Peristaltic Fine Spray: no mist: no fog coolant pump

[Vixen]

I guess most of us will have tried one (or more) of the varius pressurised container, fogger, mister or air tool lubricator systems that are offered for sale. Most work on the pressure balanced spray gun principle and are generally difficult to set up and use. It's famine or feast; either no fluid or too much. Some have the unfortunate habit of filling the workshop with a fog of coolant. It always appears difficult to find the "sweet spot" and keep it there.

I decided to try something different; to build a mist lubricator system, where the fluid supply was totally independant of the air supply. In fact, there are two separate pumps; An air compressor and a peristaltic fluid dosing pump. You can operate either or both independantly.

Small Peristaltic pumps are now readily available on the net. They are used to deliver controlled doses of fluid in chemical, pharmacutical and aquatic applications. This is the one I selected.   https://www.ebay.co.uk/itm/403142010424?var=673262876871     you need a pump with the smallest 1 x 3 size tubing but as they seem difficult to find, so use a 2 X 4 pump and buy some 1 x 3 silicon tube elsewhere. This pump, when fitted with the smallest 1 mm bore silicon tubing will deliver 11ml/min. This low dose rate can be reduced further if the 12 volt pump is driven by a suitable PWM motor controller.

This is the PWM motor controller I selected.  https://www.ebay.co.uk/itm/373747433026 Lots of choice for these. I bought one with a reversing switch but that was unnecessary as the rotary knob already has an 'off' switch position. You run the peri pump in the top 2/3 of the knob range.

I also bought a new link-lock delivery hose. https://www.ebay.co.uk/itm/402926661688. I will replace the big brass nozzle with a standard orange plastic one.



So what did I do with all that stuff?        The Peristaltic pump and the PWM motor controller were mounted in a small plastic box, a standard wall wart supplies the 12 volt. I collect these, as you never know when you need a convenient low voltage supply for something or other.







I mounted the link-lock supply pipe to the spindle head, so that it moves up and down with the spindle head and keeps the nozzle directed at the cutting zone.





This shows the installation on the mill. The peristaltic pump is self priming so the fluid supply container can be positioned in any convenient position.








I joined the 1 mm bore silicone pipe from the pump to the 3 mm bore nylon pipe with and adapter made from two diameters of brass tube soldered together





So how well did the pump work?          With the PWM knob set at max, the pump delivers 3 to 4 small drops per second. When the PWM knob is turned back, the pump flow can be reduced to one drop every three seconds and that is independant of any air flow through the delivery pipe. The first two photos show the pump delivering one drop every three seconds with no air supply.  It's actually difficult to catch the drops falling.






This final image shows how the air flow effects the distribution of the coolant/ lubricant. The pump flow rate was turned up for this shot.





For the initial tests I used a water soluble cutting oil, the neat cutting oil is red and the immulsion is that pink colour.      I am still undecided what to use for the coolant/ lubricant. Some people recommend water soluable cutting oil, some say to use neat cutting oil, others say WD40, or neat paraffin for aluminum and there is always KoolMist and the like.    It is so easy to replace the fluid in the bottle, a differnt coolant/ lubricants can be used for different stock materials; iron, steel, brass or aluminium. the choice is yours.

Now I need to do some serious machining to understand just how well this perisataltic pump system works.

Mike

[Jasonb]

It will be interesting to see how it performs Mike. Two thoughts I had since your recent PM were:

Firstly if any of the lubricants may affect the silicon tube as I know some oils and solvents can swell silicon (o rings and fuel tube) and I noticed that other sellers of systems with these pumps (cold end) warn against this happening.

Also as your liquid is not under pressure it will be interesting to see if the flow is reduced as the pressure within the pipe is increased, hopefully not as the end is open to atmosphere and not a lot of pressure is needed.

Look forward to seeing your soggy chips

[Vixen]

Hello Jason,

Silicone tube is so inexpensive, you can quickly replace it, if there are compatability issues. I would expect hydrocarbons (paraffin, WD40) to be more problematic. the only way to know is to try it. Unfortunately the product sold by 'Cold End' is difficult to import these days

The pristaltic pumps are fixed displacement/ fixed delivey pumps and the supply pipe is always open to atmosphere, so there should be no change in flow rate or pressure build up.

