C
Claude Hopper
Guest
If you cut plywood with a laser will it catch on fire?
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Claude Hopper
? ? Ľ
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Claude Hopper
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M
Michael A. Terrell
Guest
Claude Hopper wrote:
Why do you think cut wood would make the laser catch on fire?
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There are two kinds of people on this earth:
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The first sign of insanity is denying that you're crazy.
Why do you think cut wood would make the laser catch on fire?
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Jeff Liebermann
Guest
On Mon, 27 Oct 2008 18:13:58 -0400, Claude Hopper
<boobooililililil@roadrunner.com> wrote:
laser power, concentration (kerf size), plywood thickness, type of
plywood (glue content), air flow, and dwell time. You can dig out
specific values for material ignition by radiation from any fire
safety or building design handbook.
Since you didn't supply any numbers, so you get to do the calcs.
Wood ignites at about:
0.8 cal/cm^2-sec or 177 BTU/ft^2-sec or 33.5 Kw/m^2
This is for open air. If you restrict the air flow in the kerf area,
cut the values to half or less.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
<boobooililililil@roadrunner.com> wrote:
The depends on how much energy you supply, which is a function of
laser power, concentration (kerf size), plywood thickness, type of
plywood (glue content), air flow, and dwell time. You can dig out
specific values for material ignition by radiation from any fire
safety or building design handbook.
Since you didn't supply any numbers, so you get to do the calcs.
Wood ignites at about:
0.8 cal/cm^2-sec or 177 BTU/ft^2-sec or 33.5 Kw/m^2
This is for open air. If you restrict the air flow in the kerf area,
cut the values to half or less.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
M
Mark D. Zacharias
Guest
"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:dmddg4did1h15g2m4q102ho6e57mjdjrba@4ax.com...
If the laser is cutting the wood, it can only do so by burning, yes? In this
event I would think there is at least a very significant chance the burning
would spread to the wood as a whole. I suppose it could be prepped or
shielded in such a way as to minimize this.
Mark Z.
news:dmddg4did1h15g2m4q102ho6e57mjdjrba@4ax.com...
Jeff is obviously knowledgeable on the subject but my take is simply this:
If the laser is cutting the wood, it can only do so by burning, yes? In this
event I would think there is at least a very significant chance the burning
would spread to the wood as a whole. I suppose it could be prepped or
shielded in such a way as to minimize this.
Mark Z.
W
William Sommerwerck
Guest
Would does not burn. It is the gasses emitted by hot wood that burn. The
laser does not heat up a sufficient area of the wood to cause the entire
piece to go up in flames.
J
Jeff Liebermann
Guest
On Tue, 28 Oct 2008 06:20:24 -0500, "Mark D. Zacharias"
<nonsense@nonsense.net> wrote:
steel rule die blanks for cutting patterns out of cloth, rubber,
cardboard, and other sheet material. Something like this:
<http://www.die-cut.net/steel_rule_dies.htm>
The blanks and backing were made from 3/4" maple plywood. The
traditional method was to use a router, but that was inefficient.
Trying to cut a 0.1" dia (or less) kerf into incredibly hard maple
plywood and heavy plywood (at 50 lb/ft^3) would wreck a carbide router
bit every 10-20ft. So, we used a CO2 laser. The problem was we
didn't want to cut all the way through the plywood, just enough to
hold the steel rule cutter blade. That meant the hot gasses and and
carbonized wood tended to remain inside the cutting area, where the
accumulation of heat in a small area would tend to create some
localized burning. The solution was to simply blow lots of air into
the hole to remove both the heat and the waste. The trick was also to
keep heat, gases, and waste away from the laser lens.
The only way that plywood is going to burst into flames is if the
localized heating is allowed to accumulate. Wood is a fairly good
thermal insulator, but far from perfect. Anything that dense, heavy,
and massive is going to act as a heat sink, no matter how lousy a
thermal conductor. The glue and filler used in plywood are not so
good. They tend to spread the heat into rest of the plywood sheet.
The laser keeps pouring more and more heat into the kerf and the
plywood slowly spreads it out, thus spreading the heat affected zone,
and cooling the kerf. The ejection of gasses and carbonized fiber
also cools the kerf area. The only way the wood will combust is if
more heat is dumped into the area, than the plywood sheet and air can
remove.
If you wanna try a crude simulation at home, grab a sheet of heavy
plywood, and hit it with a common hand propane torch with the smallest
diameter flame possible. After igniting the torch, but before
applying it to the plywood, weigh the torch and tank. After reaching
ignition, record the elapsed time. Turn off the torch and weigh it
again. The difference is that propane consumed. Propane is about
71,000 Btu/gal, so you can calculate how much energy is required to
initiate combustion. Now do the same calcs with the energy delivered
by a random commercial CO2 laser and see how close you get.
Incidentaly, it's difficult to tell from the original question,
whether the OP wants to prevent the plywood from burning, or is
building some kind of Star Wars death ray designed to set fire to the
neighborhood.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
<nonsense@nonsense.net> wrote:
In my wasted youth, I once worked with products that required making
steel rule die blanks for cutting patterns out of cloth, rubber,
cardboard, and other sheet material. Something like this:
<http://www.die-cut.net/steel_rule_dies.htm>
The blanks and backing were made from 3/4" maple plywood. The
traditional method was to use a router, but that was inefficient.
