How to work with Inventor’s sketch blocks.
It is common for a CAD application to have the means of grouping objects together. The grouped objects then behave as a single element. AutoCAD does this through blocks. To the surprise of many, in Inventor’s sketch environment, you can also group elements together into blocks.
Sketch blocks improve productivity. Why redo when you can reuse? Blocks build consistency, as you use the same block symbol repeatedly. Update the block definition and all instances update to match it.
For parts and assemblies, it not only supplies a way to reuse common shapes, but it also supplies a different method of tackling designs. The block instances keep the degrees of freedom you allow, making them perfect for simulating kinematic assemblies. Because they are sketched objects, it can be easier (and quicker) to simulate the design before committing to 3D modeling.
Sketch Blocks in Parts and Assemblies
In a sketch, create the geometry. If it is not complete, you can always add to it after. Make sure to add the base constraints like horizontal, vertical, and perpendicular. As is true with 3D models, degrees of freedom play a big part in the use of blocks.
There are objects ineligible for sketch blocks. This includes projected and derived geometry. Inventor ignores these ineligible objects if you try to add them and shows no messages.
Sketch tab > Create panel > Create Block (or in the Layout panel)
To create a block, follow these steps:
- Select the objects for the block. Do this by making an individual selection or by selecting multiple objects with a selection window.
- Select the Insertion Point. This is the point used when you insert instances into sketches. Enable Visibility to see the point.
- Set the Name. This is what shows in the browser.
- Optionally include a description. The description can help find which block to use when the file contains many blocks.
Here I create a block for a hydraulic cylinder. As the purpose is to make a schematic representation, there is not a lot of detail.
Block definitions appear in the browser, in the Blocks section. Insert instances by dragging and dropping the block (or using the right-click Insert option) into any sketch in the model. Inventor suffixes each instance with a colon and the instance number.
A sketch block behaves like other sketch objects. Constraints limit changes. You can constrain and dimension a block to other objects in the sketch, including other blocks.
Here I constrain two blocks to build a hydraulic cylinder. Before adding a dimension, I can dynamically drag the cylinder rod. By adding a dimension, I use it to manage the amount of engagement. Because a point on the block is fixed to the origin, I can rotate the unit by dragging.
You can build a block of blocks by nesting blocks within other blocks.
By default, this block is rigid, freezing all open degrees of freedom in its subcomponents. You can make the block flexible (via the right-click menu) to open it, allowing you to use the open degrees of freedom.
By combining blocks with parametrics (constraints and dimensions), you get a simple yet powerful method to test designs before committing to 3D modeling.
To edit a block in-context (as in where it sits), select Edit Block from the right-click menu (or double-click the instance). To edit the block out-of-context, you’ll want to double-click the definition in the Block folder.
While editing, you can adjust sizes as well as add and remove geometry. The changes made to the block affect the definition, propagating to all instances. When you are done, right-click in the graphics window and select Finish Edit Block.
To adjust the properties, right-click the instance and select Block Properties. Here you can change the Block Name, Description, and Insert Point.
You can adjust the properties for each instance. Select the block, right-click, and select Properties. Here you can change the line color, type and weight. This supplies a method of differentiating block instants.
Explode, as it sounds, blows up the block. This removes the grouping, restoring the objects as individual objects. This does not remove the definition, even if you are exploding the only instance within the model. A typical use is to explode an instance so that you can make changes and define a new (but similar) block.
So why use sketch blocks? It’s easier to reuse geometry. It makes it easier to work with the geometry because you can group related objects. You can quickly simulate assemblies before committing to 3D. And as a bonus, you can use sketch blocks as the basis for a top-down design layout.
