Posts Tagged ‘Simulation’

The Analysis Tools Sanity Check

Friday, July 31st, 2015

Let’s call it a ‘sanity check’.  Sometimes you need to prove to yourself, or possibly your boss, that your analysis tools are calculating results correctly.  Maybe you’re reviewing the results and something doesn’t look quite right.  There are plenty of scenarios where you may be called upon to use hand calculations to back up what your workstation and software can do for you in seconds, minutes or hours.  With our designs becoming increasingly more complex, this can definitely seem like an impossible task.  Fear not!  With Engineering knowledge, understanding how your analysis tools operate, plus a bit of diligence you can do just that.

Here is an example of using hand calculations to verify results from a SOLIDWORKS Motion analysis of a three component linkage.  I’ve simplified the analysis to consider the starting, static position because, well, you have to start somewhere!  The plot for calculated motor torque appears to be incorrect.  The Motion analysis result for motor torque at the starting position is 24 lbf-ft while the expected result should be approximately 10 lbf-ft.

When beginning your hand calculations, be sure to note any assumptions that you need make.  In this example, I am neglecting the mass of the components at the starting position, friction at the mate locations and gravity.

Analysis Tools 2015-0630a Hand Calculations


Now that I have the calculations in as simplified a format as possible (equation D), I can set up an Excel spreadsheet to calculate what Motion should have generated as a result.

Analysis Tools 2015-0630b Excel Calculations

My next steps are to investigate the original Motion study and SOLIDWORKS assembly to determine why the software didn’t calculate motor torque to be 10.8 lbf-ft.  In this example, it has to do with the mate scheme used for building the mechanism.  SOLIDWORKS Motion used the mates directly from the assembly, so how the mechanism was constructed is extremely important.  In the original design, my mate scheme had four redundancies, as indicated on the Mates folder inside the Motion study.  In SOLIDWORKS Motion, a redundant mate occurs when more than one mate constrains a specific degree of freedom for an assembly component.  The redundant mates have to be excluded from the Motion analysis before the mechanism calculation begins.  This is what caused the motor torque output to be incorrect.

Analysis Tools 2015-0630c Motion Incorrect

Now that I have determined it was my faulty mate scheme that led to the incorrect calculation, I can modify my assembly mates to work towards a mechanism with zero redundancies.  A mechanism with zero redundant mates will allow SOLIDWORKS Motion to correctly calculate forces acting on the mechanism.

The changes I made to the assembly were adding hinge components to the assembly, fixed the hinge components in space to provide an established path to ground and changed the mate scheme for the linkages.  The linkages were originally positioned with mates attached to an assembly sketch.  By adding the pins I can replace multiple mates connecting the linkages to sketch entities with a few hinge mates.  Reducing the number of mates in the assembly helps to remove redundancy from the mechanism.

Analysis Tools 2015-0630d Motion Correct

Now that my Motion study is calculating the correct motor torque at a known position, I can increase the complexity of the analysis and have a high level of confidence regarding the results.  My next steps would be to include the mass of the components by unsuppressing gravity from the Motion study.  I would then change the motor definition to move the mechanism through the appropriate range of motion.  Eventually, I would include the effects of friction on the mates.  But I could not take any of these additional steps without first verifying that I was obtaining the correct output utilizing hand calculations.  So the next time you’re not sure if your analysis tool is giving you the correct result, do the smart thing – trust but verify!

Now go make your products better with SOLIDWORKS Simulation. Use the comments section below to share any success stories. I would love to hear how you are using it in your designs!

Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Nominal Wall Thickness Inside Plastics Simulation

Thursday, July 16th, 2015

Wall Thickness – a major concern when designing a plastic part.

During the injection of the mold the melted plastic flow front will always move in the direction of least resistance. You can think of this similar to water flowing through a pipe.  The larger the pipe the easier the volume of water will flow.  If the wall is too thick in comparison to other sections of the part the plastic flow will “Race Track” or move ahead of the rest of the flow front.  This causes issues such as air traps, weld/knit lines, and possible cosmetic problems.  If the walls are too thin this can cause issues such as “Short Shot”. Short shots occur when the flow front becomes to hard to push by the machine (typically reaching the maximum injection pressure), or the flow front cools too fast due to the lack of volume.  Short shots do not fully fill the cavity and create an incomplete plastic part.  Ideally a part will have a uniform wall thickness.  In real life this is hard to accomplish but being able to predict areas that may be a problem before running an injection analysis helps an engineer find a good balance.

