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Understanding G-codes

G-code is what SmartBench reads in order to bring a CAD/CAM model to life. 

It is a set of instructions that tells CNC machines where to move, how fast to move and what path to follow. Each separate line or block contains a machining instruction.

Functions of G-codes

The table below shows some frequently used G-codes along with their functions:

Structure of G-code

G-code programming is structured in a systematic way for efficient manufacturing. A typical structure of a G-code program has the following:

A: Preparatory functions

This is where the machine sets up the starting tool, unit of measurement, plane, etc of a workpiece.

B: Dimension words

This is where the machine understands your stock dimension and a profile that needs to be cut, along with information such as spindle speed and feed rate.

C: Miscellaneous or machine function

This is where the machine functions are executed. For example: extraction on or off, spindle on or off.

 In a human language the above G-code would direct a CNC machine as follows:

• Load the starting tool (T1).

• Plane for machining is XY (G17).

• Set program length unit in millimeters (G21).

• Set distance mode to absolute coordinate (G90). 

• Turn the spindle on (M3) at 1000 rpm (S1000.0).

• Start the workflow at a given feed (G1) in the Z-axis (Z-0.300) at feed rate 100mm/min (F100.0).

• Rapidly raise the spindle (G0) in the Z-axis (Z7.500) .

• Stop the spindle (M5).

How is G-code produced?

The process for turning a design into G-code usually looks like this: 

• First, the 3D model is generated in CAD software.

• The 3D CAD model is then imported into the CAM software, and the machining operations (toolpaths) are defined, e.g, roughing, finishing, drilling etc. 

• The post-processor (which will normally be part of your CAM software) converts the machine operations to G-code (click here to learn more about post-processing).

Sample G-code example

This section will show you how G-code is generated from a simple 3D model. 

CAD model generation

The model is a 100x100x50 mm wooden block, which was modelled on Solidworks (CAD software).

CAM generation

The model is imported into CAM software (Vectric in this example), and the toolpaths are generated. 

The colour coding is as follows:

• The blue line shows the cut profile (100x100x50 mm), and is used to represent the coordinates in the X and Y axis.

• The green line shows where the tool retracts and engages with the workpiece (Z-axis).

• The red line indicates the safety height above the workpiece.

D: Stock

E: Profile to be cut

Click here to learn more about Vectric. 

G-code generation (post-processing)

The CAM toolpaths are converted into G-code, via a post-processor. 

Click here to learn more about post-processing.

G-code example

This is the G-code for this cut:

SmartBench

The G-code is then simply transferred to SmartBench, ready for manufacture.

Click here to learn more about how to transfer your G-code file to SmartBench.

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