2D Part Design Lesson 2 - BobCAD-CAM

2D Part Design Lesson 2
For this lesson we are going to take a look at the steps to create the following drawing using
the tools inside of the BobCAD-CAM software.
First we must decide how we are going to approach this drawing. The features that stick out
are the bolt pattern of holes, the five large pockets, the center hole, and the outside profile.
The easy part will be drawing the bolt pattern so we will start there.
Drawing the Bolt Pattern
• Begin by starting a new drawing inside of the software by clicking the File Menu and
selecting New.
• It is always good practice to separate your major part features into different layers. So
we will create a new layer for this drawing and name it HOLES. Use the following
steps to create the HOLES layer:
◦ First make sure the layer tab is selected in the Layer-UCS-Post Manager and right
click anywhere inside the window.

◦ Next select Add Layer and a new layer will be added to the layer list.
◦ Type in the name for your new layer and name it HOLES. (Note: If the cursor is
not all ready flashing in the name field for the layer, the user can click+pause+click
the text in order to edit the name.)
◦ Click on the HOLES layer icon so that a check mark appears, making it the active
layer.
• From our print we can see that we are going to create 10 equally spaced 0.2500”
diameter holes in a circular bolt pattern, starting at 0 degrees and no holes are
skipped. We also need to decide where to place the holes in the CAD window. Being
that all of the radii are measure from the center it seems best that we should center
this drawing around 0,0 in the workspace. Let's begin drawing our bolt pattern.
◦ In order to draw a circular bolt pattern, we can simply click on the Other menu, and
select Hole Pattern. Use the following settings in the Hole Pattern edit dialog in
the Data-CAM Tree Manager and click OK:

• That completes the hole pattern. Next we will move on to drawing the outside profile.
Drawing the Outside Profile
• Before beginning drawing the outside profile of the part, start by creating a new layer,
naming the layer PROFILE, and making this the active layer. The steps for creating a
layer can be found in the prior section Drawing the Bolt Pattern
• We can see from the print that there is are ten 0.25 radius arcs around all of the holes
that also share the same center point as the hole itself, all connected by 5” diameter
arcs, with 0.25” radius fillets in between. Noticing that all of these shapes are exactly
the same, we will draw one, and use the Rotate command to save a lot of drawing
time.
◦ First lets draw the 0.25 radius arc that shares the same center as the hole set at 0
degrees.
▪ Start by clicking the Arc Menu and selecting Arc Snap.
• Enter 0.25 for the Radius
• Leave the Start Angle and End Angle at 0.000 and 360.000 respectively.
▪
Next while holding the Shift key down on your keyboard select the farthest right
hole in the bolt circle. This will activate the snap points allowing the user to
select the arc center. Click the center snap point to create the new arc. The
result should look as follows:

◦ Next lets draw the 5” diameter circle centered around 0,0.
▪ Click on the Arc Menu and select Arc Coordinates.
▪
In the fields enter the following values and click OK:
◦ Next we need to get rid of the extra geometry we have in the workspace. In order
to do this we are going to need to break the arcs in the workspace.
▪ Click the Utilities Menu and click Break and select Many.
• Select the two arcs we have just created and right click and select OK.
(Note: Instead of right clicking and selecting OK, the user can also press the
space bar to finalize their selection)

◦ Now that our two arcs have been broken at their intersections, we can delete the
unnecessary geometry from the workspace.
▪ With the Break Many function still active, select the shown below and press the
delete key on the keyboard.
▪
Finally click the Cancel button to cancel the Break Many function.
◦ Next we need to add our fillets between the two arcs we have created for the
outside profile.
▪ To do this, click the Arc Menu and select Fillet.
▪
Enter 0.25” in the Radius field and click the two arcs in the following locations:
◦ That completes are desired shape so now we can use the Rotate function to create
the other 9 copies of this geometry.
▪
Start by clicking the Utilities Menu and selecting the Rotate function.
• We know that there are 10 equally spaced copies of this geometry, so to
determine angle to rotate enter 360/10 into the Z field because we want to
rotate around the Z axis.
• Click the Copies button to enable the copies field and enter 9 into the field.
We want to create 9 copies because we want 10 of these shapes and we all
ready have one.

• In the Origin box, choose Enter and leave all fields set to 0.0000 since we
will be rotating around the origin.
• Next we need to select the 0.25” radius arc entities we wish to copy. Select
the arcs shown below and right click in the workspace and select OK
• Finally press OK in the Data Manager to complete the rotate command. The
result should look as follows:
◦ The final step to completing the outside profile is to simply remove the extra
geometry left from the 5” diameter circle by breaking all of the entities at their
intersections.
▪ Click the Utilities Menu and click Break, then select Many function.
▪
▪
We do not want to break any of the holes from our hole pattern, so we can
simply blank this layer by clicking the small black square next to the HOLES
layer in the Layer-UCS-Post Manager.
Now that the HOLES layers is blanked, click and drag a window around

