The CNC process

Well Since I don't have much to post after this weekend disaster, I'll just take you through all the steps involved in CNCing (the machine that cuts out the foam blanks)

1st

Design your part in 3d... this is the lathe chuck designed in Rhino3d



















2nd
Look at the part and visualize how the steps will be performed on the machine.
Then it's on to generating the "toolpaths" this is how the physical cutter will move through the material.. It is different for nearly every CAM (Computer Aided Manufacturing) software Package there is... For this Chuck design I've used the add-on to Rhino3D called RhinoCAM.

This the toolpaths calculated for the face of the chuck.

This one will cut the outline of the chuck ...



Note the Blue lines is where the centre of the 3mm flat cutter will move. This package automatically calculates the tool cutter offset.. That means it will move half the diameter of the cutter away from the part and the resultant cut will be exactly to the measurement of the design.







This cut will "pocket" out the centre cross slide grooves.















3rd
Next thing will be to translate this tool paths into a language that the machine interpreter will understand.. The language is called G-Code, owing to the fact that all operations start with a G-code word..

This translation is called post processing.. so the blue cutting lines in the software package will look like this when processed..

N1 T2 M6
N2 S4851 M03
N3 G00 X-6. Y83.5
N4 Z5. D0
N5 G01 Z-10. F 500.
N6 Y77.5 F 800.
N7 X-5.8496 Y76.1649
N8 X-5.4058 Y74.8967
N9 X-4.691 Y73.7591
N10 X-3.7409 Y72.809
N11 X-2.6033 Y72.0942
N12 X-1.3351 Y71.6504
N13 X0. Y71.5
N14 X4.1574 Y71.379
N15 X8.3006 Y71.0165
N16 X12.4158 Y70.4138
N17 X16.489 Y69.5727
N18 X20.5064 Y68.4963
N19 X24.4544 Y67.188
N20 X28.3197 Y65.6525
N21 X32.0891 Y63.8947
N22 X35.75 Y61.9208
N23 X39.2899 Y59.7374
N24 X42.6968 Y57.3518
N25 X45.9593 Y54.7722
N26 X49.0663 Y52.0072
N27 X52.0072 Y49.0663
N28 X54.7722 Y45.9593
N29 X57.3518 Y42.6968
N30 X59.7374 Y39.2899
N31 X61.9208 Y35.75
N32 X63.8947 Y32.0891
N33 X65.6525 Y28.3197
N34 X67.188 Y24.4544
N35 X68.4963 Y20.5064
N36 X69.5727 Y16.489
N37 X70.4138 Y12.4158
N38 X71.0165 Y8.3006
N39 X71.379 Y4.1574
N40 X71.5 Y0.
N41 X71.379 Y-4.1574

NB. This is just a very small portion of the file, the actual file is about 100 kB of pure text... it's a LOT of lines.

If you look at the code you'll see it's nothing but a list of Cartesian coordinates.. A cnc machine is actually nothing but a Cartesian robot with a cutter attached. The same principles are used for robotic assembly lines, pick and place robots that assemble computer motherboards etc. etc. etc.

4th
Load the G-code file in the machine interpreter software, I use an old DOS based program called TurboCNC.. it looks like this with the file loaded.











Then it's time to load the material on the machine. Make sure that it's positioned correctly and then "jog" the machine into the correct position to start. This is usually coordinates X,Y,Z(0;0;0)

This software will send electronic pulses via the printer port of the pc to the electronic drivers which in turn moves the motors to the correct position.



this is the electronic drivers made... The motors used is also not ordinary motors that spins continuously these are stepper motors which turns exactly 1.8 degrees every time power is supplied in a specific sequence. The software outputs signals to step the motor and the electronic drivers then set up the correct sequence to step the motor in the right direction.






And the result of all these things coming together is this..





























... And there you go That is a short run down of how to go from a 3D design to a real life model using the easiest of grade 6 trigonometry.

It's not only simple shapes that can be cut out. Here is another project of mine.. a Concept model of a peugeot... It's still a work in progress though.












Hope you enjoyed this .. and maybe it inspires you to start your own Cartesian robot one day...