4. Modeling concept and basic manipulations

If you notice, the TinkerCad workspace has a horizontal platform on which we design the model. It is possible to change the grid of this base, its step. The step of movement of the part will depend on it (Figure 25).  

The grid does not have an absolute coordinate system. That is, where you placed the shape, the program calculates  the start of the coordinates. Dragging the  object, the deviation is calculated relative to the previous location. 

^{Figure 25.  Change the grid step} 

According to the modeling rules, the  model is projected into an XY plane that coincides with the ground. To project in a different direction, you must first change the working plane. 

Let’s try to design the model of Figure 26 (1).  

1. Let’s drag the cube into the working field and set its dimensions 40x100x80 
2. Also drag cylinder to the scene. If you notice, the background of the cylinder coincides with the working plane. We can solve this problem in two ways: 

• • Change the working environment to the side of the box 
  • Rotate the cylinder 90 degrees to the x axis 

Changing the working plane. Select the "workplane" icon (Fig. 26 (1)) and click on the box wall (Fig. 26 (2)). Now that the cylinder is pulled, its base will coincide with the new working plane, which means with the side plane of the box. 

^{Figure 26. Changing the working plane}

Cylinder rotation. Drag cylinder and select it. Click on the arrows showing the rotation with respect to the x-axis and set the rotation angle to 90 degrees.

^{Figure 27. Rotation of the cylinder with respect to the x axis}

3. Location of cylinder hole. For moving cylinder to special location, we must change working plane to the side of the box. So it is better to change it before including cylinder shape.  

• • Align both shape by one edge.  
  • Move cylinder 35 mm to the right and 25mm to the top  
  • Change working plane to the ground and set navigation bar to TOP 
  • Move cylinder vertically and fit to the box  (Figure 28) 

4. Now as cylinder is in correct place, we can change type of shape to “hole” 

5. Select both shapes, set “group” 

6. Export file to *.stl 

Figure 29 shows how final model looks in TinkerCad program (left) and as *.STL file (right)

^{Figure 28. Moving cyliner}

  ^{Figure 29. Final model in TinkerCad environment and *.stl file} 

TinkerCad is convenient to try modeling tool for beginners. For complex projects it is better to choose Blender program.  

Short review, how this simple model could be created using blender. Default view of starting program is in image 30. Default shape is cube, units – meters, length 2m.  

Steps to begin:  

1. Change units to millimeters 
2. Change length of edges to x, y and z axis 40x100x80 
3. Select shape and press CTRL+A and select Scale. With this operation we set new shape of box as default. 

^{Figure 30. Box transformation} 

4. Press Tab to switch to Edit Mode 

5. Press SHIFT+A and select Cylinder shape. 

6. This shape by default is oriented by Z axis (Figure 31). So we need to change options of it: 

• • Radius of background is 15mm 
  • Rotate by Y axis 90 degrees 

^{Figure 31.  Cylinder options} 

7. Now we have two duplicated planes – box and cylinder background. Delete theses planes (two backgrounds of box and two of cylinder). 

8. To make a plane between edges of box and cylinder auxiliary edges are needed. It is simple to calculate distance between point of circles diameter and box edge horizontally. It is 35mm. Select circles diameters point, press E (extrude), lock Y axis and set 35 (Figure 32). At the top left corner you can check what options are set. 

^{Figure 32.  Auxiliary edge for planes} 

9. The same step for opposite side of circle. And for opposite background. 

10. Now as we have auxiliary edges, dividing background plane to two part, we can select separately parts as it shown in Figure 33a. Then press “F” (Face). The Face is created between selected points (Figure 33b) 

11. Make the same step to second part of background. Also the same steps for opposite background.  

12. Press TAB  to switch to Object mode.  

13. The last step is to export to *.stl file: File>Export>(*.stl) 

14. The view of final shape in Blender program and exported to *.stl file is shown in Figure

 ^{Figure 33.  Select points(a) and create Face between them (b)}

^{Figure 34.  Final object in Blender enviroment and created *.stl file} 

It seems Blender is easer tool to create such model. But you have to know a lot of things to use it, such as different modes for editing, for plane direction and ect.