Archive for March, 2008

Tackling the LARGE DISPLACEMENT Error Message

Friday, March 28th, 2008

What does one do when he/she sees the error message shown in the picture:

large displacement error message

This error message is probably one of the most common ones that a COSMOS user encounters in analysis. The first reaction that one gets is that this is impossible. You know for a fact that the load cannot possibly cause large deflections. Statistically speaking, the confidence levels on FEA drops drastically at this point, and I would not blame you for it right now (later, maybe)!!

So, how does one negotiate this message? You have a simple decision to make at this point:

  1. Hit YES, and it will say that the analysis failed, and it requires you to activate the large displacement flag (this flag is used if you know that the geometry is undergoing large displacement, and you want to solve this is a geometrically non-linear problem). However, that is against your gut feeling since you know this load cannot cause large displacements!
  2. Hit NO, and it will seemingly complete the calculation and give you Result Plots (inaccurate since the solver came up with an error message in the process of the calculation).

Since this message can pop up either at the part or the assembly level, let us investigate them one at a time. For both cases, make sure you select NO at the error message window before proceeding.

PART LEVEL

There are three possible causes for this at the part level.

  1. Your load is way too high – probably an oversight when defining the force/pressure condition in terms of either number of 0’s, or the units.
  2. The material properties are incorrect – inconsistent units or the values of the material properties while custom defining materials.
  3. Insufficient/negligible restraints – The location of the restraint was way too small to support the entire load, and/or the part is swiveling about one of the axes at the restraint location (as if it were hinged at that location).

SOLUTION – Check the values indicated in the first two cases above as a first step. If they look correct, then take a look at an animation of the displacement plot (set the deformation scale to automatic). The animation will tell you as to what direction(s) are still unaccounted for. If the directions of restraint are accurate, then examine the location, and see if it is on an edge or a small face. Make sure that the restraints are on the right areas.

ASSEMBLY LEVEL

SOLUTION – The problem at the assembly level is a superset of the part level issue. Thus, the first steps would be to try out the fixes recommended in the above section for each part in the assembly, and each restraint/load defined in the property manager.

If those do not fix the issue, then there exists only one possible cause – one or more of the components in the assembly is not sufficiently restrained. In other words, there are components that are freely positioned in the assembly, and the moment the solver tries to apply the load to the structure, these components freely float away in one of the unrestrained directions. This can be verified either by animating the displacement plot and looking at which components fly off in space.

Will mating them correctly in SolidWorks help?

The answer is negative. Mates in SolidWorks are a way of dictating the initial position of the components, and they do not carry over into COSMOS.

Hence, the resolution is to either add restraints to the un-constrained components, or to bond them using local contact sets to the adjoining components that carry sufficient restraints. Either of these methods will sufficiently constrain the free component.

These above methods should sufficiently address the large displacement flag. This flag is very easy to tackle since it is completely dependent on what you defined in the pre-processing steps. Keep in mind that a good analysis is one where you do not encounter any error messages, and the animation of the displacement plot is consistent with what intuitively makes sense. If FEA is garbage in garbage out, then re-cycling garbage has to give you a good usable solution!! So keep at it in terms of trying to troubleshoot your analysis studies.

Vikram Vedantham

Simulation Product Manager 3DVision Technologies

The Ten Commandments of FEA

Thursday, March 27th, 2008

Analysis is a lot like training for the marathon. You can easily upgrade from being a novice to becoming a power user if you strategize your approach towards FEA. Use the guidelines below to chart out a plan to become an FEA expert:

