[joeavaerage]

Hi,
The table I used was actually given to me as it was going to be scrapped. It was the base of a 'pick and place' machine. It is 1300mm x 1100mm and about 600mm high. It has a half inch slab of steel
on top and was used to bolt the pick and place machinery direct to it. The whole thing weighs about 300kg on its own. It was on good heavy castors, but I replaced them for even heavier ones (250kg each).
The whole machine sits in what looks like a shower tray I had my sheet metal guy bend up for me. It means that I can contain flood coolant pretty well.

If you are going to use flood coolant, and if you are serious about using your mill you will be, then give a lot of thought to containing it, where and how you are going to pump it and especially
how you are going to filter it and get rid of the chips. If you design well it will be easy to use....design poorly and it will be a never ending hassle.

I use quite a bit of plastic and also use fibreglass in the form of circuit boards. Both materials are inclined to make sludge in your coolant tank, and hence you have to clean it out periodically.
Having a tank you can easily remove, and maybe even wheel around on its own castors so you can scoop out the sludge is the ticket.

My plan is to have a continuously flowing recirc pump (low pressure, high volume) pumping from the tank to an in-line filter, and have a second pump, lower volume but much higher pressure
feed from the inline filter to the coolant nozzles. Flood coolant is particularly good when a high velocity stream can be directed at the cutzone, and that in turn requires fairly fine nozzles, say 3mm
or so. Such nozzles tend to block up so you really want freshly filtered coolant at several bar pressure. When you are working you will find it necessary to push tools pretty hard, spinning them at,
or even faster than manufacturers recommendations, at high chip loads. Uninterrupted, well directed flood cooling is essential. Ten seconds where that coolant is misdirected or blocked and
your brand new 10mm $50 endmill goes red hot .......and that's the end of it. Burning up tools is an expensive pastime!!!

As you can tell I have given a lot of thought to coolant and chip control. My results are much better than they used to be, but I'm still only half way to where I want to be. This is a much MUCH
more practically important consideration than a cabinet or table. I tend to focus my attention on those areas that have proven to be critical to producing good parts quickly and easily.

Craig

[maxki]

Indeed, I tend to always plan builds to be upgradable, so my initial bench will only have a simple slab that doesn't catch chips, coolant, etc,
and I'll refrain from flood cooling, but the day I decide it's time, I'll make a "junk catching" chip pan, with the sheet metal I will have accumulated.

Nice mill BTW, I assume it's your creation, it looks well thought out !

Hi,
if you are using coolant you need a much bigger table top. You need sides to surround the whole machine otherwise coolant will go EVERYWHERE. I had flood coolant on my first
mini-mill but it was not particularly well thought out.........and I seemed to spend a lot of time cleaning up coolant leaks.

My new mill is vastly better, but still not as good as it should be. Hopefully sometime over the next twelve months I'll get to re-do the coolant system. I want a 100l tank, a pull-out tray filter and be able to remove the tank easily
to clean it out completely. I promise you'll have to do it every once in a while....and making it easy to do is a priority. I did my coolant tank over the weekend (annual event), took several hours, where with good design I should
be able to do it in under and hour.

Craig

[joeavaerage]

Hi,
flood cooling is just so much the 'night and day' difference that I sought. I use to use air-blast and oil spray, and it worked OK.

With sticky grades of aluminum (3000 series and some of the marine 5000 series) I still had trouble with chips adhering to the tool. Same with plastics. Most plastics cut well
but the chips are very inclined to adhere to the tool and wreck the job. The main requirement for any 'cooling' solution for these materials is to clear the chips away rather than
having them be re-cut and thereby adhere to the tool. Air-blast works, but flood cooling works better.

With steel its about cooling and secondarily about lubricity. Most hobbyists use high speed, low torque spindles, say 24000rpm. They are cheap and extremely useful, but bloody hopeless in steel. With steel you
need much lower speed and much higher torque. You might reasonably point out that there are many videos on YTube all running tools in steel fast.......but what you do not see is that those tools last
1/2 an hour, an hour, maybe more or maybe less....but not long enough for expensive tools.

I work on this rule of thumb:

100m/min for uncoated carbide tools in mild steel. 125m/min to 150m/min with coated carbide tools. For tough steels, eg 4340, reduce the surface speed by 25%. For stainless reduce by 50%.

All of these imply and require well directed, uninterrupted flood cooling or the tool fries up within 10 seconds to a minute.

For example I use 1/8th" Destiny Tools Raptor tools. They are just a good US brand, nothing extra special, just good, with good AlTiN coatings. I run them at 15000rpm or 147m/min,
and with steady flood cooling I get 4 to 5 hours tool life in mild steel and 6 to 8 hours if I slow it down to 12000rpm (117m/min).

If your mill is conventional, that is to say with a belt or gear driven spindle then its likely the rpm range will be low and high torque. This is good for steel. You will even get good
tool life without cooling and coated carbide tools, ,but your tool life will double or treble with well directed, uninterrupted flood cooling.

The worse thing about flood coolant is that it sprays around when you direct at a rotating tool. You may well have seen otherwise fairly conventional mills but with a large tray underneath and low walls
up to somewhat over the tool height to contain the worst of the coolant. With high speed spindles that coolant hits the tool and almost turns into a spray....and those walls need to be much higher
or even enclose the whole machine.

Craig

[joeavaerage]

Hi,
last week I was doing a job for a customer where I had to make 14 parts out of acetal. The total machine time was about six hours.

My coolant tank is only 10l, and yet through the course of the day I topped up the coolant four or maybe five times at 4l per top up.
Where does it all go? Sure I still have a few little leaks and there was some coolant on the concrete floor but I'd swear no more than 0.5l....
so I can only guess that when the coolant hits the tool and turns into spray that a larger proportion evaporates than you might think.
When I'm doing plastics I don't bother with soluble oil, that I save for metals, so its not like it was costing anything...but still is a mystery where
it all goes.

Craig