3D Computer Graphics Using Blender 2.80 - Modelling Methods, Principles & Practice

          Blender Tutorials: Machined Metal Gear- part 1

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Creating and Texturing a Gear - Part 1

Following on from the Precision Modelling Guide, which walked you through the basics of producing dimensionally accurate models and outputting them to scaled dimensioned drawings. I thought it would be good to describe the process of turning those 3D representations into an almost photo realistic image, suitable for use in technical or marketting literature.

This won't be an in depth guide to modelling, thats already covered in the Precision Modelling Guide and I am assuming you have already looked over those tutorials before starting this.

Textured Gear

Blender Mechanical Gears Manual The process of creating the geometry of a gear is quite complicated and if done manually will require quite a bit of maths, fortunately for Blender users, there is an excellent add on script created by Stefano Sellery called Blender Mechanical Gears, that does all the hard work for us.

If  you haven't come across Blender Mechanical Gears before you will find there are two scripts, the first called BMGm-0.0.2.py generates a mesh of a gear tooth to the peramiters you set, the second BMGs-0.0.2.py allows you to animate the rotation of the gears so they spin in perfect mesh. For this tutorial we will only be using the mesh script.

If you havent already got it the script can be downloaded from the Blender Wiki. Contained in the zip file is the two scripts and an excellent .pdf manual. You will need to put the scripts into your Blender scripts folder. All the instructions for doing this are in the BMG manual.

Once you have loaded the BMG scripts go into Blender and split the 3D view into two screens and change one of them to a script window. On the scripts menue ckick Scripts>Mesh>Blender Mechanical Gears. If Blender was already open when you added the scripts to the script folder  the scrip won't be showing in the list of available Mesh scripts so click Scripts>Update Menues, then try again.

The BMG interface will open in the Scripts Window which contains a lot of options for different gear types, the BMG Manual contains all the information on how to setup different gear profiles. For this tutorial we only need to have a basic gear shape so the default settings shown opposite will suffice.
Blender Mechanical Gears Interface

Gear Tooth Profile
If you click generate the script will create two gear teeth, the main gear centred on the scenes origin (located at 0,0,0) and a pinion tooth perfectly meshed to it.

We don't need the pinion and could have clicked No Pinion in the BMG interface, so select the pinion and delete it.

The object centre of the teeth are on the centre axis of the gear allowing us to snap the cursor to the centre point and Spin Dupe the tooth profile around the centre point.

The tooth has a pitch circle radius of 5 Blender units and we need to add a bore of 2 blender units diameter (it makes sence for one Blender unit to equal one centimetre on this project)

If you Tab into edit mode you will see the geometry of the tooth, the inner diameter is constructed of 4 vertices (A) which need to be joined to the bore of the gear and the tooth has an unnecessary edge loop running horizontally through it (B).

select and delete X Edge Loop the unnecessary edge loop(B).
Tooth Geometry

Gear construction

1. With the cursor on the object centre and in top view add a circle with 60 vertices ( 20 tooth gear x 3 vertices = 60)

2. In front view, raise the circle 0.5 Blender units to align it with the top face of the gear

3. Delete all the unnecessary vertices from the inner diameter, then select the 4 inner vertices on the top of the gear tooth and the 4 inner diameter vertices.

4. Add feces between the selected loops F Skin Face/Edge loops
Ctrl-R to add a loop of vertives and slide them to point (A)
Ctrl-R between the new vertices and the original gear tooth vertices and press number 5 on the keyboard (not Num Pad) to add 5 more evenly spaced loops that will make up the gear recess (B).

Copy Shift-D the new vertices from the top face of the gear and snap them to the bottom face using Blenders Magnet Snap feature (on the 3D view headder) set to Closest
Copy and snap to other face
Select the vertices on the inside diameter and F skin new faces

Skin Faces

The default setting of 1 Blender unit for the thickness of the gear is a little thin for our purposees, so increase the thickness of the gear to 3 Blender units. To do this Box select all the vertices on the top half of the gear and move them G in the Z axis 1 Blender unit. Then deselect All, Box select the bottom vertices and move these G Z -1 Add thickness to gear

Scale recess
To complete the tooth segment we need to add the top and bottom face recess.

To do this Alt-RMB the top centre vertex loop then Shift-Alt-RMB select the coresponding loop on the bottom face.

Turn on Proportional Edit on on the 3D view headder and set it to Sphere Falloff.

Scale the vertices on the Z axis and adjust the proportional edit influence with the mouse scroll wheel until you achieve a similar result to this.

In top view Tab into Object Mode and snap the cursor to the Object Centre Shift-S Cursor->Selection then Tab back into Edit Mode.
In the Mesh Tools panel set Degr:360 and Step:20 and press Spin Dup. The 20 tooth gear will be generated.
Select All and Remove Doubles W, then Set Smooth W.
Press Ctrl-N to recalculate the normals to the outside.
In the Modifiers panel click Add Modifier and choose EdgeSplit with the default settings.

Having the triangular faces on the top and bottom face of the gears Set Smooth, will cause some shading problems so in front view Box select the top most vertices and Set Solid W. Repeat this for the vertices on the bottom face of the gear.
Select top face
Spin Dupe

That almost completes gear model, all thats now left to do is add the keyway into the bore.

Gear Profile

With the cursor on the object centre, in Edit Mode and Top View add a Plane and scale it by 0.2
Insert Plane

Move G the plane on the Y axis 1 Blender unit

Cutting Reference

Select All and use the Knife tool to cut new vertices for the keyway using the vertices of the Plane as a cutting reference to snap to. You will need to realign the corner vertices onto the vertices of the plane. This can be done precisely by snapping the cursor to the corner of the Plane and scailing the corner vertices on the X-Y plane (Shift-Z) to the cursor, with the Pivot set to 3D Cursor.
Cut and Realign Verts

Fill in Faces
Once you have cut the keyway profile, remake the missing faces.

That completes modelling the gear. If you haven't already saved it now is a good time to do so. You should also give the gear a meaningfull name in the Link and Materials Panel.
Completed Gear Model

In the next section we will be unwrapping the gear into a two dimensional UV layout ready to apply some image textures.

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Gear Part 2 UV Unwrap >>

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