SolidWorks has always had the ability to check the thickness of a part through the evaluate tab of the command manager.  The command is “Thickness Analysis” and it has been the go to command to determine different thickness within a part.

Thickness Analysis

Nominal Wall Thickness Command

Now SolidWorks offers a “Nominal Wall Thickness” tool under the Advisor category of the Plastics Tree.  The “Nominal Wall Thickness” command allows a user to compare thickness in the model based on a value or percentage.  This addition gives the user a quick thickness analysis right inside the Plastics Interface.

Nominal Wall Thickness


Property Manager

The results are a quick and easy to understand plot that facilitates the reduction in sink, short shot, and warping.



Nominal Wall



Have you used this command before? want to learn about a different command in SOLIDWORKS? Let me know in the comment section below!

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Natural Frequency Analysis

Thursday, July 2nd, 2015

Natural Frequency analysis in SOLIDWORKS Simulation allows us to efficiently investigate the resonant frequencies of a design.  This analysis type helps us ensure that the natural modes of vibration are well away from environmental forcing frequencies that a design might encounter during service.  Like all analysis work, effective post-processing of your Natural Frequency analysis is key to communicating results to others.  The standard output of a Natural Frequency analysis are the resonant frequencies and associated mode shapes of the design, which we can easily plot in SOLIDWORKS Simulation.

Natural Frequency analysis

In SOLIDWORKS Simulation 2015, there were three additional frequency plot options added that are beneficial to conveying your Natural Frequency analysis results.  Those plots, or Frequency Response Graphs, are Mode Number, Effective Mass Participation Factor (EMPF) and Cumulative Effective Mass Participation Factor (CEMPF).  You can create these plots by right-clicking on your Simulation Results folder and choosing the option “Define Frequency Response Graph…”.

Natural Frequency analysis

The Mode Number plot shows a graphical representation of the natural frequencies calculated by the analysis.  This is a step up, in my opinion, from the simple list that is provided by right-clicking on the Simulation Results folder and choosing the option “List Resonant Frequencies”.

Natural Frequency analysis

The second frequency response graph, Effective Mass Participation Factor (EMPF), helps us visualize how the mass is vibrating in X, Y and Z, for each natural frequency.

Natural Frequency analysis

The third frequency response graph, Cumulative Effective Mass Participation Factor (CEMPF), helps us visualize the accumulation of mass participating in vibration as we calculate an increasing number of natural frequencies of our designs.

Natural Frequency analysis

The EMPF and CEMPF plots are especially important when we are calculating Natural Frequencies of a design that will be subject to time dependent loads during normal product use.  I plan on using these plots as I begin working on dynamic studies when investigating product performance subjected to random vibration or harmonic loading conditions.

Be sure to check out the three new Frequency Response Graphs in SOLIDWORKS Simulation 2015 to see how they can improve your Frequency Analysis post-processing.  Now go make your products better with SOLIDWORKS Simulation!

Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Show Plot on Selected Entities

Monday, April 13th, 2015

Show Plot on Selected Entities vs Isolate Command

Post-processing your SOLIDWORKS Simulation results is an important step of your analysis work.  It is also the step that most of us spend the least amount of time on because we’ve focused our efforts in the pre-processing phase.  While there are several options available to you for improving your post-processing efforts, I’m going to discuss a Simulation tool that you can use instead of a SOLIDWORKS tool.  Specifically, I’m going to describe how to use ‘Show Plot Only on Selected Entities’ instead of using ‘Isolate’.

The Isolate command was introduced in SOLIDWORKS 2007.  It allows you to set all components, except the ones you have selected, to be hidden, transparent or wireframe.  This allows you to focus on just the selected components and not the entire CAD model.  Isolate can be used in conjunction with Simulation when viewing analysis plots.  Using Isolate with Simulation, you need to save an image of the plot and then include that with the report.  While these extra steps don’t take much time, there is a better option.

The ‘Show Plot only on Selected Entities’ option was introduced in SOLIDWORKS 2013.  While this has been around for a couple of years, I find that it is highly underutilized.  You access this option when creating or editing most Simulation result plots.  You’ll find it by expanding the ‘Advanced Options’ section of the plot property manager.

