[boydage]

Hi. Im not a newbie. I am though, a newbie to commercial manufacture of a bunch of parts using my awesome home build machine that bores my children, and puts me in the shed for hours at a time.

I am an aircraft engineer. One of the stages of that career (dont do it anymore its not that cool to work on aircraft) was working in the powerplant rebuild workshop. We used to take a 44000RPM gas turbine, low torque high RPM output, and wack that either by gas coupling or straight into the gearbox. The gearbox was a planetary style, that would take that singing RPM all the way down to 1384. The smallest turbine I worked with, its little first stage hot wheel, was only about 140mm in diameter. We would get 1000HP at the prop.

Has anyone seen, purchased, or built a gearbox to take the 24000RPM spindle output of the most common 2.2kw spindle, and taken it down to something more usable? It would decrease the speed, heighten the torque, and just makes things so much better! And what would something like that cost to manufacture on mass?

I would love to hear from you if you know about this? I am thinking I might build one, but my machining skills are not the best...... I might try. I might try to buy one too. Ha

[joeavaerage]

Hi,
yes you could use a gearbox, at the cost of frictional losses.

Another way is to uses multi-pole motors.

A typical Chinese 2.2kW spindle has 6 poles, arranged as two poles (a pair) for each of it three phases. Depending on where you are in the world that would
be called a two pole motor, common terminology in the US and Europe. In the UK and Commonwealth countries it might be referred to as 'one pole pair per phase.
Despite the terminology difference they mean the same thing.

A two pole (one pole pair) motor has a synchronous speed of one revolution per Hertz. Thus a two pole (one pole pair) motor is excited by 100Hz AC voltage
it will rotate at 100 revolutions per second or 6000 rpm. The same motor excited by 400Hz AC would rotate at 400 revolutions per second or 24000rpm.
Note that that is synchronous speed, all induction motors have some slip, that is to say they rotate slightly less than synchronous speed, say 97% of synchronous
speed. Its still close to 24000rpm, but not quite.

A four pole (two pole pair) motor excited by the same 400Hz AC voltage would rotate at half the speed of a two pole (one pole pair) motor,
ie 200 revolutions or 12000 rpm. You might ask 'why anyone would make a motor that rotated more slowly?'....the answer is that while it rotates at half the speed it does
so with twice the torque.

Likewise an 8 pole ( four pole pair) motor would rotate at 6000rpm but at four times the torque to it indentically sized two pole (one pole pair)
brother.

So if the motor is constructed with multiple poles it has the same effect as a gearbox but without the cost and frictional losses of a gearbox.
So you might ask 'why aren't there spindles out there like that?'. Well there are, but not commonly el-cheapo Chinese made spindles.
Look at the Perske or HSD catalogues and you will find two pole (one pole pair),four pole (two pole pair) and eight pole ( four pole pair) motors
but they are real quality and mega expensive.

Do yourself a favour and look to modern AC servos, they are commonly eight and twelve pole wound synchronous motors and have high
torque density. An AC servo has high flux density rare-earth permanent magnet armature within a multi-pole three phase winding.
Because they have a permanently magnetized rotor they do not have slip like an induction motor.

I bought a second hand 1.8kW Allen Bradley AC servo and drive as a spindle motor. Its rated at 3500rpm, 6.2Nm (cont), 18Nm (overload)
with a single phase 230VAC supply to the servo drive. It KICKS ARSE!!!. Allen Bradley is a real quality brand that wipes the
floor with anything I've ever seen coming out of China.

In addition to the high torque (albeit slower speed) being a servo is position loop capable, so you can have an indexing spindle and
even use it as a C axis for the most precise rigid tapping spindle. High torque, lower speed, indexing, C axis capable....WIN WIN WIN.

Craig

[boydage]

Craig thanks for that. I read that twice it was so good. Hey you dont have a pic of your setup by chance? I would be keen to see what you have built. Regards Boyd

[joeavaerage]

Hi,
my mini-mill is at work and we are locked down for another fortnight or more.

There is nothing particularly clever about it, I direct coupled an ER25 Rego-Fix cylindrical toolholder running in angular contact bearings.
It is in a 65mm cylindrical housing which allows me to remove my existing 65mm diameter 750W 24000 rm spindle and substitute the
low speed/high torque spindle for when I cut steel or stainless.

Craig

[footpetaljones]

There is one guy who has put a video on youtube of his G0704 with a 2.2kw spindle. I believe he used a belt reduction, but I'm not sure on the ratio. You can find his video just by searching "g0704 2.2kw".

[joeavaerage]

Hi,
this is the sort of thing I meant:

https://www.ebay.com/itm/Allen-Bradl...4AAOSwxaNeG80-

The basics are 1.8kW @ 5000 rpm, 4.2Nm continuous, say 12Nm peak with a drive powered by single phase 230VAC. Note this particular servo has a 10:1 reducer,
not that you probably want that for a spindle motor. By the way don't sneeze at the cables, they are rare as rocking horses****t. I paid about $200
to secure cables and/or the parts to make one (the encoder cable).

This is a suitable drive:

https://www.ebay.com/itm/ALLEN-BRADL...YAAOSwVJFdqPun

Note this is the somewhat rarer DSD-030 model, that is 3kW(nom) from a single phase 230VAC input. This is to my knowledge the most powerful
single phase servo drive on the market.

