Hi all; I'm posting this in case it helps others out...
If you've read my review of the NM-200 you will see I love it BUT I hate the coolant system it comes with. Long story short, It's still plaguing me with no end of problems but I think I've got them all worked out now so I wanted to post this here to get feedback and suggestions from others as well as see if this helps people in my position.
First and foremost, the built-in coolant system holds far too little coolant. At full blast you will run out quickly and it isn't particularly strong. Also, the provided nozzle shoots a flat jet that is both difficult to properly direct and disperses too much to really scrub away the chips on a large flat workpiece.
So the first thing I did was create a new tank - I used a large tupperware-style storage bin from Walmart. Something in the range of 30 gallons. Then I used this pump:
1 HP, 3400 GPH Dirty Water Submersible Pump with Float
One huge feature of this pump is that it supports particulates in the water up to 5mm, that covers most swarf no problem.
Obviously that pump puts out far too much coolant - it would spray a long ways so I plumbed in a bypass. Basically the outlet from the pump goes into a three-way T with one leg going through a ball valve and right back into the tank. The other leg goes to the coolant nozzle on the mill. This lets me control the major flow amount by adjusting the ball valve. I can use the small valve at the mill to control the coolant even more precisely though I've not needed that.
Now this solved the volume and pressure problems of the existing pump but it brought a new issue. The danged coolant lines at the mill (not the return lines) and the coolant nozzle would clog from swarf far too easily. A better filtering system was needed.
To solve this problem, I took a 5 gallon bucket and drilled 1/2" holes all around the circumference of it at about the 1/2 way point up the side. Then I took fiberglass window screen and I doubled it up and secured it around the rim of the bucket with bungee cord. This made a cone of screen down into the bucket. Finally, I directed the outflow from the mill into the center of the bucket and I put the bucket inside of the coolant tank. Presto - instant filtering system that has worked flawlessly. The coolant has to flow through the screen and then fill up the bucket 1/2 way before it overflows into the tank proper. The combination of screen filtration and gravity working against the heaver-than-water chips has proven to be very effective. I've already dumped out about 3 gallons worth of swarf it's captured. The coolant is nice and clean and swarf free.
Finally, a new issue has come up - the last I believe. The "cup" attached to the mill enclosure that then attaches to the coolant return line has far too small of a hole to properly pass swarf. Specifically, the spirals of aluminum you get when drilling at the right feed/speed are often long enough to span the hole horizontally and they act like a log jam for swarf. A few minutes later, enough has built up to block the flow and if you are not careful the enclosure will overflow. I'd rather have coolant on the floor than a broken workpiece or burned up bit so the coolant tank has FAR more coolant than the enclosure can hold - thus far I've never had a big spill but it's coming unless I solve this last issue.
Here is my fix, I think drilling out the bottom of that cup with a nice step drill or hole saw until it's something more like 1.5" or 2" in diameter and then using a shower drain PVC bulkhead to a PVC compression fitting will work. The bulkhead will be siliconed in place and held securely by the PVC glued to it. A compression fitting will allow the return line to be moved or replaced. A drain this wide would be vastly harder to clog than the current design (which is smaller diameter than my index finger). The line to the tank would then also be far larger and thus capable of much more flow. I think this is likely a better solution than adding more return lines to the enclosure.
So that's my story. All of this has been done so I can use the mill in a far more "production" capacity. I have a full-time+ job where I work at home already. I can mill a ton of things IF I can leave the machine unattended. Thus far, between a good fixture plate, careful piece layout, and tormach tooling I've been able to really get the machine to run without touching it at all. Only the coolant clogging has prevented me from leaving it for hours at a time on longer jobs. I plan on doing this last step this week before I start another production run this weekend.
Whew, lots of typing and rambling. Hope this helped someone and I'd love to know how others are handling this as well - it's been a nasty thorn in my side. Actually, it's been the only persistent issue with my mill at all. Everything else has run flawlessly for the most part.
Thanks!
