I recently received a question from a CNC beginner who was having trouble setting up his machine. He asked me how to set up a CNC router table coordinate system? He asked this question because his machine did not move in the proper direction when he pressed the arrow keys on his keyboard while using Mach3.
It took us a while to find out what the issue was but it turned out to be quite simple. He had connected the stepper motor controller wire to the wrong motors. This resulted in his machine cutting letters backwards and sideways. I realize this is quite a common problem for beginners 
so I decided to share my thoughts on the issue.
Controversy?
Many people think it does not matter how you set up the coordinate system on a CNC router table as long as you are consistent. I disagree. In my opinion the smartest way to set up the CNC Router Table Coordinate system is the same way we all learned in Algebra, the Cartesian Coordinate System (That math you swore you would never use). More specifically the first quadrant of the Cartesian system.
For those of you who managed to wipe the Cartesian Coordinate system from your brains, here is the short version. Draw a horizontal line on your graph paper and then split that line down the middle with a vertical line. The Horizontal line is the X axis (from left to right is positive). The Vertical line is Y ( from bottom to top is positive) Where the two lines cross Intersect) is Zero. See the chart below.
CNC ROUTER TABLE COORDINATE SYSTEM
CNC router table coordinate system uses Quadrant I of the Cartesian System. All numbers are positive.
ADVANTAGES
There are several advantages to setting up a CNC router table coordinate system to match the Cartesian system. The biggest advantage in my opinion is never having to deal with negative numbers. When you draw an object in the first quadrant, every point can be described using positive numbers. Positive numbers are easier to add and subtract without taking your socks off.
Positive numbers are easier to work with than negative numbers. Do you remember how to add and subtract negative numbers? Chances are you will get it wrong more frequently then adding and subtracting positive numbers.
Uniformity is also a big advantage with this system. If all CNC Router Tables are setup to the same coordinate system standard then trouble shooting problems becomes easier. If the machine does not move correctly or if it is losing steps as it moves, it is easier to measure and track down which axis is not moving correctly.
One other bonus to me with this system is that it is the same system Vectric VCarve Pro uses as default. So most larger CNC machines are already using this system. It is also the default system that Inventables uses in Easle software which is designed for small DIY systems like the Shapeoko, Stepcraft2 and Xcarve.
VIDEO
Here is a quick video that shows how I setup the CNC Router Table Coordinate System on my machine.
PODCAST
If you have questions about CNC Router Tables I would be glad to answer them on my Podcast, CNC ROUTER TIPS Podcast. CNC Router Tips is a podcast that answers your questions about how to build operate and use a CNC Router table to build a business or hobby. If you have a question for the show you can leave a voice mail at http://cncroutertips.com/askme. Or you can listen on iTunes CNC Router Tips. at https://itunes.apple.com/us/podcast/cnc-router-tips-podcast/id1031116372?mt=2
