0:17Welcome to another Lightblade Learning Lab. Today it’s a lovely sunny day
0:22outside you may be able to hear some pigeons cooing in the background and the
0:27dogs next door barking but trust me it’s a beautiful day out there so why are we
0:33worried about the winter well it’s all to do with this thing here no I haven’t
0:40taken this out of my machine this just happens to be a spare tube that I need
0:46to just talk to you about you have a very valuable machine here and one of
0:51the most vulnerable parts of the machine is this bit here and in the winter we’ve
0:57got water in the cooling jacket and a cold possibly getting close to freezing
1:03temperature in this unheated workshop and the two things just don’t go
1:07together so what I’m going to do today is to show you how I have protected this
1:13machine with what I call a winterizing kit people have tackled this freezing
1:19water problem in different ways one of the most obvious ways is to put
1:23antifreeze in your system can I recommend you don’t there are several
1:32good reasons why you wouldn’t want to put antifreeze in here but the most
1:37important one comes down to and let me just take you to here this is the brass
1:42water jacket that’s being used to protect the partially reflecting mirror
1:48that’s mounted on the end of this tube here now the mirror itself is attached
1:55to the tube with as you can see something like an epoxy resin two
2:02reasons why you wouldn’t want to put any sort of slightly corrosive or dodgy
Transcript for Winterizing Your Laser Machine (Cont…)
2:07chemicals into the water. Brass which is ninety percent copper and 10% zinc is in
2:13itself quite vulnerable to chemical attack and that’s one good reason why
2:18you wouldn’t want to put anything like an ethyl glycol or
2:22propyl glycol mixture of water into this tube now yes it will stop it freezing
2:29because it pushes the freezing point of water down to probably something like
2:33about minus 20 or minus 30 degrees C so it does a fantastic job but it also over
2:39time will corrode any metal parts that are in the system the other thing that
2:45I’m worried about is it causing damage to this seal just here this epoxy seal
2:52now I’ve got no idea what the chemical reaction between epoxy and the glycols
2:57are but it’s not a risk that I’m prepared to take. Now if you go on to
3:03various user groups you will find people proclaiming the advantages of using
3:09things like ethyl glycol and propyl glycol but as I said disadvantage number one is
3:16itis corrosive they also claim that it has the great advantage of assisting the
3:23cooling effect well that’s both true and untrue they’ve
3:31misunderstood the physics of what is actually going on when they make that
3:37claim if you’re using it in a car as an antifreeze it does a fantastic job of
3:45preventing your radiator from freezing but two bits of physics that I need you
3:51to understand first of all water boils at 100 degrees C if you raise the
3:57pressure of the water and you do that with the radiator cap which holds the
Transcript for Winterizing Your Laser Machine (Cont…)
4:03pressure in the tank at about 15 psi above atmospheric pressure what that
4:08does that causes the temperature of the water the boiling point of water to go
4:14up by probably about 10 degrees C so that automatically raises the point at
4:19which your water will boil and the second thing is if you add a water
4:23glycol mixture to your radiator that will raise the temperature by
4:27another 10 or 15 degrees C so you could possibly get up to about 130
4:32degrees C before your water boils in your radiator now the great
4:36advantage of that is because the water temperature can go higher the amount of
4:43energy that you can dissipate the amount of heat that can be lost gets greater
4:47because the bigger the difference in temperature between the radiator and the
4:51ambient air the greater the heat flow and the more efficient the heat flow
4:56that works fine at 130 degrees C but we’re not going to run this at 130
5:03degrees C we’re going to run this at around about 20 or 25 degrees C and
5:08there you’re relying upon the thermal transfer rate of the fluid itself now in
5:14the center of this tube we’ve basically got lightning in a bottle there’s an
5:17incredibly high temperature in this pink beam that you see in here now it might
5:22not be a large amount of energy but it’s very specifically somewhere right
5:27in the center of that beam the temperature could be as high as maybe a
5:31hundred thousand degrees C now I’m not a physicist but that’s what I’ve read
5:36we’ve got heat that we’re trying to transfer away from this inner tube to
