Posts Tagged ‘gcode’

Let’s go under the hood of the G-Code program

Tuesday, October 7th, 2008

gcode program

Next, we are going to go through an example of cutting out a 2” square with a CNC Plasma Cutter.  Then we will look at the G-Code to see what is happening.

2” Square G-Code:
The numbers on the left of the G-Code are the sequence numbers of the code and the order it will be executed in.  I have added notes after different actions to let you know what that line of code means.  My note starts with a “-“ then continues.  A “-“ means nothing in G-Code.

򾛠 (Filename: 2INSquare.txt) – Name of File
򾛪 (Post processor: Plasma.post) – Name of Post Processor Used
N0020 (Date: 8/1/2007) - Date G-Code was generated
N0030 G20 (Units: Inches) – Measurement Units Used
N0040 G53 - Machine co-ordinate system
򾜒 ᰖ – Absolute Programming
N0060 G40 – Tool radius compensation off
N0070 ʽ – Feedrate of 1” per min
N0090 (Part: Square) – name of the part
N0100 (Process: Plasma,  DEFAULT, Plasma, 0.01 in kerf) – Tool to be used
N0110 G00 – Go to Home
򾝘 X0.1113 Y-0.0904 – Move to this exact X, Y position
򾝢 G04 P2000 – Pause for 2 seconds, this is in milliseconds
N0140 ḗ – Fire the plasma torch
N0150 G04 P500 - Pause for .5 seconds, this is in milliseconds
N0160 ᮿ X0.0000 Y-0.0050 I-0.1113 J-0.0298 F40.0 – move to this X, Y position in an arcing movement at a feedrate of 40 inches per min
N0180 ᮽ ͼ.0000 – Travel in the Y+ direction for 2 inches to X0, ͼ
򾞨 ᮽ X2.0000 – Travel in the X+ direction for 2 inches to X2, Y2
N0220 G01 ͺ.0000 – Travel in the Y- direction for 2 inches to X2, ͺ
򾟐 ᮽ X0.0000 – Travel in the X- direction for 2 inches to X0, ͺ
N0250 ᮿ X-0.1113 Y-0.0904 I0.0000 J-0.1152 – move to this X, Y position in an arcing movement
N0260 M05 – Turn off the plasma torch
N0270 G04 P2000 – Pause for 2 seconds, this is in milliseconds
N0280 G00 – Move to Home
򾠌 M30 – End Program

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What is G-Code?

Sunday, October 5th, 2008

cnc tutorials

G-Code is the common name for the programming language of CNC Machines.Somewhat of a general, catchall term for CNC programming language.  Very few machines adhere to this standard today.  There are as many varations as there are manufacturers.

This is how I think of G-Code.  It is a simple language built off of the Cartesian Coordinate System for motion control.  That is a mouthful.  I don’t know if that is exactly right, but you will get my meaning in a second when we go through some code line by line.  You will remember your High School Geometry soon enough.  For the real pros out there, you know there is much more to G-Code then that, but it is a good place to start thinking about it.

You will see many variations of the G-Code name like:
Gcode
gcode
G-Code
g-code
G Code
G-Code

Are there other “Codes?”
In a word…Yes.We will get to that information in just a minute.  G-code is also the name of any command in a CNC program that begins with the letter G.  G-Codes generally tell the machine to perform an action.  G-Codes can tell machines to move a certain distance in the X-Axis for example.  Or, make a rapid move to another location.  Or, move in an arcing fashion while milling.  An on and on and on.

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how can I learn more about G-Code

Saturday, October 4th, 2008

learn cnc

In a word, no.  You will probably need to know how to quickly scan your G-Code if you are having problems during your machining simulation.  Other then that G-Code and a CNC program are throwaway programs for the most part.  What do I mean by that?  Let me explain.

Let’s look at a specific design.  Let’s say a 12” by 12” square.  You build your model, run it through your CAM Software and create a CNC Program made up of G-Code instructions to your machine.  Say tomorrow the job requirements change to a 24” by 24” square.  Do you go into your G-Code line by line and change the code?  Most people wouldn’t.  They would go back into their CAD or CAM program and scale the square up to 24” by 24”.Then postprocess the job to get their new CNC Program.

There are some people that would do this editing line by line because the design is simple.  Now think of a complex shape and what scaling it up or down would entail.This would include changes to the G-Code and reviewing it line by line.  We are talking thousands of lines here vs. going back and quickly scaling the model and spitting out some new G-Code.  And that is why G-Code is throwaway.  Use it over and over when you can, but don’t fret over archiving it if something changes.  It is much better to make a copy of the design (CAD File) in its original state and save that somewhere.  That is much more useful.

