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# Using Global Variables for Speed Modelling

Friday October 19, 2012 at 11:28am

Global variables are a useful tool for allowing quick changes to key dimensions within a model. This technique is useful when situations require speed modelling, whether this is during SOLIDWORKS exams or to quickly produce variations of a design for your CAD manager.

Global Variables can be found in the Equations interface under, Tools > Equations. This menu has had a revamp since SOLIDWORKS 2012 version.

For this example I have modelled a simple screwdriver, with a global variables added to change the values for “Shaft Length” and “Head Width”.

To ensure that the shaft remains thick enough for any sized Head Width, there has been an equation added to the shaft diameter. This ensures that the shaft is always 1.5 x “Head Width”.

To apply this to a sketch dimension, double click the dimension to bring up the Modify box. Insert an equal sign and choose the appropriate global variable. When in this mode, normal mathematical functions (+, -, /, *) can be applied as well as more complex functions (Cos, Tan, If, etc)

To apply a global variable to a feature, the Feature Dimensions need to be shown. This is done by right clicking on the Annotations folder in the Feature Manager Design Tree and selecting “Show Feature Dimensions”. When the dimensions are visible, double click it and edit the modify box in the same method as for a sketch dimension.
However this is changing in SOLIDWORKS 2013, allowing equations to be entered as the feature is applied.

After the global variables have been applied, they can be easily changed in the equations interface. This will update the model allowing for quick changes. In the examples below I have changed the “Shaft Length” from 400mm to 250mm and the “Head Width” from 10mm to 18mm. From changing these dimensions I can quickly produce multiple sizes of screwdrivers.

During SOLIDWORKS Certifications, this method can be used to quickly change dimensions for continuing questions with different dimensions.

If you are interested in becoming a Certified SOLIDWORKS user, there is a usual webcast on SolidSolutions.tv, which runs through a past exam question. The link for this can be found below.

Richard Earley
Applications Engineer

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