Modeling the body

Exercise 1: Modeling the body

• Open the file "01_usb_stick.3dm" in your contents folder.
• Unfold the "Exercise" layer folder and make the "usb stick body" layer the active layer.

The body of the USB stick consists of two symmetric parts. Both halves have a slight draft on the sides. The size of the body in top view is 16 x 29 mm

• Make a _Rectangle from center, having its center at (0,0,0), length of 29 and width of 16:
  • at the "First corner of rectangle" prompt use (Center)
  • at the "Center of rectangle" prompt, type 0 > [Enter]
  • at the "Other corner or length" prompt, type 29 > [Enter]
  • at the "Width. Press Enter to use length" prompt,  type 16 > [Enter]

Rhino accepts a simple 0 as the origin coordinate. In most other CAD software you need to type the full x,y,z values like 0,0,0

• Extrude the rectangle over a distance of 3.7mm with draft angle of 2 degrees. For this use _ExtrudeCrvTapered:
  • at the "Extrusion distance <1>" prompt use (DraftAngle=2)
  • at the "Extrusion distance <1>" prompt use (Solid=Yes)
  • at the "Extrusion distance <1>" prompt,  type 3.7 > [Enter]

The 2 edges on the side where the usb connector sticks out are filleted with a radius of 2mm, the other 2 edges have a fillet with a radius of 3mm.

• Fillet the short edges with _FilletEdge:
  • at the "Select edges to fillet" prompt,  type 2 > [Enter]
  • select in top view the right 2 edges
  • at the "Select edges to fillet" prompt,  type 3 > [Enter]
  • select in top view the left 2 edges
  • to complete the fillets type [Enter] > [Enter]
• Chamfer the top edge loop with _ChamferEdge, radius 2 with option (Railtype=DistBetweenRails):
  • at the "Select edges to chamfer" prompt type 2 > [Enter]
  • at the "Select edges to chamfer" prompt use (ChainEdges),
  • at the "Select first chain segment" prompt click on one of the top edges, followed by [Enter]
  • at the "Select next chain segment. Press Enter when done" prompt,  type [Enter]
  • at the "Select edges to chamfer. Press Enter when done" prompt, type [Enter]
  • at the "Select chamfer handle to edit" prompt change the option (Railtype=Rollingball) to (Railtype=DistBetweenRails)
  • at the "Select chamfer handle to edit" prompt type [Enter] to create the chamfer.
• _Mirror the part in front view over the X-axis to complete the body:
  • at the "Select objects to mirror" prompt, select the body in front view and make sure copy option is on (Copy=yes)
  • at the "Select objects to mirror. Press Enter when done" prompt, press [Enter]
  • at the "Start of mirror plane" prompt,  type x > [Enter] to mirror over the X-axis in front view.

Modeling the led light

Exercise 2: Modeling the led light The led light in the body is a cut-out that is flush with the body. To model this, we first draw the shape of the light and then use _BooleanSplit to split the led light from the body. The led light has a full rounded edge. Because Rhino cannot make full-round fillets, we build the shape with a _Rectangle and a _Circle

• Make a _Rectangle from (-17,-1) to (-10,1):
  • at the "First corner of rectangle" prompt, type -17,-1 > [Enter]
  • at the "Other corner or length" prompt, type -10,1 > [Enter]
• Make a _Circle at (-10,0) with radius of 2 mm:
  • at the "Center of circle" prompt, type -10,0 [Enter]
  • at the "Diameter <1>" prompt type 2 [Enter]
• use _Trim to trim away the inner parts of the overlapping rectangle and circle.
• _Join the remaining lines together.

 

• Move the curve in Z-direction 1.5 mm by using the Gumball:
  • click on the blue arrow once and type 1.5 > [Enter]
• _Extrude the curve with option (Solid=yes) 7 mm.
• Use _BooleanSplit with option (DeleteInput=yes) to split the top of the body with the generated shape.

• Compare your result with the "usb stick body" layer in the "Results" folder by making this layer visible.

Modeling the cap

Excercise 3: Modeling the cap

• Make the layer "usb stick cap" layer active under the "Exercise" layer.
• Hide the layer "usb stick body"

 

• Make a _Box that measures 33 x 16 x 10 mm with its center at (0,0,0):
  • at the "First corner of base" prompt, use the (Center) option
  • at the "Center of base" prompt, type 0 > [Enter]
  • at the "Other corner of base or length" prompt, type 33 > [Enter]
  • at the "Width. Press Enter to use length" prompt, type 16 > [Enter]
  • at the "Height. Press Enter to use width" prompt, type 10 > [Enter]

Creating the cut-out

Now we make a scaled copy of the box to later cut it out from the first box:

• Make sure that "Project" is on in the Osnap toolbar and the object snaps "End" and "Mid" are active.
• Use _Scale1D to make a box that is 1.3mm smaller in height on both sides (see fig. below):
  • at the "Select objects to scale" prompt, click on the box
  • at the "Select objects to scale. Press Enter when done" prompt, press [Enter]
  • at the "Origin point" prompt, use (Copy=Yes)
  • at the "Origin point" prompt, click in the mid of the right edge in front view
  • at the "Scale factor or first reference point" prompt, click on the top right corner point
  • at the "Second reference point" prompt, type 3.7 > [Enter]
  • at the "Second reference point" prompt, press [Enter] to end the command
• With Gumball move the scaled box 1.3 units to the right in front view, so that it sticks out on one side.
  • Activate Gumball in the status bar
  • Select the scaled box.
  • Move it 1.3 units to the right by clicking once on the red arrow and typing in the box that appears 1.3 > [Enter]

