Startup Simulation Xpress and go through the wizard.