  1. Train hard: It is impossible to overstate the importance of FEA training. While analysis has come a long way in becoming a much simpler tool to use, it is still a tool that requires good mentoring to properly interpret the output.
  2. Make sacrifices: Take time to go over the information gained through training. A lot of times, confidence in FEA is obtained by re-visiting a previously tested model and reproducing the failure using FEA. Take the time to do such small projects, and this will help fine-tune your skills in using COSMOS.
  3. Make positive choices: Analysis is a numerical approximation method. Assumptions and approximations form the basis of performing FEA. The ability to make valid assumptions is an art that you develop over time. Verify your choices of boundary conditions and pre-processing with your local support team before you go through the first few runs. This will help you understand if your notions of simplification are accurate.
  4. Carry adequate firepower: It is vital that you are equipped with the right hardware, software, and data to get the most out of analysis. Read our blog article on hardware recommendations for analysis.(http://www.3dvision.com/wordpress/2008/01/14/what-machine-should-i-buy-for-running-cosmos/). As far as data is concerned, make sure you have the right material properties/curves pertinent to the type of analysis you are required to perform. For instance, a thermal analysis requires thermal conductivity; a static analysis requires elastic modulus; and so forth.
  5. Seek your potential: Be cognitive of your abilities in FEA. A lot of times, cross-checking with peers and colleagues open up a new window of insight into a problem that you may have failed to visit. Share your interpretation with others to see if you are indeed making the right judgment.
  6. Set reasonable goals: Every FEA simulation should be preceded by a statement of intent/problem definition. Once the objective is outlined, the subsequent steps in setting up the model would become instantly clear. It is very easy to fall off the track if the goals are set too high. Consider splitting up a task into multiple steps if it helps simplify the problem.
  7. Relax under pressure: FEA is designed to fail unless you exercise good control. Do not panic under timelines and shop-floor requirements. Try to observe alternative methods of setting up a problem. Make sure you re-visit boundary conditions comprehensively if the results do not match expected numbers.
  8. Attack pain: If you fail at first, give it another try. Do not give up because FEA seems to frustrate you. You will win the battle eventually, but not if you give up midway. Keep in mind that tough times don’t last, but tough people do!!
  9. Work as a Team: Utilize all available resources. Help your superiors understand the workflow and limitations in FEA. Until you are self-sustaining, do not hesitate to rack the brains of other peers using COSMOS (great sources are the 3DVision Team, COSMOS User Groups and sites like www.eng-tips.com). Also, make note that analysis and physical testing go hand-in-hand. Make sure you test your final results with a prototype before releasing production drawings into the shop floor.
  10. Run to win: Start projects with analysis taken into consideration. Do not allow FEA to be an accessory to designs, but an important portion of your design-cycle, by exploiting the seamless integration that SolidWorks and COSMOS offer. The most successful implementations of FEA have been observed if a company starts using it at the conceptual stage of a new design.

In the words of the famous Australian athletic coach Percy Cerutty, “Hard things take time to do. Impossible things take a little longer”. The benefits of FEA will be seen sooner than you would think!!

Vikram Vedantham

Simulation Product Manager 3DVision Technologies

Pro/E files work with PDMWorks Enterprise

Tuesday, March 25th, 2008

I have seen the future….and it is pretty cool.

I got a copy of the beta version of PDMWorks Enterprise SP4 and it handles Pro/E files! Yup, you can drag and drop Pro/E files into the vault, PDMWorks Enterprise recognizes the meta data and the parent child relationships. There is even an interface now built into Pro/E.

Works with Pro/E 2001 and the first three Wildfires. [For those of you scoring at home, PDMWorks Enterprise can now work in SolidWorks, AutoCAD, Inventor, SolidEdge and Pro/Engineer environments.]

Jeff Sweeney

CSWE Engineering Data Specialist 3DVision Technologies

DriveWorksXpress hates lightweight mode

Tuesday, March 25th, 2008

I was working with a customer in Indianapolis who had a huge DriveWorksXpress implementation. The problem he was having was that DriveWorksXpress could not switch to derived configurations of his sub-assemblies. [It wouldn't drive dimensions either.]

Turns out since he was working with rather large assemblies, most of his parts were lightweight. DriveWorksXpress cannot modify parts that are lightweight. Thus, you need to resolve all of your parts before you run a specification with DriveWorksXpress.

You won’t find this in any help file, but who needs a help file when your old buddy Jeff has your back?

Jeff Sweeney

CSWE Engineering Data Specialist 3DVision Technologies

Applications for SolidWorks on a stick

Monday, March 17th, 2008

This year at SolidWorks World, SolidWorks announced to a select number of people they are piloting a project where they installed SolidWorks on a USB jump drive! I, like nearly everyone else in the room were pretty impressed and looked forward to playing with it….but really had a hard time coming up with practical applications for it. I figured if nothing else, once the trial period timed out I was getting a free 2GB jump drive.

