Step1: The work before generate the Gerber file 

Before generate Gerber file, you need to set criteria, but for most of PCB designers, these are not necessarily. The following is a brief explanation of these settings, You can also ignore these setting when generate Gerber file. 

1. The settings of PCB shape and size, generally are mechanic1,2 layers.

2. Before generate the Gerber file, the preprocessed of PCB file.

The preprocessed include:

a. Add break away rails of PCB

b. Add stamp hole.

c. Add the machine jack.

d. Add mouting hole

e. Add drilling description.

f. Add dimension description.

g. Set the origin

Step2: Generate Gerber file

1. Open the Gerber Files.

File -> Fabrication Outputs -> GerberFiles.

2. Parameter setting.

a.    “General” setting

• Set Units to “Inches”

• And Format to “2:5”

 b  “Layers” setting

• Select “Used On” in Plot Layers

• Select “All Off” in Mirror Layers

• Check “include unconnected mid-layer pads”

•  Uncheck all in Mechanical Layers to Add to All plot

c.    “Drill Drawing” setting

• Uncheck all boxes.

• Select “Graphic Symbols” in Drill Drawing Symbols

d.  “Apertures” setting 

• Select RS274X

e.    “Advanced” setting

• Select “Separate file per layer” for Batch Mode

• Select “Suppress leading zeroes” in Leading/Trailing Zeroes

• Select “Reference to relative origin” in Position on Film

• Select “Unsorted” in Plotter Type

• Click “OK”

Gerber Files are automatically loaded in the Altium cam viewer. This tool allows you to verify that all layers have been generated correctly and that they are all in positive mode. 

3. Generating NC Drill File

a.In the PCB view, and select : File / Fabrication Outputs / NC Drill Files

• Select “Inches” in Units

• Select “2:5” in Format

• Select “Suppress leading zeroes” in Leading/Trailing Zeros

• Select “Reference to relative origin” in Coordinate Positions

• Click “OK”

b. Import Drill Data : Click “OK”

c.Import Mill/Route Data : Click “OK”

4. Package Gerber File

Compress all the files in a single .zip file.All Gerber and NC Drill files generated by Altium Designer are automatically saved in the Project output folder.