My servo came with a DSD-020, that is a 2kW(nom) drive and its been perfect. They are much easier to find
and cheaper:

https://www.ebay.com/itm/Allen-Bradl...QAAOSwt-Bd9MXY

Craig

[rcheli]

I used a DMM DYN4 1.8kw servo motor on my spindle. I geared mine 1:1.8 for a target spindle speed of 5400 rpm. I think it was in the video that joeaverage referenced the guy had his geared 1:2 for 6000 rpm. I used a timing pulleys from https://www.sdp-si.com/ So far this setup has worked great. I just had to add an index signal on the spindle and I was able to do rigid taping.

I also added and second 2.2KW water cooled 24k rpm spindle for times when I want a high speed spindle for engraving or very small bits.

John

[joeavaerage]

Hi,
I had an urgent job so was allowed to get into work and picked up my spindle. Pic attached.

As I posted earlier the servo and drive are rated to 1.8kW, (3500rpm @ 6.2Nm continuous, 18Nm peak).
The tool holder is a Rego-Fix (Swiss made) ER25 with 20mm cylindrical shank. The bearings are P4 matched pair of NSK angular contact bearings
at the nose and 2 x 602 series deep grove bearings at the tail. The shaft of the servo is direct coupled (Oldham coupler) to the tail of the tool holder.
The housing I made myself.

It works well. Long periods running at rated speed result in the bearings running hot, most probably small angular misalignment given that I turned the housing
myself. While I am happy with it is not perfect by any means. I've had several hundred hours use from it so far, but I suspect the bearings will not last as long as
they should.

Note also that I ensured that the bearing housing was 65mm in diameter so that I could remove my existing 24000 rpm spindle and replace it with this
one, only takes a few minutes.

Craig

[boydage]

In the times of the Covid I have been through my lathe and my router. Thanks guys for this, I have a lot to go away and consider. Definately going to look at upgrading my spindle to something slower with more torque, yet do like the idea of retaining the high speed as well.

Be well. Thanks and regards

Boydage

[joeavaerage]

Hi,

Thanks guys for this, I have a lot to go away and consider. Definately going to look at upgrading my spindle to something slower with more torque, yet do like the idea of retaining the high speed as well.

Wouldn't we all....and you can....if you have thousands and thousands to throw at it. Do you not suppose that I considered that??
Its impossible WITHOUT spending MEGA dollars.

That why I made it interchangeable with my highspeed spindle....it was the closest I could come to having the best of both worlds for the
money I have.

Craig

[boydage]

Im not sure if you just yelled at me or not there Craig. Thats what caps means.And my words were thanks for what you showed me, great idea, I may, or I may not go in that direction. And I dont have thousands of bucks to spend either. I also liked the example that footpetaljones had where the guy had a belt drive spindle. John thanks for your input too. B

[joeavaerage]

Hi,

Im not sure if you just yelled at me or not there Craig. Thats what caps means.

You're being oversensitive...caps might also mean that I'm trying to emphasize the point. High torque at low speed AND high speed operation in one
spindle=MEGA dollars. If you don't have mega dollars then you'll have to compromise as I did.

Craig

[boydage]

Ha. It certainly looked like you got emotional. I grew up in a place called Poroti, I was in a minority, and played rugby with my Maori friends. Skinny white boy quickly learned not to be sensitive - we dont use pads here for full contact sports. Another thing about NZ, is we dont have the access to Ebay without being reemed to almost paying double the item price again in freight.

So I am also in the boat, but even your megga dollars (with the NZ Peso in mind) is even MORE..... megga here. lol. Craig I would even have trouble buying your setup locally here.

I did like what you did, appreciate the pics. I was running a business with my router, when the bearings got noisy in my 2.2kw spindle I bought a new one, and some replacement bearings (so much cheaper off the factory with a new unit). Far out, I am actually considering using my old 2.2kw spindle as a belt driven spindle. It would be so easy to do, kind of like the guy on Youtube who built one similar.

[joeavaerage]

Hi,
I'm Kiwi and I use Ebay and I use it to get stuff from overseas......stuff costs, end of strory.

Craig

[joeavaerage]

Hi,

Craig I would even have trouble buying your setup locally here.

By the way I bought the servo and drive (no cables) from a bloke in Hamilton for $800NZD, it was on Trade-Me.
It pays to look on Trade-Me, this sort of stuff does not come up frequently but it does come up.

Craig

[joeavaerage]

Hi,

in fact check this Trade-Me listing right now:

https://www.trademe.co.nz/business-f...61d2851470-002

Whoops, when i read more closely its not quite as good as I thought.
Firstly its 480V_rms so its intended for a three phase input driver. It would run on a single phase input driver but it wouldn't make
its rated 8000rpm, but more like 4500rpm before it runs out of puff.
Secondly I saw M₀=2.7Nm, but I realize thats its peak torque, not it continuous torque.

torque= power / angular velocity
= 650 / ((8000/60) x 2 x PI)
=650 / 837
=0.77Nm (continuous)

3/4 Nm is OK for a 3mm tool in steel but really marginal for a 6mm tool.

You really want 4Nm or better as that will drive an 8mm tool is steel as agressively as you like. You'd probably want more torque for 10-12 and 14mm tools.

You may have seen that a company is selling Fanuc DC servos, this is 37NM stall:

https://www.trademe.co.nz/business-f...61d2851470-002

Note only 1200 rpm, but plenty of boogie!

Craig