Lego Assembly Tutorial
 

Before beginning this tutorial you must download the lego design files

In this tutorial you will learn how to create assemblies using simple lego bricks. To create assemblies you add components and put the components together through a series of constraints. The constraints you can apply are as follows:

  • Align: This will forces two surface to lie in the same plane
  • Mate: This will force two surfaces to face each other
  • Offset: Apply a mate or align but supply some distance to separate them by
  • Center Axis: Takes two cylindrical objects and forces their axis to be centers
  • Orient: Makes one surface point in the same direction as another surface

Start a new design file and set the units to inches

  • Tools>Options>Units>Select Inches for the design

We will start by adding the first 2x4 block to the assembly

  • Assembly>Add Component>Select the 2x4_block.des

This block will be the base for the entire assembly. So that the assembly can be fully constrained and not free float the base part should be fixed in its present location

Use the select component and select the 2x4block (should be highlight red)

  • Assembly>Fix Component
Change you object browser (upper left corner) to Components (this will allow you to see all the components in an assembly) Click the plus (+) sign next to the 2x4_block to see what constraints have been placed on it. It should now be fixed (represented by the clamp)

Now that the base block is fixed lets add in the top flat plate

Assembly>Add Component>Select the 2x8_flat.des

By using the component select you can click (hold) and drag a component anywhere on the screen. Move the flat plate somewhere near the 2x4 block.

 

Start by aligning the front of the 2x4 block with the front of the 2x8 flat.

Using the select surface tool select the front of the 2x4 block. To select multiple surfaces you must hold the shift key so hold the shift key then select the front of the 2x8 flat. Pro/D now knows the you want to do something with 2 surfaces. Right click to get the selection menu and choose Align.

Align surfaces means that they will be in the same plane or "be even with each other"

 
The aligned surface should now be even with each other. Use the component select tool and select the 2x8 flat. Try to move the flat plate. Notice how the range of motion is restricted by the align constraint.

 
Note the addition of the align constraint in the object browser

 
Rotate the assembly so that you can see the underside of the blocks. Select the outer lip underside of the 2x8 flat. Then rotate the assembly and SHIFT select the top of the 2x4 block. Right click and choose mate. The bottom of the 2x8 flat is now mated with the top of the 2x4 block.

 

You have now applied two constraints to the components. Note that it generally takes 3 constraints to fully constrain a component so that it cannot move. Select the 2x8 flat and notice that you can still move it. The 2x8 flat moves in the only direction that has not been constrained

 

 

The final constraint will be an offset align. Select the side of the 2x4 block and SHIFT select the side of the 2x8 flat. Then right click and choose offset. Enter -0.3125 in the offset box. Select the align button

Each lego prong is .3125 inches. This means that the 2x4 block is .625 inches by 1.25 inches. By offsetting the align command the 2x8 flat is moved one lego prong row in. Positive/Negative numbers only decides the direction of the offset.
Try playing with the offset value. Double click the last align under the 2x8 flat in the object browser. Change the offset to .625. Try both positive and negative to see what it does. When you are finished put the align offset back to -.3125
Your assembly should now look like the assembly below:

 

Now add in the 1x2 block_axle_holes.des component

Assembly>Add Component>Select the 1x2 block_axle_holes.des component

  • Align the rear of the 1x2 with the rear of the 2x8 flat
  • Align the side of the 1x2 with the side of the 2x8 flat
  • Mate the bottom of the 1x2 with the top of the 2x8 flat

 

Now to add the axle we will use a center axis command

Assembly>Add Component>axle.des

Select the axle outer surface and SHIFT select the hole inner surface. Right click and choose center axis

To finish the object, offset, align the end of the axle and the side of the 1x2 by 1 inch

 
  • To add the final piece add the 1x4 block_axle_holes.des component.
  • Center the axis of the axle on the center hole of the 1x4 block_axle_holes
  • Align the end of the axle to the side of the 1x4 block_axle_holes

To the 1x4 block_axle_hole you need to orient in to the rear of the assmebly

  • Select the rear of the 1x2 block_axle_hole
  • Shift Select the rear of the 1x4 block_axle_hole
  • Right Click>ORIENT>45 degrees

When you save an assembly file it will also have the .des extension. To avoid confusion always include the letter asm in the file name so that you know it is an assembly. (ie: schweitzer_lego_asm.des)

 

 

Coloring Components
To color the components select a component then right click and choose select Component Color.
Hiding Components
Sometimes when making an assembly it is necessary to hide some of the components so that you can see surfaces. To hide a component, right click the component in the object browser and select hide. To unhide something, right click the hidden component in the object browser and deselect hide.

 
Edit Components in Context

When doing an assembly it is sometimes necessary to edit one or more of the original component (design) files. You can do this by just loading up the component (design) file, changing it then re-saving it. All changes will automatically be updated in the assembly.

If you want to edit a component and see it in the assembly while you are editing it you can edit a component in context (or simply put edit a part with the assembly showing)

Select the component in the object browser, then right click and choose Open Part in Context. The component design file will open up but the assembly will show in faded gray. Make any desired changes to the design file, save it, close it. The assembly file will be automatically updated.

 

 
Checking Interference

When an assembly is finished you should make sure that none of the parts are overlapping or interfering with each other.

Tools>New Measurements>Interference

In this assembly there should be some very very small interference with the 2x8 flat and the 1x2 block axle hole. It is caused by a slight error in the radius of the hole in the block.

CAUTION CAUTION CAUTION

When you are done looking at the interference ALWAYS hit CANCEL. If you select okay then the interference check will be added to the variable list. This will force Pro/D to do an interference check everytime you change anything in the assembly. This will cause huge system slow downs!!!!! If you accidentally hit okay you can remove the inference check by doing the following:

Tools>Variables>Open up Measurements, Click on interference, hit the delete key

 

 

 

 

  
Tutorial Created by Steve Schweitzer