[george1980m]

Hi,

I'm wondering why most non gantry mills are using spindle cartridge type with either gear/belt instead of running self-contained spindle. I mostly see self-contained spindle being used in router mill.

I understand traditional milling requires lower RPM but what about high speed machining? Can I strap a high speed self contained spindle (20-40k RPM) to my mill and do HSM?

Why isn't this done often?

[Jim Dawson]

No reason it couldn't be done if the spindle is build to take metal cutting loads. Such spindles exist, but be prepared to spend a lot of money. It is probably less costly to use a cartridge type spindle and a large conventional spindle motor to drive it.

[mactec54]

Hi,

I'm wondering why most non gantry mills are using spindle cartridge type with either gear/belt instead of running self-contained spindle. I mostly see self-contained spindle being used in router mill.

I understand traditional milling requires lower RPM but what about high speed machining? Can I strap a high speed self contained spindle (20-40k RPM) to my mill and do HSM?

Why isn't this done often?

Most of the CNC mill built today do have a option for self contained spindle meaning the spindle and motor is one unit, the reason for spindle gearing is for heavy Milling rigid tapping of large threads


The high speed 2 Pole spindles you are talking about are not designed or suitable for milling metal, engraving and Aluminum is about the limit and aluminum is not that great as well, there are some that are but have a high price tag to go with it and are 4 Pole they have a different Bearing arrangement that is better suited to cut metal, they are still light weight compared to what a CNC Machining Center are built with


Can you add one many have for light machining

[george1980m]

Thanks Jim & Mactec54

I'm looking at these pretty pricey Chinese spindle ?$1400 for 2.2kW). They are 4 pole, 24k RPM. Same as this one:


https://www.youtube.com/watch?v=pWNeW-lH9RA


Can they be used to cut steel in high speed if I have a G0704 type frame CNC?


I'm thinking about two options:

1. Belt drive ATC spindle + motor - 10k rpm
2. Integrated watercooled ATC spindle - 24krpm


They run about the same cost. Which one is better for general metal machining?

[Jim Dawson]

Thanks Jim & Mactec54

Can they be used to cut steel in high speed if I have a G0704 type frame CNC?

The G0704 is not a very robust machine, but if you stay within the limitations of the machine rigidity it should work OK. I have no idea what material removal rate you could expect, but I'm guessing with a higher speed spindle and HSM tool paths you would have some gain over the stock spindle configuration.

[mactec54]

Thanks Jim & Mactec54

I'm looking at these pretty pricey Chinese spindle ?$1400 for 2.2kW). They are 4 pole, 24k RPM. Same as this one:


https://www.youtube.com/watch?v=pWNeW-lH9RA


Can they be used to cut steel in high speed if I have a G0704 type frame CNC?


I'm thinking about two options:

1. Belt drive ATC spindle + motor - 10k rpm
2. Integrated watercooled ATC spindle - 24krpm


They run about the same cost. Which one is better for general metal machining?

It will depend on the Bearing configuration yes there are many of those ATC spindles you will have to ask the manufacture if the spindle you want can be used to mill steel most of them will be a no

[handlewanker]

I suppose it can be said that anything is possible if you use it not as intended one way or another.....dropping the speed of the spindle to 10K and using a carbide cutter will allow you to machine any metal that is capable of being cut with carbide.....it just depends on the depth of the cut and the amount of material you need to remove...….anything is possible.

If you only get a .010" depth of cut on a 6mm diam cutter in mild steel you will be there 'till Xmas but it can cut......just not practical.

Short answer is …..use what other people are using and stop wishing for the stars.

However, if you already have a self contained spindle and VFD you "could" use it to drive a cartridge spindle using a belt drive reduction at 1:4 ratio.....that would raise the torque capacity X4 and drop the revs X4 in one hit, but I would not suggest doing that as an ideal to do exercise when other BLDC or 3 phase motors are available and would work with a VFD.
Ian.

[mactec54]

I suppose it can be said that anything is possible if you use it not as intended one way or another.....dropping the speed of the spindle to 10K and using a carbide cutter will allow you to machine any metal that is capable of being cut with carbide.....it just depends on the depth of the cut and the amount of material you need to remove...….anything is possible.

If you only get a .010" depth of cut on a 6mm diam cutter in mild steel you will be there 'till Xmas but it can cut......just not practical.

