A very good reason to never leave a laser cutter unattended

[David Buggs]

Laser Cutter Fire/Manufacturing Update

I looked around quickly today and did not see any fire extinguishers at the space.  For Lenox we should have them prominently inside big red painted squares or in red boxes mounted on walls.  I'm saying RED even though I am admittedly severely color blind so any contrasting color against the walls would be fine for my purposes.

Buggs

[Pete Prodoehl]

I saw a room full of fire extinguishers at Lenox... I hope we get to keep them all! (And that they're all good.)


Pete

[Dennis]

Yes, those are our fire extinguishers.  We'll be testing them and distributing them appropriately based on how the space ends up being laid out.

--
 
 
 

--
Dennis

[Brent Bublitz]

FIRE EXTINGUISHER FIGHT!

> --
>
>
>

[Kevin Crowley]

If the air assist was switched from compressed air to a bottled nitrogen system, Which I believe is of a moderate cost, the risk of a fire would be reduced.  Granted even with keeping the lid closed you would not reduce the O2 content to even close to zero but even if cut only by a 1/4 reduces the flammability of many materials.  Of course that also presupposes that the laser cutter in question is being vented to the outdoors. Hypoxia is not to be trifled with.

I believe I have seen mention of nitrogen generators having some cost benefits over bottled but I have no idea if that is true or practical.

--

[Ed Hagopian]

There is a fair volume of gas's going through that thing. I suspect wed exhaust nitrogen fairly quickly. Better to just stick around the laser when in use and have an extinguisher close.

[ironmonger]

Would CO2 work in place of nitrogen? Lots cheaper.
Might also consider a pressure swing adsorption nitrogen concentrator. These occasionally show up at industrial auctions. If you find an oxygen concentrator the high pressure units can fill oxygen tanks.... The 'waste' gas is nitrogen.

Paul
WB9HCO
No trees were killed sending this message, but a tremendous number of electrons were terribly inconvienced...

On Oct 23, 2012 9:59 PM, "Ed Hagopian" <edhag...@gmail.com> wrote:

There is a fair volume of gas's going through that thing. I suspect wed exhaust nitrogen fairly quickly. Better to just stick around the laser when in use and have an extinguisher close.

--

[Kevin Crowley]

CO2 is cheaper than nitrogen?  I have not priced either in so long that I have no knowledge in current price structures.

As for how much gas would be used in the air assist system while I most definitely do not know what the volume is I suspect it is much less than might be supposed.  I also suspect this is all academic as a modest expense is still more than no expense.

--
 
 
 

[Tom Gralewicz]

Since CO2 is in liquid form in a pressure cylinder you got quite a bit more than in a Nitrogen tank, hence its cheaper.

The laser wants 2.5 CFM for the air assist, an average sized tank of nitrogen is around 250 cubic feet, that gives you 100 minutes of run time per tank, only if the automatic system turns it on and off.  Leave it on once and your tank is empty.

There is a tank of CO2 on the gray cart by the welding area (the red and silver tank) and there should be fittings and regulators as well, why don't we give it a try and see how it works?

Tom

--
 
 
 

--
Tom Gralewicz
Miller Electronics Recycling
(414) 380-1716
www.deadcomputers.com

[Brent Bublitz]

I was always under the impression that the air assist was more to keep
stuff out of the lens and clear smoke and dust from the working path,
not to prevent fires. If your work is flaming up, you are generally
doing something wrong. Multiple passes might be required instead of a
single slow pass, your material is too thick or your focus is off,
things like that. I don't think plumbing in an inert gas is a good
idea, fiscally. We could use that money somewhere else.

> --
>
>
>

[Bill]

The cost for gases is a combination the boiling temp ( lower boiling temp = more expensive hardware = more costs) and relative abundance (argon costs >> nitrogen although it has a higher boiling point). But given the abundance of CO2 and N2, CO2 will always be cheaper for similar purity levels. Now if you come up with a good way to catch Xenon and Krypton, we can corner the 248nm Excimer laser market.

[Kevin Crowley]

I certainly wouldn't mind helping with an experiment.  An experiment or two is worth 10,000 speculations.

I am in total agreement  that an expense that can be avoided is the proverbial penny earned.  That being said there may be some benefits accrued by using it in appropriate situations.  There are many materials that seem to flare and scorch melt and boil and then flare. So one thing to experiment with is can you get a cleaner cut by reducing the available oxygen near the cut.

Just so I know what does a tank of nitrogen of the size mentioned cost?  If the the experiment has some benefit I have some thoughts on how to reduce gas use to just a few CF per use.



I certainly would not

On Wed, Oct 24, 2012 at 11:15 AM, Bill <wrmu...@gmail.com> wrote:

The cost for gases is a combination the boiling temp ( lower boiling temp = more expensive hardware = more costs) and relative abundance (argon costs >> nitrogen although it has a higher boiling point). But given the abundance of CO2 and N2, CO2 will always be cheaper for similar purity levels.   Now if you come up with a good way to catch Xenon and Krypton, we can corner the 248nm Excimer laser market.

--

[Have Blue]

Assuming that you have an empty tank (the vast majority of welding suppliers simply do tank swaps - you bring in an empty, they give you a different tank already filled), you'd probably pay around $30-$50 for a tank of Nitrogen.

Also, be aware that paintball shops and players will sometimes use the term 'Nitrogen' to refer to plain old compressed air (HPA - High Pressure Air), since 1) that's mostly what's in air anyway and 2) early on, some fills _were_ actually pure Nitrogen (but that's hardly ever the case any more).

As Bill mentioned, you'll be better off price-wise by using CO2 instead.  Since CO2 actually is a liquid when stored in tanks/bottles, it is much denser, so you can have much more CO2 in a tank than N2.  You can easily regulate it down in pressure and feed it into the laser cutter.

But all this discussion has mad me realize another building suggestion - a dewar for liquid N2 storage.  Quick, to the wikimobile!

--
 
 
 

[Tom Gralewicz]

Call a welding supply company and ask they what Nitrogen and CO2 cost, try to compare cubic feet of expanded gas rather than size or weight of the cylinder.

The place we currently use has just given me the first tank in the past:  Valley National Gases

http://www.yellowpages.com/oak-creek-wi/mip/valley-national-gases-1798292

--
 
 
 

[Kevin Crowley]

Energy density and cost is why hydrocarbons are still used for rockets.

per the dewar flask.

In my ill spent youth i used to obsessively read all of the Amateur Scientist columns in the Scientific America. I remember an article for making your own.
Does any one have access to the columns between '68 and '78?

On Thu, Oct 25, 2012 at 7:04 PM, Have Blue <have...@airsoldier.com> wrote:

--
 
 
 

[Kevin Crowley]

I will cal around tomorrow afternoon.

--
 
 
 

[David Buggs]

Doesn't look like it would be difficult to build a C02 generator, or simply buy one..

http://compare.ebay.com/like/170907889458?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar

Buggs

--
 
 
 

[Tom Gralewicz]

Interesting idea.....

Except it just vents the CO2, it doesn't channel it.

It only makes 16 to 26 cubic feet per hour (we need 4 per minute)

And is likely more costly to use than buying bottles of CO2 that are a waste from industrial processes.

Can you say "global warming in a box"?    :-)

Tom

--
 
 
 

[Brent Bublitz]

Once again coming up with excessively elaborate solutions to a problem
that only sorta exists.

> --
>
>
>