Peristaltic Fine Spray: no mist: no fog coolant pump

[Vixen]

Hello Hugh and Jason,

I have been looking at the A4988 stepper drive module. They look to be a quick and easy to add and would give me back the big 4.7Amp stepper driver to use with the 4th axis. The only reason I have not done it yet, is the hassle of cutting a hole in the enclosure back panel to fit an additional bulkhead connector,

Looks like there are now three different options to generate the step pulses, 1) N555 pulse generator module  2) modify the HAL software in LinuxCNC  2) Hugh's Arduino.

If you are already using LinuxCNC then the easiest route is to edit the HAL file by adding the six lines of code I showed earlier. No need to understand the intricacies of the HAL programming language. I have done that for you, so just copy and paste into the HAL file.

Thinking again about the mist fluid. I will only get a small amount of lubrication from the 4% imulsion delivered a 15 drops per minute, it will mostly cool. For better lubrication, it will be necessary to increase the strength of synthetic cutting oil imulsion or go for straight 'mist' fluid.  Jason and I are both having difficulties in sourcing smallish quantities in the UK, it only appears to be available in industrial quantities of 25 litres or more.       So I have a plan....... I am going to take one of my model engines along to one (or more) of the local machine shops and ask them what cutting fluids or mist fluids they use and where do they obtain them from.  Hopefully they may offer to give me a small quauntity to try. And, by good fortune, I happen to have an empty 1 litre container in the car.

Mike

[Jasonb]

Sounds like a cunning plan

[Vixen]

Sounds like a cunning plan

Blackadder : "Baldrick, I have a very, very, very cunning plan."
Baldric : "Is it a cunning and subtle one?”
Blackadder :  “Yes Baldrick. A really cunning and subtle one?”
Baldrick : "Is it as cunning as a fox what used to be Professor of Cunning at Oxford University but has moved on and is now working for the U.N. at the High Commission of International Cunning Planning?"
Blackadder : "Yes it is."
Baldrick : "Hmm... that's cunning."

[Hugh Currin]

Mike:

Do you then have to modify LinuxCNC to change the pump rate? That would necessitate restarting the controller. Using an axis for this would only require an MDI command to change pump speed. But then you can't change flow rate during a program run. I do like the external pot for flow adjustment, but a lot more parts to accomplish it. I do like the pump you found and I may have to try the mods to LinuxCNC.

Thanks.

If you are already using LinuxCNC then the easiest route is to edit the HAL file by adding the six lines of code I showed earlier. No need to understand the intricacies of the HAL programming language. I have done that for you, so just copy and paste into the HAL file.

[Vixen]

Hugh,

The modifications to the linuxCNC HAL file only give a fixed flow rate. It can be adjusted, up or down but requires a restart. I am not convinced for the need for variable flow


You cannot use of the 4th (rotary) axis to drive the peri-pump, other than for test purposes. An MDI command or a programmed command is a 'move to' command, and all 'move' commands are sequential, you must finish one move before the next can commence.  The pump would just stop at the end of the 4th axis move and would be off while the subsequent command lines were executed. We therefore need an independant means of continuously providing the stepper motor with step pulses at the required rate. Hence the  N555, HAL file changes, or the Arduino options.

I had a look at the A4988 stepper driver data sheet. The A4988 needs two power supplies, 5 volt for the logic and 12+ volts for the motor. Not very convenient. There are other inexpensive, single supply, stepper driver bricks available.

Mike

[Vixen]

About two and a half years ago Jason and I experimented with two different  peristaltic pumps to produce a good reliable MQL (Minimum Quantity Lubrication) system for our CNC milling machines. The objective was to provide a spray of very fine droplets onto the workpiece, with no fog or mist.


One option we tried, was to replace the standard DC motor on a 'Grothen' peristaltic pump with a 60 RPM reduction gear head DC motor to reduce the 'Grothen' peristaltic pump speed sufficiently to deliver the required 15 drops per minute (one every four seconds). The pump speed is still controlled by the same PWM speed controller I described previously.

I also followed a different route using a stepper motor controlled by the CNC machine. I ordered a brand new Nema 17,  45Ncm  (3D printer) Stepper Motor from E bay for less than £10 and a different peristaltic pump head from China https://www.ebay.co.uk/itm/373670936415 for £12.50. The pump head cost about 1/3 that of a complete pump fitted with a motor by the factory.

Here are the new stepper motor and peristaltic pump components. You can see the new peristaltic pump rotor has 6 rollers, whereas the 'Grothen' pump only has three rollers.

The new stepper driven pump can be plugged into my 4th axis (A axis) port and will deliver exactly one drop ever four seconds (15 drops per minute) with the command G01 A9999 F2.5 ( where A9999 is the largest A axis move possible and F 2.5 is the required feed rate for 15 drops per minute). With the air supply switched on,it produced a spray of very fine droplets onto the workpiece, with no fog or mist.






Here is the new Peristaltic pump in position on the inside of the mill's enclosure. The pump rotor (blue circle) is very visible and can be seen to rotate at the desired rate.




