# Cooling Tool Tip With Co2



## JPH (May 4, 2015)

If I am breaking any rules by starting this thread, please let me know and we can shut it down.

I was inspired by the silly youtube video below, in which a guy makes dry ice (solid CO2) from a container of compressed CO2.  Also, there are videos of professional tools that use CO2 for cooling.  

How about making a jig or a tool to direct CO2 to the tool tip; let the CO2 re-solidify, thus, dry-ice can be placed directly on the site of the cut where the heat is generated.

We would make this effort, hence the results of the endeavor, open-source.  In layman's terms, by that I mean if we talk about how to make such a cooling system, make the tool, and test the tool, then all the intellectual rights would be in open-source, under one of the many such licenses:  anyone would have the right to use the ideas, drawings, etc, but any derived ideas and or improvements must continue to be in the open-source.  Anyone can use the ideas for private use or for commercial use as long as buyer is notified that the intellectual rights are in open-source.

So, if you are interested in the endeavor, please let me know.

CO2 is easily available.  I just got off the phone with an industrial gas supplier.  It looks like for about $100 for the tank, and perhaps another $50 or so for valves, etc., one can have a source for CO2.  20 pound of CO2 costs about $50.  I have to do some calculations, but 20 pounds of CO2 can cool a lot of cutting.

I'll start by digging up the physics or chemistry of CO2.










JPH


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## ScrapMetal (May 4, 2015)

That thought occurred to me as well.   It seems systems like that do exist but for larger scale operations and are expensive.

http://www.mmsonline.com/products/co2-cooling-system-reduces-friction

http://www.coolclean.com/cooling.php

http://www.moldmakingtechnology.com/articles/machining-with-advanced-co2machining-spray-technology

It would be neat to see if a system could be devised for a small shop or hobbyist.

-Ron


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## T Bredehoft (May 4, 2015)

seems to me that releasing large (or even small) quantities of CO2 in the atmosphere might upset the weather cycle. But that's just a theory.


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## JPH (May 5, 2015)

ScrapMetal said:


> That thought occurred to me as well.   It seems systems like that do exist but for larger scale operations and are expensive.
> 
> http://www.mmsonline.com/products/co2-cooling-system-reduces-friction
> 
> ...




Hi Ron,

It's encouraging to see that someone else might be interested in CO2 Dry Ice injection into the cut zone.  Thanks for the references.  

What I envision is something that a hobbyist can build for himself.  Through-tool and such techniques are beyond what most hobbyists can afford, at the present time.

I started to gather basic information about CO2 Dry Ice so as to convince myself that enough CO2DI can be deposited on the cut zone and the tool to make a difference.   I'll post the information here.

When I did a similar basic computation concerning RHVT (Ranque, Hilsch vortex tube), commercialized as 'Cold Gun', the basic numbers were not encouraging:  it called for a tornado.  The output of the RHVT is cold air:  the specific heat of air compared to water is in the order of 440 to 1;  how do you couple high velocity cold air with the cut zone and the tool?  And sure enough, I ran across an article, last night, in which the research compared (actual machined) flood cooled cutting, dry machining, and RHVT cold air cooled cuts.  The conclusion was the effectiveness of blasting with cold air was inconclusive.

So, CO2DI (carbon di-oxide in dry ice state) is unique in that there is a chance for it to couple with (stick to) the cut zone and the tool.   DI falls out of a stream of expanding CO2.  That's the advantage.

I can do the back of the envelop calculations, but a simpler test would be to rig something up and see if it works:  first make snow, then deliver it to a specific spot; then see the quality of the cut and the life of the tool.

I joined hobby-machinist.com to read about how people are using their Precision Matthews lathes and mills which are sold by Matt at http://www.machinetoolonline.com

I am getting an order for a lathe and a mill ready:  the question of whether to order flood cooling or not arose and I started looking at what people are doing.  I decided CO2DI would be a neat project.

That's all for now.

JPH


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## JPH (May 5, 2015)

T Bredehoft said:


> seems to me that releasing large (or even small) quantities of CO2 in the atmosphere might upset the weather cycle. But that's just a theory.




Thanks for the comment.  At least this thread can be reached.  It was moved, and I could not find it.  Thought for a while: 'Wow, I must really have offended the moderator."

As I told Ron, above, I will do a back of the envelop calculation first; but then I am thinking of getting a container of compressed CO2 and see if I can make controlled dry ice snow.

