3DVision Technologies Blog

What’s better than free?

…yeah I can’t think of anything either. For the past few days I have been playing with a fun little application named Mojopac.

Think of it as a way to have SolidWorks on a stick but now you have an entire OS too! PC on a stick! …or even PC on a iPod! (I am using a portable hard drive) It feels a lot like Virtual PC except you do not have to buy an additional OS and it is portable.

The free version does not allow you to use it for commercial use (there is a version you can buy) but it is great fun to play around with. I have installed SolidWorks 2009 on it. Pretty snappy!

It appears the folks at SolidWorks heard my gripe about their naming convention. Though the name couldn’t be much longer.

SolidWorks’ virtual components are so, so sweet. The fact that SolidWorks Enterprise PDM supports them adds just a bit more butter on top of the piece of toast. …but…what if you need to assign a virtual component a part number before you save it out as its own file? You cannot use SolidWorks Enterprise PDM’s serial number generator because you have no way to get the number nor tell the generator you manually assigned a number.

Here is a nice little SolidWorks macro to get you started. It simply finds the next available serial number and returns it to the user in a message box. The user can use this assigned number in anyway he chooses.

[You’ll need to replace “Trains” with your vault name and “PartNumber” with the name of your serial number.]

'remember to add PDMWE Type Lib as a reference!
Sub main()
Dim objVault As IEdmVault8
Dim objSerNoGenerator As IEdmSerNoGen6
Set objVault = New EdmVault5
objVault.LoginAuto "Trains", 0 'use name of your vault
Set objSerNoGenerator = objVault
strNewNumber = objSerNoGenerator.GenerateSerNo(_
"PartNumber", 0, "", 0, 0, 0, 0)
MsgBox "The next avaliable part number is: " _
& strNewNumber
Set objSerNoGenerator = Nothing
Set objVault = Nothing
End Sub

Anytime you need the next avaliable serial number this could be used. i.e. files added via Pack and Go, drag and drop…

The first pre-release of SolidWorks 2009 is out. This release still isn’t intended for production, but we can now at least talk about it outside of the beta confidentiality agreement.

2009 appears to be a pretty good release, I think I am going to like it better than 2008 even though there aren’t as many “big hitter” new features. Download it and give it a spin.

I think my favorite new thing is that they have finally ported SolidWorks 2009 to the Commodore 64 (VIC-20 is due SP2). No more hassle with the RealView graphics cards and video drivers. 16 colors and a 40 character display are for me! It is on 783 cassette tapes, so ensure your mailing address has a loading dock. Estimated download times with your 300 baud modem are 43 months, assuming your mom doesn’t pick up the other extension during the download. The SID chip really sounds good during collision detection.

Did you know that you can compare data between multiple studies by using functionality in COSMOS called COMPARE TEST DATA?

Let us take an example of a model with multiple studies defined. We are interested in comparing the stress and displacement results at a specific strain gauge location (located by a vertex shown in the figure).

You can access the compare test data tool by right clicking on the part/assembly name as shown.

In the Compare pop-up window, the user is required to select the vertex where the data is to be studied by clicking the “ADD” button. The user can select the type of quantity to be studied there as well (stress, displacement etc.).In the bottom portion of this window, the user can select which studies are to be compared. Once the user selects the “COMPARE” button, COSMOS would list out the results by comparing the different quantities against the selected studies.

Upon assigning the vertex/vertices where the result quantity is to be studied, as well as the studies in the bottom panel which are used in the comparison, the values are computed. These results are shown in the adjoining figure. Note that the percentage deviation from the first study in the list is also indicated in the columns. This helps estimate the error/eccentricity in results when comparing multiple “what-if” scenarios.

Be the first kid on your block to see what is new in SolidWorks 2009…

Date: September 18, 2008
Time: 05:30 PM - 08:30 PM
Length: 3 Hours 0 Minutes
Location: Gander Mountain
8001 Old Troy Pike
Huber Heights, OH 45424

Agenda:
5:30–6:00pm - Registration, food, and networking
6:00-7:00pm - Avelino Rochino from SolidWorks presentation on Sheet Metal-CSWP
7:00–7:10pm, Break
7:10–8:10pm, Randy Simmons is going to do the abbreviated version of what’s new in 2009
8:10–8:20pm, Discussion about next meeting date and what we would like to cover
8:20–8:30pm, Wrap-up and prize giveaways

SolidWorks: Heard! is a great little place where you can hear podcasts relating to SolidWorks. Make sure you hear podcast #162, Maria Sarkar co-founder of DriveWorks is interviewed.

PDMWorks Enterprise 2008 introduced a new ability to automatically export your BOMs during transitions in your work flow. To date though I had not found any example code of how to extract the information from the XML file once it was created.

Luckily, I caught my buddy Philip Stears deep down in his dark lab writing this little diddy.

'Create the document object ready

Dim document As New XmlDocument()
Try
'Load the document from disk
document.Load("WorldDominationPlan.xml")
' Get hold of the root element in the XML file
Dim rootElement As XmlElement = document.DocumentElement
' Go through each element in it called "Property"
For Each childElement As XmlElement In _
rootElement.GetElementsByTagName("Property")
' Get the name and value attributes
Dim name As String = childElement.GetAttribute("Name")
Dim value As String = childElement.GetAttribute("Value")
'Do something clever with them
TakeOverTheWorld(name, value)
Next
Catch ex As Exception
' Foiled again, try again tomorrow
Foiled(ex)
End Try


He was in process of writing the “TakeOverTheWorld” subroutine, luckily I caught Philip just in time. Engineering Data Specialist Man saves the day again!

