In this entry, we show how to design DYOR bPED with QCAD step by step (this is a complete version of it).
Our proposal for the design of DYOR in 2D is shown here:
Base design
Create a rectangle of dimensions (82,97) mm, place the first corner at position (0,0) mm.
Now, with the rounding too [R,N] with a radius of 5 mm round the corners of the base:
Starting 8 mm of distance from the sides, we can create two circles to pass through the servo cables with radius 4.5mm. The centres of the circles are actually in coordinates (8,8) and (74,8) mm, respectively.
Create two rectangles for the leg servos. The first rectangle has, as first coordinate the corner at (0,30.4) mm and the second corner coordinate at (11.8,53.6) mm. The second rectangle has as first coordinate the point (70.2,30.4) mm and as the second coordinate (82,53.6) mm.
Now, we create holes for robot’s face. The first rectangle is placed at corner (22,89) mm from the origin and the second corner is placed at a relative position @10,3 mm from the first corner. For the second hole, we repeat the procedures, but now the first corner is placed at (50,89) mm from the origin.
Now, we should remove unnecessary parts for laser cutting. In particular, we will remove the lines of the servos in coincident with the robot’s base. So the actual design should be as shown:
Finally, we will set all created objects to belong to the “Cut” layer and join them to create a single polyline with command [O,G].
Foot design
The foot design is same for both feet and a vertical mirroring is required once one of them is created to create the other one.
On a new drawing, create a rectangle of dimensions (66,75) mm, place the first corner at coordinate (0,0) mm (some parts of this rectangle will be removed later on).
Now, with the rounding tool [R,N] with a radius of 10 mm we will round the corners of the foot:
Now, we will create holes to insert the ankle part of the robot. They are two rectangles of dimensions (5,3) mm. The first corner of the first hole is placed at coordinate (28,4) mm, while the second corner is at coordinate (33,7) mm. Repeat the process for the second hole with coordinates (38,4) mm and (43,7) mm, respectively.
Now, with the ellipsis tool, we can create three ellipses at the front of the foot, to represent the toe’s nails. Their position and size are not relevant as long as they satisfy minimum manufacturing constraints:
Finally, with the arc segment tool, we can create the toes. Again the position and size are not relevant, but we must concatenate arc segment ends, so the end point of one must be the starting point of the next one. The easiest way is to use the option to create the arc segment by specifying three points.
Now, we can move all elements to the “Cut” layer and join them to create a single polyline using the command [O,G].
Leg Design
The leg is composed of three parts: the front part, fixed to the feet servo; the rear one, in contact with the ankle part and the top one attached to the servo leg. All three parts must create a “U” once assembled.
Let’s first create a polyline with the following coordinates:
0,27 @0,-27 @5,0 @0,3 @5,0 @0,-3 @5,0 @0,27
Now, let’s create a circle with radius 5mm and centre (7.5,33.5) mm:
Now, we will create tangent lines to the circle with initial points the ends of the polyline:
To remove the part of the circle not belonging to the periphery, we can use the Divide tool [D,I], select the circle and the intersection points. Once the circle is divided, we can remove the arc segment we are not interested in.
Now, we can create a circle with radius 3.5 mm and centre (7.5,33.5) mm.
and another smaller circle with radius 2 mm and centre (7.5,19) mm.
To generate the servo horn, we can create tangent lines to both circles.
Now, we will create an arc segment with radius 3.5 mm and end points coincident with ends of the two recently created lines. This arc segment appears selected in the image.
Finally, we can divide the smaller circle into to at the tangent points as before with the Divide tool [D,I].
Now it is convenient to move the periphery objects as well as the big circle to the “Cut” layer and the objects corresponding to the servo horn to the “Engraving” layer.
As a reminder, you can join all objects with the command [O,G].
Rear Leg
Based on the previous design, we can remove the inner objects and create a circle with centre (7.5,33.5) mm and radius 2.45 mm for the ball bearing. All elements must be moved to the “Cut” layer as a single polyline.
Top Leg
Create a polyline with the following commands:
0,3 @5,0 @0,-3 @5,0 @0,3 @5,0 @0,33 @-5,0 @0,3 @-5,0 @0,-3 @-5,0 @0,-33
Now, we create three circles with centers and radius as indicated:
- First circle: Center (7.5,19.5) mm and radius 3.5 mm.
- Second circle: Center (7.5,5.2) mm and radius 2 mm.
- Third circle: Center (7.5,33.8) mm and radius 2 mm.
Now we create four line segments tangent to the circles as shown:
Now, let’s divide (with command [D,I]) the circles into two at tangent points and remove the reminder arc segment. To make sure that the dividing point is the correct, it should be indicated as “intersection” when placing the cursor over it.
Now, to avoid getting confused, it’s better to move the polyline and the central circle to the cutting layer, which will be temporarily hidden.
Create another circle with centre (7.5,19.5) mm and radius 3.5 mm and as before, we divide the circle into four segments with at the contact points with the lines and remove the reminder segment at the sides and move them to the “Engraving” layer. The expected result is shown below (remember to join all polylines):
Ankle Design
The ankle is a part with a small hole for a rivet passing through the ball bearing (inserted in the rear leg part). Let’s first start with a polyline with the following commands:
0,9.3 @0,-9.3 @5,0 @0,3 @5,0 @0,-3 @5,0 @0,9.3
Now, let’s create an arc segment with radius 7.5 mm and end-points the ends of the polyline.
Finally, we will create a circle with radius 1 mm and centre (7.5,9.3) mm.
Now, we can move all objects to the “Cut” layer and join them to form a single polyline with command [O,G].
Face Design
Let’s start by creating a polyline:
0,70 @0,-67 @11,0 @0,-3 @10,0 @0,3 @18,0 @0,-3 @10,0 @0,3 @11,0 @0,67
Holes for the sonar sensor are circles of radius 8 mm, with centres (17,57.5) mm and (43,57.5) mm, respectively. On the other hand, the hole for the buzzer is a circle with radius 6 mm with centre (30,37.5) mm.
For the holes corresponding to the LED strip with 7-LEDs, the “mouth”, we will start by creating a square with 5×5 mm dimensions (corresponding to the LED in the centre position). The first corner of the square is the coordinate (27.5,14.1) mm, while the second corner with (32.5,19.1) mm. Select the square and create a copy of it [M,V] and introduce as the reference point any corner of the square and as a target point @8,0, that is, the new square will be placed 8 mm to the right (make sure you don’t delete the original during copying). In order to create rotated copies, we will first create an auxiliary line between the middle points of the central square (so that we can choose later on the middle point as a pivoting point.
Now, we can select the square to the right and create 5 copies rotated 60º with the command [R,O] and selecting as pivoting point the intersecting point of auxiliary lines. After that, we can remove auxiliary lines.
Now, we can draw the hair, in a similar way we did the toes, by drawing connected arc segments.
Now, we can move all object to the “Cut” layer and join the elements with the command [O,G].
Note
In the basic version of bPED, the LED strip is not created because this LED strip only works with 3.3V.
The basic design is therefore very similar without the LED strip and the Powerbank (replaced with a 9V battery holder to reduce price). As a consequence, the face is 29.8mm shorter and the robot base is 21mm smaller.
