Advice on current project about lenses and power needed.

[neilhooper]

Hi All,

I quick introduction, my name is Neil and I'm based in the UK. This is my first post on the forum and I hope that I'm posting this in the correct section, please tell me if I'm not.

I want to replace the pointer in this project ,http://www.lamja.com/?p=635 with a laser to remove the marker. The easiest way to get the gist of it is to watch the video.

I've posted a similar thread on LPF which I'm aware that some of you may have seen but I've not had much luck. I'm not being rude but the best advice that I was given was to search the forum as it's been covered many times before which is OK if you know what you're searching for. In fact numerous searches didn't turn up much where as two or three searches on this forum at least gave some information about lenses.

I'm not looking for ultimate speed as it's not a commercial application.

To keep things accurate I would like to keep the travel speed down although I may be able to increase it as it's non contact.

I'm not looking to burn away the copper on the board, in fact, the complete opposite, just the marker coating.

I've done a lot of reading and things start to get way above my head quite quickly.

I've worked out how I switch the laser on and off using GCODE and I've built a driver circuit using a LM317 in constant current mode which is adjustable for testing purposes and have managed to get some diodes working from some DVD writers but that's as far as I've got.

I think I need to use a G2 lens as I would like to create a 'dot' of somewhere between 0.10 and 0.25mm and I can have PCB as close, or up 150mm away but I think relatively close would be better again for accuracy. I'm really not sure as I know less about lenses than I do about lasers and that's not much.

My biggest headache is what diode do I need? Am I better off going for something more powerful and not running it too hard as it basically needs to run for about 1 1/2 hours at the current speeds that I'm thinking of using with only a small amount of off time when the carriage is moving between points. At this time I don't know whether I need Red, Green, Blue, Violet, UV or something in between.

I'm aware that cooling will be an issue so intend to fan assist any heat sink that I use.

The other issue is cost. The doesn't appear to be the plethora of suppliers of the items needed over here. I can send off for them but this doesn't allow for a lot of experimentation as just the carriage costs in some cases are more than the parts cost and I don't have hundreds of £££ to spend on this. Of course that might make it a non starter

Any advice, even if it is not to bother and maybe why would be appreciated or some pointers in the right direction.

Thanks for reading.

- Neil

[Eidetic]

Interesting project, but I fear you may still be in the wrong forum to really find the answers you're looking for. You apparently seek information about materials processing with lasers. LPF is for the pointer kids, this place is for light show operators and artists, and while a few in both places may have experience in laser ablation (the proper term for what you want to do), it may be a while before they see and/or respond to you. On first thought, you may be needing a pulsed source, maybe an Nd:YAG laser. That could blow your budget. That's just a guess though. Good luck! Post results here. You're certainly closer to where you need to be here than at LPF.

[neilhooper]

Interesting project, but I fear you may still be in the wrong forum to really find the answers you're looking for. You apparently seek information about materials processing with lasers. LPF is for the pointer kids, this place is for light show operators and artists, and while a few in both places may have experience in laser ablation (the proper term for what you want to do), it may be a while before they see and/or respond to you. On first thought, you may be needing a pulsed source, maybe an Nd:YAG laser. That could blow your budget. That's just a guess though. Good luck! Post results here. You're certainly closer to where you need to be here than at LPF.

Thanks for the reply, you're right it's in the wrong place I think after having done a lot more reading on this forum that I should have put it under the Exigent Circumstances > 445nm section where there are complete threads on what I'm trying to do. What caught me out is that I've always seen that the news and admin stuff is at the top of the forum 'tree' with the rest descending from there. In this case the Exigent Circumstances section is at the top thus suggesting that the forum is more swayed towards what they're trying to do but I realised this after I had posted and I can't see a way to move it now. However I have learnt something in that what I'm trying to do does actually have a name. On a positive note I now have on the way a 1.8W 445nm A-Type M140 Blue diode in it's housing with a G2 lens from Jordan at DTR who helped me out in jiffy last night.

I must say that some of the things that I've seen on this forum over the last couple of days are amazing. I think that lighting can be fantastically creative and find myself mesmerised by good lighting. It takes me back to when I was younger and running my mobile disco back in the 80's where lighting was big on our agenda as I think it's more important than the music. I drool over some of the kit that's available today and can't help thinking to myself, If only we had all of this in my day ..... I know you might not think it but if that's your job then as far as I'm concerned your doing the dream job.

I actually use coloured lighting to great effect around our house with RGB LED strips doing a very slow and subtle colour changing effect and as we have all white walls the house is 're-painted' every half hour. I'm now up to just over 1600ft of it. I don't think the wife will let me start with lasers although I'd love to and then my budget would be truly blown.

- Neil