First adventures in the CNC milling world

M.daSilvaM.daSilva wrote 05/03/2017 at 11:37 • 4 min read • Like

Nothing I though worth writing a entire project about, it's a project I did last year, to get my feet wet with metal CNC milling.

I built a Bluetooth speaker with cheapo eBay modules: Bluetooth audio module, audio amplifier, USB charger, boost converter, and a recovered Lithium-ion battery from a laptop.About 10€ in parts altogether.

The main case was 3D printed, and some hot glue was involved.

The lid had to be done, and I had an opportunity to use an Arrow 500 CNC mill... A small machine :p

Aluminium it is then!

A quick modelling and schematic was carried out on Solidworks (dimensions in non-freedom units):

I quickly printed it out to check the fit with the case.

The G-code was hand-typed, I used CIMCO to carry out the simulations before using the real thing.

G40 G17 G90 G54 G94
T3 M6 '(4mm mill)
G0 G43 H3 Z50 '(tool compensation, high axis speed)
G0 G94 S6000 M3 '(mill motor start, clockwise)
'(4 mounting holes)
G0 X3.5 Y3.5 Z2 M8 '(bring the tool closer to the part, start coolant)
G1 F50 Z-4
G1 Z10
G0 X139.5 Y3.5 Z2
G1 Z-4
G1 Z10
G0 X3.5 Y39.5 Z2
G1 Z-4
G1 Z10
G0 X139.5 Y39.5 Z2
G1 Z-4
G1 Z10
'(central switch hole)
G0 Z50
T7 M6
G0 G43 H7 Z50
G0 G94 S6000 M3
G0 Z2 X71.5 Y21.5 M8
G1 F83 Z-4
G1 Z10
'(speaker holes)
G0 Z50
T3 M6
G00 G43 H3 Z50
S6000 M3
G0 X21 Y21.5 Z2 M8
G1 X21 Y21.5 F140 G40
G176 X21 Y21.5 Z-4 R10 D3 E100 K6 Q13.5 P30
G1 Z2
G0 X122 Y21.5 Z2 M8
G1 X122 Y21.5 F140 G40
G176 X122 Y21.5 Z-4 R10 D3 E100 K6 Q13.5 P30
G1 Z2
'(final plate cutout)
G0 Z50 
T5 M6
G00 G43 H5 Z50
S5406 M3
G0 Z10 X0 Y0
G0 Z2
G1 X0 Y0 G42 D5
G1 F60 Z-4
G1 F180 G42 D5 X143 Y0
G1 X143 Y43
G1 X0 Y43
G1 X0 Y-2
'(program end)
G1 Z10 M9
G0 Z50
G0 Z50
T0 M6
As you can see, the program was split up in four sections:

The code is fairly standard, G1s were used for straight cuts/holes. The only exotic one is the G176, which is used to mill out the pockets for the speaker holes.

After simulation on CIMCO (which is, BTW, incredibly expensive... The interface still looks like an MS-DOS prompt, even through it's a 2015 software!), the code was transferred over to the Mill (which is a genuine DOS machine, also a royal PITA to operate). Lots of small tweaks had to be done, the holes weren't correctly centered, tool compensation was off, ...

I cut the part off a 4mm aluminum painted plate.

After lots of sanding, it was finally mounted onto the speaker.

And voilà! :)

Now, there are a few things I could've done better here:

This could've taken waaay less time on a manual mill, or even with a bandsaw, a drill press and some files, but it sure was a fun and an interesting way to learn how to manually write G code!