• Use _BooleanDifference to cut the small box from the big box:
  • at the "Select surfaces or polysurfaces to subtract from" prompt, click on the big box
  • at the "Select surfaces or polysurfaces to subtract from. Press Enter to continue" prompt, press [Enter]
  • at the "Select surfaces or polysurfaces to subtract with" prompt, use (DeleteInput=Yes) and select the small box.
  • at the "Select surfaces or polysurfaces to subtract with. Press Enter when done" prompt, press [Enter] to end the command

Move the object so that its center lies on the XY-plane:

 

• Select the result and use the Gumball to move the object's z-center to the XY-plane:
  • Make sure the Gumball is using "Snappy Dragging".
  • Start dragging in Z-direction, type 0 > [Enter], this way the shape moves exactly with its center to the XY plane.

Creating the curved sides of the cap

Exercise 4: Making the curved sides.

• Draw a Control point curve by running the _Curve command with coordinates (-18.5,7), (-2.5,10) and end point (18.5,3.5)
  • at the "Start of curve" prompt, type -18.5,7 > [Enter]
  • at the "Next point" prompt, type -2.5,10 > [Enter]
  • at the "Next point" prompt, type 18.5,3.5 > [Enter]
  • at the "Next point" prompt, press [Enter] to finish the curve
• Extrude the curve, run _ExtureCrv to both sides 6mm:
  • at the "Select curves to Extrude" prompt, select the curve
  • at the "Select curves to Extrude. Press Enter when done" prompt, press [Enter]
  • at the "Extrusion distance <1>" prompt use the option (BothSides=Yes)
  • at the "Extrusion distance <1>" prompt, type 6 > [Enter]

• _Mirror the surface over the X-axis.

We will use these surfaces to cut the cap into shape, but first we apply a fillet to the outside and inside of the cap.

• Apply a fillet to the outside and inside of the cap with _FilletEdge : A radius of 3 for the outside, and a radius of 1.7 for the inside.
• Check the normal directions of the cutting surface with _Dir : The direction of the cutting surfaces should both point towards the center of the solid. Clicking on a surface will change its direction.
• Boolean the cap with the two surfaces using _BooleanDifference.

Finishing the edge of the cap

Exercise 5: finishing the edge of the cap Along the outer edge of the cap, there is a small chamfer to make the cap look optically thinner. In order to make a smooth chamfer that runs along the complete outer edge, we first put a small fillet on the four short edges.

• Use _FilletEdge to fillet the short edges with radius 1.3
• Use _ChamferEdge to chamfer the edge with a radius of 1 - again use (ChainEdges) to simplify the edge selection - and make sure you use again (Railtype=DistBetweenRails)

Creating the holes in the cap

Exercise 6: Creating the holes There is a hole on both sides of the cap. These holes are rounded on either side. Because Rhino cannot make full-round fillets, we build the shape first with a box and two cylinders, and combine them into 1. These shapes are then used as cutters for the Boolean operation.

• Make a box  that measures 7 x 2 x 7 mm by using _Box with option (Center) at (0,0,0) and draw two cylinders as indicated in the drawing below.
• Combine the primitives into one solid with _BooleanUnion and use _MergeAllFaces to clean up the model.

• _Move the shape from (0,0,0) to (-14,0,3) and _Mirror it  to the other side like this:

• Use _BooleanDifference to cut out the holes. The cap is now finished.

• _Move the cap -4.5mm in X-direction
• Compare the result with the layer "usb stick cap" under the "Results" layer.
• Save the document

Inserting the connector

By default, when you insert another file, it imports as a "block instance". It will then be a single block item that you can move and rotate, but the individual parts in the block cannot be changed. The advantage of using blocks comes when you have several identical parts in your file that are subject to change. An example is a car model where you want the four wheels to refer to the same part. Blocks keep their reference with the original file, even if you choose embed. This means you can always update the block if necessary, but the placed block only alters when you want it to.

Excercise 7: Inserting the connector

• Hide the "usb stick cap" layer and show the "usb stick body" layer.

We will now insert the connector as a block instance and place it at the side of the connector that has the smaller fillets.

• Use _Insert to insert the file "01-usb-connector.3dm" using the option Embed at (13,0,0):
  • At the "Insert" dialog, click on the yellow folder icon to browse for the file called "01-usb-connector.3dm".
  • When you see the dialog, make sure it is set to option Block Instance, click OK and in the next dialog, use the Embed and Link option and click OK.
  • Rhino will now ask you for the insertion point. Type 13,0,0 > [Enter]
• Show the layer "usb stick cap".

Congratulations! You've now created the complete product from start to finish. There is still some work left to do though, but this will be saved for the next lesson. There we will look into adding details like a logo on the cap, the modeling of the inner cavities in the body and cutout for the usb connector part.