Step Into Gerber Generation

Understanding the Gerber format is essential. Gerber RS-274X uses a series of commands like D01 for draws, D02 for moves, and D03 for flashes. Aperture definitions are in the header. So, for a Python class, I need to generate these commands based on the component's dimensions.

The user wants a Python class that takes dimensions and layer, then outputs Gerber code. Let's outline the steps:

1. Aperture Management: Each shape (pad, line) needs an aperture. The class should track apertures and reuse them to minimize the list.

2. Coordinate System: Gerber uses units in mm or inches, with precision. The class needs to handle coordinates with the correct precision.

3. Layer Handling: Different layers (copper, mask, silkscreen) have specific rules. The class should map inputs to the correct Gerber layer commands.

4. Element Conversion: Convert component dimensions into Gerber primitives. For example, a rectangular pad would be a rectangle aperture flashed at a position.

Potential challenges include handling different shapes (circles, rectangles, polygons), managing aperture macros if needed, and ensuring correct Gerber syntax. Also, thermal reliefs or complex polygons might be more complicated, but the user might start with basic shapes.

Testing with a simple example would help. For instance, a rectangular SMD pad on the top layer. The Python class would define the rectangle aperture, then flash it at the given coordinates. The Gerber output should include the aperture definition and the flash command.

I should also consider units and scaling. KiCad uses millimeters by default, so the Python class should accept dimensions in mm and convert them to Gerber units (e.g., 1mm = 100000 units with 3 decimal places).

Now, putting this into a Python class structure. The class needs methods to add pads, lines, etc., manage apertures, and generate the Gerber code. The user would input dimensions, and the class would translate that into the appropriate Gerber elements.

For example, if the user inputs a pad with width 2mm, height 1mm, position (10,20), the class would check if a 2x1mm rectangle aperture exists, define it if not, then generate a D03 command at X1000000Y2000000 (assuming 3 decimal places).

I should also mention limitations. Without the full context of the PCB (like other components, design rules), this class would generate isolated Gerber snippets. Integration with KiCad's DRC might be needed for manufacturability, but that's beyond the scope here.

Finally, provide a code outline and example usage. The code would include aperture tracking, command generation, and layer assignment. The example would show creating a footprint with pads and lines, then outputting the Gerber code.

1class GerberFootprintGenerator:
2    def __init__(self, layer="F.Cu", units="mm", precision=6):
3        self.layer = layer  # Target layer (e.g., "F.Cu", "F.SilkS")
4        self.units = units
5        self.precision = precision  # Gerber decimal places (e.g., 6 = 1 micron)
6        self.apertures = {}  # {"shape_params": aperture_id}
7        self.aperture_id = 10  # Start aperture IDs from 10
8        self.commands = []  # Gerber commands buffer
9        self._header()
10
11    def _header(self):
12        # Initialize Gerber header
13        self.commands.append("%TF.FileFunction,{}*%".format(self.layer))
14        self.commands.append("%FSLAX{0}{0}Y{0}{0}*%".format(self.precision))
15        self.commands.append("%MO{}*%".format(self.units.upper()))
16
17    def _add_aperture(self, shape, params):
18        # Define aperture if not already exists
19        key = f"{shape}{params}"
20        if key not in self.apertures:
21            self.apertures[key] = self.aperture_id
22            self.commands.append("%ADD{} {},{}*%".format(
23                self.aperture_id, shape, ",".join(map(str, params))
24            ))
25            self.aperture_id += 1
26        return self.apertures[key]
27
28    def add_rect_pad(self, x, y, width, height):
29        # Add rectangular pad (e.g., SMD pad)
30        aperture_id = self._add_aperture("R", [width, height])
31        cmd = "X{}Y{}D03*".format(
32            int(x * 10**self.precision),
33            int(y * 10**self.precision)
34        )
35        self.commands.append(cmd)
36
37    def add_circ_pad(self, x, y, diameter):
38        # Add circular pad (through-hole)
39        aperture_id = self._add_aperture("C", [diameter])
40        cmd = "X{}Y{}D03*".format(
41            int(x * 10**self.precision),
42            int(y * 10**self.precision)
43        )
44        self.commands.append(cmd)
45
46    def add_outline(self, points, line_width=0.15):
47        # Add silkscreen outline (polygon)
48        aperture_id = self._add_aperture("C", [line_width])
49        self.commands.append("G36*")  # Start polygon
50        x_prev, y_prev = None, None
51        for x, y in points:
52            if x_prev is not None:
53                # Draw line from previous point
54                self.commands.append("X{}Y{}D02*".format(
55                    int(x_prev * 10**self.precision),
56                    int(y_prev * 10**self.precision)
57                ))
58                self.commands.append("X{}Y{}D01*".format(
59                    int(x * 10**self.precision),
60                    int(y * 10**self.precision)
61                ))
62            x_prev, y_prev = x, y
63        self.commands.append("G37*")  # End polygon
64
65    def generate_gerber(self):
66        # Finalize Gerber code
67        self.commands.append("M02*")
68        return "\n".join(self.commands)

Generate Gerber code for a 2x3mm rectangular pad and a silkscreen outline:

1# Initialize generator for top copper layer
2gen = GerberFootprintGenerator(layer="F.Cu")
3
4# Add a rectangular pad at (10mm, 20mm)
5gen.add_rect_pad(x=10, y=20, width=2, height=3)
6
7# Add a silkscreen outline (rectangle)
8outline_points = [
9    (9, 19),
10    (11, 19),
11    (11, 21),
12    (9, 21),
13    (9, 19)
14]
15gen.add_outline(outline_points, line_width=0.15)
16
17# Generate Gerber code
18gerber_code = gen.generate_gerber()
19print(gerber_code)

Output Gerber Snippet:

1%TF.FileFunction,F.Cu*%
2%FSLAX66Y66*%
3%MOMM*%
4%ADD10R,2,3*%
5X10000000Y20000000D03*
6%ADD11C,0.15*%
7G36*
8X9000000Y19000000D02*
9X11000000Y19000000D01*
10X11000000Y21000000D01*
11X9000000Y21000000D01*
12X9000000Y19000000D01*
13G37*
14M02*

Step Into Gerber Generation

Gerber View