Soggy chips  Yuck   

Mike

[Hugh Currin]

Mike:

Very intriguing. Where do you mix the coolant and air? I didn't see that "block" in your descriptions or pictures. It does sound like the passages and build are less critical than for a no fog mister. Nice job.

Please do report back on your results.

Thanks.

[fumopuc]

Hi Mike, that does look very functional.
The main difference in functionality to the Coldend from Sebastian seems to be the manual on and off switch.
I can not recognize any connection to your CNC controller software at the moment.
The Coldend is ready to be used by a controller signal and and simple push button is in his system for any kind of manual needed running of the pump at any time.
I.e. if the pump is dry by any reason.
If needed, you can buy the Jokisch stuff at the Sorotec shop.
I do use it since 3 or more years now for everything.

[Vixen]

Hello Hugh,

Well, thats the beauty of a peristaltic pump arrangement. There is no mixing unit and no needle valves with which to try and contol the air and coolant flows.

The air supply is provided by the compressor and the fluid is directly pumped by the peri-pump down a separate tube to the tip of the link-lock pipe. The two flows are independant of each other and do not interact



Hello Achim,

I took my inspiration from Sabastian's Coldend system. I thought I could make one for a fraction of the price. 

It is easily possible to make LinuxCNC or Mach 3/4 control the operation of an electrical relay to apply power to the peri-pump. But, you know, I am still quite capable of operating a switch manually, the computer does not have to do everything. 

Which Jokisch fluid do you use? I checked their website and thay have hundreds to chose from. I would like to find a UK distributer who can supply the fluid in smaller quantities than 5 litres. Importing stuff from Europeis no longer as easy, since we regained our independance earlier in the year.

Mike

[Jasonb]

The Cold End ones use a stepper motor driven pump so will dose at a very low rate as you have more control over the 6 roller pumps revs and I think the rate can be varied by the computer so if you were say running with a tool changer it could up the flow if drilling or boring and reduce it when you change to an external adaptive. It will also adjust air flow by the use of one of the two solonoid valves. This also means the circuitry inside his black box is a bit more involved.

But for a lot of us a simple on off switch and a twist of the pot to get the flow we want at the start of a run is good enough.

https://www.ebay.co.uk/itm/224415115638?hash=item34402ee976:g:ESgAAOSw0Y9gbWsC

It was not so much the cost of replacing a swollen silicon tube I was thinking of but if it's going to swell overnight then having to pull the pump out of the enclosure, replace the tube and put it all back together again would be a bit of a pain and I would probably move away from my Usual paraffin on aluminium and try something else that was safe with the tube

UK dealer for the Jokisch is given on their site https://www.jokisch-fluids.de/catalog/en/dealer-search/ The S3G seems to be the same one both Seb End and Sorotek sell

[fumopuc]

Which Jokisch fluid do you use? I checked their website and thay have hundreds to chose from. I would like to find a UK distributer who can supply the fluid in smaller quantities than 5 litres. Importing stuff from Europeis no longer as easy, since we regained our independance earlier in the year.

Mike

Hi Mike, it is Monos Miko S3G.
https://www.jokisch-fluids.de/catalog/en/jokisch-monos-miko-s3g-p1055/?search=1
https://www.sorotec.de/shop/Monos-Miko-S3G-Cooling-Lubricant.html


http://www.jokisch.co.uk

[Vixen]

Hello all,

Thanks for the information about the correct Jokisch fluid and the UK agent, I will see what they can do.

Using a stepper motor drive will certainly give more computer control over the pump but at a cost. Integrating an additional (5th) axis to control the pump is possible, but not so easy, with LinuxCNC.  The manual PWM control of a DC pump motor, is both simple and inexpensive

Thats an interesting stepper motor driven peri-pump you found on e-bay. The manufactures name amused me,   SHENZHEN MORNING THUNDERCLAP TECHNOLOGY CO LTD.

BTW the reason the working head of the peri-pump is outside the box enclosure, is to make access to the silicone pipe straitforward. If there are compatability issues, a change of fluid as well as a new silcone pipe is advisable. I am going to suspend samples of my silicon pipe in various candidate fluids and see what happens.

Mike

[Dave Otto]

Hi Mike

Your new system works very much the same way as the Microdrop system I use on my mill, that is as far as how the lubricant is delivered to the tip. The Microdrop does use a pressurized container which forces the lube through the line and does use needle valves for air and fluid control. I have never had an issue setting these.

