100 Watt CNC Laser Installation

I sold some stuff on ebay and got a little more liquid. I been buyin' stuff.

encoder
3, $49.00 = $147.00

cable (same site)
3, $7.00 = $21.00

flow switch
1, $65.00 = $65.00

gecko drive
3, $114.00 = $342.00

machine shop parts
1, $215.00 = $215.00

keyboard
1, $35.00 = $35.00

stepper controller
1, $250.00 = $250.00

1 inch thick honeycomb
1, $44.55

nitrogen regulator
1, $50.00 = $50.00 ebay estimate

oxygen regulator
1, $20.00 = $20.00 ebay estimate

oxygen tank
1, $75.00 = $75.00 need estimate

nitrogen tank
1, $75.00 = $75.00 need estimate

Current total: $1,280.00

I'm thinking of buying this system:

http://www.pico-systems.com/univstep.html



White, Owen wrote:

> Jon,
> Gotta question for you.
>
> The project I'm working on is to build a cnc table which handles xyz
> control for a CO2 laser. Control of the table will be like many others
> -- its driven using servos and gecko drives, and it will require home
> switches and e-stop. The laser has a number of I/O controls. There's
> four digital lines from the laser which report its status. There's a
> laser enable, and I've got to run solenoids to control things like
> water flow, and nitrogen flowing to the laser.
>
> I also have to control the laser power. The laser is driven by a duty
> cycle that ranges from 5 to 999 microseconds. I'm planning on using
> EMC and I'd like to control the laser power when running g-codes using
> that software.
>
> So when running EMC, is it possible to monitor all these input lines,
> set digital outputs, run the servos, and manage the laser duty cycle
> using your Universal Stepper Controller?
>

Yes, I think it is possible to do what you want. The USC board has 16
inputs that can sense whatever you need. A few of them are used up by limit
and home for each axis. There is an amp fault signal for each axis that is not
used by the current software. So, that provides 3 inputs that are available for
use. If you don't use a 4th axis, there are 2 more inputs. There are 8
digital outputs, with one dedicated to estop and/or servo enable.

EMC has a facility to pipe spindle speed to an unused motion axis, so the 4th axis can be set up to generate something close to a PWM waveform. What it really does is produce a constant pulse width with a varying rep rate, by using the step rate generator of the 4th axis. If that won't work, there is an additional 8-bit digital output from the board that could be used to generate your PWM for the laser.

Do you need the laser power to ramp up during the acceleration at the
beginning of a move? EMC, at present doesn't do this, but I think that it could be accomplished outside. If you only need to set the power for each move with a G-code, the spindle speed control of EMC should do it.

The S word in the G-code commands sets spindle speed. This can be routed to any spare axis output (A DAC for analog servos or the rate generator for step/direction, as on the USC board). I need to do a little tweaking of the software to send spindle speed to that extra digital ouput of the USC. But, that should work with the circuit you described in your 2nd message.

Jon

Got the parts back from Haas, which was fairly non-eventful. Now that I got those I can design the last parts that will join the optics chain to the laser head. I marked up these pics:





And faxed them off to a machinist.

I'm still waiting for parts and working on software so this weekend I just cleared more space in the shop and made this storage area:



Its just a bunch of cabinets installed underneath steps.

The plitron transformer produced too much voltage. I used the formula from their site but I should have gone with vdc = 1.4 * vac out of the transformer.

To lower the voltage on the transformer, I did the following.

I drilled out the epoxy core on the drill press in about ten minutes. The heat shrinkable wrapping around the windings completely prevented the epoxy from entering any windings. After chipping out the remaining epoxy block I removed the heat shrink wrap. The secondaries wires were very accessable and I didnt have any problem unwinding them.

I went with about 5 windings first prior to testing. I carefully checked for shorts between any of the exposed wires. (Its a bit of an act of faith that the enamel around the wires will prevent any shorting but it does the job.) After checking as much as I could, I hooked up the transformer and measured the voltage. The first time the voltage the wasnt even close. I unwrapped some more, eventually got to the right voltage, trimmed the secondary wires, soldered new connectors and put heat shrink tubing around solder joints.

I have some heatshrinkable sheet which I wrapped around the donut. I didnt like that result but left the sheet on, and followed up with lots of wraps of electrical tape. I popped the transformer back in the power supply enclosure and I'm operating at the right voltage.

Owen

Ventilation [pics]

To remove fumes from the bead-making process I put ventilators into the studio. This tech manual has some information on choosing a system. The recommendation for fume removal is to be running around 1000-2000 fpm and I had a losone ventilator that uns at 700 cfm. From this you can calculate that if you want to maintain the right fpm you'll need 6 inch sized vents.

I worked up a spread sheet. Costs were pretty reasonable at under $500. I got the parts from Air Handling Systems. They have a good online catalog and pretty reasonable on the phone. The configuration I used was to put reducers at the torches to just look cool, and put blast gates above the reducers. The blast gates pipes run up to a y-branch which then enter the losone. The losone exits into a flexible rubber hose and then vents out of the house.

I got the plitron transformer. Put the remainder of the power supply togehter. I used a full wave bridge circuit. I put it on my osciloscope and there was absolutely no ripple, which seemed a little surprising, but I aint complaining. The voltage is 79vdc. The box is canibalized from a Sun harddrive. Its a nice enclosure that comes with fans and a 5VDC power supply.