▪
everything in the workspace to select all of the entities. After making sure all of
the visible entities are highlighted, right click in the workspace and click OK.
Finally, highlight the extra entities shown below in the workspace and press the
Delete key on the keyboard to remove the extra entities.
▪ That completes the outside profile for the part. Next we will need to draw the 5
pockets inside of the part. The HOLES layer can also be made visible again by
clicking the square located to the left of the layer name in the Layer-UCS-Post
Manager.
Drawing the Interior Pockets
• Before beginning drawing the interior pockets of the part, start by creating a new layer,
naming the layer POCKETS, and making this the active layer. The steps for creating a
layer can be found in the prior section Drawing the Bolt Pattern
• We have multiples of the same interior shape equally spaced around this part, so again
we are simply going to draw one interior pocket and use the Rotate command to make
the extra copies of this interior pocket.
• To create the outer arc of the pocket select the Arc Menu and select Arc Coordinates.

◦ Enter 2.25 in the Radius field
◦ Set the Center X, Center Y, and Center Z fields to 0.0000
◦ Enter 0.0000 in the Start Angle.
◦ Enter 360.000 in the End Angle to draw a complete circle.
◦ Click OK to create the arc in the workspace
• Next, create the inner arc of the pocket by simply changing the radius field to 0.75 and
clicking OK. We chose 0.75 because as we see in the print, the radius of the inner arc
of the pocket is 0.25 inches bigger than the 0.5 inch radius arc in the center of the part.
• Next to create the edges of the pocket we will first draw a construction line. Start by
clicking on the Line Menu and selecting Join.
◦ To draw the reference line, first click the top of the inner arc followed by a second
click on the top of the outer arc to complete the line.

• In our print, notice that the ribs between the pockets are going to be 0.25” wide, so we
will need to create a parallel line half this distance from this center line we had just
created.
◦ First click the Line Menu and select Parallel
▪
▪
Enter 0.125 in the Distance field since this is half of the rib.
Click the reference line we had just created and click anywhere in the
workspace to the left of this reference line to create the parallel line.
▪
Next repeat this step creating a parallel line to the right.
• Next zoom into the area near the end of these newly created lines and the inner arc
and notice the gap between these entities. We will need to fill this gap by using the
Trim function.
◦ Select the Utilities Menu, click Trim and select One Entity.

◦ First click the end of the line near the inner arc
◦ Next click the inner arc to complete the function. The line will automatically extend
to the inside arc.
◦ Repeat these steps for the other parallel line we created.
◦ Repeat these steps again, except now trim the rib edge lines to larger outer arc of
the pocket.
• Next we need to create the opposite side of the pocket.
◦ Select the Utilities Menu and select Rotate.
▪
▪
▪
▪
▪
▪
Enter 360/5 in the Z field because we
are creating 5 equally spaced pockets.
Entering 360/5 will give us the 72
degrees we are looking to achieve.
Select Copy and enter 1 in the field.
Under Origin, choose Enter
Enter -0.125 in the X field.
Enter 0.125 in the Y field.
Enter 0.0 in the Z field.
◦ Select the right edge of the rib we created
and right click in the workspace and select
OK.

◦ Finally click OK in the Data Manager to complete the Rotate command.
• Now that the outside perimeter of the pocket is created, we need to get rid of the extra
geometry by breaking the entities at the intersections.
◦ Select the Utilities Menu and select Break and click Many.
◦ Click the two edge lines of the pocket and the inner and outer circle that comprise
the pocket and right click in the workspace and select OK.
◦ Finally highlight the entities shown below and press the Delete key on the keyboard
to remove the unnecessary entities. (Note: In the event that the entities shown
cannot be highlighted the same way as shown below, it will be necessary to go
back and make sure the rib edges were trimmed properly to the inner and outer
arcs, and repeat the break many function)
• To finish the pocket we simply need to add the 0.25” radius fillets to all of the corners.
◦ Select the Arc Menu and click Fillet

▪
▪
Enter 0.25 in the Radius field
Click the entities in the order shown below to create all of the necessary fillets.
• Now to complete all of the interior pockets we need to rotate the shape around the
origin creating 4 copies.
◦ Select the Utilities Menu and select Rotate.
▪ Enter 360/5 in the Z field because we are creating 5 equally spaced pockets.
Entering 360/5 will give us the 72 degrees we are looking to achieve.
▪ Select Copy and enter 4 in the field.
▪ Under Origin, choose Enter and set all of the fields to 0.0000
◦ While holding the Shift key on your keyboard click on one of the entities of the
interior shape to highlight the entire chain and then right click in the workspace and
select OK.

◦ Complete the function by clicking the OK button in the Data Manager.
• The last step to completing this part will be to draw the final circle at the center of the
part.
◦ Select the Arc Menu and select Arc Coordinates.
▪ Enter 0.5 in the Radius field
▪ Set the Center X, Center Y, and Center Z fields to 0.0000
▪ Enter 0.0000 in the Start Angle
▪ Enter 360.000 in the End Angle to draw a complete circle.
▪ Click OK to create the arc in the workspace
You have completed 2D Part Lesson 2!