. .
Page 2 of 2 FirstFirst 12
  1. #11
    I'm sure that Kitwn is right in saying that you could get much more coolant flow with bigger tubes, but in my own case (usual 2.2KW motor) I use a small pump designed for a caravan water supply, fed from a 5L bucket under the bench I have a switch that allows me to feed the pump from its design 12V, but almost always (except when filling) run it on 5V. Slow flow but the motor case temp never gets more than a few degrees above ambient. OK, I probably don't drive my machine that hard - I'm generally cutting things where other constraints rather than spindle power apply - but you might not need very sophisticated coolant setup. I've been running that spindle setup for a few years now, including runs of hours rather than minutes. As always, though, what you are going to do with the machine might change this.Most people use these big spindle motors because of the ER20 collet size rather than needing that much power.

  2. #12
    Neale,
    You're absolutely right about not needing a sophisticated set-up for cooling. We've seen people using radiators and fans normally used for PC cooling which is unecessary, but how are you supposed to know? I've seen no information from the spindle manufacturer on required water flow and the only clue you get is looking at the rough size of the pumps provided in the all-included kits Huan Yang sell.
    What made me decide to replace the 5mm tube with 8mm was a test of the flow rate with and without the long length of tube. The pump capacity was just being wasted and I wasn't confident that 30l/min would be enough. I documented this elsewhere on the 'Plumbing a water cooled spindle' thread.

    One thing that did surprise me was the difficulty in finding a small enough barb to fit to the pump, especially when the pump box didn't specify it's thread size. My local hardware store helped me identify the thread and we found a fitting, but I had to modify it in my lathe to make it fit. One of the plastic fittings in the pump box was just right for the 8mm pipe and I'd recommend going down that route just to avoid the problems I had. Those of you who live a little nearer to the centres of civilisation may well have less of a problem though.

    Kit
    An optimist says the glass is half full, a pessimist says the glass is half empty, an engineer says you're using the wrong sized glass.

  3. #13
    Kit - do you really mean 30l/min, or is that a typo? That sounds more like a bath tap flow! I doubt if my system is pushing much more than a few litres a minute through the system. I think the pump is rated at something lkke 10L/min at 12V and from watching the speed of odd bubbles running through the pipes, I would guess at rather less than half that at 5V.

    So, trying to put a bit of science behind these finger in the air estimates, I come up with the following. Does this make any sense?

    Let's assume motor running flat out, absorbing a total of 2.2KW. As a rough rule of thumb, an electric motor might hit around 75% efficiency, so about 550W is wasted and appears as heat in the motor, the rest being absorbed by the load. 550
    W (and here I have to go back to my schoolday units which is where I was supposed to have learned this stuff) is about 132cal/sec. Starting with an assumed flow rate of 1lit/min, that's 1000/60g/sec, that is 16g/sec. That heat input into that amount of water suggests that the water will be heated by 132/16 = 8degC (I'm rounding a bit here). So, with this low flow rate and the motor running flat out, the water coming out will be around 8C hotter than the water going in. I'm probably running at about 5l/min, so temp differential in/out through motor will be about 1.6degC. Given that I have around 8-10m of pipework (my cooling pipes run through the cable chains) and the surface area/volume ratio of the pipes is pretty high, I'm probably dissipating a lot of heat through the pipe walls anyway. And that is with a motor running at max load, which I doubt many of us achieve in a home machine. Looking at those figures, I'm not surprised that my motor case temp never seems that much above ambient!

    Does this make any sense? There are other drivers, of course - pump availability, and the problem of different fitting sizes on pump and motor. I made use of a local yacht chandler who stocked a wide range of plastic tube of various sizes to find one size to fit the pump, another to fit the motor, and which fortunately also fitted inside each other with the aid of some small jubilee clips.

  4. #14
    Oooops!
    That should have been 30l/hour. 500ml/min which didn't seem like much to me at the time, especially as I'd measured 4 times that with a short 250mm stub of the 5mm tube from the same pump.
    I have no problem with your calorific maths, it all looks fine to me.

    One thing I do, which I think we exchanged some comments on in the 'plumbing...' thread I mentioned above, is leave the pump running continuosly when the VFD is switched on. This ensures the bearings get maximum cooling between sucessive jobs. This is done to avoid the 'Perth Transformer Effect'. A few years back I worked for the WA power utility company. If we had a sudden spell of hot days in summer there would be a rash of transformer failures on the third day...Maximum load is around 4pm when everyone gets home from work ( we tend to work 7 - 3:30 over here) and switches on their air-con. The transformers heat up on day one and cool down overnight, but start day two hotter than they started day one. Day two follows the same pattern. On day three the starting temperature is so high that by early evening there are plenty lof angry, sweaty poeple around and plenty of power company workers missing dinner but earning lots of overtime replacing burst transformers. That was a massive problem in 2003-4-5 with everybody fitting the ever-cheaper but more power-hungry refrigerative air-conditioning and peak demand changed from heating in winter to cooling in summer.

