CAM Process

cnc machining

Process of CAM
Computer Aided Machining is a process just like the rest of the steps in CNC.  You need to do certain things before it spits out the tool paths and then the G-Code.  These things you need to define change with the type of CAM you are using and the CAM program you are using.  They are all similar, but a bit different.

Here are the CAM Steps:
Define Material
Define Stock Size
Define Coordinates
Define Tool
Define Feeds and Speeds
Simulate Machining
Post Process

Define Material
You will need to define your material before you begin your machining.  For example, if you are machining wax, your feeds and speeds you define later can be faster.  If you are machining steel, you will need to slow things down.  Most times the type or composition of the material will not need to be defined in the CAM program, but you will need to be very aware of it.

Define Stock Size
Next, you will need to let the CAM program know what the size is of the stock you will be using.You are usually going to define a “box” or “cylinder” you will begin with.  The machine needs to know where the stock starts and ends so it can make sure to remove all the material it needs to.

Define Coordinates
How will the machine know what is 0,0,0 in the coordinate scheme?  You need to tell it.  You will pick a corner of the stock box and let the machine know that is exactly 0,0,0.  That is also where you will need to “zero out” your machine at.  This is the beginning point for the CNC Machining operations.  It is also usually the ending point of the program as well.

So what is the best spot to pick for 0,0,0?  There isn’t one.  It depends on your machine and how the axis’ are laid out in your brain.  For me, I like to pick the “Highest Z Point” and the “South West Corner” because that is where zero is in my brain.  I have also set all my machines up that way.

Define Tool
Defining the tool is an easy process.  If you were going to use a tool, would you like to know what it is and how you are supposed to use it?  You need to let the machine know what tool it is holding and what size that tool is.  The machine needs to know the diameter, length, offset, and how far the tool sticks out from the spindle so it does not crash.  If the tool is a plasma cutter, the CAM program will need to know the width of the torch cut.  It can then compensate for it.

Define Feeds and Speeds
Next, you need to let the cam program know what feed rate want the machine to move and how much material you want to remove with each machining pass.  This is where defining your material above comes in.  I will not get into the calculations here, but each material and tool combination has an optimal Feedrate.

You will also be adjusting the spindle speed in this step as well.  All these pieces of the puzzle interrelate with one another.  Imagine the spindle going slow, with a fast feed rate.  You will probably damage your machine.  Imagine the spindle going fast, with the feed rate extremely slow.  You will have low productivity and probably prematurely wear your tools.  All this adds up to the fact you will have to use your brain and gain some real life experience.

Simulate Machining
This is my favorite step.  Here you run your program on your virtual piece of stock and watch the material being machined away.  How cool is that!You get to see what you did before you try it out on your High Cost CNC equipment.  As I said before, this is like proof reading what you did while programming.I have found many problems and fixed them before I got out to my shop.

Tool Paths
When you are done simulating the machining, you will see tool paths.  Tool Paths are one of the outcomes of our CAM process.  Tool paths are literally that, the path that the tool will follow while machining.  CAM Software shows us these paths so we can follow what is going to happen.  The logic of the CAM Software determines where these paths will be and in what order they will happen.  The tool paths will then be converted into G-Code in the next step.

What are tool paths and how do you create them?
Tool paths are the paths the tool will take around and through the piece of material to create the part.  Tool paths show up as a very thin wireframe movement paths in the CAM process.  This is to show you where the machine will be traveling.  You want this so you can see if there will be any interference issues while machining.

Once the tool paths are generated, you can usually watch an animation of the action.  You can “virtually” watch the machine work and machine the material.  This is a very helpful feature of modern CAM programs.  I don’t know how many times I have found a problem in the simulation before I ever made it to the shop.

Post Process
Finally, you post process the program you created.  This is where the G-Code is created.  You pick the appropriate post processor for your CNC Machine and press a button.  The CAM program takes all your inputs and spits out a G-Code program that you can load into your control software and away you go.

Post processing is literally a one-click process for most CAM programs.  The only pitfall as I said was that you must pick the right post processor that is matched to your machines set up.  Most CAM programs come with dozens of post processors and one is going to likely fit your setup.

CAM Programs
SheetCAM
RhinoCAM
LazyCAM
MeshCAM
MasterCAM
Alphacam
Artcam
Edgecam
Featurecam
GibbsCAM
OneCNC
Plasma Cam
SmartCAM
SurfCam
VCarve

CNC Machining Simulators
Most CAM programs come with a simulator.  Some are basic and weak.  Others are outstanding.  There are a few stand-alone simulators on the market that you can run your G-Code through.

CNC Simulator Examples:
Cncsimulator.com
Mach

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