"You will need to know CAM these days." Has someone said that to you at work? Nobody tends to sit down and explain what CAM actually does for you, or how it differs from writing the program by hand.
This article explains what CAM is from a lathe machinist's point of view, for someone meeting it for the first time.
CAM turns a drawing into an NC program
CAM (Computer Aided Manufacturing) is, in one line, software that generates the NC program, the G-code, from drawing data.
CAD, the one it is always mentioned with, is the software you draw in. The split goes like this.
| Job | In → out | |
|---|---|---|
| CAD | Design and drafting | The shape in your head → drawing data (DXF and so on) |
| CAM | Getting ready to cut | Drawing data → toolpath → G-code |
Break CAM's job down and there are three parts.
- Read the geometry — pull the profile you want to cut out of a DXF or similar
- Calculate the toolpath — work out how the tool should move for the tool, the cutting conditions, and the operation (roughing or finishing)
- Post the G-code — write the program out in the format your control reads
The part that matters is that CAM outputs G-code with the nose radius compensation and the repeated depth-of-cut arithmetic already done. The work you used to do with a calculator and a pencil is taken off you entirely.
Hand programming versus CAM: what changes
Change 1: how long a program takes
A plain stepped shaft takes a few minutes by hand. Put a taper and an arc in it, add a few grooves, and the coordinate maths alone starts running to half an hour or an hour. With CAM you load the drawing and that time goes to almost nothing.
Change 2: the kind of mistake you make
What bites you in hand programming is the slip. A coordinate worked out wrong, a number keyed in wrong, an offset not applied. CAM almost eliminates that kind of error. What matters instead is checking the simulation. Pick the wrong tool or set the wrong conditions and CAM will happily give you a path you did not intend. Being able to see it is what quality assurance looks like once you are using CAM.
Change 3: no more re-programming the same part
Most of the programming in a shop is "something like the one we did before". Starting from a blank screen every time is a waste. With CAM you swap the drawing and the program for the same setup is there.
Why lathe shops kept saying they did not need CAM
In the machining centre world CAM is simply how it is done. On lathes you still hear that CAM is unnecessary and it is quicker to type it in. The reasons are not mysterious.
- Lathe geometry is essentially two-dimensional, and hand programming has coped
- Commercial CAM is expensive, and hard to justify for a lathe on its own
- There is a lot of setup and a lot to learn, so it ends up feeling quicker to type it in
So it is not that lathes do not need CAM. It is that there was very little affordable CAM that suited a lathe shop. Meanwhile, in a shop where the experienced hands have gone, and for anyone learning the trade, the coordinate maths and the nose radius are exactly as hard a wall as they ever were.
Now there is a third option: CAM that runs in a browser
There is now CAM that runs in a browser with nothing to install. It works on a phone or a tablet, so nobody is queueing for the CAM machine in the office. You can try it before committing to an expensive package, and that is a real difference.
LATHE-NC, which I build, is one of these. The aim is simple: stop re-programming the same part, and be usable by someone new to machining. It is not for difficult multi-axis work. It is for getting the everyday OD, ID and grooving jobs done by loading a drawing.
Choosing your first CAM: what to check
- Does it cover your operations? On a lathe that means OD, ID, grooving, the things you use every week
- Does it handle nose radius compensation for you? Whether you can hand that over changes the difficulty enormously for a beginner
- Can you check it in simulation? Seeing it before the machine sees it matters for safety and for training
- Can you start cheaply? For an individual or a small shop, start with something free or low cost
- Can you read the G-code it outputs? CAM you can see inside teaches you something
Summary
- CAM generates G-code from drawing data. CAD is the drawing side.
- Coordinate maths, nose radius compensation and repeated cuts all get handed to CAM.
- CAM never took hold in lathe shops because of price and complexity. Browser-based CAM changes that.
- The skill that matters now is reading the simulation and the G-code.
Make LATHE-NC your first CAM.
Lathe CAM that runs in a browser. Load a DXF, check the simulation, output G-code.
The beta is free for the first 100 users.