CNC-Fräse: Unterschied zwischen den Versionen

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== Introduction ==

A CNC mill like the dear Geil-O-Mat has three axis that can be moved independently. A spindle with a [http://de.wikipedia.org/wiki/Fr%C3%A4swerkzeug mill cutter] typically removes material.

Each axis is driven by one(Y and Z) or two (X) stepper motors. Basically, theses motors can only rotate in 1.8 degree steps, and hence no secondary encoder is needed for the machine knowing its current location. By a trick called "microstepping", currently the resolution is increased to 1/8 of 1.8 degrees.

As the stepper leads in to a "Zwillings-Trapezgewindespindel", the rotation is transformed into linear motion, one revolution= 6mm.

Warning: If there is too much force for the motor to move one step, it skips the step, typically failing also in subsequent movements, resulting in an ugly noise, and shift in the positioning.

The Motors are connected to a driver device, which sits on top of the whole machine. It creates the strong currents for the stepper drivers, out of signals from the PCs parallel port.

Hence, the computer has to send signals telling which axis should move one step forward or backward at a given instance. This can/is done by a software called "EMC". It is open source, and the thread doing this parallel port communications is using the patched real time Linux-kernel.

There are some GUIs for EMC, the most relevant is "AXIS", which graphically displays the current machine position, the paths it should travel the track history, and further stuff. Also manual movement can be performed.

The language to specify the movement of the machine is called "GCODE". Some of its statements are starting with G01,or G00, hence the name.

A simple Gcode can look like this:

; i am a comment

F100; move with 100mm/min while cutting

G0 Z10; fast move to Z-coordinate 10

G1 Z0; drill down until Z=0 with the speed given by the Feedrate

G1 X10; move to the new location X10 while cutting

G0 Z10; and back up with large speed.

M30; end program

One can do a lot of things, e.g. have variables (#1=10), and do loops , evaluate mathematical expressions (G1 Z[#1*2].

So basically, real hackers write gcode by hand, while Chuck Norris sends movement commands to the steppers.

However, as we are all lacy, and things can get quite complicated, there exists software to convert 3d/2d CAD files, grayscale depthmap images, 3d-stl objects and other things into Gode. This is often called "CAM"-Software.

If you have a 2d-cad file (e.g. dxf) and specify depths for some areas that should be milled away, one speaks of 2.5D-CAM. This is performed e.g. by CamBam, or Camexpert.

== Current Status==