My spindle design

[GeorgeD]

Lighten up,Ross...I was only jesting.

[routercnc]

Hi Ross,

I asked about balance because the spindle I bought had balance holes in the collet nut. It's another step towards a more refined and accurate machine.

The material you were researching is from manufacturers who make machines which run all day, and under a high workload. They are always pushing the boundaries of what is possible, and charging £1000's for them. Maybe you're beating yourself up a bit there with what you might achieve, but bravo for giving it a go.

I've yet to run my machine yet (hobby on back burner for now) but similar machines on the internet spin up nicely to 24,000rpm and I'm expecting the same. No it's not geared - I suspect it is like the section view I posted a while back.

This is the machine I bought:
http://cgi.ebay.co.uk/1-5KW-WATER-CO...item35aaca00f4

Sorry, this is the blind leading the blind unless some has actually done this . . .

[Ross77]

Lighten up,Ross...I was only jesting.

I know. how about this??

Sorry, this is the blind leading the blind unless some has actually done this . .

Thanks Steve....... I Wonder if I will ever get this working..

I asked about balance because the spindle I bought had balance holes in the collet nut. It's another step towards a more refined and accurate machine.

Not the dreaded vibration stuff again :naughty: there is a version in my mind that inverts the motor so it is parallel to the spindle and mounted the opposite side of the y axis gantry but running the opposite way to the spindle to cancel out the inertia (not sure of the terminology)........

Maybe you're beating yourself up a bit there with what you might achieve,

yeah I'm under no illusion that I can make a super accurate precision spindle that can run 24/7, but I would like to have a fighting chance of making a decent home use one.

I've been looking at the A/C bearings and there are so many to choose from with different angles and precision ratings, I can get a budget one for around £12 but the proper matched pairs can be around £100 or more. I just need to work out if using good bearings will average out my machining skills or if they are a waste of money at the moment.

I can see my self just getting the cheap ones and a few deep groove ones and then just trial and error... if the run out is acceptable and it doesn't flex or chatter when cutting then job done

[GeorgeD]

To be honest with you here Ross...I would rather go and buy one of those Chinese spindles on ebay,just seen one for £130 or nearest offer.

Your taking this to the extreme by worrying about precision from the motor and its housed bearings arrangement,too much headache.

Whats your goal in the CNC ie what do you want to achieve in terms of product?

[routercnc]

George,
Some of Ross's goal is hinted at in post#1.

Ross,
I wonder if you need to break this down a bit. Maybe convert a big old mill to cnc for the lower speed, big roughing out work in Ali, and concentrate on making a high speed VFD controlled spindle (20,000 - 30,000 rpm) for the gentle stuff and the routing in wood.

Taking a punt, several of the Chinese spindle boast 'imported bearings' or similar, so maybe they suffered early on from the cheap ones. I'll stick my neck out then and say go for the £100 A/C combo, plus a cheaper ball bearing at the other end.

As for the drive, I think that even with the parallel mounting idea, unless they are out of balance by the same amount, and the oob is in the same place radially, you'll not improve things.

[Ross77]

To be honest with you here Ross...I would rather go and buy one of those Chinese spindles on ebay,just seen one for £130 or nearest offer.

Yes but I want a ER 32 collet and 8000rpm is still to fast for milling. its also part of a whole one piece Z axis that I'm trying to design.

Your taking this to the extreme by worrying about precision from the motor and its housed bearings arrangement,too much headache.

Well its my hobby and I like to do things properly. I what to learn how to machine accurately so If nothing else it will be a learning exercise.

I wonder if you need to break this down a bit. Maybe convert a big old mill to cnc for the lower speed, big roughing out work in Ali, and concentrate on making a high speed VFD controlled spindle (20,000 - 30,000 rpm) for the gentle stuff and the routing in wood.

Yeah I'm coming to that conclusion. Although not with two machines (I'm not made of money...) but with a cartridge type spindle that can be swapped for different jobs, A/C for high speed and taper bearings for high load.


From what I've found the problem seems to Lay with heat.....

For high load you need a high contact angle 40 deg or more and therefore more friction, and heat but for high speed you need the opposite, a low contact angle (15 to 25deg. seems to be the favorite) which reduces the heat but also the load capacity. so therefore it would seem you cant have both (Unless any one knows different?)

The heat also affects the preload which in turn affects rigidity. for high speed you need a variable spring loaded one but the most rigid is the fixed permanent type

Hence "Mills for milling and routers for routing", but at least I now know why :heehee:

Anyway this should really simplify the design and manufacture of the separate spindles

[GeorgeD]

Are those motors that poweful?

I know when I messed about with RC fuel powered model engines,these type of motors were not known back then.

The little bee engine I bought I affixed it to a piece of wood and the darn thing took flight towards the ceiling and bored a hole in the ceiling.

sorry for the ramble.

[Ross77]

Wrong thread George you want The "hope it'll cut Ali" one

Back to the bearings I have found an excellent company called Bardens and the catalog is full of bearing usage and design guides but in nice easy to understand format. The big upside is that they have a UK branch just down the road from me, but I expect they will be mega bucks and wont deal direct with a small time hobbyist. Still nothing ventured nothing gained.

Heres the catalog if any ones interested http://www.bardenbearings.co.uk/c2/u...20uk%20cat.pdf

Theres also some precision bulletins that deal with effects of high speed and using smaller lower mass balls to counter effects, scroll down the page a bit.

http://www.bardenbearings.com/literatr.htm

So maybe I can build just one spindle after all

[GeorgeD]

lol sorry about that Ross.

[GeorgeD]

I mentioned in one of my post about the use of a Treadmill motor,these are slim and 118v? to run it we'd need a dropper supply....hmmmm,ain't microwave power supplys 240v primary and 118v secondry.