More hardware

Just as I get the CNC router to make it's first movements I found a bloke selling one of those cheepo Chinese lasers engravers on ebay. I thought it was worth a punt as it was an auction and had the potential to go for less than a new one, especially as it was one with a parallel port connection and had a fault that stopped the laser from turning on when the controller told it to. so £500 new, i got mine for £390 inc postage. Woooo!! The fact that it is parallel and the controller didn't work dosen't bother me as I want to put a new controller in it anyway so now I  have yet another project.

I have posted some pics here of my initial investigations. It's not going to be long before someone gets hurt by one of these as they are VERY badly designed, but they do give you all the complex bits of a decent laser engraver so so long as you know what you are doing and modify it correctly it can be made to be safe.

THESE THINGS ARE LETHAL. DO NOT BUY ONE OR FIDDLE WITH THEM IF YOU DON'T KNOW WHAT YOU ARE DOING. IF FACT EVEN IF YOU DO KNOW WHAT YOU ARE DOING IT WOULD STILL BE VERY EASY TO GET SERIOUSLY BURT OR BLINDED OR SET ON FIRE.

Why are they so bad? Well let's see;

1. It's a Class 4 in there and there are no interlocks, no beam tubes, no key switch and no emergency stop button. also missing the big yellow "Class 4 Laser Product" sticker. (admittedly if it had all that stuff it could probably be Class 1 laser product as everything would be enclosed.)
2. The cutting compartment has vents in the sides and holes in the bottom so there is always the chance that a shiny thing could send the beam out one of said holes and set something near by (or not so near by) on fire or blind or burn you.
3. There is no laser supervisor system. A 40W laser needs looking after. You need to make sure the pump hasn't died or a pipe clogged and than the cooling water is actually cold. You need to make sure the power that its drawing is not above the damage threashold. You need to make sure that the flying optics are in flight, if not it will just start a fire (like if the firmware crashes and stops the motors moving but doesn't turn off the laser.) Its also nice to know how long the laser has been on and at what power so you can schedule tube and optics replacements when they come to the end of their life
4. The work area is pathetic. The optics fly over a much larger area than they give you to work in, I can only assume its space to accelerate.
5. The case is massively too big for what's in it. (Although that does mean that there is room for all the things it is missing)
6. The cooling system is a bucket of water and a fountain pump that they have modified with hot glue to fit the pipe they are using.
7. The extractor fan is just a ceiling fan but not a good fan, probably the worst one i have ever seen
8.  Electrically they are abysmal:

• Mains and low voltage wiring not well separated (although better than some I have seen)
• Wires going through burred holes in steel with no grommets,
• No real isolation barrier for the controller
• Front panel controls connected to rectified mains!!
• Laser current meter connected in series with laser, which operates at 22kV!!! (OK, on the low side but if anything goes wrong with that big ceramic ballast resistor...)
• The fan and pump both have American plugs and are designed to run from 240VAC, not a good combo.
• The laser is turned on and off by a 24V signal going to an opto-isolator but that signal goes through a connector with pins right next to the signal pins at rectified mains potential so not that well isolated.
• The laser PSU is built around a TL494 on which they change the current by fiddling with the potential on the timing resistor, very odd.

There are probably a few more things to add but I can't remember them all, it's just that bad. It wont be long before trading standards clamp down on these things which will probably be for the better but hopefully someone will do safe one at a decent price soon (there are these and these but the price is still a bit high)

So what am I going to do?

1.  Interlocks. I like to have anything that can blind me or set me on fire with an invisible and non dispersing ray of light locked away when in use. It's just a good idea. While I am at it, a key switch and stop button.
2. I need to baffle up all the vents so nothing can get out and weld up all the left over holes.
3. The optics need cleaned and aligned.
4. An air assist needs to be installed.
5. A pair of alignment lasers need to be added.
6. A new power supply
7. Rewire everything.
8. Replace the current meter with a hall effect current sensor around an appropriately insulated wire.
9. Replace the twiddly pot for current setting with a dig-ipot and ensure it is opto-isolated from what ever controls it.
10. Opto-isolate the inputs to the laser PSU
11. New control board.
12. Supervisor board.
13. Fit all the cooling in the case. I am thinking of something similar to a liquid cooling system on a computer (laser tube should be dissipating around 300W in heat so should be doable)

After all that is done, then I have for some time wanted to write something similar to this as I have a Cameo and although a little annoying at times and massively bloated the functionality of the software is quite good and some thing like that would be excellent for 2D and 2.5D CNC machining. I have experimented with pygame but the lack of GUI was annoying, and VB but the lack of speed was equally frustrating so hopefully something built in pyGTK will do the job.