5:41the outer tube where the water is flowing now to squash the myth that you
5:47get better cooling because of having an anti freeze mixture in your water I need
5:54you to just understand a little teeny weeny bit of physics something called
5:58thermal conductivity of materials there are two components that go into an
Transcript for Winterizing Your Laser Machine (Cont…)
6:02antifreeze mixture one of them is water and the other one generally is ethylene
6:08glycol sometimes you can use propylene glycol it really depends on which
6:12antifreeze you choose now what I’ve got down here are numbers I’m not going to
6:19bother about the unit’s because they just confuse but basically these numbers
6:23down here show you the conductivity the thermal conductivity or the ability of a
6:29material to let heat travel through it these are all relative numbers from very
6:36poor to excellent now you wouldn’t think the diamond was the most effective
6:43conductor of heat but hey the figures are what they are
6:47and that’s what it says water is in itself 0.6, ethylene
6:54glycol is 0.258 so if you mix those two together you’re going to actually reduce
6:59the thermal capability the thermal transfer of water so it’s not going to
7:05be able to pick up heat as easily if you mix it with ethylene glycol now the
7:09other thing is which is very interesting and I have to admit that I didn’t
7:13understand that this was quite as bad as this I always thought that glass was
7:18actually a worse conductor of heat than water but it turns out not to be the
7:23case, actually glass conducts the heat better than water so that lightning in a
7:30bottle that we talked about transferring heat through the glass jacket is
7:35actually quite efficient not very efficient but just quite efficient but
7:40the water on the outside needs to be kept as cool as possible and the way you
7:45keep the water cool is to make sure that it flows so that it doesn’t get a chance
7:51to pick up huge amounts of temperature before you whip it away and then you put
7:55more cool water in to help draw the temperature away and that’s the mechanism
7:59for drawing the heat away from the tube so risk of corrosion and reduced thermal
Transcript for Winterizing Your Laser Machine (Cont…)
8:04conductivity of the water are two good reasons why you would not use antifreeze
8:09in your system. Winter proof in the UK means we have to survive occasional very
8:17cold weather spells but we’re talking about maybe at the most a week of
8:21sub-zero temperatures that could go down minus three minus five not every year
8:28but I can’t take the risk that that tube full of water there will freeze so
8:35consequently that’s why I am winterizing this machine. Winterizing comprises of
8:42two things really first of all I’ve added some halogen
8:48lights and that’s 100 watts of power there which will be immediately in this
8:54tube enclosure but because the enclosure is not completely sealed
8:59the heat will percolate into the main body of the machine as well and prevent
9:02condensation in there the other part of the exercise is to winterize the chiller
9:10or the water system and I’ve done the same thing there if you look inside the
9:15chiller unit I’ve installed a couple of those halogen lights as well and if we
9:21look at it from the other direction you can see that those halogen lights are in
9:25fact pointing at the cooling coil to heat it I’m also producing a little
9:33control box which I’ll show you as well okay well now we’ve got the winterizing
9:38kit controller mounted on the back here basically what we’ve got we’ve got a
9:44cable that comes in here from an external power supply now this power
9:48supply here which is regulated by the machine itself in other words when the
9:51machine is on this power supply’s on or when the machine is off there’s no power
9:55in this line so the machine is off at this moment in time so there is no power
10:00in this line but this line would normally go to the chiller but this time
Transcript for Winterizing Your Laser Machine (Cont…)
10:04I’ve intercepted that line here and it goes into the normally open contacts on
10:11the relay and it also goes onto the coil for the relay as well so when I turn the
10:19machine on the coil will energize and it will connect this through here through
10:25that relay and out to the chiller and the chiller will operate as normal okay
10:31so you can see the controller coming on and now it says the temperature is too
10:37low switch on the lighting the heating I
10:41mean I’ve got this thing set at the moment too far too high the temperature
10:45in here measured by this probe says that it’s ten point four degrees C well the