Show Plot On Selected Entities

When checked, the ‘Show plot only on selected entities’ option provides the flexibility to show results on either selected faces from the CAD model or on components of the assembly.  Using this tool will allow you to customize the look of result plots that you generate during post-processing your analysis results.  The benefit of utilizing this feature is that each new plot you create with this option will be saved inside the Simulation study and, when you generate a report, the plots will be included automatically.

Show Plot On Selected Entities

This should be your go-to plot option in place of Isolate!  Be sure to investigate the other plot options available to you when performing your post-processing activities for Simulation.  I’m sure you will find many other tools to help make your Simulation reports look like a million bucks!  Now go make your products better with SOLIDWORKS Simulation!

Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

SOLIDWORKS Simulation 2015 – Favorite Materials

Friday, February 20th, 2015

I like simple UI changes that save time.  The favorite materials list within SOLIDWORKS Simulation 2015 is one new example.  We’ve been creating custom lists of our favorite materials in SOLIDWORKS for some time now.  How long?  Well, I had to go back through all of the What’s New PDFs to find out.  The Materials Editor Property Manager was added in SOLIDWORKS 2004!  This screen capture shows what we’re used to seeing in our SOLIDWORKS Feature Tree for adding materials with a simple right-click.

SOLIDWORKS Simulation 2015 Favorite Materials List

If you are following the best practice of applying a material to your part files, the material definition is automatically transferred into your finite element model.  If you are not following the best practice, then you must assign a material within Simulation.  Prior to SOLIDWORKS Simulation 2015, you would have to open the Materials Editor and then make your selection.  Now you can be faster with assigning materials by having access to your material favorites list within SOLIDWORKS Simulation.  Look for the Favorites tab in the Materials Editor Property Manager to customize your list of often used materials.

SOLIDWORKS Simulation 2015 Favorite Materials List

This list of your favorite materials will show up on your right-click menu, both when working with your part files and your Simulation studies.  Here is what you now will see with SOLIDWORKS Simulation 2015 – a highly customized favorite material list!

SOLIDWORKS Simulation 2015 Favorite Materials List

Be sure to check out this new feature and many others in SOLIDWORKS Simulation 2015.  Now go make your products better with SolidWorks Simulation!

Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

SOLIDWORKS Simulation 2015 – FEA Solvers

Wednesday, November 26th, 2014

A few years ago I wrote an article regarding Solver Selection for SOLIDWORKS Simulation.  At that time we had two solver choices – FFEPlus and Direct Sparse.  Last year, SOLIDWORKS Simulation 2014 introduced the Large Problem Direct Sparse Solver.  Now with the introduction of SOLIDWORKS Simulation 2015 there are improvements to the FFEPlus solver as well as a new solver, the Intel Direct Sparse Solver.

2014-1125 Solver Options

Per the SOLIDWORKS 2015 What’s New documentation, the FFEPlus solver has improvements to connector formulation and contacts.  The new Intel Direct Sparse solver is available for static, thermal, frequency, linear dynamic and nonlinear study types.  Like you, I want to see how these changes affect the solution times for my finite element studies.  Faster solutions are always welcome!

Using SOLIDWORKS Simulation 2014 and 2015 I solved several different study types to compare solver performance.  The benchmark files I used were a combination of SOLIDWORKS Simulation Training files and customer files from technical support cases.  All of these files were originally in SOLIDWORKS 2014 format.  For testing these models in 2015, I used Pack-and-Go to create a version to update.  Once I opened the files in 2015, I forced the model to rebuild then saved them to the 2015 file format.  In Simulation, I updated the components for the FEA study and re-meshed the finite element model.  Finally, after the solution completed, I recorded the solve time for each study type and solver combination using the Solver Messages information.  The results of my testing can be seen in the included picture.

2014-1125 Solver Performance Blog

For the improved FFEPlus solver in 2015, I calculated how much faster a study ran compared to the 2014 solution.  Half of the study types investigated had improved solution times while the other half were slightly slower.  Until I can investigate several more finite element models, I’ll consider this a draw.  As for the new Intel Direct Sparse solver, the solve times calculated were quite impressive!  The percentages shown are how much faster the Intel Direct Sparse solver was compared to either the (original) Direct Sparse or the Large Problem Direct Sparse solver.  In all six studies, the Intel Direct Sparse solver performed better than the other Sparse solvers.  The Intel solver really shined for Steady State Thermal (62%), Linear Buckling (46%) and Linear Static (31%) studies for the models I investigated compared to the Direct Sparse solver.  To be fair, the Large Problem Direct Sparse solver is intended for Finite Element Models with greater than 1.5 million degrees of freedom, which I did not investigate during this testing.

