Flood coolant for a horizontal mill, minimum pump power?

[RainbowsParticipant @rainbows]

Hey its about 2 and a half years since one of my first forum posts about trying to attach flood coolant to a Super Adept, how times have changed.

Now for the Centec. I want something that can blast chips out of whatever slot I am cutting.

Had a look about ebay, there was an old colchester pump at 240V, 0.3A for a 66W power. I can see 60W oil pumps on ebay for only £20 though I imagine duty cycle wouldn't be as good.

The £20 pump advertises 0.8MPA at 4L/min.

As a reality check would this sort of pump work? I'm hoping to get a fair bit of pressure for chip clearance rather than just a gentle drip, though I guess the drip would still be better than nothing at all.

[RainbowsParticipant @rainbows]

[Anonymous]

I think the industrial coolant pump on my horizontal mill is 1/8hp. It provides a good flow but not much pressure. Flood coolant is just that, a flood. It washes the swarf away in a flood of coolant rather blasting it away with high pressure.

If you want pressure and flow then none of the standard coolant pumps are going to delivery, so to speak. On modern CNC machines there are options for high pressure coolant (hundreds or thousands of psi) for through tool coolant, but I bet they're not cheap.

The pump linked to states the pressure and flow as maximums. It doesn't say you get both together, and you won't.

This is flood coolant, not much pressure, but plenty of liquid, and the flow is throttled slightly to stop it overflowing the table onto the floor:

Andrew

[Steve PaveyParticipant @stevepavey65865]

If you want chip evacuation then a mister operated from a compressor might be the answer.

[David George 1Participant @davidgeorge1]

The pump for coolant usually gives a flow rate and a lift height so if you ask a pump to lift a greater height you lose pressure so if you lift the collection tank you will be able to get a higher pressure. Also you should use a large diameter pipe as small bore pipes will reduce flow and pressure I like to use at least 1/2 inch bore up to the tap and delivery nozzle which would be much smaller(I use a 1/4inch lockline and a 4 mm nozzel on a 1/4inch tap). The pump should be continuous rated may be a proper coolant pump but a pond pump will last for quite a long time if you filter the metal particals out etc gauze sheet divider. Don't forget to have as much volume in the tank as possible to prevent running dry and to prevent overheating the coolant. Don't forget to put up some sort of shield to keep coolant and swarf on the machine I use polycarbonate sheets with magnets to hold them in place .

David

Edited By David George 1 on 16/10/2017 09:03:33

[Chris Evans 6Participant @chrisevans6]

I have seen coolant pumps/tanks on offer from MSC at times at around the £70 mark. No idea of there performance.

[HOWARDTParticipant @howardt]

You need to consider your guarding and or enclosure of the machine. High pressure coolant requires full enclosure or you are going to get wet very quickly and you health will suffer. A good flood is about the best you can achieve with an open machine and even then will require good shielding to keep it within the machine.

[not done it yetParticipant @notdoneityet]

The typical washing machine pump is about 90W. You would not want that gushing across your table at full bore! Output depends on lift height (flow is zero at maximum lift) for an impellor pump. Nozzle velocity might well depend on its size, too. So, more to think about than simple wattage. Oil pumps are likely positive displacement, so not the best idea with potential swarf contamination in the feed. 10^5 Pascals is one atmosphere, by the way!

[RainbowsParticipant @rainbows]

To steal from the well known Joseph Noci

Ultimately the machine is gonna have this sorta stand. As a temporary measure its getting a basic box section stand with a steel top and wood shelves. After getting some practice at sheet metal work though I want to make something of Noci grade finish with a drawer, cupboard, worklight and flood coolant.

Any motor I can have a return valve if I find its overkill though.

[not done it yetParticipant @notdoneityet]

Any motor I can have a return valve if I find its overkill though.

Could be dangerous if a positive displacement pump. Correctly, you would need a pressure relief valve. PRVs likely don't take kindly to abrasive liquids at high velocity, either.

[MuzzerParticipant @muzzer]

Most of the industrial coolant pumps use a centrifugal design, with a simple impeller. As mentioned above, they are generally for low pressure, high-ish flow rate for keeping the (HSS) cutter cool. If you are looking to clear swarf using the same coolant, you need a higher pressure, lower flow rate – probably a positive displacement type (gear, piston etc). The problem then is that you need to ensure the pump doesn't see any particles of swarf or it won't last very long, ie would need a decent filter system before the pump inlet. The centrifugal type pumps are very tolerant of swarf but tend to have limited pressure.

I am finding the same issue with my CNC machine now. I can achieve very high rates of swarf generation but if they aren't quickly evacuated from the vicinity of the tool, it can become very expensive in terms of cutter breakage. For my situation, the solution seems to me to fit proper (shower!) curtains around the machine and use an air nozzle to keep the cutter clear, in addition to the coolant supply. I can tell you that without the curtains, things get messy and the coolant doesn't last long.

On my manual mill, I have a decent quality Grundfos centrifugal central heating pump. These have a pretty good static head (4-5m), so could potentially generate a decent jet, capable of clearing chips. The downside is that they are not self-priming, so the pump must be lower than the reservoir. That rules out the use of a sump (if your machine has one) and in my case I placed a catch tank below it, in case of a leak.

The installation was a bit messy but cost very little and worked well. From recent experience with other brands of CH pump, I can say that they are certainly not all similar in terms of performance.

If you use compressed air, I doubt you would need a high flow rate so much as a high pressure, which tends to be available anyway.

Murray

Edited By Muzzer on 16/10/2017 13:17:51

[David George 1Participant @davidgeorge1]

Hi Murray If you fit a non return valve below the surface of the coolant in the tank you would get rid of the problem of self priming many industrial machines use one and you can get them from a local pipe fitting supplier.

David

[MuzzerParticipant @muzzer]

Yes, good point, perhaps if combined with a manual primer (ie a second non return valve with a funnel?). I suspect most horizontal mills on here would get only very intermittent use.

Murray

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