Trying to cut a 0.1" dia (or less) kerf into incredibly hard maple
plywood and heavy plywood (at 50 lb/ft^3) would wreck a carbide router
bit every 10-20ft. So, we used a CO2 laser. The problem was we
didn't want to cut all the way through the plywood, just enough to
hold the steel rule cutter blade. That meant the hot gasses and and
carbonized wood tended to remain inside the cutting area, where the
accumulation of heat in a small area would tend to create some
localized burning. The solution was to simply blow lots of air into
the hole to remove both the heat and the waste. The trick was also to
keep heat, gases, and waste away from the laser lens.
The only way that plywood is going to burst into flames is if the
localized heating is allowed to accumulate. Wood is a fairly good
thermal insulator, but far from perfect. Anything that dense, heavy,
and massive is going to act as a heat sink, no matter how lousy a
thermal conductor. The glue and filler used in plywood are not so
good. They tend to spread the heat into rest of the plywood sheet.
The laser keeps pouring more and more heat into the kerf and the
plywood slowly spreads it out, thus spreading the heat affected zone,
and cooling the kerf. The ejection of gasses and carbonized fiber
also cools the kerf area. The only way the wood will combust is if
more heat is dumped into the area, than the plywood sheet and air can
remove.
If you wanna try a crude simulation at home, grab a sheet of heavy
plywood, and hit it with a common hand propane torch with the smallest
diameter flame possible. After igniting the torch, but before
applying it to the plywood, weigh the torch and tank. After reaching
ignition, record the elapsed time. Turn off the torch and weigh it
again. The difference is that propane consumed. Propane is about
71,000 Btu/gal, so you can calculate how much energy is required to
initiate combustion. Now do the same calcs with the energy delivered
by a random commercial CO2 laser and see how close you get.
Incidentaly, it's difficult to tell from the original question,
whether the OP wants to prevent the plywood from burning, or is
building some kind of Star Wars death ray designed to set fire to the
neighborhood.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
P
Peter Hucker
Guest
On Tue, 28 Oct 2008 06:52:18 -0000, Michael A. Terrell <mike.terrell@earthlink.net> wrote:
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Those who jump off a bridge in Paris are in Seine.
Har har....
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Those who jump off a bridge in Paris are in Seine.
C
Claude Hopper
Guest
Peter Hucker wrote:
--
Claude Hopper
? ? Ľ
--
Claude Hopper
? ? Ľ
K
kilowatt
Guest
Hi
A CO2 laser of about 250W will do 3/4 inch plywood, only if the
plywood is very clean gluewise and no knots. The beam will do a clean
cut of about .010 width. The laser leaves a smooth burnt surface in
the cut. No sawdust.LOL.
The example I saw used birch plywood and was used to make holders for
box cutting knives.
Works very nice, but the laser is expensive and cuts at about 5 inches
per minute..
KW
***************
On Oct 28, 12:29 pm, Claude Hopper <boobooililili...@roadrunner.com>
wrote:
A CO2 laser of about 250W will do 3/4 inch plywood, only if the
plywood is very clean gluewise and no knots. The beam will do a clean
cut of about .010 width. The laser leaves a smooth burnt surface in
the cut. No sawdust.LOL.
The example I saw used birch plywood and was used to make holders for
box cutting knives.
Works very nice, but the laser is expensive and cuts at about 5 inches
per minute..
KW
***************
On Oct 28, 12:29 pm, Claude Hopper <boobooililili...@roadrunner.com>
wrote:
Peter Hucker wrote:
On Tue, 28 Oct 2008 06:52:18 -0000, Michael A. Terrell <mike.terr...@earthlink.net> wrote:
Claude Hopper wrote:
If you cut plywood with a laser will it catch on fire?
Why do you think cut wood would make the laser catch on fire?
Har har....
That's why they make prepositions and conjunctions.
--
Claude Hopper
? ? Ľ
M
Mark D. Zacharias
Guest
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:ge6ta3$j1k$1@registered.motzarella.org...
a situation. Thanks for the clue.
Mark Z.
news:ge6ta3$j1k$1@registered.motzarella.org...
This is what happens when I try to apply my half-baked, uneducated logic to
a situation. Thanks for the clue.
Mark Z.
J
Jeff Liebermann
Guest
On Tue, 28 Oct 2008 16:29:10 -0400, Claude Hopper
<boobooililililil@roadrunner.com> wrote:
conjunctions, neither of which you've used, will not help determine
what you mean by "it".
There's also some question as to how you plan to use the laser to cut
plywood. It might be the optical laser beam, or you could sharpen the
casing and try to saw your way through the plywood with the laser. Now
way to tell from here.
