Grounding... How far to go with it???

[Toasty]

I've been having great luck with my converted machine. It's running great and if everything holds up it should be a really nice little machine.

I'm turning my attention to the last few details. First off is grounding. My machine has real grounds but I'm wondering if I should add any additional ground points.

I read in one post by Marco (where did he go btw? he no longer answers emails) that mentioned grounding the case of the dsp display. Has anyone on here done that? I haven't seen that in any of the photos.

I also noticed a photo of someone's machine where they had a ground wire going from one of the mounting screws on the dsp's controller to the case. I didn't think this was necessary since the dsp's power supply is grounded. Any ideas?

Also, anyone on here ever experienced this:

http://eng-serve.org/buildlog/forum/vie ... &start=310

Scroll down to the guy talking about his laser tube leaking current into the cooling water. I think my machine does this a bit. I had a thermometer in the water to keep an eye on the temps. The thermometer has a metal wire going to the probe (it's meant to be used in ovens). The wire was slightly touching my arm and I noticed a slight shock when the laser initially fires just like the post in the link talks about. Doesn't do it when it's cutting but you notice it when it's engraving since it's pulsing on and off.

Oh, and before someone asks, the tube isn't broken at all. If it was I assume the current would be very high in the water all the time when the laser is firing. This is just that initial pulse which I assume is very high voltage for a second.

Is this normal? I assume just like in that post that the current is so high when the power supply fires that some of that 20k volts leaks past the glass into the water. Very scary stuff and I won't be using a probe with a metal wire any more.

Again, any thoughts?

[Tech_Marco]

Marco is always here. I didn't recall seeing your email(s). May be in spam or may be network glitch or I oversight (if so, I apology for my mistake)

FYI, even though I'm busy everyday, I answer email within 12hrs unless I oversight it. If I didn't reply you, please send again and I don't believe that there is any chance I can miss your email trice. But please, do not say that "no longer answer email" because my mistake(if any). I do answer email a lot daily and I have to do phone support as well.

BTW, if your guys have question, please post it on the forum as this is the only way we can learn by sharing question and answer. Please note that I'm just an armature of CO2 laser so please do not expect that I know everything or having a solution of your question. All I can do is doing research myself or ask laser manufacturer in China. So, I'm not better than you folks, it's just that I move one step further. I learned laser technology by "hands on experience". I do test for something I don't understand and if I can't get myself a solution after running all test I can do, then I ask help from others. That's how I learned laser.

Please accept my apology for not answering email on time. March is a tax season and I was in Big trouble. Plus there were other issues bothering me(health, warehouse, loan,..dsp...). But I really did my best to help.


Marco

[Toasty]

Whoa, I apologize if I offended. I probably should have worded it a bit different. I should have said "there have been no replies to MY emails".

I completely understand how stressful running a business can be. I'm a one man show at my business so everything falls on me too.

I will say, however, that with the kind of products being sold here you probably get an unbelievable amount of questions and rightfully so. These machine are not toys and I personally think it's important that they're done right.

But since we're on the subject. A couple of suggestions, and I hope you don't take them as being too critical... I think some of the information here is very scattered. The pdf you made for putting the kit together is wonderful but even that is hard to find if you're new here. Basically, the information for the conversion is available in the forum but most of it is buried deep in message threads. It would be nice if the important things like wiring diagrams were put in a sticky at the top of the forum. I see the same questions being asked over and over on here and it would probably save you a ton of time in the long run.

And I've said it before and I'll say it again, I think the conversion is wonderful and I'm thrilled with the results. I just want to make sure everything is done correctly.

[Tech_Marco]

Toasty, Sorry I have to pick on you. I hope that you understand how much stress I have had for last couple weeks. So, bear with me for my 'blow out' to release some pressure here once a while.

Regarding the topics issue, Yes, I agreed with your point. For important doc like the K40 conversion pdf, I posted it exclusively on "Manual Download" section. For other question, so far I really have no idea how to do sorting. Well, I guess folks need to use "search" function on the forum to find the info they need. I already lower the filter '% index' so one will be able to search topic with 50% key words used.

Any better solution, let me know


Marco

[nephertiti]

Scroll down to the guy talking about his laser tube leaking current into the cooling water. I think my machine does this a bit. I had a thermometer in the water to keep an eye on the temps. The thermometer has a metal wire going to the probe (it's meant to be used in ovens). The wire was slightly touching my arm and I noticed a slight shock when the laser initially fires just like the post in the link talks about. Doesn't do it when it's cutting but you notice it when it's engraving since it's pulsing on and off.

Hi

Same thing happened to me. When I touch cooling radiator I noticed shocks so I decide to add grounding wire to radiator and fixed my problem. I asked Marco and he said ground everything so I grounded frame too and other things

Now everything looks good.

[Toasty]

Same thing happened to me. When I touch cooling radiator I noticed shocks so I decide to add grounding wire to radiator and fixed my problem. I asked Marco and he said ground everything so I grounded frame too and other things

Now everything looks good.

Thanks for the reply. I assumed there were probably other people that have experienced this.

So, my next question is, for those out there that have grounded their dsp display, what screw did you attach the wire to?

Also, does anyone have a picture of how they wired the emergency kill switch that comes with the kit?


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[Things]

The CO2 laser leaking a bit of power into the water is common, it's called "capacitive coupling" if you want to read into it more.

As for grounding, 95% of the time it's purely for safety. Because the laser PSU operates at high voltage, if it were to arc to the case of the laser at any point, you'd get a very nasty shock. The shock probably wouldn't kill you, but I wouldn't be surprised if it gave you violent muscle spasms, sending anything you're holding flying across the room while you scream expletives. I've been shocked by 15kV at 30mA before, but AC, and I can tell you, it's an experience you want to avoid at all costs.

Grounding your machine means that if something does go wrong, the current will flow to ground, instead of through you.

However, grounding is also a factor if you notice interference between components. If your DSP is mounted to the metal chassis of the laser, which is grounded, then you shouldn't have any issues, but note that the negative of the power supply is NOT always ground. On many switchmode power supplies, their negative connections are actually isolated, which makes it easier to use them in series and as split rail power supplies. You can test it yourself with a simple continuity tester, try between the negative terminal on the power supply, and the case of the power supply (while it's off and unplugged of course).

As far as I'm aware, the DSP control panel itself is actually made out of PCB, probably FR4, which isn't conductive. They are probably attaching it to the metal box on the back of the display.

If you aren't having issues though, there is no need to go that extreme on grounding. But if stuff acts erratically, then it's the first thing you should check.

In most cases, simply grounding the machines chassis to your mains ground (If it's available where you operate the machine) is sufficient.

As for the emergency switch, typically that just goes in series with one of the mains input lines. Where the power comes into the machine, you need to cut (and extend if needed) one of those wires, so that the emergency switch is the FIRST (Or 2nd if you have a fuse in the machine) thing connected to your main power input. So just grab either the active or neutral wire, cut it, extend it, and run it through the emergency switch. You only need to run 1 wire of the mains input through it, either neutral or active.