I took a few minutes to sketch up the Microdrop nozzle, I thought you might find it interesting. They are easy to make and would improve the performance of your system.
Attached are a few screen shots of the assembly. The brass hex has had the points turned down and the Loc-Line nozzle has been reamed so the brass tip is nice push fit into the Loc-Line tip. The lube flows up the center and the air comes down the flats. You can see as the air flows down the tip it collects the droplets of fluid and carries them on to your part. 

Dave

[Mcgyver]

Good stuff!

I also built a mist coolant system mostly for use on benchtop tool and cutter grinder.  I've larger T&CG that has flood but the little guy wasn't set up for it.  After a lot of research on what others had built and what worked and didn't, I concluded you need separately pressurized coolant and air and a way to control the pressure of each.  I built a sort of double regulator and supply it with shop air and control the air coolant and pressure independently.

The ideal scenario for grinding is stream of droplets at a tangent to the grinding wheel at about the speed of the grinding wheel so they more less land on it and stay there.  It worked really well, I can plunge to the motors power capacity into a HSS bit with out overheating things and get no fogging in the shop.  It makes it quick to grind tools.  You usually get a stalactite of damp, ground HSS particles hanging form the bottom of the tool!

[Jasonb]

I am going to suspend samples of my silicon pipe in various candidate fluids and see what happens.

That has saved me chopping off a bit of fuel line to put in paraffin tomorrow, but let me know if you don't have any of that to test and I'll see what happens.

I've just been out playing with my air and can now get good regulation of the air flow while still having a high volume coming through to the blow down gun so looks like I may now be buying a few components.

The Cold End one actually uses the pump to regulate how much of the pressurised liquid is released into the air stream rather than pumping the liquid in. I'll try an unpressurised container first and see what happens though I think the 1 drop every few seconds may still be a bit high for me basing it on what I dab on with the brush.

[Dave Otto]

Good stuff!

I also built a mist coolant system mostly for use on benchtop tool and cutter grinder.  I've larger T&CG that has flood but the little guy wasn't set up for it.  After a lot of research on what others had built and what worked and didn't, I concluded you need separately pressurized coolant and air and a way to control the pressure of each.  I built a sort of double regulator and supply it with shop air and control the air coolant and pressure independently.

This is exactly how the Microdrop system works, they are not cheap but work quite well, I also use their synthetic lube with mine. I have one with two lines and have it controlled by the CNC.

Dave

[Dave Otto]

All the peristaltic pumps that I have been around over the years have used Tygon tubing designed for the pump. It doesn't seen that you would be limited to silicone tubing?

Dave

[Vixen]

Thanks for all the feedback guys.

'There are more than one ways to skin a cat'.  My experiments with the peri-pump are just another approach to the problem. Use what you have and are happy with.

That has saved me chopping off a bit of fuel line to put in paraffin tomorrow, but let me know if you don't have any of that to test and I'll see what happens.

Best for you to put a sample of fuel line in some paraffin, as I am not about to invest in a 5 litre can, just for a compatability test.

I just found this on a RC flying site. "Tygon is a little stiffer to work with and tends to very slowly harden a bit with use and age while
silicon tends to be a little nicer to work with but tends to slowly soften and swell with use and age. As noted above if silicon is used with gasoline, pump diesel, kerosene or Jet A it will rapidly swell and soften becoming unusable in a very sort time."

So maybe it's time to start looking for Tygon tube as an alternative. Either way, it looks like regular pump tube changes will be required.

This all points to the need to use non mineral fluids, such as Jokish fluids, or others still to be identified.


Mike

[Jasonb]

I've got some Tygon fuel line and it is indeed quite a bit stiffer, more like the old red line fuel tubing if you ever used that in the past.

Maybe in a thinner wall section it would be OK in the pump but initial thoughts are that the stuff I have is going to load the pump up a lot as it does not compress anywhere near as easily.

Will do the paraffin test but from what was on RCFlying it seems my thoughts on the problem were right.

[Dave Otto]

https://kinesis-usa.com/knowledgebase/tygon-soft-wall-tubing-for-peristaltic-pumps

Dave

[Hugh Currin]

Mike:  Thanks, that answers my question. The mixing is at the end of the nozzle. Simple. I like the idea of a constant volume pump for coolant. It would give a lot more control than a needle valve I'm now using.