The term "cut" is rather vague. Are you planning to cleanly cut (i.e.
bisect) the plywood in two pieces, route a groove, trim the edges, or
possibly create a decorative pattern. While all of these involve
cutting in some manner, their tendency to burn the plywood varies
substantially. I suggest you be more specific in the manner of which
you plan to do your cutting.
There's also a problem in your use of the "catch on fire" phrase.
Nobody is going to throw or catch the flaming plywood or laser.
Therefore, the term "catch" is improper. I suggest you modify your
question to use something more specific to combustion, such as
"ignite". That also makes the "on fire" part redundant.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
<boobooililililil@roadrunner.com> wrote:
There's an ambiguity in your abuse of the term "it". Prepositions and
conjunctions, neither of which you've used, will not help determine
what you mean by "it".
There's also some question as to how you plan to use the laser to cut
plywood. It might be the optical laser beam, or you could sharpen the
casing and try to saw your way through the plywood with the laser. Now
way to tell from here.
The term "cut" is rather vague. Are you planning to cleanly cut (i.e.
bisect) the plywood in two pieces, route a groove, trim the edges, or
possibly create a decorative pattern. While all of these involve
cutting in some manner, their tendency to burn the plywood varies
substantially. I suggest you be more specific in the manner of which
you plan to do your cutting.
There's also a problem in your use of the "catch on fire" phrase.
Nobody is going to throw or catch the flaming plywood or laser.
Therefore, the term "catch" is improper. I suggest you modify your
question to use something more specific to combustion, such as
"ignite". That also makes the "on fire" part redundant.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
P
Peter Hucker
Guest
On Tue, 28 Oct 2008 20:29:10 -0000, Claude Hopper <boobooililililil@roadrunner.com> wrote:
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Two aliens landed in the Arizona desert near a petrol station that was closed for the night. They approached one of the petrol pumps and the younger alien addressed it saying, "Greetings, Earthling. We come in peace. Take us to your leader." The petrol pump did not respond. The younger alien became angry at the lack of response and the older alien said, "I'd calm down if I were you." The younger alien ignored the warning and repeated his greeting. Again, there was no response. Annoyed by what he perceived to be the pump's haughty attitude, he drew his ray gun and said impatiently, "Greetings, Earthling. We come in peace. Do not ignore us this way! Take us to your leader or I will open fire!" The older alien warned his comrade saying, "You don't want to do that! I don't think you should make him mad." "Rubbish," replied the cocky, young alien. He aimed his weapon at the pump and opened fire. There was a huge explosion. A massive fireball roared towards them and blew the
younger alien off his feet and deposited him a burnt, crumpling mess about 200 yards away in a cactus patch. About half an hour passed. When he finally regained consciousness, he refocused his three eyes, straightened his bent antenna, and looked dazedly at the older wiser alien who was standing over him shaking his big green head. "What a ferocious creature!" exclaimed the young fried alien. "He damn near killed me! How did you know he was so dangerous?" The older alien leaned over, placed a friendly feeler on his crispy friend and replied, "If there's one thing I've learnt during my intergalactic travels, you don't want to mess with a guy who can wrap his penis around himself twice and then stick it in his ear!!"
Not required if you can undersatand context.
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Two aliens landed in the Arizona desert near a petrol station that was closed for the night. They approached one of the petrol pumps and the younger alien addressed it saying, "Greetings, Earthling. We come in peace. Take us to your leader." The petrol pump did not respond. The younger alien became angry at the lack of response and the older alien said, "I'd calm down if I were you." The younger alien ignored the warning and repeated his greeting. Again, there was no response. Annoyed by what he perceived to be the pump's haughty attitude, he drew his ray gun and said impatiently, "Greetings, Earthling. We come in peace. Do not ignore us this way! Take us to your leader or I will open fire!" The older alien warned his comrade saying, "You don't want to do that! I don't think you should make him mad." "Rubbish," replied the cocky, young alien. He aimed his weapon at the pump and opened fire. There was a huge explosion. A massive fireball roared towards them and blew the
younger alien off his feet and deposited him a burnt, crumpling mess about 200 yards away in a cactus patch. About half an hour passed. When he finally regained consciousness, he refocused his three eyes, straightened his bent antenna, and looked dazedly at the older wiser alien who was standing over him shaking his big green head. "What a ferocious creature!" exclaimed the young fried alien. "He damn near killed me! How did you know he was so dangerous?" The older alien leaned over, placed a friendly feeler on his crispy friend and replied, "If there's one thing I've learnt during my intergalactic travels, you don't want to mess with a guy who can wrap his penis around himself twice and then stick it in his ear!!"
A
Ancient_Hacker
Guest
It may catch on fire. Some solutions:
(0.5) Cool the wood first down to -250F
(1) Use a pulsed laser to ablate off the wood.
(2) Squirt water on the wood, just enough to stop the flame area from
heating up.
(3) Douse the area with some non-flammable gas, such as Xenon,
Helium, or CO2.
(0.5) Cool the wood first down to -250F
(1) Use a pulsed laser to ablate off the wood.
(2) Squirt water on the wood, just enough to stop the flame area from
heating up.
(3) Douse the area with some non-flammable gas, such as Xenon,
Helium, or CO2.