Peristaltic Fine Spray: no mist: no fog coolant pump

[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.

<a href="https://www.youtube.com/watch?v=lv8NjdoIjAk" target="_blank">http://www.youtube.com/watch?v=lv8NjdoIjAk</a>

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.

<a href="https://www.youtube.com/watch?v=thXfkacDkJ0" target="_blank">http://www.youtube.com/watch?v=thXfkacDkJ0</a>

[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.