Short answer is …..use what other people are using and stop wishing for the stars.

However, if you already have a self contained spindle and VFD you "could" use it to drive a cartridge spindle using a belt drive reduction at 1:4 ratio.....that would raise the torque capacity X4 and drop the revs X4 in one hit, but I would not suggest doing that as an ideal to do exercise when other BLDC or 3 phase motors are available and would work with a VFD.
Ian.

I think you mean 4:1 4 turns of the motor to 1 turn of the spindle, BLDC motor don't work well with VFD Drives the best they would do is smoke


Here is a video of one of these ATC spindles, this is extreme in this case but shows why they are not that great for milling steel, see if you can see why these spindles are not great for milling steel


https://www.youtube.com/watch?v=qLFjhMN3kOg

[Jim Dawson]

I think you mean 4:1 4 turns of the motor to 1 turn of the spindle, BLDC motor don't work well with VFD Drives the best they would do is smoke


Here is a video of one of these ATC spindles, this is extreme in this case but shows why they are not that great for milling steel, see if you can see why these spindles are not great for milling steel

Because the spindle slides in and out at the tool change and thus has to be loose enough to slide in the bearings or whatever?

[handlewanker]

Because the spindle slides in and out at the tool change and thus has to be loose enough to slide in the bearings or whatever?

I think Mac has once again gone to the extreme with the example, totally out of context.....the poster probably has a simple Chinese 25,000 rpm spindle and that is what the question was about...…...not some exotic ATC spindle like Mac showed.
Ian.

[mactec54]

I think Mac has once again gone to the extreme with the example, totally out of context.....the poster probably has a simple Chinese 25,000 rpm spindle and that is what the question was about...…...not some exotic ATC spindle like Mac showed.
Ian.

Not out of context, it's a very good example of what happens with these HS Spindles, it's how they are Designed

The spindle the OP was looking at was one with a ATC

[mactec54]

Because the spindle slides in and out at the tool change and thus has to be loose enough to slide in the bearings or whatever?

What is happening is in this video happens with all these spindles, this is extreme in this video and it can be adjust to be much less movement than that, they have up to .030" when in normal operation


This is the AC Bearings moving not the spindle shaft moving in the bearings it is the Bearings Preload unsetting, so when you use an End Mill in a spindle like this a Endmill pulls down and removes the Bearing Preload and we know what happens next when you have loose Bearings

[mactec54]

Because the spindle slides in and out at the tool change and thus has to be loose enough to slide in the bearings or whatever?

What is happening is in this video happens with all these spindles, this is extreme in this video and it can be adjust to be much less movement than that, they have up to .030" when in normal operation


This is the AC Bearings moving not the spindle shaft moving in the bearings it is the Bearings Preload unsetting, so when you use an End Mill in a spindle like this a Endmill pulls down and removes the Bearing Preload and we know what happens next when you have loose Bearings

[handlewanker]

Mac...when I said 1:4 this is stated as a reduction ratio ……….the other way round, or as you state, is 4:1 which indicates that you are driving in top gear with an output of 4 times the input.

As an expression of a ratio it has nothing to do with a fraction representation which in a fraction sense would be written as 1/4 for a reduction or 4X for a multiple.

Sorry about the mix up with the BLDC.....I actually meant a 3 phase motor and a VFD.....I don't know much if anything about the BLDC requirements for driving......I assumed they were both frequency variable in their speed adjustment...….with some deep thinking and guesswork I would think the BLDC motor, by it's title, is a brushless DC permanent magnet motor controlled by feedback and varying the current or voltage input to maintain a preset speed against the loading.....whatever.

It seemed like a logical solution to use it (the water cooled self contained spindle motor) for a drive, when you have one, with belt and pulley reduction.....like the BLDC drive on my Skyfire SVM-0 mill.

However, in the case of the SVM-0 mill, the top speed of the BLDC motor is 7,000 rpm so it does get a smaller pulley driving a larger one for reduction to get more torque down the way and the opposite way round with a bigger pulley driving the smaller spindle pulley for more revs when you want to do small cutter work at higher speeds or some wood or plastic carving etc.

I can't think of any reason that a 24,000 rpm motor rev range can't be reduced by a 1/4 with belt reduction to get a more meaningful cutter speed to enable it to cut metal......something you couldn't do by slowing the motor down to a crawl and overheating it.
Ian.