I played with it on two of my machines, it did quite well! Seemed a little slow starting up, but once it was running, it seemed nearly as fast as a normal installation.

But what can I do with it?

  1. It could be a poor man’s network installation. Say you have a computer in the back that you use only occasionally, -don’t want to consume a full SolidWorks license -don’t want to pony up for a network license either
  2. If you have several customers, each demanding you provide them with SolidWorks data in a different version. Today you can duel-install, or even tri-install but several SolidWorks installations on the same machine takes up a lot of disk space.
  3. Hate doing SolidWorks upgrades? Imagine just walking to everyone’s cubical and handing them a new USB key. “Here use this one instead”
  4. How much time do you spend evaluating a new service pack before you roll it out to your users? This time could be cut drastically, if a service pack turns out to be a dud, just tell everyone to use the old drive instead!

Doesn’t take much to then imagine CAD managers walking around with a key chain full of SolidWorks installations. -Probably makes the SolidWorks licensing department’s heads spin! Will SolidWorks on a stick ever become a reality? I hope so; I suppose it is up to the lawyers.

Jeff Sweeney

CSWE Engineering Data Specialist 3DVision Technologies

The Jeff Ray tour continues

Monday, March 17th, 2008

After Jeff Ray, the CEO of SolidWorks fills up with pizza in Columbus on the 25th, he is going to Painesville Ohio to visit the North East Ohio SolidWorks User Group on March 26th.Visit their website for full details.

Two stops in Ohio in two days! If you want to meet the man who controls the tool you use every day, there has never been a better opportunity!

Jeff Sweeney

CSWE Engineering Data Specialist 3DVision Technologies

Flattening Imported Sheet Metal Part Files

Monday, March 17th, 2008

SolidWorks gives you some great tools to flatten imported sheet metal part files. The tool called “Insert Bends” automates this process. After identifying the fixed face, SolidWorks adds sheet metal information such as Bend Allowance, Auto Relief, as well as Rip Parameters. This works great as long as you have a part with uniform wall thickness. If you find yourself with a part who’s thickness varies (as is the case often in bends), then here is a trick to try out.

  • Right click on a face as shown below and pick “Select Tangency.” This should highlight all of the faces on one side of your part. Now use the surfacing tool “Offset Surface,” setting the offset value to zero. This creates a surface that is wrapped on the top or bottom of your part.
  • Locate the Folder titled “Solid Bodies” near the top of your Feature Manager. Expand this folder, select the body that is listed and choose “Delete” (from right click or keyboard). Now you are left with only the surface body that you have created.
  • Select the surface body and use the “Thicken” (Insert/Boss Base/Thicken) feature to create a solid by thickening the selected surface in the direction and value that you select. This process ensures that you now have a uniform wall thickness.
  • Now you are ready to flatten the part as usual with the “Insert Bends.”

This process is one that I use a lot when dealing with problematic sheet metal files. The steps above should help you create geometry that is able to be flattened if the error initially was a result of inconsistent material thickness.

Sheet_Metal_Flattening

Daniel Graham

Daniel Graham
Applications Engineer
3DVision Technologies

Miami Valley SolidWorks User Group Announcement

Thursday, March 13th, 2008

The next Miami Valley SolidWorks User Group meeting is scheduled for April 28, 2008 at Gander Mountain.

Guess who the speaker is going to be! Yup your favorite blogger! -Nope not Lombard, – - it will be ME! I will be presenting: “How to write a Best Practice Document” – essentially the same presentation I gave at SolidWorks World.

Here is the current agenda…

5:30pm – 6:20pm Registration, food, and networking.
6:20pm – 6:30pm Opening Remarks.
6:30pm – 7:30pm Speaker
7:30pm – 7:35pm Rousing rounds of applause
7:35pm – 7:45pm Break.
7:45pm – 8:05pm Review Tips & Tricks that everyone has brought to share.
8:05pm – 8:15pm Discussion about next meeting date and what we would like to cover.
8:15pm – 8:30pm Wrap-up Prize giveaways.

