PCB CNC

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gmoney484
Posts: 17
Joined: Wed Nov 09, 2016 8:52 pm

PCB CNC

Postby gmoney484 » Thu Feb 16, 2017 2:57 am

Hi all
Just showing off our CNC. We are a secondary school and we use this primarily for milling PCB boards for our senior electronics class.

It started off as a C-Beam machine from OpenBuilds, but its been modified and upspec'd along the way (big shout outs to CNCkits and Protoneer for their help).

The original control was via MACH3 and a MACH3 parallel controller. You can see the custom made control and power box. Three power supplies:
- 5v for Mach3
- 12v for spindle
- 24v for steppers
- emergency stops and all that sort of stuff needed for Health and Safety.
[img]
cntlr1sml.JPG
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The spindle is a ESC type (the first iteration was a much larger one, but too big for our needs). There was a small board to convert the PWM to ESC, but we replaced that. We also used a Protoneer arduino CNC shield.. but.....

The new controller was simplified because I realised I didn't need that sort of power for PCBs and also I hate pin connectors.. i love screw connectors so I went with the Raspberry Pi CNC Shield (simply because of the screw connectors..).. could I use it in place of the original CNC shield without a Pi? I wonder.
[img]
cntrlr2sml.JPG
[/img]
Anyway, the Pi running bCNC works perfectly, so I replaced the original control box with parts recycled from a PC including the power supply - its a neat solution. Sadly, my 160W supply is too small to run steppers and spindle so Im going to upgrade to a 400W supply this week.

I also replaced the PWM to ESC circuit board with an arduino. I used software to do the conversion, but Im still going to add a low-pass filter to smooth things out.

Not everything is working completely yet. I need to tweek the arduino, add end-stops, calibrate GRBL etc etc, but it makes pretty sweet PCBs.

More to come.
Attachments
cntrlr2sml.JPG
cntrlr2sml.JPG (171.61 KiB) Viewed 209 times
cntlr1sml.JPG
cntlr1sml.JPG (163.65 KiB) Viewed 209 times
CNCsml.JPG
CNCsml.JPG (148.05 KiB) Viewed 209 times
Last edited by gmoney484 on Sat Feb 18, 2017 7:58 am, edited 1 time in total.
Gavin Milne
HoD Science
Dilworth School

Bertus Kruger
Site Admin
Posts: 633
Joined: Wed Feb 03, 2016 10:26 pm
Location: Wellington , New Zealand
Contact:

Re: PCB CNC

Postby Bertus Kruger » Thu Feb 16, 2017 10:23 pm

Nice work,very neat setup... Do you have any sample PCB's?

gmoney484
Posts: 17
Joined: Wed Nov 09, 2016 8:52 pm

Re: PCB CNC

Postby gmoney484 » Mon Feb 20, 2017 6:31 pm

It's gone? It's back :)
Gavin Milne
HoD Science
Dilworth School

gmoney484
Posts: 17
Joined: Wed Nov 09, 2016 8:52 pm

Re: PCB CNC

Postby gmoney484 » Sun Feb 26, 2017 11:18 pm

Version 3 of the controller and case.

650W modular power supply - 54A should do it ;)

Zalman case (cheap as chips and comes with 3 fans and fancy blue LEDs)

Emergency stop button will be connected via cable and sit beside CNC. I will connect up the cases USBs to the Pi's so I can easily connect keyboards etc. I'll also connect the probe via one of the 3.5mm audio jacks on the front.

The Arduino (by power supply) converts PWM to ESC - I tried a variety of software smoothing algorithms, but a physical low-pass filter built on-board still gives the best results - ripple voltage <0.01V

Tested at full speed and there's more than enough current from the single supply.

Not sure why the picture ends up upside down.. sorry

cntrlr.jpeg
cntrlr.jpeg (112.34 KiB) Viewed 176 times
Gavin Milne
HoD Science
Dilworth School

Bertus Kruger
Site Admin
Posts: 633
Joined: Wed Feb 03, 2016 10:26 pm
Location: Wellington , New Zealand
Contact:

Re: PCB CNC

Postby Bertus Kruger » Wed Mar 01, 2017 6:53 pm

Wow!!! That is a nice build... Love the black finish. 8-)

gmoney484
Posts: 17
Joined: Wed Nov 09, 2016 8:52 pm

Re: PCB CNC

Postby gmoney484 » Thu Mar 02, 2017 3:42 am

To all reading this, I strongly recommend using a PC ATX power supply, There are a few reasons for this:

they are relatively cheap, but good quality
they usually come with fans and are quiet
you can choose whatever power you need - I use 650W at 54A 12V - more that enough for steppers and spindle
the motherboard connectors can supply 5V for the Pi CNC shield (via the purple) that is always on, even in standby
you can control the main power via an E-Stop button - the green cable (and connect the E-Stop to the HOLD pin on-board)

The Pi CNC is always running (as is bCNC and GRBL) and the E-Stop kills the rest of the power (steppers spindle) and pauses bCNC.

So simple..
Gavin Milne
HoD Science
Dilworth School


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