Modeling a spoon

Posted by fuccaro on 13th August 2003

Conventions: I marked with red the last constructed or modified entity. Also I have rotated the view when I thought that it will help me to give a better explanation . You don’t need to follow me each time.

I marked with capital letters the entities as I created them. The numbers refers points or surfaces.

I assume you know the basics so I often omitted the details.

When we extrude shapes the needed height usually is not known. Keep in mind that it is easiest to use a part of a “longer” solid than extend a small one, so make it “long enough”.

We are working “by eye”. Sometime, if you don’t like the shape, you will need to use Undo several times to modify a dimension or a distance and then to remake the loosed steps. This job is easier to complete in other programs like 3D Studio, but AutoCAD can handle it too.

I used AutoCAD 2000

Words in UPPERCASE represents commands or options and those in Italic are the prompts and answers returned by AutoCAD.

Let’s start!

Create 3 layers named Spoon, Work and 2D. Make 2D the current one.

Set DELOBJ to zero.

Draw a horizontal line (A) and move it on the layer 0. We will use this as symmetry axis for our models. Draw a circle (B) with the center on the axis. Copy it (C) and draw an other circle (D) tangent to the first two (image 1).

Trim the circles until you got the shape presented in the second image. Draw a polyline between the points 1 and 2. Select it, right click and choose Polyline Edit. Press J for join and select the arcs. Now you have a closed polyline (E).

Revolve it around the axis defined by the points 1 and 2. Move the resulted solid (E) to the layer Spoon. Make this layer current and freeze the 2D.

Slice the solid. When prompted:

Specify first point on slicing plane by [Object/Zaxis/View/XY/YZ/ZX/3points] enter ZX and click in the point marked with 3 in the image 3.

Use 3Dorbit to rotate the view as in the image 4. Use Solidedit to create the cavity: SOLIDEDIT > BODY > SHELL.

Remove faces or [Undo/Add/ALL]:

Click the face marked red in the image 4. Enter the offset distance (I marked it with two clicks on the screen). Now we have a shell (image 5).

Set the layer Work as current.

Now we “only” need the handle. Pay attention to the joint of the two parts!

Due to symmetry is enough to draw only the half handle.

Draw a rectangle (G) intersecting the shell (image 6). Extrude it. The height of the extrusion must be at least the half width of the handle (image 7). We need the intersection of the solids F and G. But we don’t want to loose the F so we will use INTERFERE instead of INTERSECT.

INTERFERE

Select first set of solids: Select objects: select the F solid

Select objects: Select second set of solids: select the G solid

Create interference solids? [Yes/No] <N>: y

The H solid is now created (image 8 ). Freeze the layer Spoon, unfreeze 2D.

Draw a horizontal line marked I (image 9) and a circle J tangent to E and I. The circle J must meet the polyline E over the solid H. Trim the circle J using as cutting edges the line I and the polyline E. Delete the line I (image 10).

Draw a polyline K between the corner of the solid H and the arc J (image 11). Edit the polyline K: add to it (join) the arc J (image 12).

Now we will curve the top of the solid H

SOLIDEDIT > FACE > EXTRUDE

Select faces or [Undo/Remove]: select the top surface (marked with 4 on the image 12)

Specify height of extrusion or [Path]: enter P

Select extrusion path: click the polyline K.

You have something like in the image 13, right?

The end of the handle is curved (5, image 13). We are going to change it.

Rotate the UCS with 90 degrees around the OX axis. Draw a line Ltrough the corner 6 like is showed in the image 14. Slice the handle. When prompted about 3 points enter the two ends oh the line L and for the third one enter @0,0,1<enter>. Delete the line L.

You must have something like in the image 15. Extrude the face marked red in the image 15. The result is shown in the image 16.

Slice the handle:

Specify first point on slicing plane by [Object/Zaxis/View/XY/YZ/ZX/3points] <3points>: enter ZX

Specify a point on the ZX-plane <0,0,0>: click the endpoint marked with 7 (image 16)

Now slice it again, this time by a XY plane passing through point 8

The result is in the image 17.

Rotate again the UCS with 90 degrees around the OX and draw a polyline M to give shape for the rest of the handle (image 18 ).

Use SOLIDEDIT > FACE > EXTRUDE. By extruding the face marked red in the image 19 along the polyline M you got the handle as in the image 20.

Return to the previous UCS and draw a polyline N to shape the half of the handle. There are some restrictions regarding this polyline (see image 21): at the end marked with 9 the polyline must exceed the handle (H) but at the end 10 the polyline must be inside of the handle. Also at the end 10 the last arc must have the center point at the same Y co-ordinate as the spoon axe is. Otherwise the handle will be not smooth.

Mirror the polyline N and get the polyline O (the mirror axis is the same as the spoon axis). POLYEDIT the polyline O: join N and than close it. See image 22 for the result.

Extruding the closed polyline O we got the solid P. Be sure that P intersects the handle H, move P along the OZ axis if needed (image 23).

Intersecting the solids P and H we have the half of the handle (image 24).

On my spoon there were unwanted edges on booth sides of the handle. I used FILLET to get rid of them. As radius you should use the maximum allowed value. So try a radius, undo, try again, undo again…

The rest is trivial: mirror the half handle and use UNION to combine the three solids in a single one. Try to FILLET every edge to give a more polished look.

Enjoy your meal!