-Mike
On my NM135, the drain hole would similarly clog. The solution was to put a dome-shaped sieve over the hole, with the dome oriented up. I used the sieve (basket) from http://www.novakon.net/wpimages/wp5083f61a_05.jpg. The sieve just sits loose. It will stay unclogged for a few hours of milling, after which I pick it up and give it a whack over the garbage can to clean it off.Originally Posted by webgeek
Mike,
Thanks for the detail description to modifying the Novakon NM-200 series mill cooling system.
It sure would be nice if you would post detail pictures of your cooling project.
This seemed like a great idea so I went ahead and gave it a shot using two different kinds of kitchen strainers from the local dollar store. Both are domes, one is quite large and the other just barely covered the drain. Both of these are an improvement to nothing at all but at the same time neither would give me more than an hour or so of full-on coolant before the coolant level started to rise in the mill. The bigger one worked great until about 90 minutes where it was plugged to about 1/3" high all around at which point the coolant started the pool heavily in the mill. Neither are quite the "unattended" solution I need for 3-4 hours of straight machining.
So I sat back and had a bit of a brainwave. I had some 4" PVC elbows from a previous project and so I decided "to heck with it all!" and I chopped off the bottom of the cup with a reciprocating saw vs. my original idea of enlarging the hole and adding a PVC bulkhead. Once that was done I simply used some bolts to pin the PVC elbows in place on the cup and presto - MASSIVE DRAINAGE. It's effectively un-cloggable now. Literally. I could flush 3" diameter parts down the drain without any problem. There is no narrowing or restrictions in the system anywhere. It's full diameter all the way to the coolant swarf trap. I'm going to call this issue BUSTED at long last
FYI: 4" PVC is too large. I'm willing to bet you could make due with 3" no problem as long as it was a female connection on the side where the cup goes. IE: start with an elbow or an adapter.
Uh... To be honest the design is so ghetto and half-a**ed I'm a little embarrassed to show it. It's really quite nasty (though highly effective) - once I get some time to clean it up I'll take some shotsIt sure would be nice if you would post detail pictures of your cooling project.
-Mike
Thanks for the posts!! I might just go directly to using a big ol' pipe straight down from the chip tray (I don't think I need the coolant reservoir "hidden" in the base).
Are you going to put a coarse strainer/filter over the hole? I would be afraid of dropping parts into my coolant bucket. To stick with the kitchen tool theme might I suggest a http://www.amazon.com/Helens-Kitchen-5-Inch-Spider-Skimmer/dp/B000PKQ3YW/ref=sr_1_3?s=home-garden&ie=UTF8&qid=1294620819&sr=1-3]skimmer?
Big ol' pipe is what I ended up with in the end. 4" PVC is pretty massive and works flawlessly. The trick was ZERO restriction in the flow or places to catch chips.
As for a skimmer, I've tried several varieties. They all require frequent cleaning if you are making a lot of chips. Normal milling chips don't seem the be the issue. The issue is from when I use drill bits at the proper feeds/speeds. They create long spirals that gum up the flow of chip by binding them all together. Basically little log jams in the coolant flow which in turn fill up the machine.
My coolant reservoir is not hidden in the base either, it sits next to it under the enclosure. Filtration is handled with a bucket and window screen which I talk about in the first post. I just dumped out more than 5 lbs it captured from the last run.
-Mike
Not having the existing coolant system as yet, can I assume that there is a relay-controlled AC circuit that switches on the coolant via M-code?
Yup, I've not gotten around to actually testing but that's how it appears. I'm currently manually turning my coolant on and off with the new coolant system. Only problem I see is that the built-in system is going to be 220 so I'll need to wire a second relay to drop it to 110 for my pump.Not having the existing coolant system as yet, can I assume that there is a relay-controlled AC circuit that switches on the coolant via M-code?
-Mike
Quick update: I milled 5 jobs, 20 minutes attended with another hour unattended per job this weekend with zero coolant problems so this issue is clearly solved. Cutting the bottom off the drain was the trick to ensure it worked consistently.
-Mike
You don't need a transformer. Take 120V from the 3 lines supplied to the pump (Hot & Gnd, since you don't have true neutral available there anyway). Add a second ground, if you're using grounded cable, to the electrical cabinet.
