Unit 6 : Dimensioning & Parametric Constraints DT2510: Advanced CAD Methods

Using Dimensions Understanding the Components of a Dimension Creating a Dimension Style Drawing Linear Dimensions Dimensioning Non-orthogonal Objects Adding a Note Applying Ordinate Dimensions Adding Tolerance Notation Unit 6 : Dimensioning & Parametric Constraints

Dimensions are an essential part of technical drawings as they describe the exact size and locations of elements in the design. When using dimension, it helps to know the name that AutoCAD gives to the parts of the dimension so that later, when you need to make adjustments to dimensions, you will know what AutoCAD is referring to. Unit 6 : Dimensioning & Parametric Constraints

Out of the box, AutoCAD gives you dimensions in a style that is suited to mechanical drawings. like the top dimension in this figure. In AutoCAD this is called the standard dimension style. You can set up other dimension styles like the architectural style shown just below the mechanical example. AutoCAD also offers a variety of other arrows shown at the bottom. Unit 6 : Dimensioning & Parametric Constraints

To create a dimension style like the architectural one shown in the previous slide, you use the Dimension Style Manager. Choose Format > Dimension Style to open the Dimension Style Manager dialog box. You’ll see the Standard style already listed in the Styles list box to the left. click the New button and the Create New Dimension Style dialog box appears. Enter a name for your new style and click Continue. Unit 6 : Dimensioning & Parametric Constraints

The tabs give you an idea of the settings you’ll find. The lines tab shown here lets you set the different characteristics of the dimension lines. This is where it pays to know the names of the dimension parts. Unit 6 : Dimensioning & Parametric Constraints

This image shows you what some of the settings are for in a dimension. Other tabs let you set the location and orientation of text, text style and size for dimensions and many other dimension features. Unit 6 : Dimensioning & Parametric Constraints

When you’ve finished setting up your dimension style, click OK in the New Dimension Style dialog box and you return to the Dimension Style Manager. Select your new style and click the Set Current button, then click Close. This will ensure that your new style is the current one. Unit 6 : Dimensioning & Parametric Constraints

You can also select your dimension style from the Annotate tab’s Dimensions panel drop down list to make it current. Dimensions panel Dimension Style drop- down list. Unit 6 : Dimensioning & Parametric Constraints

Once you’ve set up your dimension style, you can begin to add dimensions. There are several dimensions you can create. The most typical is a linear dimension. Choose Linear from the Dimension flyout on the Annotate tab’s Dimensions panel, then select two points the define the length you want to dimension. The dimension shown here includes an alternate dimension for metric distances. Unit 6 : Dimensioning & Parametric Constraints

If you are adding a string of dimensions, Choose Continue from the Annotate tab’s Dimensions panel, then select the next set of points you want to dimension. Unit 6 : Dimensioning & Parametric Constraints

Once a dimension is in place, you can make adjustments to the location of the dimension using it’s grips. Unit 6 : Dimensioning & Parametric Constraints

Besides linear dimensions, you can add angle, diameter, and radius dimension. Unit 6 : Dimensioning & Parametric Constraints

If you have a radius dimension that has a center that is beyond the drawing area, you can use the Jog dimension. The length of an arc can be dimensioned using the Arc Length dimension. Unit 6 : Dimensioning & Parametric Constraints

A note with an arrow can be added using the Leader option. Unit 6 : Dimensioning & Parametric Constraints

Ordinate dimensions are also available. Unit 6 : Dimensioning & Parametric Constraints

Tolerance notation can be added through the Geometric Tolerance dialog box. Unit 6 : Dimensioning & Parametric Constraints

Choose Tolerance from the Annotate tab’s expanded Dimensions panel open this dialog box. Click in the Sym or sample box to open the Symbol dialog box. Unit 6 : Dimensioning & Parametric Constraints

Making “Smart” Drawings with Parametric Tools What Are Parametric Drawings? Adding Constraints to an Existing Drawing Removing Constraints Adding Individual Constraints Adding Dimensional Constraints Unit 6 : Dimensioning & Parametric Constraints

Don’t let the term parametric drawing scare you. Parametric is a word from mathematics, and in the context of AutoCAD drawings, it means that you can define relationships between different objects in a drawing. For example, you can set up a pair of individual lines to stay parallel or set up two concentric circles to maintain an exact distance between each other no matter how they may be edited. Unit 6 : Dimensioning & Parametric Constraints

Parametric drawing is also called constraint-based modeling, and you’ll see the word constraint used in the AutoCAD Ribbon to describe sets of tools. The term constraint is a bit more descriptive of the tools you’ll use to create parametric drawings because when you use them, you are applying a constraint upon the objects in your drawing. Unit 6 : Dimensioning & Parametric Constraints

The drawing to the right shows two versions of the same part. The bottom version was derived just by changing the overall horizontal dimension. All of the other changes – the resizing of the arcs and cricles – were take care of by what are called geometric and dimensional constraints. Unit 6 : Dimensioning & Parametric Constraints

With constraints, you can also mimic the behavior of a mechanical assembly to test your ideas. The parametric drawing tools let you create linkages between objects so that if one moves, the others maintain their connection like a link in a chain. Unit 6 : Dimensioning & Parametric Constraints

The tools you’ll use to add constraints to a drawing can be found in the Parametric tab. Unit 6 : Dimensioning & Parametric Constraints

One simple way to add constraints to an existing drawing is to use the Auto Constrain tool in the Geometric panel. Unit 6 : Dimensioning & Parametric Constraints

For example, you can click the Auto Constrain tool, and then select the lines and arcs in this simple drawing. Unit 6 : Dimensioning & Parametric Constraints

AutoCAD will automatically add constraints to the objects. Unit 6 : Dimensioning & Parametric Constraints

Once the geometric constraints have been added, a change in one part of the drawing will affect the others. Unit 6 : Dimensioning & Parametric Constraints

To remove a constraint, select it, right-click and choose Delete from the right-click menu. For example, you can delete one of the parallel constraints in this example… Unit 6 : Dimensioning & Parametric Constraints

With the parallel constraint removed, you change the arc diameter and the lines no longer remain parallel. Unit 6 : Dimensioning & Parametric Constraints

Geometric constraints can be used to aid in the drawing process. For example, you can use the concentric geometric constraint to move this circle so that it is concentric with one of the arcs. Unit 6 : Dimensioning & Parametric Constraints

Geometric constraints can be used to aid in the drawing process. For example, you can use the concentric geometric constraint to move this circle so that it is concentric with one of the arcs. Unit 6 : Dimensioning & Parametric Constraints

Dimensional constraints enable you to control the dimensions of a drawing by changing a dimension value instead of changing the drawing itself. Unit 6 : Dimensioning & Parametric Constraints

When geometric and dimensional constraints are combined, a change in a dimensional constraint results in changes to other parts of the drawing as shown in the first example. Unit 6 : Dimensioning & Parametric Constraints