CO2 emission is a serious problem.  But when I read about industrial CO2, most of it is captured gas from other processes as in fermentation (do you drink commercial beer?) and so on.  Anyway, when a horse power motor is used something in the order of 700 watts is consumed ... how many dinosaurs is that?


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## ScrapMetal (May 5, 2015)

It seems to me that between what look to be fairly simple devices like these -

http://www.katssafety.com/Products/Frigimat-Junior-Dry-Ice-Maker.aspx




http://www.polar-tech.com/main_dryicemaker.htm

One should be able to come up with something that one could fab in his shop.

Oh, and Tom, if you think it'll help the CO2 levels I can try to exhale less.  

-Ron


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## RJSakowski (May 5, 2015)

T Bredehoft said:


> seems to me that releasing large (or even small) quantities of CO2 in the atmosphere might upset the weather cycle. But that's just a theory.


The CO2 is most likely manufactured by compression and condensation from the atmosphere and, as such is, carbon neutral (aside from the CO2 generated during the production of the energy to run the manufacturing process.


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## RJSakowski (May 5, 2015)

CO2 snow has an advantage over chilled air in that the latent heat of vaporization of the snow is 137 calories/g compared to the specific heat of air somewhere in the neighborhood of .2 calories/g.   Additionally, to be effective the air jet would have to be directed in a manner that would allow the efficient transfer of heat from the tool and part to the air stream.  The CO2 snow would be in close contact with tool and part and most likely remain until it vaporized, taking the heat with it in the process.


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## John Hasler (May 5, 2015)

> ...any derived ideas and or improvements must continue to be in the open-source. Anyone can use the ideas for private use or for commercial use as long as buyer is notified that the intellectual rights are in open-source.

I like your idea and I am an enthusiastic supporter of Open Source but I must point out that ideas are not protected by intellectual property law and so anyone is free to use them without restriction.  Inventions can be protected but only if you file for patents on them before publishing.  If you don't patent them anyone can use them without restriction and can patent improvements.  The Open Source concept is really only relevant to copyright.


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## Tony Wells (May 5, 2015)

I have a DI maker of the sort Ron posted (pic 1). Bear in mind that the Carbon Dioxide that these makers requires a dip tube cylinder as they actually convert the liquid Carbon Dioxode to the DI, not the gas. In my experience, I was a bit disappointed in the amount produced per cylinder. I was using a DI/Acetone bath and needed a fair quantity.


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## JPH (May 5, 2015)

Thanks all for you comments.

In this note I will try to answer some basic questions:  

Is it cheap?  

What does the heat distribution of a cut zone look like?  
What is the gross functional requirement?
How much DI dry ice has to be delivered to the cut zone?
Discussion of how to deliver DI will follow.

1.  It is cheap:  I just went by the local grocery store.  They have DI for $1.19 per pound.


2.  Heat distribution of a cut zone.  So, here is the motivation:  The following video shows that the tool and the cut gets hot, but it is localized.





3. The functional requirement is to get DI onto the cut and onto the tool bit.  Instead of DI snow (precipitation from decompression), how about shaved DI.  Tomorrow I'll get a chunk of it and see what its physical properties are w/r/t a micro tool that might deliver pieces of DI to where it is needed:  Shaved ice, or pellets,  is what I am thinking. 

4.  To answer how much DI is needed, we have to know how much heat will be sucked up by the CO2 as it changes state from solid, DI, to gas.  We also have to know how much energy is in a delta of 1 *C in carbon steel and tool steel.  I will use the units of J, which is one watt second:  a hundred watt bulb for one second is 100 J.  I will also use cm^3, which is something like a sugar cube.  

All of the data used below are available on the internet.  If I made a boo boo (I hope I didn't loose a factor of a 1,000 somewhere) in the computation, please let me know.

Putting DI on a cut will not work unless the sublimation temperature is lower than the temperature at the cut zone; the carbon steel and the tool steel must conduct heat; there has to be coupling between the deposited DI and the hot metal.

Heat conductivity of carbon steel is 30 and that of silver is 230; that of copper is also about 230,  in constant (the same) unit system.

It looks like one volume of DI can lower the temperature of similar volume of carbon steel by 214*C.  The specific heat of tool steel is in the same order of magnitude as for carbon steel.  So, there would be similar results for the tool. 