Dave:  That Microdrop system looks more like a no-fog set up? There the coolant reservoir is pressurized with needle valves to control the air and coolant flow separately. From Microdrop's site I didn't see a coolant pump in the system? But the nozzle looks simpler and a lot easier to make than a valve block for a no-fog mister discussed previously. First here and then here.

It would be "easy" to put a solenoid valve on the air supply and a relay on the coolant pump for CNC control. That does leave a valve for air flow and a knob to control the pump under manual control. Those could be computer controlled but harder and less useful. I've not seen G-codes for "more coolant", just coolant on and coolant off. You could use two setting, one using M7 mist command and one M8 flood. But I think these setting require observation of the cut. I've not seen coolant settings along with a feeds and speeds table.

Thank you all, good discussion.

[Vixen]

As with everything else, there is more than one grade to Tygon tubing. The ones identified by Dave are specialy formulated soft wall tubes meant for Peri-pumps. Most probably a completely different tubing to that stiffer material used for model fuel tubes.

If you stick with the low cost Grothen pump you are limited to 1mm wall thickness tube. ie. 1 x 3, 2 x 4 or 3x5. Only the 1 x 3 mm tube gives suitably low flow rates; 11ml/min max.

My system is filled with a pink 5% emulsion of EP287 cutting fluid and tap water. It seems happy after two or three days inside the silicon tube. The water content evapourates gradually with time.

Mike

[Dave Otto]

Mike:  Thanks, that answers my question. The mixing is at the end of the nozzle. Simple. I like the idea of a constant volume pump for coolant. It would give a lot more control than a needle valve I'm now using.

Dave:  That Microdrop system looks more like a no-fog set up? There the coolant reservoir is pressurized with needle valves to control the air and coolant flow separately. From Microdrop's site I didn't see a coolant pump in the system? But the nozzle looks simpler and a lot easier to make than a valve block for a no-fog mister discussed previously. First here and then here.

It would be "easy" to put a solenoid valve on the air supply and a relay on the coolant pump for CNC control. That does leave a valve for air flow and a knob to control the pump under manual control. Those could be computer controlled but harder and less useful. I've not seen G-codes for "more coolant", just coolant on and coolant off. You could use two setting, one using M7 mist command and one M8 flood. But I think these setting require observation of the cut. I've not seen coolant settings along with a feeds and speeds table.

Thank you all, good discussion.

Hugh, your are correct this is a no fog system and the small lube reservoir is pressurized. With the low volume of fluid and dual delivery I thought that was also Mike's intent.

I have an air solenoid in my CNC control box and it is mapped so M7 turns it on and M9 turns it off. The adjustments are still manual and for what I do is fine. If I just want air for plastics etc. I just shut the lube needle valves off.  There are at least two industrial quality systems that I know of the Trico Microdrop and Acculube, Lots of home grown stuff on the internet probably because these are ridiculously expensive. The Acculube unit has a small pneumatically operated pump which is gravity feed from the small reservoir.

Microdrop's claim is that all the lubricant is consumed in the cut so very little is used, and there is no mess. This is pretty much true, I can go for months or over a year sometimes on one fill of the reservoir, which holds maybe a pint. Both companies have there proprietary lubes and and are also not inexpensive. I started out years ago with Microdrop's vegetable based formula and it gummed everything up any dried to a sticky goo. After I worked my way through that I switched over to their synthetic formula which doesn't have these bad habits.

Dave

[Vixen]

Hi Mike

Your new system works very much the same way as the Microdrop system I use on my mill, that is as far as how the lubricant is delivered to the tip. The Microdrop does use a pressurized container which forces the lube through the line and does use needle valves for air and fluid control. I have never had an issue setting these.

I took a few minutes to sketch up the Microdrop nozzle, I thought you might find it interesting. They are easy to make and would improve the performance of your system.
Attached are a few screen shots of the assembly. The brass hex has had the points turned down and the Loc-Line nozzle has been reamed so the brass tip is nice push fit into the Loc-Line tip. The lube flows up the center and the air comes down the flats. You can see as the air flows down the tip it collects the droplets of fluid and carries them on to your part. 

Dave

Hello Dave,

Yes, I can see how centralising the fluid jet could help. One question, what is the hole diameter of the fluid jet?

