On Mon, 12 Dec 2016 14:52:09 -0800, wrote:

MQL, Near Dry Machining, are two of the terms used for describing
a machining method that uses a very low amount of cutting fluid that
is applied right at the point of cutting. A nozzle is positioned where
the cutting lube is to be applied and the lube is delivered along with
low pressure air so that the fluid is dispersed a little.
Different methods of metering the fluid are used. I have an air
powered unit that meters the fluid through a valve and the fluid
drops pass through a chamber so that they can be counted. The fluid is
then carried through a tube with low pressure air to the nozzle which
blows the fluid onto the desired area. The fluid is broken up into
tiny drops by the passage through the tube along with the air. But
they should be smaller.
Another machine uses an air powered piston pump that delivers the
lube through a tube that meets another tube with air flowing out and
the two flows are mixed at the nozzle.
I used to have a piston pump machine but it failed and the maker
considered it to be non-repairable and so did not offer any repair
parts. That machine got thrown away.
The one I have now has needed to be sent back twice to the maker to
be rebuilt because they would not sell some proprietary seals.
The units are quite expensive and now it looks like I am going to
need a couple more. So I want to make them myself. Especially because
even if I buy a couple they will most likely not meet my needs exactly
so the installation will be a compromise.
I ahve been looking online at metering pumps but they are all
really expensive. Part of the reason is because they are very
accurate. I don't need the accuracy the uniits provide. I just need to
dispense small drops of lube into an air stream. I don't need an air
powered unit either. A solenoid powered pump would be fine. I have
looked at peristaltic pumps but I don't think one would work the way I
want. I think something that works similar to an atomizer on a pump
bottle would work well. I'm pretty sure I can buy atomizer nozzles
small enough. I would like to deliver through a flexible tube at high
enough pressure for the atomizer nozzle to work properly. I also want
a poppet valve at the nozzle end that prevents the lube from flowing
until a pressure pulse causes it to open. That way the lube can't
drain away slowly when the lube system is idle. Some jobs have long
run times using regular water soluble flood coolant with the MQL being
used for only 1 or 2 short operations, tapping for example.
So after my long winded post can anyone help?
Thanks,
Eric

I've used a lot, 1/2 liter syringe, triplex diaphragm, gear. The
syringe was expensive, the triplex diaphragms with vfd drive very
expensive. Even the gear pumps were expensive. Gear and syringe pumps
were $5-10,000, triplex diaphragms $25,000 and up. All of mine were
even more expensive because of the need for mass flow meters for my
accuracy requirements, 0.1% or better.

Peristaltic pumps are much less expensive. I even saw a 3d printed
one as a feature article in the digital machining mag. Delivery can
be controlled pretty well by tube size and motor speed. Pressure
capability is somewhat limited and tubes fail.

I think you're going to have to get creative. The solenoid idea is
good if the service life is adequate. Most piston and diaphragm pumps
I used had double sapphire ball checks at inlet and outlet. I imagine
you could get by with something a little cheaper, maybe plastic.
Usually they were seated by gravity, no springs. But you'd need a
spring for a valve near the nozzle. Try disassembling some pump spray
bottles for springs and checks.

Good luck. An interesting challenge.

Pete Keillor