    Kit

    PS You never know what you might learn reading MYCNCUK!
    Last edited by Kitwn; 28-07-2019 at 01:48 PM.
    An optimist says the glass is half full, a pessimist says the glass is half empty, an engineer says you're using the wrong sized glass.

  5. #15
    Ah! That sounds better! And I would agree that 0.5l/min seems a little on the low side. I think a better value would be "a few" - and it's really not that critical, I would think.

    Science is great for giving us some insight into what's going on, but a bit of real-world experience helps a lot - like your Perth transformer example. I always remember the story of the physicist who was asked to analyse some data to do with egg production due to his mathematical background. He came up with an answer, backed by pages of analysis and calculation, but qualified this with the proviso, "but it's only true for a ideal chicken in a vacuum!"

    As for the original "where to buy?" question, though - that's in the realm of advertising and marketing hype, and no help from science there... My HY inverter and spindle came from a UK supplier who charged a bit more but reckoned that they were reselling kit from a trusted Chinese supplier. That one came with preconfigured inverter, ready to go, and it's been running for about 7 years now with no problems. I've even changed the cooling water a couple of times!

  6. #16
    Quote Originally Posted by Neale View Post
    Ah! That sounds better! And I would agree that 0.5l/min seems a little on the low side. I think a better value would be "a few" - and it's really not that critical, I would think.

    Science is great for giving us some insight into what's going on, but a bit of real-world experience helps a lot - like your Perth transformer example. I always remember the story of the physicist who was asked to analyse some data to do with egg production due to his mathematical background. He came up with an answer, backed by pages of analysis and calculation, but qualified this with the proviso, "but it's only true for a ideal chicken in a vacuum!"

    As for the original "where to buy?" question, though - that's in the realm of advertising and marketing hype, and no help from science there... My HY inverter and spindle came from a UK supplier who charged a bit more but reckoned that they were reselling kit from a trusted Chinese supplier. That one came with preconfigured inverter, ready to go, and it's been running for about 7 years now with no problems. I've even changed the cooling water a couple of times!
    Sounds great:)

  7. #17
    "An ideal chicken in a vacuum", I'm going to remeber that one. It's near my bedtime here, but if we're going to talk science and in view of the recent anniversary, my most startling discovery of the last month was that when the Saturn V lifted off the pad back in July 1969 it took the power equivalent to fifty-five modern diesel railway locomotives just to run the fuel pumps!!!!!
    As I've always said "Rocket science isn't that complicated. It's just BIG!)

    Kit
    An optimist says the glass is half full, a pessimist says the glass is half empty, an engineer says you're using the wrong sized glass.

  8. #18
    Wow! I never expected the question to provoke such a response just for info I had purchased a cheap 240 l/hr pump, I'll see what the flow is like once I get it.

    Sent from my SM-G920F using Tapatalk

  9. #19
    Even if the pipework throttles the flow back to half that, it sounds about right. One reason I run my own pump on 5V rather than 12V is that the makers only rate it for 15mins max running at 12V, even though it is submerged in water. Runs for hours at 5V, though.

  10. #20
    Charlie,
    240l/hr is what it will manage completely un-choked, no barb, no pipework, no head. Half or even a quarter of that should be enough though.
    An optimist says the glass is half full, a pessimist says the glass is half empty, an engineer says you're using the wrong sized glass.

Page 2 of 2 FirstFirst 12

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Best Place To Buy Couplings?
    By Carlb1058 in forum Marketplace Discussion
    Replies: 3
    Last Post: 16-04-2013, 02:54 PM
  2. Best place to get ballscrews?
    By Ross77 in forum Lead Screws, Nuts & Supports
    Replies: 6
    Last Post: 15-04-2013, 10:09 PM
  3. Best / Cheapest place to buy 2.2kw spindle & vfd
    By Mad Professor in forum Marketplace Discussion
    Replies: 1
    Last Post: 28-08-2012, 09:45 PM
  4. I'm in the right place
    By luke11cnc in forum General Discussion
    Replies: 8
    Last Post: 04-12-2011, 01:37 AM
  5. Pick and place log
    By Robin Hewitt in forum Pick & Place Machines
    Replies: 4
    Last Post: 22-10-2010, 03:00 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •