HackSpace_-_April_2020

TUTORIAL

An introduction to functional 3D printing

Click on the Sketch Dimension button at the top left

of the UI (two vertical lines with a double-headed

arrow between them). Then click on the two circles

one after the other again, and move your mouse off

the side and click. You should see a small text input

box where you can enter the dimension. 10 mm is a

bit much here, so let’s go for 5 mm. You should now

have what you can see in Figure 1.

Next, we need to draw our two rectangles, with

constraints, of course, to make sure everything is

nicely centred and symmetrical. To do this, first select

the Line Sketch tool and draw a line from the origin

to the top of the outer circle (this is important!), and

then use the Rectangle tool to draw a rectangle

above the circle (Figure 2). We’ll add the dimensions

in a second. First, we’re going to use the Tangent

constraint to ensure our rectangle is tight against

the ring – click on the Tangent button from the

Constraints toolbar (red circle with a black line on it)

and then click on the bottom line of the rectangle

we’ve just drawn followed by the larger of our

two circles. Next, we’ll centre it by clicking on the

Symmetry constraint (dotted line between two halves

of a rectangle), then clicking on each of the two sides

of our rectangle followed by the line we drew in the

middle of our circle. The rectangle should snap to the

centre. We can set the dimensions of our rectangle

by clicking on the Sketch Dimension button and then

the sides of our rectangle. The height of the rectangle

will be the thickness of our fence post, and the width

will be the size of the gap between the two fence

posts (21 mm each in our case).

TWO RECTANGLES + TWO CIRCLES =

FUNCTIONAL DESIGN

Our final rectangle will go above the previous one.

Sketch a rectangle (a little above the rest of our

sketch), then use the Collinear constraint to ensure

they’re always touching by clicking the top line of

our previous rectangle and the bottom line of our

new one. We can add symmetry the same way as

we did previously, using the line in the centre of the

circle as our line of symmetry. As for dimensions, this

rectangle should be around 20 mm tall and 20 mm

wider than the previous one. Finally, draw two small

lines to better connect our first rectangle to the ring

(see Figure 3) and click on the green tick on the top

right of the toolbar to finish the sketch.

The hard work is all finished at this stage – we just

need to make it 3D. Select what we want to extrude

by clicking on the inside of one of the rectangles

Figure 2

When adding the

symmetry constraint,

select the two

features you want to

be symmetrical before

selecting the feature

that will represent the

line of symmetry

Figure 3

The finished sketch with all constraints and dimensions. Notice

the small lines drawn to connect the ring to the rectangle

CONSTRAINTS

Constraints are a very useful way to define

relationships between different sketch objects.

You can define if a line should always be at a

tangent to a circle, if two features should always

be symmetrical to each other, if two lines should

always run parallel or perpendicular to each other,

etc. While this is obviously useful at face value, it

becomes vital if you need to edit any dimensions

in your sketch while preserving the important

relationships. You can find Constraints in the top

centre of your UI when you’re in the Sketch menu.

Some digital

callipers come with

‘feeler gauges’

which are awesome

for bed levelling

QUICK TIP