[henrychan]

So for some reason I liven in a place where the mains is 110v so the most powerful spindle motor/inverter combo I can find is 2.2kW. I plan on cutting aluminium 6061 mainly but will also occasionally work on harder materials like stainless steel at a lower material removal rate, therefore I want as much power from the spindle as possible. (machine rigidity will not be a huge concern at the moment)
What can I do about it? Here are a few really dumb ideas that I can think of.
1. get 2 sets of the motor/converters and slap a gear between them to combine their torque
2. use 110v to 220v step up transformer
3. (this is really stupid) use a gas powered engine

[mcardoso]

Aluminum and Stainless are two different beasts. Ignoring spindle power for a moment, lets consider speed and rigidity. If you are CNC'ing (which I assume you are), then machining aluminum would typically be done at relatively high SFM (and therefore high RPM), this is especially true for smaller tools). A router type machine will lack the rigidity to really hog into material, therefore smaller tools, higher speed, and a toolpath which minimizes cutting forces will do the best work for you. This is typically why people end up with those water cooled spindle motors that run 18-24k rpm. Now we can talk stainless. You cannot run tools very fast at all in this material (unless they are VERY small) so you typically use a slower, higher torque spindle. This imposes greater cutting forces and you will find a machine like a router table will struggle to make a decent cut. Typically if you expect to work on harder materials you would spring for a bed mill type machine like a Tormach (whose spindle is usually too slow for aggressive aluminum work with smaller tools).

Now I am not saying you can't cut stainless on a router with a high-speed spindle, but no machine does everything and those materials are on opposite ends of the spectrum.

Now for power. You are limited by the current of your utility, probably 20A max? This comes right out to 2200W. If you don't have better service, there isn't much you can do to get more power (a transformer will double your voltage, but halve your current + losses). If you were to be able to get a 30 or 40A run of 110V, then you would have more power to work with and a transformer could get you to 220V 15-20A.

[henrychan]

I think I didn’t really specify the machine I’m building. It’s gonna be a 1x1x0.5m CNC mill/router using a combination of 3”x6” T slot aluminium and steel for the frame and ball screws to move it. It will have a fixed table and moving y gantry. (Not enough space for a moving table the size I want) 2 carriages per linear rail will be used and they will be spread pretty far apart to handle the moment better. The ball screws should be able to push with 2000N force but I’m not sure how well it handles vibration.

Back to the spindle problem, I don’t really need to make too aggressive cuts on aluminium but I do want the ability to cut harder materials. I’ve tried cutting aluminium and acrylic on a 2000rpm manual mill and the cutting speed is honestly fine for me. Do you know where can I find those higher torque low speed spindle motors? Everything I see on the internet is 18-24k rpm motors

[mcardoso]

Fair enough. You might want to look at a spindle cartridge, something like this (https://www.ebay.com/itm/BT30-Spindl...frcectupt=true), and an induction motor running V belts. You can adjust the pulley sizes to get the torque/speed you need (or use a multi step pulley).

[raychar1234]

Aluminum and Stainless are two different beasts. Ignoring spindle power for a moment, lets consider speed and rigidity. If you are CNC'ing (which I assume you are), then machining aluminum would typically be done at relatively high SFM (and therefore high RPM), this is especially true for smaller tools). A router type machine will lack the rigidity to really hog into material, therefore smaller tools, higher speed, and a toolpath which minimizes cutting forces will do the best work for you. This is typically why people end up with those water cooled spindle motors that run 18-24k rpm. Now we can talk stainless. You cannot run tools very fast at all in this material (unless they are VERY small) so you typically use a slower, higher torque spindle. This imposes greater cutting forces and you will find a machine like a router table will struggle to make a decent cut. Typically if you expect to work on harder materials you would spring for a bed mill type machine like a Tormach (whose spindle is usually too slow for aggressive aluminum work with smaller tools).

Now I am not saying you can't cut stainless on a router with a high-speed spindle, but no machine does everything and those materials are on opposite ends of the spectrum.

Now for power. You are limited by the current of your utility, probably 20A max? This comes right out to 2200W. If you don't have better service, there isn't much you can do to get more power (a transformer will double your voltage, but halve your current + losses). If you were to be able to get a 30 or 40A run of 110V, then you would have more power to work with and a transformer could get you to 220V 15-20A.

Hello guys,
if i purchase a more power vfd spindle of 3kw one instead of my original planned 1.5kw one. Will the torque of of it be now sufficient to cut steel when i turn its speed down to 1500-2000rpm on my building
steel frame router machine. How their motor characteristic curves behave at low speed areas, will the torque of more power one get double as well? Thanks.

[mcardoso]

Really depends on the motor's winding although in general, yes you should have more torque. I would try to get that curve from the manufacturer.

[mactec54]

Hello guys,
if i purchase a more power vfd spindle of 3kw one instead of my original planned 1.5kw one. Will the torque of of it be now sufficient to cut steel when i turn its speed down to 1500-2000rpm on my building
steel frame router machine. How their motor characteristic curves behave at low speed areas, will the torque of more power one get double as well? Thanks.

It does not matter which of the high speed spindles you buy they have a minimum speed of 6,000 RPM anything below that speed and you won't cut any thing as they have no torque at the low speeds

There are spindles that are 4 Pole 12,000 max that you could use at lower RPM and they want to be water cooled

But it comes down to your power supply 120v supply you don't have may options and 1.5Kw is the max you can use with a 120v supply

240v is different and you could run a bigger spindles up to the max current ( Amps ) your VFD input amps requirement is

Can you use a 120v to 240v Transformer yes and a lot do but still can't go above a 1.5Kw spindle unless you have a 120v supply that has a lot of Amps

If you live in NA the power supply voltage is 120v/240v for single phase not 110v

[mcardoso]

Mactec, for my curiosity, can you link the 4 pole spindle motors? I looked in the past and couldn't find one, although they would be more desirable for metal cutting in my mind.

[raychar1234]

Hello, Mactec54, knew that, but its existing price is double!! Not really get your meaning of 120V/240V,1.5kw and VFD input issues. I guess it is 4 poles motor other than the usual one 2 poles?

[mactec54]

Hello, Mactec54, knew that, but its existing price is double!! Not really get your meaning of 120V/240V,1.5kw and VFD input issues. I guess it is 4 poles motor other than the usual one 2 poles?

For a starter what is your country's voltage 220v I think if that is your question, NA has a 120v and a 240v single phase power supply not ( 1 ) fixed 220v like you have