NM-200 coolant pump problem

[kvom]

I emailed Novakon just now, but in case someone here has had this issue solved, please post.

The coolant pump is not generating enough pressure to raise the coolant up to the spindle housing, but does pump successfully if supply hose is kept at the level of the tank. Although my mill is a series one, I supposedly have a series two coolant pump and tank.

[rayoung]

Is it possible that the supply voltage on the series one for coolant is 110V and the series 2 pump is 220V? I had this issue with another machine of mine.

Ray

[kvom]

I measured the voltage at the mill before hooking it up and it's 220v, as is the pump.

[cteufert]

I ended up taking the pump apart on my NM-145. A coating of gunk was slowing down the impeller and partially blocking the outlet. Not sure what it was but since cleaning it I have a nice strong stream of coolant. The impeller should be very easy to spin.

Charlie.

[kvom]

My impeller seems to spin freely, but I'll take it apart to see if there's anything wrong looking.

[kvom]

Everything is turning; I measured motor speed with a laser tach and it's at about 350 rpm, which seems slow. I took the cover off the bottom, and there's no blockage.

[cteufert]

maybe the impeller is loose on the shaft and not spinning as fast as the shaft. Just like the blower in our dryer that failed last night... why do things fail just in time for a holiday weekend?

Charlie.

[kvom]

Novakon is sending me a new system with the larger pump/tank. Hoprefully Canada Post is not on strike this week.

[kvom]

I got the 90W pump hooked up today with good results. It spins at 3400 rpm according to my laser tach, a big difference over the 300 RPM of the smaller pump, which was clearly defective.

[kvom]

Final report on the coolant system.

I ran my first part using coolant yesterday (Koolmist 77 31:1) with a 1/4 carbide endmill cutting a .50" deep slot in 1018. The newer coolant tank holds 8 gallons and the level in the tank was never more than 1 gallon down while running a 20 minute job. The flow (with the stock nozzle) is insufficient to wash away the chips once the slot gets deep, but the end mill remained cool all the way to the end.

I had been worried that the start of flow would have a significant delay from the start of the M7 command, but I get coolant on the tool within 2 seconds.

[JoeBean_NEW]

Final report on the coolant system.

I ran my first part using coolant yesterday (Koolmist 77 31:1) with a 1/4 carbide endmill cutting a .50" deep slot in 1018. The newer coolant tank holds 8 gallons and the level in the tank was never more than 1 gallon down while running a 20 minute job. The flow (with the stock nozzle) is insufficient to wash away the chips once the slot gets deep, but the end mill remained cool all the way to the end.

I had been worried that the start of flow would have a significant delay from the start of the M7 command, but I get coolant on the tool within 2 seconds.

If you have problems with the flow rate I'd suggest looking into replacing the pump with a system using a submersible dirty water pump. They're cheap (about $50 for 2000GPH, which is way overkill) and work great. I machine a lot of aluminum and was finding it gumming up the endmills till I upgraded the pump system. This has saved me nearly $1000 in prematurely-failed tooling in just a few months, and I don't know how much in saved parts as I've had no tool failures during cutting (even unattended) since the switch.

FYI my setup is as follows (modified from another owner's system from on here):
- I removed the drain hose and cut the bottom of the drain cup off completely, then removed the strainer and threw it away. So you now have a 4" or so hole straight down to the ground.
- I got a short piece of 4" (IIRC) ABS pipe and a coupling. I turned the ID of the coupling for a tight slip-fit over the previously cut drain pipe. Then I glued the ABS pipe and coupling together, fitted it over the cut drain, and drilled for a couple of bolts & nuts to hold it on. The finished height of the pipe is about 6-8" from the floor.
- I put the largest Rubbermaid garbage can that would fit (20gal I believe) under the drain. I cut the lid to fit the drain pipe, and I cut another hole to fit the supply line (which is 1 1/2" flex hose, which is way overkill but it was the only thing above 3/8" line that I had available locally).
- I bought some plastic window&door screen (bug screen stuff) and used some stainless wire to "sew" up a tube that was about 6" shorter than the height of the garbage can and slightly larger in diameter than the pipe. I capped the bottom of it with more screen, again sewed on, to make a cylinder that was open on one end. I put a piece of scrap as a riser in the bottom of the can, put the screen column on it and the pump inside the screen. This gives room for swarf to build up on the bottom and keeps it from getting in the pump (which wouldn't really matter as far as the pump is concerned as it can handle 1"+ solids, but it may clog upstream). I also used to have a 100W aquarium heater in the can to keep the coolant from freezing, but I keep the shop heated all year now and so don't use it anymore.
- I plumbed the supply line up through the back of the mill after enlarging the existing hole. I have an inline ball valve on the main supply line, then it feeds up to a distribution coolant collar that I made out of iron pipe that wraps around the head. There are 3 outlets on the collar, each with it's own locline nozzle with ball valve. I generally only use one at a time, but it's nice occasionally to have 2 or 3 on.
- In the electrical cabinet you should swap one of the hot lines feeding the current pump to ground, to give you 120V across your hot leads (not ideal, but it'll work). Put a plug on the end of your pump power cable and just plug your new pump in. If you ever need to replace it it's a simple matter of unplugging it and plugging the new one in.

This system allows fine adjustment of the flow rate with the main valve and the valves at each line. And these pumps have no problem running at full height/pressure, so there's no need to plumb in a bypass. I'll tell you now, though, that you really only need the smallest pump (1000GPH or so) you can find as at full flow you will easily empty the can before your drain can fill it back up. If you really wanted massive flow you could plumb in another drain or two, preferably on the other side of the mill. As is, I routinely run 2h+ long programs mostly unattended and I've never had it run dry. Works great!!

Also, make sure you have a coolant containment system in place, unless you like swimming in coolant.

As for the 2 second delay for coolant arrival, you may already know but there are a few ways to deal with it. You can set the coolant delay in the settings if you want. Oryou might want to try a subroutine like
%
O111
M7
G4 P2
%
(assuming you have your settings set for G4 units as seconds and m7 to activate the pump. If not, change P2 to P2000 and m7 (mist) to m8(flood))

Then just find/replace your M7/M8 in the rest of your code with M98 P111 L1. I actually do a variation of this - I have a bunch of subroutines for different startup parameters that I included in my gcode that set a variety of variables - units, plane, scale, offsets etc., as req'd, as well as start the spindle and coolant (if appl.). So I have these subs (and some others) saved in files and I tack the code on to my programs. I have each one labelled for the application that I found it most effective, and I call the appropriate sub at the start of a program or on a tool change. This lets me essentially "save" setups and program snippets that I found worked well so that I can reuse it down the road as needed.

[kvom]

In reality I have M7 before M3, so that with the 12 sec spindle run up delay there's no problem with the timing. I think replacing the stock wide nozzle with a smaller orifice would give enough pressure for most chip removal. I make mainly one-off parts, and lately all have been steel, not aluminum; chip welding doesn't seem to be a problem.