Fact:  DI, dry ice, sublimates from solid to gas at -56.4*C or -69.6 *F, at pressure below below 5.13 atm.  That's good because most of us live at altitudes such that ambient air pressure is somewhat less than 1 atm.

Fact:  Density of DI varies, but is about 1.4 to 1.6 g/cm^3 (water is 1.0 g/cm^3).   From http://en.wikipedia.org/wiki/Dry_ice

Fact:  The cut zone and the tool that we want to cool are hotter than the sublimation temperature.  That's good, too, because we can cool the hot using the cold.

Fact: latent heat of sublimation is about  571 J/g .
Fact: the density of DI is about 1.5 g / cm ^3.

So, the latent heat of sublimation is about 856 J / cm^3

Fact: specific heat of carbon steel is about 0.5 J/g.  Tungsten Steel, W0, etc are all in the same ball park.
Fact: the density of carbon steel is approximately 8 g/cm^3.

So, the specific heat of a volume of steel is about 4 J/cm^3.

So, assuming 100% coupling (which it is not) between the applied DI and the steel that is being cut, some volume of dry ice can cool that same volume of steel by 214 *C.

5. That's motivation enough to figure out a miniature DI delivery system to the cut zone.

If someone can fact check the above, I would appreciate it.

If anyone has suggestions on how to deliver DI shavings, pellets, or snow to the cut zone ... your comments are welcome.


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## RJSakowski (May 5, 2015)

JPH said:


> Thanks all for you comments.
> 
> In this note I will try to answer some basic questions:
> 
> ...



What you need to calculate is how much energy is going into heat.  For a ballpark estimate, you can assume that all of the electrical energy supplied is converted to heat.  If you are running a 1 hp motor to full output, you have 750 watts or 750 J/s.  This heat energy will be absorbed by the sublimation and temperature rise of the CO2 at a rate of about 600J/g.  Ballpark, you will need about 1.3 g/hp.-sec.of dry ice. Actually, some energy will go into the deformation of the chips as well as their kinetic energy.  Also some energy into sound (and hopefully, none into light).  This will work in your favor.
Regarding the open source concept, it is my understanding that ideas which are in the public domain are not patentable.  While this does not accomplish what you had hoped, at least no one can patent the concept to their own benefit.  They can, of course, make improvements and patent them.
The delivery system is best done as you had envisioned.  There is no practical way to deliver a solid material to a machining zone.


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## JPH (May 5, 2015)

Conservation of energy.  But I think lots of energy goes into the chips that are discarded.  At least, the chips that land on my arms seem to be hot.  The first time I made blue chips, I thought I screwed up, until I looked up the limits of the tool that I was using.

I have to think about it, but maybe what really needs to be cooled is the tool:  Can a cold tool cut hot metal effectively?

So if you think about the cutting process, the cutting edge comes into contact with metal again and again.  But the piece of metal that was just cut goes beyond the new cut zone.  There would be an advantage to faster feed, but lighter cut ... move the heat away.  Chill the metal to be fed in to the cut.  The old cut temperature does not affect the new cut, unless the heat rapidly spreads from the old cut to the new cut, but it is known that steel is not the best heat conduit.

It seems to me the most benefit comes from cooling the tool; then cooling the metal at the cut zone.

Has anyone had experience cutting metal at elevated temperature, on purpose?

Has anyone cut metal at lowered temperature on purpose?

You said, "1.3 g / hp - sec".    I read that as 1.3 gram for each horse power every second.  That's about a sugar cube per second for a typical machine.  Let's see ... a pound of dry ice costs about a dollar.  A pound is 454 g.  It would be good for about 6 to 7 minutes.  I figure it costs me in the order of a dollar per mile to operate my car.  So in an hour at 60 miles an hour, it costs me a dollar per minute.   CO2DI cooling is cheap if compare it to that.

But will it work?  And what exactly should we cool?


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## JPH (May 6, 2015)

The following pdf reports a study in which steel was cooled at dry ice temperature for 24 hours.  Then sophisticated equipment was used to see if there were significant structural changes.  They report no significant changes in seven studied steels.

http://iopscience.iop.org/1742-6596/217/1/012074/pdf/1742-6596_217_1_012074.pdf

This is partial good news:  what's unknown is how is steel changed when the hot cut zone is suddenly cooled to dry ice temperatures.  It's almost as though the steel is raised to some temperature then quenched.


