New to CNC and G-Code. My PCBs are 1/3 the size they should be

Hello all. I was wondering if anyone could help me.

First off I have to admit I just finishing building my 1st ever cnc machine [ebay kit] about 6 hours ago and I'm a complete newbie concerning everything to do with it. And I mean everything. I'm pretty quick at picking things up and so far I have gone from know nothing to know very little but was able to actually send a g-code to my cnc after writing the grblUload to the cnc's arduino. [I know arduino pretty well] anyway now the issue,

I have a .GBL file that I open in FlatCam so I can export g-code and send to my little cnc machine.
All that works fine with one issue. When I run it on my cnc, it cuts at about 1/3 the size it should. Instead of being about 3 inches * 2 inches, it is like 1 inch * 1/2 an inch and I can't figure out why. Well maybe I can but I can't figure out how to fix the issue.

The GBL I guess is in inches and even if I convert it to mm to create the g-code I get an odd warning

GCV use 'mm' but Grbl parser set for 'inches'

which to me would kind of explain the issue but how do I go about solving it so it actually cuts the right size?

Thanks for any help!

If you need to learn proper G Code programming and setup for your machine, go to youtube, put in my name: Heinz Putz, and you will see one of my teaching CNC DVDs.
You may be setting up the coordinates all wrong.
Good luck: Heinz.

in to mm is a 25.4 difference. in to cm is a 2.54 difference. you're definately a 3:1 difference. one way to fix it is find the steps per inch or steps per mm and change the numbers to 1/3 of the value there.

Hi....the short answer is to take some time off to learn to read and write G code even if you eventually use a CAM program to compile it......knowing how something works gives you X ray vision and a greater perception.

Bob Warfield on CNCcookbook gave out a short tutorial about the 10 most used G codes you can use to get up and running without bumping into anything.......the rest just comes as and when etc.

Of course, you have to write them in a logical sequence and also compile the necessary pre codes to tell the machine what it's working with, but even just the most used G00 and G01 will get you somewhere.
Ian.