Randy Adams is collecting RSVPs.

Hope to see you there.

Jeff Sweeney

CSWE Engineering Data Specialist 3DVision Technologies

Invest in your SolidWorks setup

Tuesday, March 11th, 2008

You know how Granny in the Sylvester and Tweety cartoons always says: “You reap what you sow”? Who do you know is wiser than Granny?

You made an investment when you bought SolidWorks. SolidWorks is making you money, but your investments shouldn’t stop after you purchase your software. You need to customize your system so it works its best in your environment.

The easiest customizations are keyboard shortcuts, toolbar configurations, file properties and drawing templates. (You would be amazed how many people aren’t even doing this! You better be!)

A purchase part library has a return on investment (ROI) of nearly one for one. Meaning the time you spend creating a part for your library is nearly recouped the very first time you use it. (It isn’t exactly 1:1; some time is lost because you need to spend a little bit of time creating the part for maximum re-usability and coming up with a location to store and recollect the file.) Certainly you will come out ahead the second time you use that part.

Putting a commonly used feature in the feature library has a ROI of 1:1.5. Again a useful library feature requires a little pre-planning; but looking up a hole pattern for a commonly used purchase part, dimensions for a lift-locate cutout, or the proper sizes for a shaft feature is a complete waste of time that you shouldn’t have to do more than once.

Smart parts have a ROI of about 1:3.7. Yeah, you have to use them almost four times to get your time investment back -mostly because they require quite a bit more pre-planning, and I at least usually end up changing my mind several times before I get one built the way I like.

DriveWorks/DriveWorksXpress’ ROI is all over the board. It depends so much on the complexity of what you are doing. Simple parts can be in the range of 1:5, large complex assemblies can certainly climb higher. Remember though, a good DriveWorks implementation can be used over and over again giving you payback for years -and be used by more than just your engineering department.

Macros. It doesn’t take me long doing a mundane task before I decide I would rather write a macro. Good macro writers can get a ROI of 1:10, but don’t forget a few good macros will get your co-workers buying you drinks for years to come.

Where did these ROI numbers come from? …okay I made them up, just me patting my head and rubbing my tummy. However I can guarantee you this: A designer who has made good investments in his system can design significantly faster [and better] than a designer using an out of the box system. Spend the time now, enjoy the fruits of your labor later. You either lead, follow or get out of the way. Where do you want to be?

These investments will certainly pay off better than my 401k has been the past few years.

Jeff Sweeney

CSWE Engineering Data Specialist 3DVision Technologies

Finding THAT Needle in a Haystack!!

Wednesday, March 5th, 2008

I was reading the SolidWorks Community online journal when I came across an interesting passage that underscored the need for an integrated data management solution to keep track of analysis results.

http://www.solidworkscommunity.com/feature_full.php?cpfeatureid=26119

At a time where huge amounts of data circulate through computers and servers, it is almost way too easy to misplace information. Haystacks of information are growing ever larger and the needles ever smaller!!

It is a routine procedure in a battery of analysis tests to make numerous modifications to geometry based on the simulation results. More often than not, reverting back to an older iteration is a common procedure. Hence, the need to accurately document simulation results even during the course of one project cannot be over-emphasized. Adding to the mix is data misplaced, lost in transition, or unsystematically archived when it has to be cross-referenced for subsequent projects. The location of folders and drives often resides on the minds of a few individuals in the organization, whose loss implies time, energy and dollars disappearing down the drain.

The need for a PDM/PLM solution cannot be overlooked. For COSMOS users, it might be worthwhile to consider using PDMWorks to check-in COSMOS analyses results into the vault along with SolidWorks model revisions. This can be done by simply activating a flag while checking a model into the vault. This assures that the .CWR file (COSMOSWorks Results file) travels along with the model through its journey in digital space.

So the next time such data is lost, it would be prudent to deliberate over a tool like PDMWorks to understand archiving data better. After all, who likes to lose luggage at the baggage terminal after a long flight?!!

Vikram Vedantham

Simulation Product Manager 3DVision Technologies

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