[hanermo]

Lots o confusion.

Self-contained direct drive spindles, are things like the integral drives made by Mori Seiki at 25.000$ a pop.
The are balanced not just statically, but dynamically, and very much engineered to control the heat expansion, and for long life at 100% load.

A 1500$ chinese spindle is not expensive, and may or may not be apt for industrial use, mostly not.

Most of the "high speed" chinese spindles are not suited, at all, to the real cutting loads imposed on actual industrial spindles, industrial in wood or metal, 5-10-25 kW++ actual power absorbed.

[handlewanker]

Hi Hanno....my opinion is that if the high speed spindle is able to function at 25.000 rpm with the loads it's designed for then if you wanted to cut steel, which means you need to go much slower, then doing a speed reduction as I stated will still put the same load on the spindle ……..PROVIDED...….you don't expect to take a heavy cut...…...milling steel is not for the unwary but as most on here do aluminium then I would say it can be done with discretion and not with overloading the motor...….I doubt that anyone has actually done this exercise but many have voiced opinions as to why it cannot be done.
Ian.

[ger21]

That's a cheap chinese ATC spindle.

[mactec54]

That's a cheap chinese ATC spindle.

They are all the same Bearing configuration Design cheap or expensive makes no difference Just showing what will happen when you try to mill steel with this type of design

[Goemon]

I researched this topic to death when I was choosing my spindle and I have done a good bit of testing (with cutting steel and aluminum) since I finished my machine. There is a lot of regurgitated innacurate and outdated info out there.

As a general point, you most definately can mill steel with even a basic wood router. There are a number of YouTube videos demonstrating this. E.g.

https://m.youtube.com/watch?v=jOvGv9aRKFs


Obviously there is a difference between milling an occasional steel pocket on a hobby CNC router and large VMCs making steel parts quickly all day every day. I wouldn't buy a Home Depot router for the latter...

As with any other type of spindle, you need to choose tools and set feed speeds and spindle RPM etc at the appropriate level for your machine, spindle limitations and work piece.


My personal experience has been that you run into other limitations like machine stiffness, poor spindle cooling, missed stepper steps and broken tools long before your spindle gets stuck due to a lack of torque. I have yet to see my 24,000 rpm spindle get stuck on any cuts when I use G Wizard, even in steel.


You only have to look at how well the Datron routers cut steel with (ultra) high speed spindles (with smaller tools). They work as fast (with steel parts) as any comparably priced VMC and they do so with very little torque. Their accuracy is top notch too. Their machines are just appropriately stiff and heavy for metal milling and have great acoustics.


It's also a myth that all mills have stronger, larger or better bearings. Obviously a $200,000 VMC spindle will have better bearings than a $300 Chinese eBay spindle. But, if you compare like with like, it's a different story. I have a 7.5hp PDS ADES 90 high speed spindle and an R8 spindle from LMS's high torque bench mill. The bearings on my PDS spindle are considerably stronger and higher quality than the cheap bench mill spindle.


If you look at the various Chinese eBay belt drive milling spindles, they use the same cheap 7007 or even 6007 bearings as their comparably priced 24,000 rpm wood spindles.


If you buy a high speed spindle that is cooled by water, electric fan or compressed air (instead of a shaft fan), you have the same (or a better) speed range as you would with any belt drive milling spindle. The main reason why cheap air cooled eBay spindles can not go below 12,000rpm is poor low speed cooling with shaft fans. My electric fan cooled spindle does fine from 50rpm up to 24,000rpm.


The main advantage with belt drive spindles is that they can use gearing to increase low speed torque. It is / was a good way to take deeper cuts with smaller 1hp or 2hp motors on manual mills (where that matters). The trend has been shifting though. Newer high end VMCs are moving towards high speed direct drive spindles to take advantage of high speed machining with the newer generation of coated carbide tools. Motor sizes have increased accordingly to maintain torque. This is key as a 3hp milling head has no more torque at 12,000 rpm than a 3hp high speed 4 pole spindle at 12,000 rpm.


Anyway, the advice I got here (and I'm glad I listened to) is to buy a spindle that is optimal for the material you will cut most often. Then, focus on building (or buying) a machine that is stiff enough to handle the work at the required level of precision. You can't put a 20hp cat 40 milling head on a cheap aluminum T slot router frame and expect good (or even safe) results.


