How To Use A Laser Cutter - Lightblade Learning Lab 30 Winterizing Your Laser Machine

13 days ago
Winterising Instructions (PDF) - http://bit.ly/2zfEMVQ (Use at own risk) Welcome to the 30th in our series of videos that aim to teach you how to use a laser cutter.

English subtitle

Welcome to another Lightblade Learning
Lab. Today it's a lovely sunny day
outside you may be able to hear some
pigeons cooing in the background and the
dogs next door barking but trust me it's
a beautiful day out there so why are we
worried about the winter well it's all
to do with this thing here no I haven't
taken this out of my machine this just
happens to be a spare tube that I need
to just talk to you about you have a
very valuable machine here and one of
the most vulnerable parts of the machine
is this bit here and in the winter we've
got water in the cooling jacket and a
cold possibly getting close to freezing
temperature in this unheated workshop
and the two things just don't go
together so what I'm going to do today
is to show you how I have protected this
machine with what I call a winterizing
kit people have tackled this freezing
water problem in different ways one of
the most obvious ways is to put
antifreeze in your system can I
recommend you don't there are several
good reasons why you wouldn't want to
put antifreeze in here but the most
important one comes down to and let me
just take you to here this is the brass
water jacket that's being used to
protect the partially reflecting mirror
that's mounted on the end of this tube
here now the mirror itself is attached
to the tube with as you can see
something like an epoxy resin two
reasons why you wouldn't want to put any
sort of slightly corrosive or dodgy
chemicals into the water. Brass which is
ninety percent copper and 10% zinc is in
itself quite vulnerable to chemical
attack and that's one good reason why
you wouldn't want to put anything like
an ethyl glycol or
propyl glycol mixture of water into this
tube now yes it will stop it freezing
because it pushes the freezing point of
water down to probably something like
about minus 20 or minus 30 degrees C so
it does a fantastic job but it also over
time will corrode any metal parts that
are in the system the other thing that
I'm worried about is it causing damage
to this seal just here this epoxy seal
now I've got no idea what the chemical
reaction between epoxy and the glycols
are but it's not a risk that I'm
prepared to take. Now if you go on to
various user groups you will find people
proclaiming the advantages of using
things like ethyl glycol and propyl glycol
but as I said disadvantage number one is
itis corrosive they also claim that it has
the great advantage of assisting the
cooling effect
well that's both true and untrue they've
misunderstood the physics of what is
actually going on when they make that
claim if you're using it in a car as an
antifreeze it does a fantastic job of
preventing your radiator from freezing
but two bits of physics that I need you
to understand first of all water boils
at 100 degrees C if you raise the
pressure of the water and you do that
with the radiator cap which holds the
pressure in the tank at about 15 psi
above atmospheric pressure what that
does that causes the temperature of the
water the boiling point of water to go
up by probably about 10 degrees C so
that automatically raises the point at
which your water will boil and the
second thing is if you add a water
glycol mixture to your radiator that
will raise the temperature by
another 10 or 15 degrees C so you could
possibly get up to about 130
degrees C before your water
boils in your radiator now the great
advantage of that is because the water
temperature can go higher the amount of
energy that you can dissipate the amount
of heat that can be lost gets greater
because the bigger the difference in
temperature between the radiator and the
ambient air the greater the heat flow
and the more efficient the heat flow
that works fine at 130 degrees C but
we're not going to run this at 130
degrees C we're going to run this at
around about 20 or 25 degrees C and
there you're relying upon the thermal
transfer rate of the fluid itself now in
the center of this tube we've basically
got lightning in a bottle there's an
incredibly high temperature in this pink
beam that you see in here now it might
not be a large amount of energy but it's
very specifically somewhere right
in the center of that beam the
temperature could be as high as maybe a
hundred thousand degrees C now I'm not a
physicist but that's what I've read
we've got heat that we're trying to
transfer away from this inner tube to
the outer tube where the water is
flowing now to squash the myth that you
get better cooling because of having an
anti freeze mixture in your water I need
you to just understand a little teeny
weeny bit of physics something called
thermal conductivity of materials there
are two components that go into an
antifreeze mixture one of them is water
and the other one generally is ethylene
glycol sometimes you can use propylene
glycol it really depends on which
antifreeze you choose now what I've got
down here are numbers I'm not going to
bother about the unit's because they
just confuse but basically these numbers
down here show you the conductivity the
thermal conductivity or the ability of a
material to let heat travel through it
these are all relative numbers from very
poor to excellent now you wouldn't think
the diamond was the most effective
conductor of heat
but hey the figures are what they are
and that's what it says
water is in itself 0.6, ethylene
glycol is 0.258 so if you mix those two
together you're going to actually reduce
the thermal capability the thermal
transfer of water so it's not going to
be able to pick up heat as easily if you
mix it with ethylene glycol now the
other thing is which is very interesting
and I have to admit that I didn't
understand that this was quite as bad as
this I always thought that glass was
actually a worse conductor of heat than
water but it turns out not to be the
case, actually glass conducts the heat
better than water so that lightning in a
bottle that we talked about transferring
heat through the glass jacket is
actually quite efficient not very
efficient but just quite efficient but
the water on the outside needs to be
kept as cool as possible and the way you
keep the water cool is to make sure that
it flows so that it doesn't get a chance
to pick up huge amounts of temperature
before you whip it away and then you put
more cool water in to help draw the
temperature away and that's the mechanism