With the majority of our work, what we care about most is getting the job done.  With regards to Finite Element Analysis, this means getting the study to calculate to completion.  If that study can be solved faster by choosing one solver over another, all the better!  For SOLIDWORKS Simulation 2015, I think I’ve identified my default solver of choice – the Intel Direct Sparse solver.  Now go make your products better – faster – with SolidWorks Simulation!

Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Stress-Strain Curves and SolidWorks Simulation

Monday, July 7th, 2014

Recently, I helped a customer create a custom material for a Simulation study.  This included the input of tensile test data to generate a stress-strain curve.  Input might be generous as it was actually copying and pasting data from a spreadsheet into the custom material dialog.  Data entry aside, sometimes you encounter a constraint that you either didn’t know or possibly forgot about.  In this case, it has to do with the number of allowable data points for creating a stress-strain curve.  Most input for SOLIDWORKS Simulation materials are limited to 1000 points of data.  Not so with a stress-strain curve.

The data generated by the test lab included several hundred lines of stress and strain values, all measured during the tensile test of the specimen material.  As Engineer’s, we like lots of data!  When I copied and pasted these hundreds of lines into the material dialog box, however, Simulation indicated it was too much.  The warning encountered was that only 200 data points are permissible.

2014-0409a S-S Curve too many points

The fix, of course, is to reduce the amount of data to 200 or less lines of input.  Yes, there is an Enhancement Request to provide a method of smoothing out imported stress-strain data, but until that is implemented we must manually reduce the data.

While on the topic of stress-strain curves, there are some materials in the SOLIDWORKS Material Library that already include stress-strain curves.  Look for any material name that has an (SS) at the end.  The source of stress-strain curve data for those materials is the “Atlas of Stress-Strain Curves (2nd Ed.)”, published by ASM International.  Also, if you’re performing a Fatigue study, there are some materials with S-N curves built in.  Look for (SN) at the end of the material name.

2014-0409c SW Material LIbrary with SS data

Now go make your products better with SolidWorks Simulation!


Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Duplicate SolidWorks Plastics Project

Tuesday, June 24th, 2014

SolidWorks Simulation allows a user to ‘Duplicate’ a study, and SolidWorks Flow Simulation allows a user to ‘Clone’ a project.  Why not SolidWorks Plastics?  SolidWorks plastics is an injection molding software that allows a user to understand the manufacturability of a plastic part.  Because this is a fully integrated SolidWorks Simulation product different Projects are related to configurations in the part.  To re-use the setup from project to project please follow the instructions in the link below.

Duplicate Plastics Project

This functionality allows a user to quickly duplicate a project to change different parameters and re-run.  If you are currently using SolidWorks Plastics this information will speed up your work flow and Simulation setup times.

Robert Warren

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

Simulation 2014 Interface Improvements

Monday, November 11th, 2013

Last month I wrote about Toolbox fasteners with SolidWorks Simulation and how they can be converted automatically to connectors in simulation studies.  Today I’m going to focus on improvements to the Simulation interface for post processing.  One thing that Simulation users can struggle with is selecting the correct option for modifying the plots generated from an analysis.  Even with as many years as I have used SolidWorks Simulation, I occasionally edit the definition of a plot when I meant to modify the chart options or the settings.  With Simulation 2014, that is no longer an issue with a unified interface.

2013-1111a Interface changes

The other welcome interface change is what has been described as ‘finally like Flow’.  With SolidWorks Flow Simulation, changing an output plot from one quantity to another is done from the plot legend in the graphics window.  In SolidWorks Simulation 2014, we have a similar interface for modifying output.  By using either the right or left button click on the legend, we have access to changing the plot type, fringe options, the probe tool, animation, legend scale and many more options.

2013-1111b Interface changes

These simple changes will reduce wasted button clicks by the dozens when post-processing Simulation results!  What other new features have you found in Simulation 2014 will help you get your work completed faster?   I’ll write about a couple more next month! Now go make your products better with SolidWorks Simulation!

Bill Reuss

Elite Application Engineer CAE Technical Specialist 3DVision Technologies

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