I'm actually doing the same thing. I bought a 2000GPH submersible dirty water pump a while back capable of passing 30mm "trash" which I'm thinking of using once I get it back from on loan. I'm thinking of cutting the drain off completely and replacing it with a PVC closet flange held from underneath with silicone & bolts, possibly with an o-ring channel milled in it to ensure sealing. I'm thinking possibly about adding a second one towards the rear of the existing one to increase flow as I plan on having a fairly high flow rate. Hopefully I can get away with just the one though.
I'm thinking of rigid piping into a large rubbermaid garbage can that will hold the coolant & pump. These are often used amongst aquarium enthusiasts (aquarists?) to hold stock, so I know they won't collapse or split from the water pressure. From there I'll pump up to the mill and distribute the coolant to the nozzles.
What do you have for nozzles, just the stock single unit? I want a decent amount of coolant, but particularly I want as high a velocity as possible as I'm having problems in some jobs clearing chips. I use air right now as necessary, or redesign the paths to be less efficient time-wise but more "self clearing", if you will.
I'm thinking splitting the coolant into two 3/4" feeds, one on each side of the head, which will then each feed 2 loc line nozzles, either 1/4" or 1/2", I'm not sure which yet. Each locline nozzle would have a valve to shut off/throttle it. The 1/2" would definitely be better in terms of maximizing flow, but as these pumps are low-pressure (mine outputs @7.25psi, the manual for yours claims 14.5psi but the head info calculates out to 11.25psi, so not sure which is right) I want as much velocity as possible, which would seem to give more merit to using 1/4". However, restricting the flow too much once it's already at maximum pressure won't increase flow rate, so I'm not sure which way will work best. How do you find the pressure from yours? I know you said it solved the pressure problem and it sprayed a long ways, but how do you find it clearing chips?
The other thing I'm wondering is whether I should attach the nozzles to the stationary part of the mill, so it keeps spraying on the part, or on the head so it's continuously spraying on the tool. It seems to me this is the more common way it's done, and so there must be benefits over the current method. Any opinions?
I'd wondered about that, thanks for clearing it up.You don't need a transformer. Take 120V from the 3 lines supplied to the pump (Hot & Gnd, since you don't have true neutral available there anyway). Add a second ground, if you're using grounded cable, to the electrical cabinet.
The tub I'm using now isn't working out as well as I'd like. Switching to the garbage can makes good sense - it will let me cover it in the summer to prevent evaporation. That's likely a real problem here.I'm thinking of rigid piping into a large rubbermaid garbage can that will hold the coolant & pump. These are often used amongst aquarium enthusiasts (aquarists?) to hold stock, so I know they won't collapse or split from the water pressure. From there I'll pump up to the mill and distribute the coolant to the nozzles.
I'm using the stock line but I've removed the nozzle itself. This actually improved things a good bit. The key to clearing chips seems to be more volume than pressure so I plan on re-plumbing the entire system when I get some spare time and have my assembly line working smoothly.What do you have for nozzles, just the stock single unit? I want a decent amount of coolant, but particularly I want as high a velocity as possible as I'm having problems in some jobs clearing chips. I use air right now as necessary, or redesign the paths to be less efficient time-wise but more "self clearing", if you will.
This is the approach I'm going to take:
CNCCookbook: Milling Machine Coolant Collar
I want to make a nice collar with 1/2" line and at least two sprays onto the cutter, one from each side. I think this will provide a huge boost in volume and get away from the flimsy long-running line it has now. That stupid thing is never staying put.
-Mike
Thanks for the link. I've read most everything on cnccookbook but I can't remember ever seeing that. The last one on the page particularly looks nice and seems like it would work well with the NM-200. I like the valves on each nozzle.
I agree the way the line is run now is a weak point. Thinking about it now, I wonder if we couldn't run everything under the Novakon-labeled cover that's on the head and keep it out of sight/protected, with the hoses out of the way (obviously the locline nozzles would have to come out through holes). Here's a pic of the head without the cover:
So basically the same as the last pic in the cnccookbook link. It would also allow us to have a good, strong mount for the nozzle by drilling & tapping the head, without needing to have a mile of locline running to get where we want to go (I hate that).
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