Thanks

Mike

[Dave Otto]

Hi Mike

I measure .04" on the ones I have here, they get kind of beat up from hitting the cutter sometimes, so be sure to make some extras.
Attached is a picture of an original with the integral hose barb. The screw in barb fitting is what I came up with to keep from having to drill a .04" hole clear through the part. The barb fittings are threaded #10-32 which is a common pneumatic fitting on this side of the pond.
Also notice that the turning on the hex only goes a short way, this acts as a stop when pushing the brass tip into the Loc-Line nozzle from the rear. What I modeled earlier was from memory because I was a work.

Dave

[Vixen]

Thanks Dave

0.04", lets call it 1.0mm. Thats the same size as the fine brass tube I have at the moment. Maybe, I just need a way to hold the brass tube central. 

Mike

[Dave Otto]

It seems that you could benefit from some restriction of the air stream to speed it up and help clear the chips. I know lots of people do it, but re-cutting chips is hard on cutters and leads to a crappy surface finish. The hole in the Loc-Line nozzle is quite large so the air velocity would not be that great, more like a gentle breeze. 

Dave

[Hugh Currin]

Dave:

I think we want consistent control of droplets, non-atomized, put into a separately controlled air flow. My home brew no-fog system doesn't give good control of fluid flow. It could be missadjustment of tank pressure or some other adjustment. It can also fog up the shop on long runs. It is better than the siphoning Kool Mist unit I used before. I've not used a Microdrop system and it may be much better. Mike's is interesting, using a pump for consistency. I've assumed that's what he's shooting for?

I haven't connected mine to the cnc control yet. It is on the list along with spindle control, limit switches and home switches. I'm working on two new benchtop machines that I need mist systems for. Very interested in Mike's results.

I'm using Kool Mist with water, a hold over from the Kool Mist system. It's pretty clean and can sit for weeks without cruding up the system. But I have no idea if I could get better results with a different fluid. I've convinced myself the Kool Mist isn't too hazardous to my health, and am leery about other fluids. If the system really didn't fog I'd be less worried.

Thanks.

Hugh, your are correct this is a no fog system and the small lube reservoir is pressurized. With the low volume of fluid and dual delivery I thought that was also Mike's intent.

I have an air solenoid in my CNC control box and it is mapped so M7 turns it on and M9 turns it off. The adjustments are still manual and for what I do is fine. If I just want air for plastics etc. I just shut the lube needle valves off.  There are at least two industrial quality systems that I know of the Trico Microdrop and Acculube, Lots of home grown stuff on the internet probably because these are ridiculously expensive. The Acculube unit has a small pneumatically operated pump which is gravity feed from the small reservoir.

Microdrop's claim is that all the lubricant is consumed in the cut so very little is used, and there is no mess. This is pretty much true, I can go for months or over a year sometimes on one fill of the reservoir, which holds maybe a pint. Both companies have there proprietary lubes and and are also not inexpensive. I started out years ago with Microdrop's vegetable based formula and it gummed everything up any dried to a sticky goo. After I worked my way through that I switched over to their synthetic formula which doesn't have these bad habits.

Dave

[Jasonb]

Well I've had a spending spree on e-bay and now it's just a case of waiting for the bits to arrive, I did include some 1mm x 3mm tube but could only find the Tygon F-404-A listed as fuel tube which I assume does not have the plastisizer added so will see about a different liquid if as I suspect the paraffin will swell the tube. (thanks for the chart Dave)

I'm going to try a different mixing method. There will be a "block" on the head of the mill with a 6mm push fit socket for incoming air, a 4mm one for incoming liquid from the pump and a BSP thread to take the smallest size loc-line that I already have. This is similar to the Cold End arrangement. The stop valve and regulator for air flow will be at the front of the machine, pump control not sure yet.

However my loc-line only acts to position the end where I want it, inside I have run a 4mm OD pneumatic PU tube and the outlet end of that has a small length of brass tube pressed in with a 1mm ID. This gives me good velocity for a small air volume and also means if I change to air I won't have so much residual lubricant left in the loc-line

[Vixen]

I did some tests and experiments today using a graduated cylinder and stopwatch. I wanted to measure the lowest reliable flow rate of the peristaltic pump. The PWM knob was turned down to find the lowest pump speed that would run reliable and would always restart. This was found to be 1 drop per second, which equates to 2 ml. per minute. The minimum flow rate did not change with or without the air blast.

