Computer Aided Drawing (CAD) and Computer Aided Machining (CAM) are two types of software packages you will need to become very familiar with if you want to make your CNC produce the designs and idea’s in your head.
CAD software packages will allow you to draw in 2 or 3 dimensions. When you get to know CAD well it’s like the best piece of paper in the world and your mouse is the worlds most advanced pencil. Imagine being able to draw your design and then rotate, pan and zoom around it in 3D. You can erase parts of it, add parts to it and modify it in any way you see fit.
CNC machines are often born in CAD, where they are conceptualised and evolved into complex, multiple component machines. It’s only right that parts that CNC machines produce are also created in CAD too.
If you look at the image on the right, the top image is a photo I took of a part my CNC produced, and the bottom photo is the CAD design it was produced from. You will notice that the two look very similar, which is what is so amazing about CAD; your designs within CAD and within the computer, with the help from a CNC machine can become real life objects.
There are many, many CAD software packages available today, some free and some really expensive. I personally suggest SketchUp, it’s free, very intuitive and easy to learn for beginners.
Autodesk also have many good CAD software packages.
Computer Aided Machining
CAM software packages are built specifically for CNC technology, whereas CAD software is for any computer designing in general. CAM is built to convert CAD drawings into a series of functions a CNC machine can carry out in order to produce a part.
CAM software will allow you to import a design that you have produced within a CAD software package, and some CAM software will even allow you to draw your design right within the CAM software itself; so in certain cases CAD wont be needed.
Once your design is ready and imported into the CAM software package you can begin to apply toolpath operations to it.
What are toolpath operations? They are a series of functions that will make a CNC machine perform a certain task. There are many variables that you can control within these functions like choosing the tool that will do the operation, the speed, the direction and a huge amount more. These toolpath operations are ultimately broken down into G-Code which a CNC controller software can interpret.
Here’s a list of some fundamental toolpath operations you’ll need to know:
A profile toolpath is used to cut something out. Just like you would use scissors to cut out a design in paper, a profile toolpath cuts around the edge of a closed shape. By closed shape I mean that it has no gaps anywhere, for example a complete circle, square or rectangle. A profile toolpath can cut inside the shape, exactly on top of the shape or outside of the shape.
Profiles are very useful for cutting out a basic profile shape and also are commonly used as the final operation in a program to cut the completed part out of its surrounding material.
A pocket toolpath just like a profile is named after exactly what it does; it cuts out pockets in the material. When a pocket toolpath is programmed to a closed shape it will lower the entire inside height of that shape to whatever you choose.
Two options we have for pocket operations are offset and raster. These both have the same end result but go about it in different ways. More importantly here I’m trying to demonstrate the difference between profile and pocket operations. You can see above the profile operation follows the edge of a shape while the pocket cuts out everything inside a shape.
A drilling toolpath is very basic and is just as it sounds; it will drill a hole at a selected location. As with the other two there are many other parameters you can specify including a function called peck drilling. Peck drilling will drill down a defined amount before retreating back up allowing any built up swarf or material to escape then it will go back down and continue drilling. This process will repeat depending on the programmed peck drill depth and the overall desired depth of the hole.
Some CAM software packages that I would personally recommend are the Vectric software packages and CamBam. Vectric’s Cut2D, V-Carve Pro and Aspire are all very high-end software, they are very easy to use and I can’t speak highly enough of their software. Unfortunately nothing that good is cheap and it is quite expensive, in saying that however if you intend on putting a lot of time into CNC machines Vetric software is well worth the cost long-term. CamBam is also an excellent piece of software and is very cheap for the functionality it provides, it isn’t in the same league as Vectric but is still very powerful software and for some people it will do everything they need. It is great for beginners as the cost isn’t high and is an excellent introduction to CAM.