CNC - Building 2 - Aerosquare

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CNC - Building 2

Computer side:

The computer

No need to use a P4 running at 2 Ghz to control a cnc milling machine. An old Pentium 200 can do the work depending on the software you use. But if you plan to use the same pc for the cad work, it's better to get a good unit to work in good conditions.
A second hand PIII 450 can be a good choice to set your cnc station. To close this chapter, the configuration of the computer should be as clean as possible. If the pc is used only to drive the cnc table, don't install other software or fancy gadgets that could interfere during the milling process.

Software

Generally when working with a milling machine you need several software. You often hear talking about"CAD-CAM" for "Computer Aided Drawing - Computer Aided Manufacturing". First of all, using a drawing software, you draw the piece you want to cut. The most famous one is Autocad. Excellent tool but unfortunately too expensive for private use. On the other hand Turbocad LE edited by imsisoft.com is a free version of Turbocad Pro. Still, it has enough functionality to draw ribs and other parts of the fuselage, or a dolls house.  Not available anymore in free version.

The geometry is normally exported in dxf format which is translated by the machining software. Some software can export directly in machine code which is used to control the milling machine. The most commonly used language is the G-code. You can see the instructions available in Gcode. In addition to the G-code, there is the Mcode (M for Miscellaneous). The M-code is used to indicate for example pauses in the milling process, a change of tool, spindle stop, input of lubricant, etc. Does it sound too complicated? don't worry! It's only for information, the code is generated by the cnc machining software.

Controlling the machine is done using a special CAM software. This software interprets the geometry of the piece you want to cut, and the mechanics are piloted via the interface boards. Before cutting whatever, you must set the software parameters so it recognizes the machine correctly. Each software settings look different, but the basic logic is the same:

- Set the parameters for the PC communication port, the paralell port in this case.
- Find the mechanical characteristics of the machine: movement on each axis, step/millimiter, distance/step, cutting speed, travelling speed

It is not difficult to set the parameters, but each one must be set correctly otherwise it will not work. Sometimes amateur builders post messages on forums accusing the control board, the PC, the motors, the weather ... because their machines do not work. In most cases it's often the parameters that are not correctly set.

There are a number of sofware solutions to control the machine. Professional solutions are often too expensive for amateurs (thousands of euros), but luckily you can find not too expensive sharewares:

Windows-DOS:

CnFraise latest version 4 created by Guillaume Coquery, author of the famous "Coquery" design.
Kellycam You have to pay for version 4. But older version 3 is still available free of charge.
Ninos CAO FAO A French shareware, very original. it can even do 3D milling. Unfortunately it doesn't go with my machine or my PC. But people have very good opinion about it.
CNC Pro from YeagerAutomation. This software works under DOS. It has of course no graphical interface and looks old fashion. However, it is an excellent product, reliable and stable. Quite affordable also (200$).

Some software work only under Windows 98 and refuse to work under Windows 2000, XP, NT.
CNC Pro runs only under "real" DOS. It means that it will not work in the Windows 2000 DOS emulation window.

Macintosh:

I don't know any Macintosh solution for milling machines. On the Seagull Technologies site you find a software developed for the Mac, but it's been in Alpha version since 1999...

LINUX

Probably the best solution for Linux: Linux.cnc.org

This list is not complete, ther are many other possible solutions.