Here is the alternative Grothen' peristaltic pump with a 60 RPM reduction gear head DC motor. The PWM control knob on the enclosure controls the speed of the pump. There is no visual indication of pump flow rate.




So, there you have it: Two different ways to achieve a pumped mist coolant supply without the fog. One using a 'Grothen' peri pump head with a gear head DC motor with PWM controller or an alternative CNC stepper controlled peri pump. Either can be built for less than £25, Euros or Dollars.

The only thing still to be decided is the type of coolant fluid. I am currently trying some pink EP287 synthetic cutting fluid emulsion.

My stepper driven peristaltic pump has been in continuous use for the last two and a half years. The air was supplied by an ancient air brush compressor at about 45 lpm flow rate. The pump was very noisy and the air flow rate was just about adequate. I discovered a range of linear actuator, low pressure, high flow, air pumps; manufactured by Hailea. They are intended for supplying large quantities of clean air to large aquarium tanks or Koi carp pools.

The Hailea air pumps are available in different flow rate sizes and readily available from your local friendly aquarium supplier or from e-bay. I chose the 70 lpm air pump which cost about £40 from-bay.



I am very impressed with these pumps. They are small and light and deliver a very good air flow. They are very quiet in operation, the loudest noise coming from the outlet nozzle on the mill.

I am well pleased, these air pumps compliment the peristaltic fluid pumps to make a top rate, reliable MQL (Minimum Quantity Lubrication) system for our CNC milling machines, by providing a spray of very fine droplets onto the workpiece, with no fog or mist. The generous air supply blows all the chips well clear of the work.

Mike

[Jasonb]

Thanks for the update Mike.

I'm affraid mine has not got put into a neat package yet. Mainly as I only tend to use lubricant when cutting aluminum and I don't seem to cut much of that. For the odd small part I have resorted to the brush rather than filling up the pump etc. I think if I were doing as much aluminium as you it would be worth sorting it out properly and also finding an alternative to my paraffin, not sure about the strawberry milkshake though!

I went the other way and got one of the "quiet" 50 lts compressors, can't tell when it is running except for when the cut out turns the compressor off.

Would be interesting to see how a "steam" engine would run off of one of those air pumps, I have the usual diaphragm type on my koi pond and 80lts and a 40lts.

[fumopuc]

Hi Mike,
this stuff has been used since years now in my MQL.
https://www.sorotec.de/shop/Monos-Miko-S3G-Cooling-Lubricant.html
https://www.jokisch-fluids.de/catalog/en/jokisch-monos-miko-s3g-p1055/
should be available in UK also.
https://www.jokisch-fluids.de/catalog/en/dealer-search/
No issues with silicon tube so far.

[Jasonb]

Do you use that neat straight out of the bottle or is it diluted? Could not see it on any of the data sheets.

[fumopuc]

Hi Jason, straight out of the bottle.
Estimated 3 to 4 liters used during the last 5 years over all projects.
My peristaltic pump is running with 1,2 rpm since month now, no further adjustment done anymore.   
Air pressure is 2 bars, as recommended by Sebastian End.
Now idea about how much drops per second.
The beginning splash is zero, if really needed I push the bottom manually for half a second.
Also for filling the system and tubes up to the nozzle first time after longer break.

[Admiral_dk]

Very interesting updates and info gentlemen - thank you 

Per       

[Jasonb]

Good service from Sorotec, ordered Friday and arrived today.

I think when I looked before they only did it in larger quantities and Sebastian does not list UK as somewhere he ships the 1lts bottles to. I also think they both rebottle it from larger containers as the makers don't list that size so UK suplier not worth it even if their website worked. Cost £21 delivered but as I don't use much it will be about 5yrs before I need the next one.

Just need to find another aluminium project to give it a try on.

[Vixen]

Hello Jason,

That's good news that you have sourced a UK supply of the Sorotec fluid in smaller, more affordable quantities. When I was more productive, I used to get through between one and one and a half litres of fluid each year.

We will have to try and devise a means of comparing the performance of the Sorotec against the soluble EP cutting oil that been using for the last couple of years. It's a lot less expensive, at around 10£ per litre, which mixes up to something like 15 litres at 6 to 7% concentration.

See you on Saturday.

Cheers

Mike

[Jasonb]

I'll decant some and bring it on Saturday. But not willing to share the Haribo

I'm interested to see if it leaves much in the way of residue on the machine. As I machine more cast iron than ali I don't want to end up with all the surfaces sticky and attracting the CI. At least with the paraffin it evaporates away in a day or two.

[Vixen]

The Sorotec monos miko feels like it offers far better lubrication than the soluble EP cutting oil I have been using so far. Well it is mostly water      The water quickly evaporates leaving a trace of an oil film on the finished parts. By contrast, the monos miko does not appear to evaporate, so the film is a little more oily. That probably does not matter as a MQL system uses such a very small quantity in the first place.

Looking back at your post, I am now not sure where you actually bought it from. Was it from a UK agent or direct from the sorotec. de on-line shop in Germany?

Cheers   

Mike