[DLF]

Hello,

I want to buy an oil pump to oil the machine guideways.

There are 3 main types available: manual, electric with timer and electric without.

I will go with an electric pump without timer. The CNC controller I will use has the timer feature. The pump I want to use is this one: https://s.click.aliexpress.com/e/bG3kM4us

My concern is related to the oil pressure. The apecs are saying 4MPa which is roughly 40 Bar!!! Other pumps, regardless if manual or electric, have specs in the same ballpark.

Isn't 40 Bar too much? I know the pump is low flow (600cc/min), but still 40 Bar is nearly the burst pressure of 4mm OD thick wall plastic tubing (which is rated at 15 Bar). And I was not even able to find plastic tubing rated above 15 Bar. Same for fittings.

What tubing and fittings are you using? I am a bit affraid because the pump might break a tube and will make a mess on the walls.

How much time do you keep the pump running and at what flow rate?

Thank you,
Andrei

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[dazp1976]

Haven't got to a stage where I was able to test mine yet.
I read that it's a relatively low pressure system.

I would say that Bar is being confused with PSI myself (40psi/2.8bar).

The norm I've seen is 4mm nylon tube and plastic type push fit fittings.
I have a mix of nylon & silicone tubing but opted for these fittings to maximise life.:
https://www.ebay.co.uk/itm/High-Pres...item3f23bdbbfa

[dazp1976]

Just unpacked my pump to have a look and the dial on mine goes up to a maximum 16 Bar.

[DLF]

I would say that Bar is being confused with PSI myself (40psi/2.8bar).

No confusion here. I also thought that and I ordered 8Bar tubing, but:

The description clearly sais 4MPa which is 40 Bar. Also the pressure gage dial goes up to 10MPa with the green area between 2 and 4MPa.

This is exactly what got me wondering. All the other people are using the 4mm plastic tubing which is clearly rated for much lower pressure and I would really like the tubing to hold.

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[DLF]

Just unpacked my pump to have a look and the dial on mine goes up to a maximum 16 Bar.

Can you please share the pump model? 16 Bar seems more reasonable

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[dazp1976]

Can you please share the pump model? 16 Bar seems more reasonable

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This is the one I got:
https://www.ebay.co.uk/itm/New-1-5L-...item2a722ce0d5
Only 1.5 litre though & with timer.
Yet to test it.

The one you looked at I see is 100w and looks pretty industrial on a closer look. You only need something that is capable of #68 way oil. That thing can take up to 420 thickness. More of a greaser than oiler.

[ninefinger]

The pump may be able to generate 40MPa but with all the outlets that will be connected and the low flow rate you'll be at a much lower system pressure. I do agree that the one you spec'd is very industrial for a hobby cnc machine.
Still - the max system pressure will be determined by the overall system restriction and with a typical system having ~ 9 outlets (3 per axis - 2 ways and a ball screw), the total pressure won't get that high. You only need to run long enough to get oil into the ways, after that its a guess how long before you should run again. Run too much and the oil ends up in your chip tray and mixes with any cutting fluid. If its controlled by the cnc controller then you can do fancier things like just before running a part, etc. Be warned, on dovetail machines if you are trying to do some really nice finishing don't have the pump run during the cut (i.e. on a fixed time interval), it can raise the table on a film of oil just enough to be noticeable in the finish (not really enough to change tolerances on most normal machining.)

Mike

[dazp1976]

Run too much and the oil ends up in your chip tray and mixes with any cutting fluid. If its controlled by the cnc controller then you can do fancier things like just before running a part, etc. Be warned, on dovetail machines if you are trying to do some really nice finishing don't have the pump run during the cut (i.e. on a fixed time interval), it can raise the table on a film of oil just enough to be noticeable in the finish (not really enough to change tolerances on most normal machining.)

Mike

That's why I got one of those manual lever type ones to try as well.

[CL_MotoTech]

I got a timed pump as well.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I haven't hooked it up yet, but I hope to do so in the next month. I'm not sure exactly how I will wire it, and there are no instructions for setting the timer, so I expect it to be a bit of an adventure.

[DLF]

Thank you for your valuable input. I placed an order for this pump: https://s.click.aliexpress.com/e/mvNuxJw

I also found 20Bar PE tubing. It seems the tubing I was looking at was PU tubing which has lower performance.

Now the high pressure pump + plastic tubing combo really makes sense.

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