Hiring guide for G-code Engineers

G-code Developer Hiring Guide

G-code, also known as RS-274, is a programming language that directs Computer Numerical Control (CNC) machines to perform specific tasks. It was first developed in the late 1950s by the Electronic Industries Association for use in automated machine tools. This universal language instructs machines on tool usage, movement and speed, essentially controlling all aspects of the manufacturing process. Over time, G-code has been modified and enhanced by various machine manufacturers to fit specific needs. Today, it remains a crucial component in industries such as manufacturing and 3D printing.

Ask the right questions secure the right G-code talent among an increasingly shrinking pool of talent.

First 20 minutes

General G-code app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in G-code application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you describe the purpose of G-code in CNC machining?
G-code is a language that is used to instruct CNC machines on how to perform certain operations. It provides detailed, step-by-step instructions that guide the machine in creating the desired part or product.
What are some common G-code commands you often use?
Some common G-code commands include G00 for rapid positioning, G01 for linear interpolation, G02 for circular interpolation (clockwise), G03 for circular interpolation (counter-clockwise), and G28 for return to home position.
Describe the difference between G00 and G01 commands.
G00 is used for rapid positioning of the tool, it moves the tool at maximum speed to the specified coordinates. G01 is used for linear interpolation, it moves the tool in a straight line between two points at a specified feed rate.
How would you write a G-code program to create a simple square?
A simple square can be created using a series of G01 commands to move the tool in a straight line along each side of the square. The program would start with a G00 command to position the tool at the starting point, followed by four G01 commands to draw each side of the square.
What are the functions of G02 and G03 commands?
G02 and G03 commands are used for circular interpolation. G02 moves the tool in a clockwise direction along a circular path, while G03 moves the tool in a counter-clockwise direction.
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What you’re looking for early on

Does the candidate have a strong understanding of G-code programming?
Has the candidate demonstrated problem-solving skills?
Is the candidate able to communicate effectively about technical concepts?
Does the candidate have experience with CAD/CAM software?

Next 20 minutes

Specific G-code development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

Describe the difference between absolute and incremental positioning in G-code.
In absolute positioning, the coordinates given in the G-code commands are based on a fixed point on the machine, usually the machine's origin or zero point. In incremental positioning, the coordinates are relative to the current position of the tool.
How would you use G-code to perform a tool change?
A tool change can be performed using the M06 command followed by the T command with the number of the desired tool. For example, 'M06 T3' would change to tool number 3.
What are some common errors you might encounter when writing G-code and how would you troubleshoot them?
Common errors include syntax errors, incorrect coordinates, and incorrect tool selection. Troubleshooting would involve carefully reviewing the G-code program, checking the syntax and coordinates, and ensuring the correct tool is selected.
Describe the difference between G90 and G91 commands.
G90 and G91 commands are used to set the positioning mode. G90 sets the mode to absolute positioning, while G91 sets it to incremental positioning.
How would you write a G-code program to create a circular hole?
Creating a circular hole would involve using a G81 drilling cycle command, followed by the X and Y coordinates for the center of the hole, and the Z coordinate for the depth of the hole.
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The ideal back-end app developer

What you’re looking to see on the G-code engineer at this point.

At this point, a skilled G-code engineer should demonstrate strong problem-solving abilities, proficiency in G-code programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with G-code.

What does the following G-code do: G01 X10 Y10 F20?
G01 X10 Y10 F20
This G-code moves the machine to the coordinates X10, Y10 at a feed rate of 20 units per minute.
What does the G-code 'G90' signify in a CNC program?
The G90 code in a CNC program sets the machine to absolute positioning mode.
What will be the output of the following G-code: G28 X0 Y0?
G28 X0 Y0
This G-code will return the machine to its home position along the X and Y axes.
What does the G-code 'M02' do in a CNC program?
The M02 G-code ends the program.

Wrap-up questions

Final candidate for G-code Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle G-code application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the functions of M-codes in G-code programming?
M-codes are used to control miscellaneous functions of the CNC machine, such as coolant control, spindle control, and tool changes.
Describe the difference between G20 and G21 commands.
G20 and G21 commands are used to set the units of measurement. G20 sets the units to inches, while G21 sets them to millimeters.
How would you use G-code to control the spindle speed?
Spindle speed can be controlled using the S command followed by the desired speed in revolutions per minute. For example, 'S1200' would set the spindle speed to 1200 RPM.

G-code application related

Product Perfect's G-code development capabilities

Beyond hiring for your G-code engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in G-code projects, and can engage in multiple capacities.