In part one of the series we looked at the trials I went through just getting my CNC cutting machine to work. Now we’ll take a look at the software I use to drive the whole show…
Once again, remember that I am no CNC guru! I’ve learned this stuff by reading the forums, blogs and manuals, and by making mistakes along the way.
Any advice you follow at your own risk and if in any doubt, ask an expert…
As I mentioned in the first article there are a number of different bits of software you will need to get your ideas from inside your head and onto your CNC machine. From what I can tell this will include (as a bare minimum):
- Some sort of design/modelling software to visualize your design on the computer.
- Some way to build your toolpaths and generate the code to drive the CNC machine.
- Software that actually “drives” the CNC machine.
I’m still not entirely sure what some of this software does and I’m pretty sure there will be better ways of doing things but I’ll take you at least through how I do it.
Hang on, what do all these weird words mean?
I’ve just realized I keep on talking about “toolpaths” and “GCode”, and even “CNC” without explaining what they actually mean. Here then is a bit of a funky table that breaks it all down:
Computer Numerical Cutting
Basically CNC cutting works by sending coordinates, in the form of numerical code, to a series of stepper motors and a drill mounted on a gantry that moves around over a cutting bed. The software that drives the machine knows how many “steps” a motor must make to move a certain distance and uses this information to move the drill point to the desired location.
All machines have at least 3 axis of movement – X, Y & Z (Z being depth). Other machines have a rotational axis as well for work on cylindrical pieces.
You can learn more about CNC Cutting Machines here.
This is where the lines of your design get turned into the coordinates that will be fed to your machine.
The toolpath is built using CAD/CAM software designed specifically for the purpose. It will contain a database of the tools that you are using and you will need to carefully set parameters such as feed rate, plunge rate, pass depth etc.
Computer Aided Design/Computer Aided Manufacturing
Software for turning your ideas into computer models that can then be transferred to the cutting machine.
This is the name given to the numerical code that is generated by the toolpath to drive the CNC machine.
Feed Rate/Plunge Rate/Pass Depth
Feed Rate, Plunge Rate, Pass Depth
This is the speed at which the material is “fed” to the cutting bit. On most table top machines this actually means the speed the cutting bit moves through the material. Too fast and the cutting bit will break.
This is the speed at which the cutting bit “plunges” into the material through the Z axis.
This is how much material is removed during each “pass” of the cutting bit.
The Software I Use
Now we have the definitions out of the way, here then is what I use:
3D Modelling and Blueprints
I do everything in Sketchup. It used to be Google Sketchup but now it is owned by Trimble (I guess the same mob that make the Gatewing UAV). Yes, I can hear some of you groaning! I know the pros will be using Solidworks, Autocad or other more advanced tools but I know Sketchup and I find it easy enough to use. It also has the benefit that when I am working with others to produce a design, Sketchup is accessible and I can send files around easily.
Once I have a workable design I use the “Flattery” plugin to export my drawings as an .svg drawing. The good thing about using .svg is that all dimensions and vectors are saved perfectly ready for the next step…
My toolpath software can only accept certain file formats and I can’t go directly from Sketchup to CAM, so I have to convert and clean up the drawing first. Fortunately I run a copy of Adobe Illustrator for work and this is ideal for the job. Opening the .svg file in AI reveals a number of additional hidden vectors so I delete those, increase the line width slightly to 0.1mm. Rotate the shapes how I want to cut them and then save as an .ai format vector image ready for the toolpath creation…
I saw Vectric Cut2d recommended on a YouTube video and took a look at the software. There were more complicated and expensive options (such as their VCarvePro software) but Cut2D seemed to do all of the things I wanted so a short credit card swipe later and it was on my desktop.
The software itself is easy to use. It is actually a simple CAD program in its own right and the interface makes it easy to import and manipulate the .ai files. One thing I did learn was that once the vectors are loaded it is a good idea to select everything and hit ctrl+j to close all the lines and make selecting paths easier.
There is a LOT more to this software that we need to talk about but I’ll get to that next time.
CNC Motion Control Software
The manual that came with my machine stated that it was designed to work with Mach3 Mill from Newfangled Solutions, so that is what I got. I am pretty sure that I am still not using this software to it’s full potential but it really is a complex bit of kit.
In a nutshell it takes the G-Code from the CAM software and sends it in real-time to the CNC machine through a serial cable. It is this software that tells the motors how many “steps” are in a millimeter and how fast to spin the drill and move the gantry. Everything starts and stops here so it pays to read the manual and at least learn the basics.
In the next article I’ll start to describe how I go from a drawing on the back of a napkin to a finished piece. It may take more than one article but we’ll see how we go for time!
In the meantime, here is a video of Mach 3 in action to whet your appetite…