I experimented with different supply voltages, from 6 volt to 18 volt to see if this could improve the slow speed running. Although the PWM knob position altered, the lowest reliable flow rate remained unchanged at 2 ml per minute. I guess the same number of watts are required to break out and restart the pump whatever supply voltage is used.

With the air blast applied the spray pattern was not unlike the pattern shown in Sebastian End's you-tube videos. My spray pattern consisted of small non-atomised fluid droplets no mist and definitly no fog. The air blast easily clears the chips from the cutting zone. That appeared to have achieved my first set of objectives.





To test the system while cutting metal, I did an adaptive clearance on a scrap block of 6082 T6 (HE 30) aliminium. Spindle speed 5300 RPM, cutter 7.0 mm dia two flute, 8.5 mm deep Ap (depth of cut) 1.2 D and Ae (width of cut) of 0.1D and a feed rate of 450 mm per minute. This was my most aggressive machining cut todate, it felt like I could have raised the feed rate further without straining the machine or cutter.

Here is the adaptive clearance underway. The shutter speed of my camera to too slow to capture the rooster tail fo chips flying to all corners of the cabinet. As you can see the cutter and work are well supplied with the pink 5% cutting fluid immulsion. There is actully a lot more fluid being delivered than I expected but it clearly is doing it's job. The water content in the coolant quickly evaporates, leaving a slight oily film over the mill and chips. 



My conclusion is the independant peristaltic coolant pump and separate air supply works well, the flow rates can be controlled independantly and there is no mist or oily fog produced. The fluid flow was a little higher than I expected and further work will be required to reduce the flow. I have reached the limits with what PWM motor control can do to reduce the speed the chosen Peristaltic pump. Next I will try to find some silicone tube with a smaller inner diameter than 1.0mm.  It may be possible to find a different motor with a gear head to reduce the output spindle speed. The alternative is a different type of Peristaltic pump, one with a stepper motor perhaps, similar to the one Sebastion End uses, but the cost and complexity of the motor control system escallates tremendously; out of my pocket money league.

Mike

[Jasonb]

After 24hrs marinating the results for the silicon tube are in.

This was basic RC model fuel tubing, the OD started out at 0.195" (4.95mm), the soluble oil at about a 10% mix had a small effect with the tube measuring 0.203" (5.17mm) but the Paraffin (Kero) took it up to a whopping 0.255" (6.5mm) some 30% increase.

So it looks like an alternative will have to be found for machining Aluminium unless I want to change the tube each time I use the pump. I'm not so keen on something that needs to be diluted as although the water may well evaporate away it is putting that moisture into the workshop air and that could well condense out onto any cold shiny metal surfaces.

[Jasonb]

Mike do you have an idea of what sort of revs the pump was doing at the lowest speed you could get it to work at?

[Vixen]

Hard to tell, I stuck a small piece of masking tape on the very end of the motor shaft to be sure it was turning at the lowest pot setting. I would guess a few hundred RPM, which gives 1 drop per second. Cannot find a way to go slower.

I am currently following up on the stepper motor option. Awating the 'slow boat from China' to deliver a new peri pump head (same type as Sebastions) I have the stepper motor working, as slow as you like, using the 4th axis port.

Mike

[Jasonb]

I've just had a small cheap geared motor land on the doormat, sold as 60rpm so with the variable speed should be able to get it quite a bit slower than that. Will let you know how it goes. but may not be until the weekend.

https://www.ebay.co.uk/itm/133588522094?var=433045011279

[Vixen]

You will need to add a long shaft extention to mimic the Grothen shaft, which drives the three rollers, diameter is critical. You may need to butcher the Grothen motor and rob that shaft

Mike

[Jasonb]

my thoughts were to make an adaptor "ring" approx 15mm long, two counterbored holes so I can screw it to the gearbox and two tapped holes so the black plastic plate from the pump can screw on. Ring will be bored large enough to take an adaptor the fits over the shortened gearmotor shaft and then reduced in dia to match the one on the pump motor. May just rob the pump shaft and loctite into the adaptor. Hopefully then the pump will just clip on and shaft push into the impellor

[Vixen]

You may need to use some heat shrink to bring the 1 x 3 silicone back to 4mm to fit into the two white clips
Mike

[Jasonb]

I got to test the geared motor today, it's happy starting in the 4rpm position on the speed control pot but may need a little more when the resistance of the pump is added, still a lot less than the peri Peri pumps motor can go down to as you can see.