for drawing the heat away from the tube
so risk of corrosion and reduced thermal
conductivity of the water are two good
reasons why you would not use antifreeze
in your system. Winter proof in the UK
means we have to survive occasional very
cold weather spells but we're talking
about maybe at the most a week of
sub-zero temperatures that could go down
minus three minus five not every year
but I can't take the risk that that tube
full of water there will freeze so
consequently that's why I am winterizing
this machine. Winterizing comprises of
two things really
first of all I've added some halogen
lights and that's 100 watts of power
there which will be immediately in this
tube enclosure but because the enclosure
is not completely sealed
the heat will percolate into the main
body of the machine as well and prevent
condensation in there the other part of
the exercise is to winterize the chiller
or the water system and I've done the
same thing there if you look inside the
chiller unit I've installed a couple of
those halogen lights as well and if we
look at it from the other direction you
can see that those halogen lights are in
fact pointing at the cooling coil to
heat it I'm also producing a little
control box which I'll show you as well
okay well now we've got the winterizing
kit controller mounted on the back here
basically what we've got we've got a
cable that comes in here from an
external power supply now this power
supply here which is regulated by the
machine itself in other words when the
machine is on this power supply's on or
when the machine is off there's no power
in this line so the machine is off at
this moment in time so there is no power
in this line but this line would
normally go to the chiller but this time
I've intercepted that line here and it
goes into the normally open contacts on
the relay and it also goes onto the coil
for the relay as well so when I turn the
machine on the coil will energize and it
will connect this through here through
that relay and out to the chiller and
the chiller will operate as normal okay
so you can see the controller coming on
and now it says the temperature is too
low
switch on the lighting the heating I
mean I've got this thing set at the
moment too far too high the temperature
in here measured by this probe says that
it's ten point four degrees C well the
intention is to put that probe inside
the main body of the machine and when
the temperature in the main body of the
machine the air temperature in that body
drops down to six degrees C it will do
just this the machine will be off the
pump is on the water is circulating
through the tube and the lights are on
in here
so there's heat inside this cabinet
there's heat down there where the coils
are likely to get cold near the tank so
in effect we've got 200 watts of energy
that could be going into the water
system to keep it warm and if I turn the
machine on the power on and then I turn
the machine on itself nothing changes
because the water temperature is still
too low so what I'll do at the moment I
will just reset this because I've set
this purposely high to demonstrate so
the intention will be to have this set to
something like about 6 degrees C so now
we'll run that down to 6 degrees C 6
degrees C and the lights go off that's
because the air temperature in here is
12 degrees C so we don't need the
heating and if I turn the Machine off
although that system is now live
nothing's happening because its
controlled by this temperature so when
the air temperature drops down to 6
degrees C the heating in there and the
pump will go on and everything will
circulate. And there we are, now you know that the
machine is in place it's carefully
sitting there watching my machine
doesn't freeze now the circuit schematic
for this little box and how it fits into
the machine will be available on the
Thinklaser website, well the sensor of
the control system is tucked over the
back there it's tied up against the
pillar now during last winter I was
checking what was going on in the
machine with this little data recorder
here now all it does it just logs
temperature every X number of minutes
whatever you decide I think I set it for
every 15 minutes or something like that
and at 15 minutes I think this will
probably run for a year taking data
points every 15 minutes so I can go and
have a look at the data for that it just
comes out on an Excel spreadsheet but
for something like about 10
pounds or twelve pounds this was an
incredible little Buy in fact I bought
several of them because what I also did
was left one of them out monitoring the
temperature in the workshop and the
other one was out monitoring temperature
outside so that I'd got a complete
record of what the air temperature was
in the workshop outside the workshop and
in the machines so I've got four of
these which I relate together well this
is the output from my data logger that
was sitting in the Lightblade machine
here I was setting it up in the office
warm the 18 degrees C and then obviously
I walked across to the workshop out in
the cold then installed it in the
machine and it settled down and started
recording what was happening in the
machine now bear in mind this is not
controlling the machine this is only
recording the air temperature that's
inside the machine so the control system
for the machine is working independent
this is just monitoring it the next day I
obviously went into the workshop and I
opened the lid and started using the
machine in some way during the day and
when I closed the lid it went back up to
control again the next day I did the
same thing opened up the lid and I
suspect that during the evening I was
using this when the air temperature
dropped and I must have been using the
extraction because look I've dragged the
temperature really way down then I
turned it off and closed the lid and
walked away for a couple of days by the
look of it because the temperatures
crept back up again inside the machine
and then it's just settle down and
hovered for two days and then I've came
in then I've come in and opened the
Machine up again and as you can see in
general it's keeping the Machine
comfortably in a sort of a a two degree
temperature band at around about eight
or ten degree C I hope that has been a
useful tip for you even if you're going
away on Christmas holiday for example if
you work in a school or in a small
workshop and you are not in control of
the heating Play safe do something like
this to protect your machine thank you
very much for your attention and I shall
catch up with you in the next session
so goodbye for now