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Spindle nose in a coolant lake

Pattnmaker

Stainless
Joined
Nov 2, 2007
Location
Hamilton, Ontario
I have a job coming up that I am going to have to cut a 6" deep depression in a part sort of like a bathroom sink shape but bigger and with no drain in the bottom. To avoid crazy long endmills or toolholders I was planning on having the spindle nose go down into the part. I often do this with our routers on wood patterns, I model the nose as part of the toolholder for simulation to ensure I don't get any collisions.

It occurred to me this week that the nose will be running in coolant if I do this. Hopefully just the toolholder but maybe the actual nose of the machining center. Its a high speed spindle 24000rpm. Is running in the coolant going to cause bearing issues? Or will the toolholder act as an impeller and keep the coolant away from the nose? I will have hours of surfacing.

I am also concerned about clearing the chips I suspect the coolant spray is not going to do much under 5-6 inches of coolant. any suggestions for clearing chips in this situation? Material is 6061 so I don't want to try running dry.
 
Can you setup an auxiliary pump or siphon to clear the coolant / chips? Or turn off the coolant manually once you have it an inch deep (or however long your tool is).
 
If it was me, I'd be asking myself which would cost me more:

1) Slowing down the spindle speed and using a longer tool and holder, setting me back a couple cutting hours.

or

2) Potentially losing spindle life if the lower bearings are compromised, therefore needing to replace the spindle (at a cost of $10K or so, and days of downtime) sooner than I'd hoped.

I think I'd go with #1.

What I'd really do is put it on the horizontal.....:D
 
I’d be more worried about all the chips you’ll be recutting and having to finish the cavity a second time to get rid of the funkiness.
 
I have a job coming up that I am going to have to cut a 6" deep depression in a part sort of like a bathroom sink shape but bigger and with no drain in the bottom. To avoid crazy long endmills or toolholders I was planning on having the spindle nose go down into the part. I often do this with our routers on wood patterns, I model the nose as part of the toolholder for simulation to ensure I don't get any collisions.

It occurred to me this week that the nose will be running in coolant if I do this. Hopefully just the toolholder but maybe the actual nose of the machining center. Its a high speed spindle 24000rpm. Is running in the coolant going to cause bearing issues? Or will the toolholder act as an impeller and keep the coolant away from the nose? I will have hours of surfacing.

I am also concerned about clearing the chips I suspect the coolant spray is not going to do much under 5-6 inches of coolant. any suggestions for clearing chips in this situation? Material is 6061 so I don't want to try running dry.

you wont hurt the spindle, but at 24k your going to have a mist so thick you can cut it with a knife.
I'm running a hog out 12k with endmill that barely clears the part. but coolant hits the spindle alot. running a mist buster on one machine nothing on the other. mist was really bad. it builds up bad in your chest and your going to be congested for a week after.
I ran 2 fans out the bay door and shut the a/c system off as it made that a/c system pretty f'n gummy.

at 24k you might throw it off balance but I dont know.
 
The more I think about this, the more I agree with the idea of having a way to pump out the cavity as you're working on it.

It'll require some extra work and program breaks to reposition the pickup, but roughing and semi-finishing in a "layer cake" manner, and doing each layer as a half-n-half (cut the front, with the pickup at the back, stop program and move the pickup so the back half can be machined) should work.

Use something like a solids-rated sump pump, so that it'll take chips and such going through it, and just dump the outlet over the side of the table. Anchor it so it won't move, find some combination of automotive radiator hoses to give you a formed shape for pickup and discharge, and you're set.

Once you've semi-finished, go ahead and finish as one program, no pump. By that time, the chips will be small enough that there shouldn't be much of a hit from recutting on the endmills or surface finish. Maybe this would be time to use a mist rather than flood coolant.

I would NOT cut into a lake. Just doesn't feel right. And I agree with wanting a good mist filter, you don't want to breathe that stuff or get it all over the building.
 
Now the weather is getting colder a mist filter is getting ordered soon. I like the idea of a pump. Recurring chips is definitely a concern. I had been thinking about feed holds and blowing them out but pumping coolant and hopefully chips would be good.
I wonder if a venturi pump would work. Not sure I want a submersible pump in the the hole. Maybe a shop vac with a pump in the vac.
 
Now the weather is getting colder a mist filter is getting ordered soon. I like the idea of a pump. Recurring chips is definitely a concern. I had been thinking about feed holds and blowing them out but pumping coolant and hopefully chips would be good.
I wonder if a venturi pump would work. Not sure I want a submersible pump in the the hole. Maybe a shop vac with a pump in the vac.

No pump in the hole, figure out what radiator hose could be adapted (or use regular hose and a few angle fittings) to go from table mounted pump into the hole.

You want a good pump that will run hours and hours on end, not usually something shop vacs do. That's why I think a good quality sump-solids pump would be a good choice.
 
Set up a pump to spray a high pressure jet of coolant into one side of the cavity. If it’s bowl shaped it will flush it right out the other side. And as a bonus, it will carry the chips out with it.
 
Set up a pump to spray a high pressure jet of coolant into one side of the cavity. If it’s bowl shaped it will flush it right out the other side. And as a bonus, it will carry the chips out with it.

My understanding of the size of the cavity in the OP's description makes me think it's going to take an almighty jet of coolant to keep it reasonably clear. Though the combination of jets and pumping would be best to get chips out.
 
Now the weather is getting colder a mist filter is getting ordered soon. I like the idea of a pump. Recurring chips is definitely a concern. I had been thinking about feed holds and blowing them out but pumping coolant and hopefully chips would be good.
I wonder if a venturi pump would work. Not sure I want a submersible pump in the the hole. Maybe a shop vac with a pump in the vac.

Maybe just a shop vac with a 55 gallon drum in line with the hose.
Set it up on a stand of some sorts, weld a 1" npt bung on the side near the bottom, so you
can gravity it back to your coolant sump every 10 minutes or so. (yes, you'll need to stop the shop vac
for this)
 
Do not breath the mist. I have 2 of these on my mill and will not run it without them. Even on low RPM jobs. My coolant pump is 13 gal/min and the splashing makes enough mist that I can feel the congestion the next day. With these running that problem goes away. The mist on low RPM jobs is very hard to see, but it is there and the intake filters on the collectors def show it.
https://www.amazon.com/gp/product/B00004R9LO/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
 
Just put a bucket of coolant on your table and see what happens when you stick a tool down in it.

At least you will know approximately what to expect in advance.

I'd say get a little bit longer of a toolholder, maybe an inch longer than what you have. I doubt you'd have to change much if it is a tad longer.
 
id be running mist/air blast or on a horizontal.
flooded coolant with a submerged spindle isn't a good idea.
last resort is an extended tool holder and lighter cuts.
 
I would avoid submerging the spindle nose at all costs. Many machines have breather holes and the spindles aren't really meant to work that way. Pulling coolant up into the spindle bearings means a rebuild.
 
This job has finally gotten approval. I think I first quoted it over 2 years ago. The plan back then was to cast and polish the part but delivery the fact that I bought a mill and some other issues made me decide to machine it. I have decided and the customer has approved doing this in 2 layers and bolting it together. This saved me $1000 in material and means I am only going 5.5 deep. As well I can bore a hole though the middle of the cavity to drain coolant and chips.

Less waste material this way but I am still milling 210lb of a 260lb block to chips.
 








 
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