So based on that I made a start on the adaptor ring and will do the shaft reducer tomorrow.

If the pump then works OK I have the "Damp End" drawn up ready to make

[Jasonb]

I made the shaft adaptor this morning from some 303 Stainless and gave the pump a try. This is it at full speed with the 2mm ID tube which should be just about right to keep swarf from sticking to the cutters when machining aluminium.

[Vixen]

I am currently following up on the stepper motor option. Awating the 'slow boat from China' to deliver a new peri pump head (same type as Sebastions) I have the stepper motor working, as slow as you like, using the 4th axis port.

Mike

As you can see above, Jason has replaced the standard motor on his 'Grothen' peristaltic pump with a 60 RPM reduction gear head motor which reduced the peri 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 contoller I used previously.

I have followed a different route using a stepper motor controlled by the CNC machine. I did some tests with a spare 3D printer stepper motor connected to the 4th axis output connector on my LinuxCNC controlled milling machine. The stepper motor speed could be controlled my changing the feed rate command value. The stepper motor ran a little hot but I knew I could reduce the drive current with the switches on the stepper driver brick.

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 abot 1/3 that of a complete pump and motor and I hoped the lower cost would be low enough not to attract the attention of the Customs inspector.

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.




It was necessary to shorten the Nema 17 motor shaft by about 3mm. The pump rotor is secured to the motor shaft by a single grub screw and four M3 bolts secure the motor body to the pump head.




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.





I adjusted the switch settings on the stepper driver brick to give 1.6 amps peak to reduce the max stepper drive current to suit the smaller motor. I may reduce it further to 1.2 amps peak if the pump motor gets too warm.  All other setting remain the same for both the Peristaltic pump and or my rotary table. The new peri pump 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). I swiched on the air supply and tried to take a photo to the fine spray pattern onto a sheet of paper (like one of Rogers injector tests) but my pink cutting fluid emulsion did not have sufficient contrast to show up well on the white paper. The spray was very fine with no fog.

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 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 emuslsion. I tried to contact the UK distributer for Jokisch cutting fluids, but they did not respond to two requests for price and delivery.

Mike

[Jasonb]

It looks a nicely made pump and quite easy to open up the head if needed to get at the tube.

I was googling about looking for reasonable quantities of fully synthetic liquid as I don't really want 25lts plus but have not come up with anything yet.

I was only peelin' steel at the weekend so ran that dry.

[Admiral_dk]

Thank you both for your ideas and tests 

I like your pumps easy opening for changing the "hose" Mike   

[Vixen]

Hello Per,

There is nothing to stop you fitting either the stepper motor or the gear head DC motor to either of the two peri-pump heads. The DC motor and a manual PWM controller will be perfectly adequate for hobby machining. The stepper motor can be CNC controlled. and is a more compact installation.

Of the two, the Chinese flip-open peri-pump appears to be the most robust. I have both available, so if one fails, I can revert to the alternative pump.

Time for a 100 hour road test. I'll call back in six months time.   

Mike

I think I should change the main title from Mist Coolant pump to Fine Spray Coolant Pump; because that describes the delivery better.

[Vixen]

I have continued to evaluate (AKA play with) with the two types of peristaltic pump. Of the two, I much prefer the stepper motor driven pump head from China https://www.ebay.co.uk/itm/373670936415 which cost me £12.50 with no added import taxes etc.

My initial tests used my 4th axis port to power the stepper motor. I was impressed with the performance and controllability of the stepper motor drive. The peristaltic pump needs to turn slowely enough to deliver the coolant fluid at about 15 drops per minute. The added air supply provides a continuous fine spray direct to the rotating cutter, without mist or fogging. I am currently using  a 4%  emuslsion of EP287 synthetic cutting fluid. but still looking out for alternatives which are easily available within UK.

Having decided on the stepper motor driven peristaltic pump, I now needed to decide how best to drive it from the CNC system. The use of the 4th (rotary) axis was OK for test purposes but being a 'move to' command, could not be used as part of a toolpath program. The pump would stop at the end of the 'move' when the subsequent command lines were executed. I therefore needed an independant means of continuously providing the stepper motor with step pulses at the required rate. These step pulses could be generated either by an external pulse generator, which requires no software changes. Or by making changes to the CNC software to generate the step puslse internally.  Making small software changes is reasonably easy to do with LinuxCNC, I cannot comment on other CNC systems.

