CATI Tech Notes

3D Sketches

What are 3D sketches and what are they good for? 3D sketches can be a valuable tool while sketching in SolidWorks. Not only do you have use of all of the sketch tools such as Lines, Arcs, Circles and Splines, but you can also use all of the Rectangle sketch tools as well. 3D Sketching can be especially useful when you are creating a path for a sweep or a loft.

To create a 3D Sketch go to Insert, 3D Sketch. This puts you in the 3D Sketch mode. Select the type of sketch you want to create like a line, circle, arc etc… You will see that your cursor now changes to show coordinate values underneath it.

The values (XY) let you know which plane you are about to sketch on, as well as the red arrows on the origin. Pressing the Tab key will allow you to switch the sketch planes from XY to YZ to ZX.

 

Pick the sketch plane you want to start on a start sketching. As you create your sketches just tab to change planes and create the desired sketch. You can add dimensions and relations just like in a 2D sketch.

Phil Whitaker         
CATI Technical Support             

Sketch Text

When trying to create text in a part with different orientations you can use centerlines.  For instance, if trying to create text in a circle just draw a circle and select "For Construction" in the property manager.  Once in the property manager for Text, select the circle and start typing the text.  It will populate along the circle.

Another problem someone might see is that when you have straight centerline lines the text populates backwards and upside down.  This is because the line was drawn from right to left and not left to right.  When you select the line, check to see what angle the line is drawn in.  If the property manager for the line says 180 degrees then the text will be backwards and upside down.  Lines are drawn in polar coordinates in SolidWorks so that will cause the text to populate wrong.

Ketul Patel
Technical Support
Computer Aided Technology, Inc.
ketulp@cati.com

Why Analyze ???

Rajat Trehan

Product Manager - Design Validation
Computer Aided Technology Inc.

Perils of Sharing System Options (where's my journal file)

The Copy Settings Wizard is a very handy tool. Personally, I love the ability to deploy system settings company wide using the .sldreg file in conjunction with an admin. image.  Others just love the ability to share their settings with another user or backup their settings in case of a machine change or registry corruption.

Recently, however, an inconvenience has reared its head.  After sharing settings from one user to another the receiving user gets an annoying message saying that they cannot create a journal file.  Now this doesn't keep anyone from modeling, it's just an annoyance.  But it occurs every time they launch SolidWorks and it's totally unnecessary.  It is also only a problem if the users do not have admin. rights. 

The reason that this occurs is that the location where SolidWorks automatically puts journal files is determined when the software is installed as "C:\Documents and settings\<username>\Application Data\SolidWorks\SolidWorks 2008".  Once this location has been written to the registry it stays there and is transported with the registry everywhere it goes.  So if the user "Administrator" installs the software and then copies his settings to share with other users, the other users journal files will be aimed at "C:\Documents and settings\Administrator\Application Data\SolidWorks\SolidWorks 2008."  In most cases the user will not have permissions to read or write to that directory and the errors will then occur.

Work around (1)

This one is easy.  But remember, torquing around with your registry is dangerous, so watch out!

First use the Copy settings wizard to create the .sldreg file to be shared.

Use notepad to edit the file (It's actually a text file that is easily edited)

Using the Find feature in the Edit menu of Notepad search for the phrase "SolidWorks Journal Folders".

Delete this entire line from the file and then save.

When the user reads the file in now this line will either remain the same as his current settings or be recreated from scratch to point to "C:\Documents and settings\<username>\Application Data\SolidWorks\SolidWorks 2008" if he does not have SolidWorks registry settings yet.

Work around (2)

This one is easy as well.  But remember, torquing around with your registry is still dangerous, so keep watching out!

First use the Copy settings wizard to create the .sldreg file to be shared.

Use notepad to edit the file.

Using the Find feature in the Edit menu of Notepad search for the phrase "SolidWorks Journal Folders".

Change the path that is already called out in the file to another location like "C:\temp".  Just make sure it is a location that all users have permissions to read and write to.