Post Processing??? - Now you have me worried.  With all the variations in G-Codes and M-Codes, how will I ever keep it straight?

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CNC controllers and CNC machines

Tuesday, September 30th, 2008

CNC Control Video

The CNC Controller generally resides in the shop somewhere near the CNC machine it is controlling.CNC computers don’t have to be the greatest, every Bell and whistle type of computer.These are the powerhouses.  Save your money for a good design computer.  You will save much more time having a fast computer for your designing.

A control computer doesn’t have to be that powerful for a few good reasons.  It doesn’t have the workload.The control computer takes G-Code and turns it into signals that transmit to the machine controller.  Turning G-Code into signals is not that labor intensive for a computer.

I have used multiple types of control computers.  Everything from a 486 DOS running “$30 special” to a modern Dell with Windows XP.  I have yet to try one with Vista.  I will keep you posted.  Generally I like to find a good used computer for a couple hundred bucks, wipe the hard drive and only load the control software onto the machine.  That way you know what you have.

There is another good reason you don’t want to spend a lot of money here.This computer will be located in the shop.  Dirt will be located in your shop.  Using logic here, dirt will be located in your computer.  If the computer does go belly up, you aren’t out your children’s college tuition.

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CNC machines need CNC machine controllers

Saturday, September 27th, 2008

CNC Drivers

Machine Controllers take your machining instructions from your G-Code and converts the G-Code into motion.  You are off to the races.  The controller interprets the signal pulses from your Control Computer and instructs the machine to move.

The CNC Machine Controller is made up of various electrical parts.  Remember earlier that I said some electronic junkies flock to CNC.  This is why.  Machine controllers can be built if you are savvy with a soldering iron.  I myself am not.  I personally always default to ordering up a Machine Controller from one of my sources.

Controller builders to me are electronic gods.  They mix power sources, match up Amp, Volts, etc into the item I need.  Generally, you can pick the number of Axis you want before they build the controller.  For example, if you are building a CNC Router you may want a two-axis controller.  Possibly a three-axis controller if you have a Torch Height Control.  If you have a milling machine or a wood router in mind, then a three axis is your ticket.  If you want to machine with a rotary axis, then you need a four-axis controller.  So on and so forth.

Here are some example controller prices
Here are some prices you might see in the marketplace.Most come with motors and cables as well.  Really, you purchase a whole kit at once if you go this route.Another way to do it is to assemble it yourself.  I wouldn’t suggest this for the beginner.

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Lessons about CNC safety

Friday, September 26th, 2008

cnc steps

Any subject that covers working in the shop should begin with safety.Safety should always be at the top of your mind.CNC is not different than any other shop topic that you will encounter.  In fact, the highest levels of safety awareness should be maintained when using a CNC machine.

CNC machines don’t have a mind of their own.  A computer gives them a command and they execute it.  They don’t care if they are cutting steel, aluminum, wood or your hand.  They don’t differentiate between materials.  You need to be aware of this.

When you are Learning CNC you should take it slow.  Do tests on a small scale, then watch and learn what happens.  For example, why don’t you let your machine “cut air” for a while when you first get it.  You don’t need to put it right to work cutting material.  Why not create a simple program, and let the machine cut the air instead of material.  Better yet, why even run the spindle during the test.

Every CNC Machine has quirks that you need to learn.  Every CNC machine has a different working envelope.  Every CNC machine is just a little bit different then the rest of them.CNC safety requires that you learn about your machine before you use it.

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CNC overview process

Friday, September 26th, 2008

cnc overview

Quick Explanation of the Process
This is how I view Computer Numerical Control.  I break it down into simple steps that I can remember.  Now, they all interact, but it is good to keep them in boxes for simplicity sake.  I also like to keep them in a logical, progression type order.  Here they are: Design, CAD, CAM, Control and Machine.

Today you are going on a journey.  You are going to learn about the basics of CNC.  I hope you are as excited as I am about this topic.

I have been using CNC equipment in my home shop for six years now.The CNC technology gets better all the time.  The software gets better every year.  At one time large companies could only afford this technology.Now there are thousands of CNC machines working in shops like yours and mine.

There are basically five elements to a CNC Project that you need to know:
Design - planning on what you want to build
Computer Aided Design - translating it into the computer
CAM - converting it into machine language
Controlling - controlling your machines movements
Machining - building the part to specifications

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