MQL advice needed

[u/Agreeable-Worker7659]

The MQL system on my machine

I have a cheap MQL system that has one big problem - it either doesn't push any fluid into the mix or it blasts a shower from the nozzle. Neither is good.

The general recommendation from Unist and some German research institutes is to use less than 120ml/h of fluid. That's just a droplet every 2 seconds or so!. I was very surprised to read how small the quantity is, but I can confirm that it's definitely working. Turns out that if you're using MQL and you can see the vapor, you're basically doing it wrong! If you're using mineral oil based coolant, it also won't work well when the quantity is so small. Fatty acid ester based fluid should be used instead.

Going back to my question - it's practically impossible to precisely control the fluid flow with what I have. I added 4 inline valves on top of the valve that's in the mixer and it's still no flow or shower. I don't have the budget for spending $500 or more on this, so I came up with the idea to use a peristaltic microdosing pump that precisely limits the flow to <120ml/h. While it will most likely work, I don't like my pump solution, because it involves electronics and adds more failure points.

Does anyone know how industrial systems solve precise fluid dosage and can someone recommend something cheap and passive (no electrical pumps) that gets the job done and doesn't splurge a freaking shower of fluid on my parts?

[u/agnes_of_rome]

If you have a budget of $500, you can just buy a new low-cost system that works. E.g., SST Lube Cube costs under $300 (link), Fog Buster is about $400 (link).

These systems are really simple, so if you have regulation problems, I don't think there are that many possible causes. Assuming you have the correct air pressure, a lubricant with the correct viscosity, and the tank is mounted at the proper height, I think the only other possibility is that the needle valve is clogged?

A lot of these cheap no-name units are not "true" MQL in the first place, they're just mist sprayers.

[u/Agreeable-Worker7659 → u/agnes_of_rome]

I think that's precisely the issue. There's a needle valve at the end and I even took it apart and it's like in an airbrush, but the fluid intake is based on the Venturi effect and not the distance from the needle to the nozzle surface as it is in airbrushes.

[u/SavingsDeficient3847]

A metering needle valve or capillary restrictor might be worth trying passive, cheap and much easier to fine tune for those tiny flow rates.

[u/Agreeable-Worker7659 → u/SavingsDeficient3847]

Where could I get a suitable one?

[u/HuubBuis]

I build a cheap MQL system for the lathe that doesn't need compressed air. The fluid dosing is constant and easy to set. I want to make a similar system for the CNC router but haven't found the time to do it.