Climb Milling

I found the following on one CNC help site, looks rubbish to me, just tighten the gibs, that just makes it stiff to move.

"The best way to correct (at least with box way construction) is to adjust the machine's gibs to eliminate the backlash all together."

All ball screws have some backlash, double ones can be adjusted,  double lead screw nuts reduce it, wear must ultimately happen with both systems.

Edited By KWIL on 09/10/2015 19:17:21

The backlash in modern machine tools comes from the compression and tension of the materials it is made from. The higher the speed, the greater the forces and so effectively more backlash occurs. Modern ballscrew nuts are preloaded together, there is no longitudinal movement in the nut assembly. The only way it can get any backlash is for the screw to stretch apart and effectively change pitch. That is why the good gear has some form of dimensional feed back, either off glass scales or laser positioning. The latest in climb milling for cnc uses only about 10% of the cutters diameter as a cut per side, so a lot less forces compared to a heavier cut, but they do it at a very high feed rate and a very high cutter surface speed. Really neat to see.

On manual mills, a finish climb cut should not be that bad on most machines, the only real issue with backlash is if you are climb milling in a pocket, and then that could be a problem. Having one of those air mist blowing over the cutter will greatly improve cutter life and surface finish, either manual or cnc.

Neil

Edited By Neil Lickfold on 09/10/2015 19:49:46

I've created a short article with the Sandvik Coromant article 'Why Climb Mill' here:

www.model-engineer.co.uk/news/article/why-climb-mill/22411

Thanks to Shaun for drawing my attention to this and Sandvik for permission to use it.

Neil

Neil,

any more info on air mist system? If it extends cutter life it would be of great interest to me at least

People out here are using an air mist , either through the spindle of the machine,or add on the side misters.

They sell special oils, but rice bran oil or sunflower oils works very well indeed. It is quite thin, alot thinner than canola oil.The amount of oil used is very small, basically you hold a piece of paper in the air stream, and after about 1 min there should be a small circular pattern showing that oil is coming out. If it is wet with oil then that is usually too much. Seems too good to be true but works very well. It is best to have 2 or 3 nozzels blowing down onto the cutter to cover for when it goes around a corner or is in a cavity. The air blast wants to be strong enough to blow the chips clear out of a cavity etc. I think the oil consumption is about 1 liter per month maybe less on the machine center.

Neil

Many years ago a company ( I think) did an electrostatic coolant system that put a tiny bit of oil on a cutter. I think the original was for a lathe tool but it should work on a mill. I think it may have been the company that bought out a round bed lathe in the 1970's or 80's. It was described in Model Engineer.

Duncan, check in my photo album for the dimensioned drawing and other shots of the misting unit I use on a milling machine.

Emgee

In a small poorly ventilated workshop there might be a health issue with mist coolant.

Doug

You are right. Soluble oil coolants should not be sprayed through an air misters. The only oils that I have been involved with in the misters have all been edible cooking oils. I would think that sulphurised cutting oils would be bad news as well. Most machining centers these days have those oil recovery systems on them, to help to clean up the air from the coolant just being hosed onto the work piece. When they use the oil mister, the air quality is better than when they use flood coolant. Now days there is more research into cutter coating for cutting virtually dry, without the use of flood cooling. Some types of work, have to be flood cooled, but the technology will be developed to the point of just air mist or eventually just air will be the coolant and chip remover of the future. Soluble cutting oils I do not think are good to any environment, and I am not sure if it can even be easily distilled out of the water supply if it gets there. Very digressed from climb milling, but probably important anyway.

Neil

If using sunflower oil as you describe, then there's less oil getting in the air than with one of THESE.

Neil

Thanks Emgee, another one on the 'to do' list.

I regularly climb mill, and I've only got an X2. Perhaps I don't know any better.

Neil

OT I know but... The name coolant mister is a bit of a misleading description which leads to the worries about suspended coolant mist and fogging. The idea with these devices is NOT to produce a mist of coolant but an airstream containing tiny droplets of coolant. I use spray coolant devices on my mill and both lathes and never suffer with fog or mist in the workshop. The units I currently use are based on the Hench fogbuster.

These work very well although I've just bought a couple of cheap spray units from china which work without having to pressurise the coolant tank. Initial experiments with these look quite promising and they are less than £10 each. The coolant in these units is drawn to the nozzle by the venturi principle.

Edited By Graeme W on 17/10/2015 17:09:32

Hi Graeme,

is your Chinese model one of these?

http://www.ebay.co.uk/itm/Mist-Coolant-Lubrication-Spray-System-CNC-Lathe-Milling-Drill-Grind-Machine-A-/371343389716?hash=item5675ca7414:g:Kz4AAOSw~OdVXUgq

If so can you let us know how well it works and how much air it uses? Don't want my compressor running all the time, but I have a little air pump I can use.

Duncan, yes very similar, it needs about 10-15 psi to get it to lift the fluid from the coolant reservoir, I can't comment yet on air consumption as I've not run it long enough. All my air powered gear runs off a 200 litre tank on the compressor so small kit like this doesn't cause the compressor to kick in very often, If you are thinking of an aquarium type air pump then forget it, they are useless for this type of device.

Hi Graeme W. I agree 100% with your description, droplets being sprayed on the work, not a true misting system which have received bad reports. My system can be seen working at the following link.

www.youtube.com/watch?v=KRiiEywpzZk

Emgee