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## JPH (May 6, 2015)

DO NOT DO THIS AT HOME.   HAVE SOMEONE WITH YOU IF YOU INSIST ON EXPERIMENTING WITH DRY ICE.  WEAR EYE, FACE, BODY PROTECTION, and GLOVES.  BE SURE THERE IS ADEQUATE VENTILATION, as in DO IT OUTSIDE.

I bought some dry ice today and put it in an ordinary plastic ice chest.  The quantity of dry ice was about 8.5 pounds.  About 4 kg.  It cost about $10.00.  It was a random amount, just a bag out of the special freezer at the grocery store.  What I want to know is how long will it keep?  I have been told there will be some dry ice for a few days.  I left the ice chest OUTSIDE, in the drive way, in the shade.  I expect the weeds will love the CO2.  It has been about 65 *F in mid day and colder at night.  I live at 6,500 ft elevation, less than 1 atm.

Secondly, I want to know what the physical, mechanical properties are.  So, I broke a piece off of the block with a blow using a pair of pliers:  dry ice breaks easier than water ice.  Then I took a box cutter (sharp flat blade) and made some shavings.  It shaves easier than water ice.  I took a pile of shavings and pinched with the pliers.  The savings stick back together, but there is no strength to it and crumbles easily.

At this moment, I am thinking it would be possible to have a small container of broken up dry ice pieces (reach into the dry ice reservoir and whack or cut a piece and place it into the container).  This could feed a crusher or shaver; the smaller pieces of dry ice could be mechanically delivered to the cut zone.  Nothing fancy.  It might be something as simple as a screw in a pipe.  I wonder how many hobby machinist can pull that off, given dimensions and acceptable material.  That's how powder is delivered to a scale in another hobby.

Here is an interesting aside:  dry ice is used in high pressure blasting.  It is useful in food preparation industry:  oil, grease, ... they just come off pots, pans, ovens, when blasted.  It is also used in building renovation:  kills fungus, etc.  But the machine delivers pounds of dry ice at high velocity.  Compressed air is the accelerant.


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## RJSakowski (May 6, 2015)

JPH said:


> You said, "1.3 g / hp - sec".    I read that as 1.3 gram for each horse power every second.  That's about a sugar cube per second for a typical machine.  Let's see ... a pound of dry ice costs about a dollar.  A pound is 454 g.  It would be good for about 6 to 7 minutes.  I figure it costs me in the order of a dollar per mile to operate my car.  So in an hour at 60 miles an hour, it costs me a dollar per minute.   CO2DI cooling is cheap if compare it to that.
> 
> But will it work?  And what exactly should we cool?


The take away is that cooling with CO2 is feasible. Most procedures on a small lathe do not require 1 horsepower.  as you point out, energy is being expended in other ways than heating the tooling and part so the 1.3 g is most likely a conservative estimate.  

In practice, the part would not be raised to a high temperature.  The DI coolant would prevent that from happening. Some equilibrium temperature would be achieved, dependent on machining parameters. The part will not reach DI sublimation temperatures unless machining stopped.  Even then, it would take some time to chill down the part.  

The DI maker shown in the second link can make 8.5 lbs/min of DI at 47% efficiency.  That is almost 50 times the above requirement.  I haven' priced large tanks of CO2.  My 5 lb. tank costs a fortune to fill (about $18, as I recall).  At that rate, my cooling cost would be  about $.60/min.  Hopefully, a 50 lb. tank would be more economical.

As an aside, at least one method of producing liquified CO2 involves the burning of oil to produce the CO2 which is not carbon neutral.  http://www.ascoco2.com/en/products/co2-production-plants/  Conceivably, the process would use the heat byproduct to do useful work. Apparently, direct condensation from air is inefficient and not used commercially.


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## JPH (May 6, 2015)

Good input.  Thank you.

I think feasibility can be performed starting out with CO2DI purchased from the grocery store.  Someone has already paid for the energy cost of converting it to solid, which I think is what I want to deliver to the cut zone.

Three interesting events.  When I first grabbed a piece of DI with a pair of pliers, there was hissing and fussing.  Later on, I could grab a piece of dry ice with the same pair of pliers and there was no such.  Then, when I was cleaning up, I noticed condensation on the pliers.  It rained about an hour later.  

I think the first was because of applying 'hot' pliers at ambient 65 *F to -69 *F  DI.  That's a temperature difference of 135 *F.

The second tells me that the pliers had been chilled to DI temperature, or near that.