When the user reads the file in now this line points to "C:\Temp."  This can make it so that these files are consistently in the same place every time on every machine.  Don't forget to go back to the original machine and change the location there as well.

Either work around will get the messages to go away.  It's just a matter of whether or not you want to go with the SolidWorks default locations for these files.  There is no other way to change the location of the journal files other than editing the registry.

Also, when working with administrative images many CAD Admins. will push out a .sldreg file with the image.  One of these work arounds should be employed before the software is deployed to clients.

Adrian Fanjoy

Technincal Services Manager

Computer Aided Technology

Copy with Mates

I think one of the most under used, but beneficial commands in SolidWorks 2008 is the Copy with Mates. It is one of those sneaky commands that gets put in a right click, but isn’t added to a toolbar by default. So if you are like a lot of SolidWorks users, you get used to the same tools everyday and don’t even notice other options that are around. When I show this to current SolidWorks users they are very excited and talk about how much time that will save them. If it is something you will use a lot, customize your assembly toolbar to include it. 

To use it, select the component(s) you want to copy. Right click on one of the components and choose “Copy with Mates." In the Property Manager on the left, it lists the selected components to copy. You can add more to here if you would like. Then you need to select the new mate references for where you are copying the part(s) to. In my example, I am going to copy the bolt and washer to a different hole on the same face. So, I am going to check Repeat to repeat the Coincident mate because the new washer is going to be coincident to the same face as the original is. For the Concentric mate reference, I will pick the face of the new hole that I want the bolt to go into. Right after you select the face, you will see the new components, hit the green check to accept and you can repeat this over and over again. Hope this tool improves your productivity with SolidWorks!

Leslie Lougheed

 

Understanding Pretty Pictures!

Interpreting results helps users understand product behavior. “Blue is good, red is bad” is the general adage. While this might hold true in some cases, it is wrong to generalize. As appeasing as color plots may seem, interpreting them could be tricky.

Animate….it’s cool!

Animations are the best way to understand part or model behavior. If the part or assembly does not move as expected, users need to go back and change the set up. This very basic method should eliminate the majority of set up mistakes. Animations also help with communicating with team members, and marketing in-house engineering capabilities on the company website.

Displacement

This indicates how much and in what direction the part moves under an applied load. If the values seem plausible, it is worth exploring the results ahead.

Failure

Whether a component will hold or fail under an applied load depends on how it interacts with the applied load. This is determined by a parameter called stress.

 

Stress

Stress is the internal reaction generated by a component to an applied load. Therefore, stress is not a material property. Meaning, stress does not depend on whether a component is made of steel, plastic or rubber. Stress can be classified into 3 broad categories.

• Normal Stress occurs normal to the face on which a load is acting.
• Shear Stress occurs when the top and bottom of a material are pushed in opposite horizontal directions.     
• Principle Stress occurs on a plane internal to a component where shear stress is zero.

When to use what? This depends upon the loading scenario.

•  First Principle Stress (P1) is the maximum stress under tensile loading, i.e. if components are being pulled apart.
• Third Principle Stress (P3) is the maximum stress under a compressive load.

Principle stress works as a failure criteria with brittle materials like cast iron, etc.

• Von Mises Stress is the overall state of stress in a component under an applied load. This combines the effect of normal and shear stresses in a component. Von Mises Stress works as a failure criteria for ductile materials like steel, aluminum, etc.

Yield Strength

Yield is the maximum load a component takes before deforming. Usually any deformation is considered as failure.

Ultimate Strength

Ultimate strength is the maximum load a component takes before failure.

Factor of Safety (F.O.S)

Factor of Safety is defined by failure mechanism for a type of loading. It is calculated as a ratio of Yield Strength to failure criteria for a component. The failure criteria can be Normal stress, Shear stress, Von Mises Stress or Principle Stress depending upon load type and material used.

