Tuesday, 19 February 2013

CNC Mill Build - It Works!

Very quick update, I did finally sort out my electronics problem and was able to mill my first piece.

Behold the power of my machine:

When I shot this video my setup looked like this.

Already I'm not happy with it, the electronics are too close and don't allow the wires enough room so I can't use the full length of the Y axis, also they really need to be covered. 

I'm currently holding work down using push pins, not a great solution.

Already working on changing all that. But for now it works !

See my next stage of improvements here.

CNC Mill Build - eLectronics

The last post saw me putting the finishing touches to my machine build, by adding the belts. Unfortunately that's the easy part over, now I'm tackling electronics.

There are two stages to controlling a CNC machine. The first is a controller which will take a Gcode file* and turn it into step and direction pulses that tell each motor when to turn.
The second is a motor driver which takes these low voltage data signals and sends high power signals to actually drive the motor.

For the driver (the second part) I'm using pololu a4988 drivers along with a stepper shield. After finally sourcing all the parts this is what they look like.

The driver is quite small, you can see one of them in the top left. The rest is just capacitors, to even out power, and connectors, to attach all the motors.

This board is a 'sheild' which is intended to be used with an arduino. You can use an arduino as your controller, but I wanted to use a PC because it gives me more control and a  nice graphical interface.

Which means I had to build a separate board to make it so the signals to and from this shield could be sent via a parallel cable.

This is what I put together. Again not much going on here, the parallel cable is broken out and the signals sent to the right sockets (so they match up when the shield is plugged in on top).
There is also a 5v regulator to supply the logic voltage and all the connections are optically isolated. This means that the CNC motors and the computer aren't physically connected, this means any noise caused by the motors won't affect the computer.

Bart Dring, of Buildlog.net designed this board which does exactly what I want. But he doesn't sell them anymore. So what I did was buy the arduino version (also designed by Bart, but now made by Reactive Substance) and adding in the missing components so that it was functionally the same. It probably would have been easier to just build the whole thing myself from Bart's schematic. But the black boards help with heat dissipation  as well as matching the drivers I bought, and looking badass.
Edit: of course now that the M6 is finished, I could design a new PCB with everything on and mill it on my machine, how ever I'm unlikely to ever get round to this.

Now the shield carrying the stepper drivers, just plugs in on top. Each one of those drivers (now with large blue heat sinks on) controls one of the motors, each motor has 4 wires.

The large silver box off to the left is the 24V power supply, this is the power that is used to drive the motors, the 5V logic is supplied by a small regulator I put on the lower board.

That's most of the hardware set up, the other end is an old PC running Ubuntu, I'm using LinuxCNC to control my machine, it's a very powerful tool (probably overkill for this little thing) but nice all the same.

What came next was lots or testing tinkering and , to be honest, swearing as I tried to figure out why it wouldn't work.

(figured it out eventually WooHoo!)

*Gcode is the end result of designing on a computer, it's composed of simple lines of text that instruct the machine where to go using an absolute positioning system. E.g. g0 x10 y10 would tell the machine to move to that co-ordinate (g0 is just max speed) so kind of like playing Battleships.

Saturday, 16 February 2013

Cardboard Boba Bucket - Range Finder

We're getting very close to the end of all my old progress pictures. I did get the helmet down the other day intending to do some more painting, but gave up before I'd even started, it's just so tedious, marking out all the shapes.

Originally Posted 27-Jul-2009

Next up is the rangefinder housing. If I remember correctly this part isn't detailed in either of Antman's threads 
(which I have been following fairly closely) So I'll try to show a bit more detail.

First of all print out a set of WoF's templates from the gallery.

I'm using 1mm thick mattboard (scavenged from an old sketch book)
So I then began to mark the various places I would have to trim 1mm off of to keep the correct shape.

The dotted lines show where I'm going to angle both edges at the corner rather than just trim one of them.

Here are the pieces cut out.

I began to angle some of the pieces with a knife and sandpaper. I also drilled out the LED holes using a 5mm wood bit.

Then I just began assembling all the pieces.

I had to be careful, trying to make sure the sides were square.

One of the pieces didn't quite fit, overtrimmed, but I'll sort that out later

After letting it dry a while I decided to paper mache' the inside, to cover the small cracks and strengthen it a bit.

Then I brought out my circuit and did a test fit, bending the LEDs into roughly the correct place.

The circuit fits easily into the housing. The only problem is that it infringes on the lens' space more than I would like. 
But I can't be bothered to move all the stuff onto a smaller board.

Saturday, 2 February 2013

Cardboard Boba Bucket - Electronics

A huge gap here, bringing us closer to the present. Now working on some rangefinder electronics.

Rangefinder Electronics

Originally Posted 27-July-2009
I haven't posted anything in ages because I've been away (doing an Architecture degree)

But now I'm back and have got thoroughly stuck into making my rangefinder.

First of all I purchased a metronome kit from Maplin as well as some green LEDs.

As soon as I got the kit I assembled it according to the instructions and then began to sync the lights up to the right speed (2.13 Hz), by adjusting the two pots to 40KΩ each.

That was fairly easy and formed the basis for my rangefinder circuitry.

Next I desoldered the 9v clip, the LEDs and the capacitors. I re-soldered the capacitors, leaving longer leads so I could fold them down flat.

I had to extend the leads of the LEDs, this was fairly simple, I just soldered on some short lengths of wire and added heat shrink tubing.

I then re-soldered these longer LED's into place.
Also I filed off the unused areas of the board.

Until I could scavenge another resistor (maplin only sell them in massive sets) I'm leaving the circuitry here.

Total spend is now £9.58.

- Large card for main helmet & mask : £2.00
- Pint o' PVA Glue : £3.00 
- Metronome kit : £3.99
- Superbright green LED : £0.59