The third says it's dangerous to leave tools around after dry ice experiments:  the pliers were still very cold and grabbing it would probably have given a "burn".

The above tells me that cooling a cut with DI dry ice is feasible.

Next, I must do a simple test.  I don't have access to machines at this time.  Only thing that I have is a 1 hp drill. I am in the middle of talking to Matt at Precision  Matthews about a lathe and a milling machine.  I could cut a large hole with the drill, with and without DI (make shift).  What would that tell me?

It would encourage me to start designing delivery systems.

A separate thought is, should, could, cutting oil be delivered with the DI?  That is, if the cutting oil does not freeze up at DI temperature.

A quick look on the internet about viscosity of oil and low temperature says it's a bad idea.

However, since I have a chunk of DI in the driveway, tomorrow, I'll do a little experiment:  drop a little engine oil on DI.  I also have some silicone oil that I can play with.

Any suggestions would be helpful.


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## Tony Wells (May 7, 2015)

One thing you may want to consider is that under many specific cutting applications, heat is an ally. At the point of cut, the temperature is elevated and the material being cut more easily does a plastic deformation just prior to the sheering action of the tool. That said, all of the heat generated by the process is not needed, or desired in the tool itself. One of the main purposes of the many coatings seen on tooling is to resist the effect of heat transfer from the workpiece. Some coatings simply reduce the friction coefficient. Others are simply harder, more wear resistant, less apt to allow a built up edge, etc., etc..

I can see the desire for clean cooling in manufacturing many critical components that absolutely cannot be contaminated, but cannot be simply dry cut. I agree that this is a fascinating project to consider, but I question the practicality or the actual use by HSM'ers. How about a Peltier device embedded in the toolholder, since keeping the tool cool is probably more important.


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## JPH (May 7, 2015)

... a thermo couple on the cutter?

http://en.wikipedia.org/wiki/Thermoelectric_cooling


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## JPH (May 7, 2015)

In 24 hours or so about half of the CO2DI  sublimated, turned into gas.  That's not scientific nor engineer-like, but "show feasibility first, then optimize".

It seems, with optimization of storage, it might be possible to go to the store to get dry ice and then be able to machine for a few days.

To me this is encouraging.


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## RJSakowski (May 7, 2015)

At a business that I was involved with, we used dry ice purchased from a supplier for preserving biochem samples.  We would get 25 lbs and store it in a Styrofoam shipping container ( about 2" wall thickness).  The containers were stored in a freezer running at about -10F.  The dry ice would not last a weekend (5 PM Friday to 8 AM Monday).

Additionally, trying to deliver dry ice snow as a solid to the cutting zone is a little like heating with a wood fire.  You will be constantly throwing gobs of dry ice snow at a moving target.  You need to be delivering the dry ice to a precision location in controlled quantities.  What you want to accomplish is keeping your tool  and workpiece temperatures at a reasonable level, not to chill them to -70F.

Running some experiments with dry ice sounds fine but for a working system, you really have to look at generating your own from pressurized liquid CO2.

A lubricant need not be conventional oil.  Kerosene has been used as a lubricant for machining brass.  One issue when using light oils is flammability however.

Re: cooling the tool by other means, Peltier devices are not very efficient cooling sources. The hot side of the device is usually physically close to the cool side to maximize heat transfer and considerably more energy is input to the device than is transferred.  A better idea would be to pump coolant through channels in or near the tool.  This concept is used on cooling systems for high end gaming computers.  It is also used for drills and end mills where coolant channels run through the tool and exit right at the point of cutting.

Finally, take a look at some of the recent YouTube videos by NYC CNC.  He has been using compressed air instead of mist or flood coolant for machining.  The air stream provides some cooling but also removes chips from the work zone , eliminating recutting  and gauging of his freshly machined surface.


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## John Hasler (May 7, 2015)

Tony Wells said:


> One thing you may want to consider is that under many specific cutting applications, heat is an ally. At the point of cut, the temperature is elevated and the material being cut more easily does a plastic deformation just prior to the sheering action of the tool. That said, all of the heat generated by the process is not needed, or desired in the tool itself. One of the main purposes of the many coatings seen on tooling is to resist the effect of heat transfer from the workpiece. Some coatings simply reduce the friction coefficient. Others are simply harder, more wear resistant, less apt to allow a built up edge, etc., etc..
> 
> I can see the desire for clean cooling in manufacturing many critical components that absolutely cannot be contaminated, but cannot be simply dry cut. I agree that this is a fascinating project to consider, but I question the practicality or the actual use by HSM'ers. How about a Peltier device embedded in the toolholder, since keeping the tool cool is probably more important.


