Cooling an endmill using air diverted from router?

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WillAdams
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Cooling an endmill using air diverted from router?

Post by WillAdams » Sat Jun 21, 2014 10:20 pm

Okay, the last two routers I've tried have integral fans which blow air downward --- would it be feasible to seal up the space above the dust shoe and direct the air from the router into a diverter which one could point at the tip of the endmill?
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Improbable Construct
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Re: Cooling an endmill using air diverted from router?

Post by Improbable Construct » Sat Jun 21, 2014 10:42 pm

You could do that...

But putting positive pressure into the dust shoe negates some of negative pressure created by your vacuum.
Also the air coming out of the spindle has already been warmed up by the heat of the motor so that makes it less desirable.
and if your dust shoe is working properly you should already have plenty of air flowing past the bit (and taking the dust with it).
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WillAdams
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Re: Cooling an endmill using air diverted from router?

Post by WillAdams » Sat Jun 21, 2014 11:19 pm

Okay, it's not a slam dunk, and it's necessary for the vacuum to be moving at least as much air as the router moves, but it seems like it'd be worth testing.

Lessee we'd need

- to measure the router airflow
- measure the temperature of the end mill

Suggestions for techniques?
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Brian
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Re: Cooling an endmill using air diverted from router?

Post by Brian » Wed Jun 25, 2014 3:14 am

What kind of materials are you cutting? As long as you have adequate chip removal you shouldn't have overheating issue with woods and plastics. When you get into aluminium you'd benefit more from a good mist setup (i use alcohol) to clear chips and keep everything cool rather than pushing warm air from the motor over it. In a perfect world the chips should draw away most of the heat from the endmill but you really cant get the necessary speeds and feeds for this to happen on the shapeoko. My router at work cuts alum at 200 IPM and the chips coming off are hot enough to burn me (happened more times than i care to admit) and the endmill stays relatively cool.
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WillAdams
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Re: Cooling an endmill using air diverted from router?

Post by WillAdams » Wed Jun 25, 2014 3:29 am

Interesting.

I was mostly curious about this idea 'cause of a paper I came across when researching things for the wiki:

''[http://espace.library.curtin.edu.au/R?f ... t_id=18869 Use of air cooling and its effectiveness in dry machining processes]''

(unfortunately, the site seems to be off-line at the moment)
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Re: Cooling an endmill using air diverted from router?

Post by Woodworker » Wed Jun 25, 2014 12:18 pm

Brian, I am curious as to why you use alcohol ? Seems to me that atomizing a flammable liquid near a sparking electric motor is not a real good idea. Personally I would never recommend this as a good way to cool the bit.
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Re: Cooling an endmill using air diverted from router?

Post by WillAdams » Wed Jun 25, 2014 12:57 pm

Okay, cooling then.

I've read a bit about it, and have thus far come across the following:

- manual cooling is potentially bad 'cause it can cause thermal shock to the endmill
- at a proper machine and spindle speed, chips carry away a significant portion of the generated heat

Liquids used / cited include:

- alcohol --- mentioned here: http://www.cnccookbook.com/CCCNCMillFee ... oolant.htm w/ a link to: http://www.datrondynamics.com/pressroom ... mental.pdf
- ethylene and propylene glycol (one is toxic, the other breaks down becoming corrosive)
- WD-40
- various oils and cutting fluids, some especially sold for this purpose
- kerosene
- turpentine
- Milk --- a fair number of the older books suggest this, it's supposed to be especially good for copper

Journal article on it here: http://www.journalamme.org/papers_vol25_2/2541.pdf
web pages:
- http://www.mfg.mtu.edu/testbeds/cfest/fluid.html
- http://its.fvtc.edu/machshop1/coolant/cutfluids.htm

Please note that I am not advocating _any_ of the above, and urge anyone considering cutting fluids to research toxicity and health effects and consider ventilation and safety.
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Re: Cooling an endmill using air diverted from router?

Post by Woodworker » Thu Jun 26, 2014 12:59 am

Seems that alcohol is used as a niche coolant and not where there can be sparks. Brian, what concentration are you using?

From Wikipedia:

Flammability
An ethanol-water solution that contains 40% ABV (alcohol by volume) will catch fire if heated to about 26 °C (79 °F) and if an ignition source is applied to it. This is called its flash point.[69] The flash point of pure ethanol is 16.60 °C (61.88 °F), less than average room temperature.[citation needed]

The flash points of ethanol concentrations from 10% ABV to 96% ABV are shown below:[70]

10% — 49 °C (120 °F)
20% — 36 °C (97 °F)
30% — 29 °C (84 °F)
40% — 26 °C (79 °F)
50% — 24 °C (75 °F)
60% — 22 °C (72 °F)
70% — 21 °C (70 °F)
80% — 20 °C (68 °F)
90% — 17 °C (63 °F)
96% — 17 °C (63 °F)
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Brian
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Re: Cooling an endmill using air diverted from router?

Post by Brian » Thu Jun 26, 2014 5:39 am

Alcohol doesn't create sparks so there is no real issue with ignition.
The big leap towards dry machining has come from, at least based on what I've read, the increased cost in coolant disposal leading to people to try and reduce costs by dry machining.

The alcohol evaporates almost immediately taking a fair amount of the generated heat away from the material and the bit meaning no disposal fees or environmental issues, the drawback being its not recyclable like flood coolant.

In a perfect world the chips should carry away almost all of the heat but the fact of the matter is that most of our machines simply cant create adequate chips to carry the heat away due to the lack of spindle power and machine rigidity. So despite the negative reviews that have been recently surfacing in regards to the various coolant methods they are our only real option to keep the bits from gumming up and the material from warping,etc. The other issues is chip clearing,I use a single flute endmill on my router at work running at 24000 rpm and it sends chips flying in every possible direction leaving the profile path relatively clear as the cutter moves through it when making multiple passes. When you are taking smaller cuts at slower speeds the ships tend to pile up around the cutter causing it to recut chips creating more heat and increasing the chance of "welding" the cutter to the material. The air blast idea would be more beneficial when used for clearing chips rather than a method to cool the tooling although both would technically have the same basic setup (flooding the cutting area with air).

Also, from what I've read another facet of the debate on cooling is how close the coolant gets to the actual cutting surface due to the heating creating air pockets on the surface when touching the liquid. If the coolant doesn't completely engulf the tool the cooling effect would be uneven which can cause stress fracturing and so on. This is why you see some high end VMCs with multiple high pressure knobs trying to force coolant in every possible facet of the cutting path.

I use pure denatured alcohol IIRC.

Sorry if my post is jumbled around, its quite late and I'm quite tired. :|
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Re: Cooling an endmill using air diverted from router?

Post by Woodworker » Thu Jun 26, 2014 12:25 pm

I am aware that alcohol doesn't create sparks but your Dremel or trim router does! I read both articles and I do not believe there is any situation using a SO 1 or 2 that would require alcohol as a coolant. I hope you never find out what an alcohol fire looks like or have to experience any damage or physical injury. This is a hobby and should be fun, not potentially dangerous.
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