I have always wondered about the perception of management towards purchase and implementation of CAE software. The benefits are seldom evident, and the success of the tool is almost always inevitably buried under the blanket. The timely rollout of the product line, minimal failures, and increased revenue are more direct indicators observed by the management. I guess the yeast is never appreciated for good bread. The dough and the bread makers are!!!

So it often becomes a big challenge when management needs to be convinced about the potential for a product like COSMOS. I found this interesting article written by Vince Adams, one of the Product Managers for the COSMOS FEA suite, where he addresses the resistance from the management and how to counter them.

http://designsmarter.typepad.com/vinceadams/

As you would perceive after reading this article, the issue lies in educating management sufficiently for them to perceive the benefits and liabilities associated with FEA. Setting good expectations would relieve a lot of stress downstream.

Continued from the previous article (Redundancies in COSMOSMotion 2008 - Part I)

http://3dvision.com/wordpress/index.php/2008/07/18/redundancies-in-cosmosmotion-2008-part-i/

THE CURRENT SOLUTIONS

The user has two choices when it comes to addressing the above problem:

1. Put some thought into creating mates. Address the five degrees of freedom by distributing them at the three hinge locations without repeating them. (As you can imagine, this can become a tedious procedure where you have to re-think the process of creating mates). However, this will ensure that the loading is distributed evenly to the three hinges. 
2. If redundancies are already present in a pre-existing model, then a workaround is to somehow make the joints have finite stiffness, instead of infinite stiffness. This will ensure that the extra weight of the door gets distributed to the other hinges.  COSMOSMotion 2008 permits the user to specify finite stiffness to the joints by specifying the values when defining the mates (Create a mate > Go to the Analysis tab in the mate property manager). However, this presents two challenges by itself:

             a) The user needs to account for a good approximation for the stiffness value and the damping effect so that the joint is neither over-stiff nor over-soft.

             b) The user needs to figure out the right combination of stiffness values for the rotational and translational degrees of freedom for the mate.

THE FUTURE

The interface behind COSMOSMotion is now being rapidly revamped, and is guaranteed to grow by leaps and bounds in the years to come. If redundancies can be addressed during the mate-creation stage, rather than putting out fires later on, then running motion simulations would become a part and parcel of every design. One possible suggestion (if the developers are hearing) is to indicate graphically on the screen right during the mate creation stage that a particular part already carries constraints in specific directions, and has only so many degrees of freedom remaining. This would help the user make the best mate-choice while initially setting up the assembly in order to achieve solution 1 (from above) a modeling practice instead of a Simulation fix!!

BOTTOMLINE

The user has to spend a little time getting these issues addressed if there are redundancies in the model. Don’t get me wrong here – COSMOSMotion is a stellar product and does more than a great job in bringing virtual simulation to desktops!! I have seen a lot of success stories with it. One customer recently told me that using it in a project helped them finish a project on time (which was a company record!!). However, it seems to be one product that is facing an uphill battle in customers accepting the technology, learning it and using it in their day-to-day decisions.

The team that went back with the training from this week is now already on their first project in getting engineering data from using Motion. They used to generate prototypes that took forever to generate, test and gather valuable data, not to mention the resources, man-hours, time and money! COSMOSMotion 2008 has equipped them with the potential to revolutionize their product cycle and time to manufacturing!

I taught Motion 2008 this week to a group of engineers from one of the larger accounts that we handle in Cincinnati, Ohio. As you might have gathered from my previous post, Motion 2008 has a new revamped interface that makes the tool easier to use. Yet, the ubiquitous problem with rigid body kinematics and dynamics – Redundancies, continues to haunt the user and make them think twice about integrating simulation directly into their conceptual stages.

BACKGROUND: What are redundancies?

Apart from a single-word definition (nuisance!!), redundancies can be understood easier by taking note of an example. Consider the door to your room that is mounted to the frame by three hinges. From Newton’s falling apple theory, the weight of the door because of gravity is opposed by equally distributed reaction forces in the opposite direction at all the three hinges. Now, if we remove the two lower hinges and let the door be mounted just with the top hinge, two things happen:

1. The opposing reaction force is seen at the top hinge, and is equal and opposite to the weight of the door. This leads to the hinge material (aluminum/steel) bending, and ultimately deforming/breaking because of its inability to carry the moment acting about the center of mass of the door.
2. The person mounting that hinge is rushed to the ER!!

The same event happening in COSMOSMotion would give the ultimately desired effect of the door standing upright without any problem! The reason for this is that COSMOSMotion considers treats every part in the assembly as rigid bodies, and every joint as a rigid joint. In other words, the hinge being used is not made of a material with a finite stiffness, but has infinite stiffness and can carry any load by itself without any deformation! What a pain – since the door motion can now be simulated by just one hinge, and the other two hinges become redundant!!!

Thus, the output in COSMOSMotion would show the opposing reaction force to be equal and opposite to the weight of the door on the top hinge, and show zero reaction force on the other two hinges!!

THE PROBLEM: What does a user do when his SolidWorks model has three hinges?

We know that any part held in 3-D space has six degrees of freedom – three rotations and three translations. When you create mates in an assembly, you are removing degrees of freedom from this part. In other words, when you mate the door to one hinge, you ensure that the only degree of freedom remaining for the door is the rotation about the axis of the hinge. The other five degrees of freedom are constrained by the mates created in SolidWorks.

Redundancies are created if the same five degrees of freedom for the door are repeatedly constrained along the same axis (even if at different locations, such as the other two co-axial hinges). In other words, if you have constrained all five degrees of freedom at one hinge, then you cannot re-account for the same at the other locations.

(To be Continued…Part II : The Solution)