Even if that weren't the case, one look at the specs of your average Bridgeport milling head will shatter any illusions one might have about mounting one on a diy T-slot build. They weigh 300lb + and they are enormous. Many VMC heads are considerably larger.


I mainly want to cut aluminum and the average RPM suggested for my 1/8", 1/4" and 3/8" carbide 2 flute end mills is between 12,000 rpm and 18,000 rpm. A low speed geared belt drive spindle would be sub-optimal for my needs.

[mactec54]

I researched this topic to death when I was choosing my spindle and I have done a good bit of testing (with cutting steel and aluminum) since I finished my machine. There is a lot of regurgitated innacurate and outdated info out there.

As a general point, you most definately can mill steel with even a basic wood router. There are a number of YouTube videos demonstrating this. E.g.

https://m.youtube.com/watch?v=jOvGv9aRKFs


Obviously there is a difference between milling an occasional steel pocket on a hobby CNC router and large VMCs making steel parts quickly all day every day. I wouldn't buy a Home Depot router for the latter...

As with any other type of spindle, you need to choose tools and set feed speeds and spindle RPM etc at the appropriate level for your machine, spindle limitations and work piece.


My personal experience has been that you run into other limitations like machine stiffness, poor spindle cooling, missed stepper steps and broken tools long before your spindle gets stuck due to a lack of torque. I have yet to see my 24,000 rpm spindle get stuck on any cuts when I use G Wizard, even in steel.


You only have to look at how well the Datron routers cut steel with (ultra) high speed spindles (with smaller tools). They work as fast (with steel parts) as any comparably priced VMC and they do so with very little torque. Their accuracy is top notch too. Their machines are just appropriately stiff and heavy for metal milling and have great acoustics.


It's also a myth that all mills have stronger, larger or better bearings. Obviously a $200,000 VMC spindle will have better bearings than a $300 Chinese eBay spindle. But, if you compare like with like, it's a different story. I have a 7.5hp PDS ADES 90 high speed spindle and an R8 spindle from LMS's high torque bench mill. The bearings on my PDS spindle are considerably stronger and higher quality than the cheap bench mill spindle.


If you look at the various Chinese eBay belt drive milling spindles, they use the same cheap 7007 or even 6007 bearings as their comparably priced 24,000 rpm wood spindles.


If you buy a high speed spindle that is cooled by water, electric fan or compressed air (instead of a shaft fan), you have the same (or a better) speed range as you would with any belt drive milling spindle. The main reason why cheap air cooled eBay spindles can not go below 12,000rpm is poor low speed cooling with shaft fans. My electric fan cooled spindle does fine from 50rpm up to 24,000rpm.


The main advantage with belt drive spindles is that they can use gearing to increase low speed torque. It is / was a good way to take deeper cuts with smaller 1hp or 2hp motors on manual mills (where that matters). The trend has been shifting though. Newer high end VMCs are moving towards high speed direct drive spindles to take advantage of high speed machining with the newer generation of coated carbide tools. Motor sizes have increased accordingly to maintain torque. This is key as a 3hp milling head has no more torque at 12,000 rpm than a 3hp high speed 4 pole spindle at 12,000 rpm.


Anyway, the advice I got here (and I'm glad I listened to) is to buy a spindle that is optimal for the material you will cut most often. Then, focus on building (or buying) a machine that is stiff enough to handle the work at the required level of precision. You can't put a 20hp cat 40 milling head on a cheap aluminum T slot router frame and expect good (or even safe) results.


Even if that weren't the case, one look at the specs of your average Bridgeport milling head will shatter any illusions one might have about mounting one on a diy T-slot build. They weigh 300lb + and they are enormous. Many VMC heads are considerably larger.


I mainly want to cut aluminum and the average RPM suggested for my 1/8", 1/4" and 3/8" carbide 2 flute end mills is between 12,000 rpm and 18,000 rpm. A low speed geared belt drive spindle would be sub-optimal for my needs.

No you can not do what this video shows with your normal wood router spindle, if you did this on a regular bases you would be needing a new spindle in no time, all it showed is a chewed up mess, not successful at cutting steel at all

You can cut steel with a Dremal so this spindle will do a similar job, I put my money on the Dremal to last longer, because of the bearing design arrangement

They do make some of these spindles that can cut steel but the Bearing arrangement is completely different