[hotponyshoes]

Hi,
I have a cnc plasma and I would like to adapt it to do a bit of laser engraving.

Basically we currently plasma cut parts from thin alloy and stainless sheet, pack them up and send them out to kit car builders.

We would like to mark the sheets out and send them whole for customers to cut themselves.

The idea we have is to engrave / etch them using a laser.

What sort of laser (co2, yag etc) would I need and what sort of power should it be?

Is something like this any good? (only a thought as it's just down the road from me)
http://cgi.ebay.co.uk/High-Power-BMI...QQcmdZViewItem

[KTP]

Wow, that is a nice looking arc lamp pumped yag laser. If you can get it cheap and it is close to you, buy it. You can always part it out and make more than your purchase price (if you don't pay too much).

To engrave steel and alluminum with a yag requires a q-switch. Put very simply, it is a device which cycles on and off preventing lasing which allows the lasing medium (the yag rod in this case) time to build up a large amount of excited atoms. Thus the laser will emit short pulses of extremely high peak power which overcome the surface reflection of metals like steel and alluminum. It looks like there might indeed be one inside there (the orange block just to the left of the laser block).

Note that this thing probably requires 3 phase 208V (or whatever you guys across the pond use for 3 phase).

[hotponyshoes]

We use 215v and 415v three phase anlon with 240v single phase.
We have all three in our workshop on 32amp supplies.

In terms of making it work is there much to it?

Could I pretty much replace my plasma torch with some optics and just use mirrors to shine the laser onto the sheet?

This might be making it a bit simple but if I got the laser at a good price would I need to spend a whole load more to start engraving? I allready have a cnc plasma tourch table which is accurate enough for anything we do!

[KTP]

the 1064nm from a q-switched yag is not really something you want to be bouncing around the shop with mirrors, unless you plan on enclosing your entire plasma system in sheet metal. Unlike the much longer wavelength of CO2 lasers (10,600 nm) the 1064nm yag will pass through glass and plastic with little attenuation. It gets focused nicely on the retina of your eye causing permanent damage or blindness.

[hotponyshoes]

Ok, Maybe not the mirrors then!

It's just the head of the thing looks alot bigger than a plasma torch!
I figured I could mount it at the end of the x axis and bounce it 90deg down the y axis and then turn it again downward to the work piece where the beam goes through the focus optic.
I suppose I could mount the head directly on to the y axis or even mount the whole thing on end in place of the torch..

[hotponyshoes]

Any idea what sort of power the yag laser in the link would be then?
Cheers!

[KTP]

I don't know if it is going to mean much to you if you don't have experience with yag lasers, but I would guess the ebay laser is around 20 to 50 killowatts peak pulse power, and maybe 10 to 20 watts or so average power if it is q-switched. Total guess based on the size of the power supply, etc.

You do understand that it is not going to cut through anything right? It will just leave a mark (if it is q-switched...if it is not q-switched it will not do anything to the steel at all).

You might make a better laser scriber out of a CO2 laser actually. If you can find something around 100 watts or so and focus it with a very short FL lens it will probably mark steel (but not aluminum).

[hotponyshoes]

The only experiance I have is with a JDS Uniphase laser with a 1watt argon head.
We have shining a matrix/grid that we check chassis alignment with.

A laser scriber is the perfect discription of what we are after. We only want a light mark on the work as some of it has to be folded.

I imagine aluminium is harder to mark as it conducts the heat away so quickly, how about marking on the plastic sheet that come stuck on it?

We have tried running with a tugsten tipped scriber in the machine but there is a risk of aluminium cracking along the line once its folded.

Co2 lasers hardly ever show up in the u.k. and I have never seen one on ebay over 50watt. The prices for something like a used Trumpf co2 start around uk£25k ($45k) and thats WAY over our pockets.

The idea is we colud sell 2 sheets ready stenciled for the customer to cut for a fair bit less than the price of the plasma cut parts out of 2 sheets.

We only turnover about 1000 sheets a year so we can't justifie spending a whole load when we have the plasma and still need to make an income from that.

The theroy was we could run off all the sheets we needed and free up the plasma table for other work, if we dont sell the marked sheets we can still use them as they are uncut.

[KTP]

I would say dont' fool with a laser if you are only doing 1000 sheets a year...unless you can charge $50 a sheet for the scribing