And then a heat pipe inside the tool to move the heat to the Peltier?

Perhaps high pressure cold gas through a hole in the tool and out through perforations near the cutting edge?  This begins to sound expensive.


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## Tony Wells (May 8, 2015)

Boy, you guys are a tough crowd. Can't recognize a facetious reply when you see one.

I'm not trying to be a wet blanket, but there are so many complications to this application that if it were practical, developers with deep pockets would already supply systems to the high end users who could justify the cost.


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## JimDawson (May 8, 2015)

I would just go with liquid nitrogen, -320F and readily available from any welding gas vendor.  Would work great in a cryogenic spray mist system, sort of.  But, it might cause the work and tools to be so brittle that it might cause some other problems.


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## RJSakowski (May 8, 2015)

JimDawson said:


> I would just go with liquid nitrogen, -320F and readily available from any welding gas vendor.  Would work great in a cryogenic spray mist system, sort of.  But, it might cause the work and tools to be so brittle that it might cause some other problems.


Jim,
I suspect you are correct about the embrittlement.  There could also be problems with localized dimensional changes.  Up here in "America's Dairyland" liquid nitrogen dewars are quite common.  I am not sure how you would deliver it to the cutting zone though.


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## John Hasler (May 8, 2015)

Don't try to make dry ice and then deliver it to the cutting zone.  Apply liquid CO2 directly.


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## Ebel440 (May 9, 2015)

I think you would be much better off just spraying with liquid co2 rather then turning it into dry ice first. It may prove to be more efficient. If I remember correctly it takes alot of co2 to make dry ice and I think you loose a portion converting it. Plus I think you need to ensure even cooling or the cutter may have issues.


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## ScrapMetal (May 9, 2015)

Ebel440 said:


> I think you would be much better off just spraying with liquid co2 rather then turning it into dry ice first. It may prove to be more efficient. If I remember correctly it takes alot of co2 to make dry ice and I think you loose a portion converting it. Plus I think you need to ensure even cooling or the cutter may have issues.



I agree.  Though there would be some "loss" but I think that a very, very small spray/nozzle could be used for delivery.  If so, this could make a tank last quite a while (in theory anyway).

JMHO

-Ron


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## JPH (May 13, 2015)

Wow, I was away for a few days and lots of good comments have been posted.  I can't wait until my lathe and mill arrive so that I can try some of the simple ideas.

I am not concerned that deep pockets have not tried one thing or another.  I have been in large groups before and there is a thing called 'group think'  that inhibits trying different ideas.  

The problem we face is if we find a trivial way to cool the tool or the work piece, how do we keep that in the open?  Deep pockets can easily take the idea and run with it, after something has been shown to be useful.  The patent laws have been changed recently to favor big companies and deep pockets:  first to file wins.  The little guy has difficulty financing the protection of even awarded patents.


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## John Hasler (May 13, 2015)

JPH said:


> Wow, I was away for a few days and lots of good comments have been posted.  I can't wait until my lathe and mill arrive so that I can try some of the simple ideas.
> 
> I am not concerned that deep pockets have not tried one thing or another.  I have been in large groups before and there is a thing called 'group think'  that inhibits trying different ideas.
> 
> The problem we face is if we find a trivial way to cool the tool or the work piece, how do we keep that in the open?  Deep pockets can easily take the idea and run with it, after something has been shown to be useful.  The patent laws have been changed recently to favor big companies and deep pockets:  first to file wins.  The little guy has difficulty financing the protection of even awarded patents.


First *inventor* to file wins.  This actually favors the little guy.  Under the first to invent wins rule they could tie you up in court proving that you invented first even though they filed second.  Now if you file first it does them no good to claim that they started work on it a year before you did (even if it's true).

A way to put an invention in the public domain is to file for a provisional patent ($100), publish it, and then abandon it.  That puts the invention in the PTO database with you as inventor.  Any kind of reasonably widespread publication in places where it is likely to be seen by "practitioners of the art" will suffice, though.


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## JPH (May 15, 2015)

The following is the url that briefly touches on some cooling systems.

http://blog.cnccookbook.com/2015/05...ail&utm_term=0_df8004b230-81bb4a9be0-45833433


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