I decided to develope both methods.

My CNC control screen can be configured with a vitual 'Coolant Mist' on / off button or by the M7 'Coolant Mist On' command. The 'Coolant Mist' button or the M7 command cause a pin (I use pin 14) on the parallel port to go logic hi (5 volts) and remain in the hi state until cancelled.

External pulse generator.     The 5 volt signal on pin 14 of the parallel port can be used to power a small N555 pulse generator module    https://www.ebay.co.uk/itm/265241859968?hash=item3dc1a59780:g:jUsAAOSwSjJg~TXD   set to provide approx 20 pulses per second. The pulses at the output pin of the N555 module are wired directly to the step input of the stepper driver brick.

Software Pulse Generator.  In LinuxCNC the software can be modified to generate the required step pulses internally, under the control of the 'Coolant Mist' button or the M7 command. Changes are made to the HAL (Hardware Layer) file to create an additional software 'stepgen' signal generator and to route these step pulses to pin 14 on the parallel port when the 'Coolant Mist' button or the M7 command is issued.

Here are the additional lines I added to the HAL file.

loadrt stepgen step_ type=0,0,0,0,0 ctrl_type=p,p,p,p,v
setp stepgen.4.velocity-cmd 20
setp stepgen.4.steplen 1
setp stepgen.4.stepspace 1
net pump-on iocontrol.0.coolant mist => stepgen.4.enable
net pump-pulse stepgen.4.step parport.0.pin-14-out

The first 4 lines create and set up the new 'Stepgen' pulse generator. The 'velocity-cmd 20' part sets it to generate 20 pulses per second, the pulse rate can be changed to a higher or lower number if required. The final two lines switch the step pulses to pin 14 of the parallel port when the 'Coolant Mist' button or the M7 command is issued. The step pulses appear at pin 14 and are connected to the step input of the stepper driver brick

Both the extenal  N555 signal generator and the internal LinuxCNC software stepgen signal generator are both proven to work well and reliably: So the choice is yours.
You can also chose beteween a stepper motor and a gear head motor (see how Jason B did it, above) to drive either type of peristaltic pump.

Mike

[Jasonb]

Well at least now you will have the 4th axis free for machining with the lubrication running.

I've not had the need to machine any aluminium yet so have not tried mine out in anger.

[Vixen]

Well at least now you will have the 4th axis free for machining with the lubrication running.

I've not had the need to machine any aluminium yet so have not tried mine out in anger.

Hello Jason,

Well not quite. I have reused the 4th axis stepper driver brick, psu, wiring and front panel connector for the peri-pump. I will have to invest in some more hardware if I wish to run both together. I can swap over the wiring between 4th axis and peri-pump in a couple of minutes.

It's interesting that you feel you need the mist/spray lubrication only for aluminium. I built my system primarily for use with machining steel, aluminium does not normaly present a problem for me.

Any more ideas about cutting fluids which are compatable with the silicon tubes?

Mike

[Hugh Currin]

Great progress. It looks like this is better in use than a no-fog mist system. I really like it.

Haven't had the time but have been thinking of using an Arduino to drive a NEMA 17 stepper. Just like Mike has but using an Arduino for step generation. (I don't know enough about LinuxCNC to dig in and add the code Mike did.) Something like this tutorial. The tutorial uses a A4988 stepper driver which should work for a small stepper and cost about $10US for five. An Arduino can be had for about $10US bare bones, or $25US with all the bells and whistles. Still need power supply, enclosure, etc.

I was thinking of a potentiometer to control the stepper speed and an Arduino input from the CNC controller to turn on and off. Add a solenoid valve for air hooked up with the mist control. So a mist on from the CNC controller turns on the air and mist. The potentiometer manually controls the mist fluid rate.

Likely cost more than Mike or Jason's solution, but it's what I though up. The stepper driver above might be an inexpensive addition to Mike's.

Thanks guys for all the great work.

[Jasonb]

That's sounding a lot like the "Cold End" one Hugh

Mike, after welding aluminium onto a couple of cutters I tend to like a bit of lubricant when machining it. From the start I have used faster feeds than you have until recently so that may be something to do with it. not come across much fully synthetic in anything less than 25lts containers, did think about getting 5lts from Sorotec but expect shipping now would almost double the price. May just be cheaper to buy 10m of replacement hose for £7.50 off e-bay.

[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