10:51intention is to put that probe inside the main body of the machine and when
10:56the temperature in the main body of the machine the air temperature in that body
10:59drops down to six degrees C it will do just this the machine will be off the
11:06pump is on the water is circulating through the tube and the lights are on
11:11in here so there’s heat inside this cabinet
11:14there’s heat down there where the coils are likely to get cold near the tank so
11:20in effect we’ve got 200 watts of energy that could be going into the water
11:25system to keep it warm and if I turn the machine on the power on and then I turn
11:30the machine on itself nothing changes because the water temperature is still
11:35too low so what I’ll do at the moment I will just reset this because I’ve set
11:40this purposely high to demonstrate so the intention will be to have this set to
11:45something like about 6 degrees C so now we’ll run that down to 6 degrees C 6
11:56degrees C and the lights go off that’s because the air temperature in here is
Transcript for Winterizing Your Laser Machine (Cont…)
12:0512 degrees C so we don’t need the heating and if I turn the Machine off
12:14although that system is now live nothing’s happening because its
12:20controlled by this temperature so when the air temperature drops down to 6
12:23degrees C the heating in there and the pump will go on and everything will
12:28circulate. And there we are, now you know that the machine is in place it’s carefully
12:33sitting there watching my machine doesn’t freeze now the circuit schematic
12:38for this little box and how it fits into the machine will be available on the
12:42Thinklaser website, well the sensor of the control system is tucked over the
12:46back there it’s tied up against the pillar now during last winter I was
12:53checking what was going on in the machine with this little data recorder
12:57here now all it does it just logs temperature every X number of minutes
13:01whatever you decide I think I set it for every 15 minutes or something like that
13:05and at 15 minutes I think this will probably run for a year taking data
13:10points every 15 minutes so I can go and have a look at the data for that it just
13:14comes out on an Excel spreadsheet but for something like about 10
13:17pounds or twelve pounds this was an incredible little Buy in fact I bought
13:22several of them because what I also did was left one of them out monitoring the
13:27temperature in the workshop and the other one was out monitoring temperature
13:30outside so that I’d got a complete record of what the air temperature was
13:35in the workshop outside the workshop and in the machines so I’ve got four of
13:40these which I relate together well this is the output from my data logger that
13:44was sitting in the Lightblade machine here I was setting it up in the office
13:48warm the 18 degrees C and then obviously I walked across to the workshop out in
13:54the cold then installed it in the machine and it settled down and started
14:00recording what was happening in the machine now bear in mind this is not
Transcript for Winterizing Your Laser Machine (Cont…)
14:04controlling the machine this is only recording the air temperature that’s
14:08inside the machine so the control system for the machine is working independent
14:13this is just monitoring it the next day I obviously went into the workshop and I
14:19opened the lid and started using the machine in some way during the day and
14:23when I closed the lid it went back up to control again the next day I did the
14:30same thing opened up the lid and I suspect that during the evening I was
14:33using this when the air temperature dropped and I must have been using the
14:37extraction because look I’ve dragged the temperature really way down then I
14:41turned it off and closed the lid and walked away for a couple of days by the
14:46look of it because the temperatures crept back up again inside the machine
14:50and then it’s just settle down and hovered for two days and then I’ve came
14:55in then I’ve come in and opened the Machine up again and as you can see in
15:00general it’s keeping the Machine comfortably in a sort of a a two degree
15:04temperature band at around about eight or ten degree C I hope that has been a
15:08useful tip for you even if you’re going away on Christmas holiday for example if
15:13you work in a school or in a small workshop and you are not in control of
15:18the heating Play safe do something like this to protect your machine thank you
15:23very much for your attention and I shall catch up with you in the next session
15:27so goodbye for now
