# Using Blender for Technical design

Blender 3D may seem for non-user quite difficult to approach, and yet there are a lot of ways to use it accuratly with measures and tree function structure.
This tutorial will design a precise screw.
It is a near way of approaching technical design. Yes, it will not be as quite easy as solidwork or others, but the aim is to be more precise with blender.

1. ### Step 1: Getting started

Load Blender 3D 2.90 and delete the cube

Goto EDIT/PREFERENCES

Activate the add-on 3d View : MeasureIt

When you enter the edit mode you are in, the mesh of the object, this is where you can change shape of each vertice of the object.

We are going to rotate this plane so it is face to us (in th ZX plane)

Type R X 90 (rotate along x axis 90°) and click anywhere in the scene to confirm

In blender dont mix up the coordinate of the vertices and the coordinate of the object

We did not rotate the object 90°, we rotated the plane that makes this object 90°, if you check the coordinate of the object it is still x 0 y 0 z 0 and that is good !

Now type 1 to get a face view of the scene (with no perspective)

You will notice that the indication of the unit is precious for us

10 centimeters means the smaller grid size you can see is 10 cm.

As we want to design a 5 cm screw we will have to resize this plane (the points that define the plane will than move alltogether to smaller coordinates, once again we are not modifying the global scale of the object, this is important)

Since our plane is 2000x2000 mm we will scale this plane to 0,01

(dont forget to select all if deselected : A )

Scale the plane to 0.01 :

S 0.01 clic on scene to validate the scalling operation (or press enter)

Zoom in (Mouse wheel), use SHIFT + center wheel button clicked to scroll keeping in front (well, as every new application you will have to get use to navigation)

If your loose the front view juste type 1 again

Now we see that each little square is 1 milimeter

Clic on the VERTEX SELECT button to only select vertex

Put the magnetic grid on by selecting SNAP TO INCREMENT and ABSOLUTE and MOVE

Then clic on the magnet and make sure it is lighted

There are a lot of ways we could have begun this tutorial, this is one of them, now we are going to move, add, vertices so we can approach the shape of the screw

2. ### Step 2: Modelling the screw precisely

Select vertices and then type G to move them as they snap to the grid you can easely start to draw the general size of the srew

Now we need to ADD some more vertices

Click on the EDGE SELECT so you can select an edge

Subdivide this edge

Select the vertices again and add as much point you want

Add some cotation with the Addon tool (optional for fun and check)

(Note that these cotation are not controlling the drawing)

To make this add on appear press N

I am discovering this add on and this is not a tutorial how to use it

Leave the edit mode and go back to Object mode (using TAB)

Be sure you are in the object mode (1)

Be sure your object is selected (2)

Go to the modifier Properties (3)

Goto to the treeview structure and rename the "plane" in Screw Body for example

3. ### Step 3: ISSUE, It is hard to stay on a plane

From time to time you will at first have difficulties drawing on a same sketch plane, if you move vertices around not facing the sketch, vertices move in all x,y,z direction and the drawing is no more aligned.

That is a big problem but you can easely correct and avoid this.

If you want to quickly put back every point, lets say on th xz plane (wich is a front view) :

Just type A for all

Type S for scale

Type Y so you can scale every vertices that went wrong along the Y axes and put them back on a XZ plane

Type 0

Type Enter

Example :I went completly wrong with this drawing, 2 points are no longer in the XZ plane

The sequence :

A S Y 0 enter will repair everything

How to move all points to a perticuliar plane ?

Face the "side view" of the plane

in our example if I type 3 (side view) I will see everypoints from side view

Activate the magnetic snap to absolute grid (1)

Lets say we want to move my Vertices (2) to (3)

just type A (for all) G (for move) and move your Vertices to the good position then left click mouse button.

How to avoid having points away from my sketch plane ?

• Always draw facing the sketch using : 1(face), 3(side) or 7(top) or 9(opposite of the actual view))
• OR Press G to move points then X, Y or Z to force the movement in one of these direction
• OR G to move and then Press SHIFT Y for example to forbid movement along Y axis (same for X, Z)

4. ### Step 4: Creating multiple function

This is where you can approach tree function :

Each modifier is an equivalent of a function in any mechanical CAD modeling

We will insert equivalent of a REVOLUTION function

The volume appears, we will have to increase a bit the resolution (2)

We could have chosen an another axis of rotation than Z, an empty object for example.

There is an important step to achieve

Put the viewport and render to 32 so we can get an accurate rotation (1)

(we will smooth later on with another function, dont put this resolution to very high value, it is useless waist of memory)

Put the distance to 0 (because we have a very little object we need the vertices to really merge at short distances) (3)

Scale it and position it on top of the screw

Rename it

Go in to edit mode : Add some more points and position the right way

Extrude along Z axis : E Z

Exit the EDIT MODE and go back to OBJECT MODE

Select the screw and add a boolean modifier

The object is still visible, because only the screw is affected, we must hide this "top screw print" but before we hide this part (so we can see the boolean operation) we must "parent" it to the screw body. Why ? Because if later on we move the srew, the object that defines the top screw print will not follow, and the boolean operation will just stay where it is.

Select the object that defines the operation (1), select Object properties(2) Relation (3) and parent it to Screw body(4)

Select the Top screw print and hide it H or use the treeview (alt H to unhide all)

Lets smooth the 3D :

Select the screw body object; Go to Object and select SHADE SMOOTH (don't worry everything looks worse)

Goto OBJECT DATA PROPERTY (1)

Goto NORMALS (2)

Check Autosmooth (3)

Optional : You can modify the angle between face normal considered to be smooth (4)

5. ### Step 5: Going further

For the body : We made a revolution wich is linked to the Z axis

It would be wiser to create an empty arrow

I had to rescale it so we can see something (2) BUT DONT DO THAT NOW

be sure the empty is in 0/0/0 (1) and everyscale is at 1 (and not 0.1)

Now we will link the revolution (screw modifier) function to that empty object

Select the Screw(1), edit the Screw modifier choose the empty as the object

If we move the empty we see that the screw is linked in it's function (and everything goes wrong )

A good thing to do is to PARENT this screw to this empty.

It will then follow every displacement/Rotation or scale from the empty

(that is why I didn't want you to rescale to 0.1 the empty, the screw would have become 10 times smalers !)

1) Select the screw, 2) select the object properties 3) Select Relations 4) 5) Choose for the screw the empty as a parent

Now we can move the empty around, rotate it, and the screw will follow

We can then PARENT the thread to the screw. so every things follows

1) Select the thread and parent it to the Screw body 2) 3) 4)

Notice 5) that we see how things are Parented together.

We must also define the spining of the thread linked to the empty

Now we can rotate the empty and move it, and every thing will follow !

What is great about that ?

Well no functions are baked, you can still change whatever dimension you want :

All these function let you create you model as you would in a parametric 3D app

If you want to bake your design, you can always apply the modifiers, be carreful in wich order you apply things.

Dont forget we juste hided the function of the Top screw print, so probably we will sooner or later want to just apply this function and then supress this object.