Co- relating Analysis to Test data

If you are measuring the response of a structure using strain gages make sure they are mounted at locations where stress varies gradually. Also, the direction in which strain gage is mounted plays a big role.

While setting boundary conditions, make sure the physics in the model is considered. If material properties are changing with temperature or load scenario, make sure to model that into the simulation.

Also, make sure to model part interaction in assembly environment. If parts are lubricated to smooth the movement make sure to model that with the appropriate friction factor in simulation.

Rajat Trehan
Product Manager – Design Validation
Computer Aided Technology Inc.

What Do Your Designs Rely On?

Engineers are considered to be logical, thoughtful and precise with everything they undertake. Perhaps this is one reason why everyone calls themselves an engineer. A housewife calls herself a “Domestic Engineer”.  Doesn’t she organize, construct, manipulate, manage, contrive? All used to define an engineer, as per the Merriam-Webster dictionary. So next time you boast your engineering skills, remember that the over-friendly cookie baking lady has exactly the same skill sets.

There are certain tools any type of engineer would rely upon.
(a) legacy data
(b) testing
(c) intuition

Legacy Data works while designing a family of products. Meaning, similar shaped parts subjected to different magnitudes of load. Hopefully, the initial design was well engineered and optimized for material and life cycle expectancy.

Testing historically has proven to be expensive, time consuming, but definitive. Need to reduce design cycle time, and ability to match quality is the need of the hour. Depending on the nature of the industry you are in, testing more than a couple designs isn’t economical anymore.

Intuition to me works if you have worked in the field for a considerable time. I have known engineers who have spent 10 years designing a pressure vessel or a nozzle. They obviously understand different conditions that components are subjected to. The kind of experience only years of practice can give. Their first shot is very close, if not always on target to an optimized design.

The ability to test multiple concepts and improve existing designs, will define product success and market acceptance. Be it machine design or product design, everyone needs to tune up the design process or face competition from every corner of the globe.

SolidWorks Simulation or COSMOS are tools engineers rely upon to make sure their designs perform optimally. There are budget / time constraints at any given moment to ponder upon. If we prove to your management that technology works, and is economically viable will they work with us?

Rajat Trehan
Product Manager – Design Validation
Computer Aided Technology Inc.

Status code: 9 MATRIX_Singular_OR_INDEFINITE

Some error messages make you wonder, what does it take to get something simple done? I have often wondered how coders come up with names for errors and claim them to be logical? One common bane is “Status code 9." This message is often followed by a second message claiming there aren’t enough restrains defined.

Basically, the software cannot figure out how parts are interacting in 3D space. Every solid or surface body has six degrees of freedom available to it (three translational and three rotational). When users define loads and restraints they remove degrees of freedom from the model.  Behind the scenes (in SolidWorks) equations are being written to solve for deformation and strength of components. The equations are balanced out using generated reaction forces. If there are not enough conditions defined, i.e. the software cannot identify what is happening in a specific direction, equilibrium is not achieved and hence the solution fails.

Is there a magic button that makes all this go away? I usually refrain from making blatant promises. But an honest answer would be Yes and No!

 

 

 

 

 

 

 

Use Soft Spring to stabilize a model

Using Soft Spring to stabilize a model is a good way to make things work. Users can reach this by accessing study property. This adds artificial spring stiffness to the model eliminating rigid body modes. The stiffness value added is very small and can be neglected in most cases, but it is recommended to correct this approximation. One good technique is to check displacements in x,y and z directions. The direction in which there is the most displacement needs to be restrained.

Use inertial relief

This does exactly the same thing as the Soft Spring option in a different fashion. Inertial relief (as the name suggests) will add artificial mass in directions needed. This option is especially useful if loads are imported from motion analysis.

Do not use both the Soft Spring and inertial relief options at the same time. They would be counterproductive. If both are used in conjunction, the software will make significant assumptions and generate erroneous results.

Rajat Trehan

Product Manager – Design Validation

Computer Aided Technology Inc.