[ely862me]

Hi guys ! Thank you everyone for pushing and pulling things around !

I am a complete newbie and if you see something displaced with my thinking or else, please, feel free to correct me.

I am building a cnc machine and I came closer to mount my spindle on the Z axis. I have bought the spindle from Germany, but it is made in Italy. It is a 21 years old Giordano Colombo spindle. It is a 3phase 220v(5hp)-330v(7hp),12A,12000rpm-18000rpm at 200Hz and 300Hz motor. It is like this one Giordano Colombo Spindle Motor RV 90.2.SB CNC Mill Engraver Router w/ Set Collet . The seller told me the motor runs alright.

I have bought for this spindle a frequency inverter Yaskawa V1000 -- CIMR-VCBA0018BAA , 200 V, CT: 17,5 A / 4 kW, IP20.

I have managed to set them right I believe(but I am not sure) and I discovered that the rotor is getting hot, no matter how fast the motor works. In about 30 60 seconds it starts to heat up. Initially I thought the problem are the bearings, but then I let it to heat up a bit in the bearings cage and I dismantled it quick and I have found out that the rotor was the one that built up heat and not the bearings.

Has any of you used an Yaskawa drive ? Maybe some settings are bad, I have successfully performed the Auto-Tuning and it runs quite alright, but from time to time It sounds like the speed gets lower and rise up again.Thing is on the display, the V and the Hz and the A are constant when this happens. Without load the motor eats up 5.5 A .

Some said my rotor is in shortage, but there are no visible cracks in the aluminum cage and no color differences on the surface of the core.

[ely862me]

Update..

The motor was/is OK. After running a few hours, it only gets warm. I guess it needed a brake-in in a lower rpm and after that the temperature settles.

It seems a bit weak, with a 20mm end mill and eating 5-6mm of wood, the rpms drop quite a bit from 12000.


You can read(romanian only) an see(not much) the machine on a local forum. Router cnc 3/4 axe - Pagină 5 - Hardware CNC - Forumul Electronistilor

[Al_The_Man]

This is why spindles of this nature are often water cooled, due to the amount of iron in the rotor, the rotor is very low inductance which causes heating at lower rpm, this does not show up so much at higher rpm, but can limit the minimum operating frequency/rpm.
Al.

[ely862me]

Do you guys know why at low speeds(6000 rpm) this motor is so underpowered ? I was cutting aluminum with a depth of 0.5mm with a 6mm 4 theet endmill and the motor died on me .. I was like :O .. How can I help it ?

Attachment 321780

It moved my table like 2cm until I managed to stop the machine. Lucky me it is still an improvised table otherwise goodbye endmill.

[mactec54]

Do you guys know why at low speeds(6000 rpm) this motor is so underpowered ? I was cutting aluminum with a depth of 0.5mm with a 6mm 4 theet endmill and the motor died on me .. I was like :O .. How can I help it ?

Attachment 321780

It moved my table like 2cm until I managed to stop the machine. Lucky me it is still an improvised table otherwise goodbye endmill.

If this is an air cooled spindle it can't run that slow, it would overheat, and stall very easy at those speeds, this high speed spindle will have very low torque also at this speed, what parameter settings do you have in the VFD, you may not have it set correct as well, even if you have the correct Parameters set, this spindle can not run that slow, air cooled usually can run around 4,000 RPM less the what the Max RPM are

[ely862me]

Yes, it is air cooled and the parameters are alright, I checked them a dozen times.
My settings are at 220v(5hp) 12A,12000rpm at 200Hz . At the time I think I was running it at about 6000 rpm. If I can't run it lower it means I can't mill aluminum ? As I hear aluminum has to be milled at low rpm. I initially ran it at 12000 rpm and it melted at some points and the surface finish was mainly porous.
Thanks !

[A_Camera]

Do you guys know why at low speeds(6000 rpm) this motor is so underpowered ? I was cutting aluminum with a depth of 0.5mm with a 6mm 4 theet endmill and the motor died on me .. I was like :O .. How can I help it ?

Attachment 321780

It moved my table like 2cm until I managed to stop the machine. Lucky me it is still an improvised table otherwise goodbye endmill.

What was the feed rate? Did you try with a two flute? Maybe that would be better. Also, some VFD allows for torque boost at low speed. Check if your VFD has a setting for that and try play with that setting.

[ely862me]

I believe it was 120 mm/min but looking at the screen I think I boosted it at 350mm/min. You can hear how the motor is dying when it goes full cut.
https://youtu.be/b07LcBoAqEY

I will check the VFD manual to see if there is a setting to boost the torque at low speeds.

Thanks !

[mactec54]

I believe it was 120 mm/min but looking at the screen I think I boosted it at 350mm/min. You can hear how the motor is dying when it goes full cut.
I will check the VFD manual to see if there is a setting to boost the torque at low speeds.

If that is the fastest you can run it 350mm/min that is very slow for the RPMs you are running you should be around a minimum of 1000mm/min

The Yaskawa VFD has torque boost, almost all VFD Drives have torque boost, you have to calculate how much that you can give your spindle at the RPM you are running at or you will burn it out, it works on a progressive scale, from what the spindles rated max torque is at max RPM, I think you have an auto torque boost also, which would be your best place to start this you can set by a percentage, which is a lot easier to do, to try this out

[ely862me]

No, that's not the fastest, but since the spindle is dying on this low speed how would it work with a faster feedrate ?

[mactec54]

No, that's not the fastest, but since the spindle is dying on this low speed how would it work with a faster feedrate ?

You add more RPM to suit, then the motor torque will also increase, you have to find where it will work best, without stalling, you could also damage the motor if it keeps stalling, so you don't want this happening

[G59]

As I hear aluminum has to be milled at low rpm.

Not true. Aluminum can be milled at relatively high RPM( over60krpm). The limiting factors are machine rigidity, coolant/lubricant, stepper or servo power of your linear axis, feedrate mm/ipm and spindle horsepower. There's a sweet spot in every machine and it's great when you find it. Get yourself HSM advisor(trial is free for 30 days), plug in your horsepower etc..etc.. and see what it suggest for DOC WOC RPM etc...
You are gonna like the advantage of a high rpm spindle then.

Like Mactec says at 6000 rpm you are going to cook your spindle.

Steel is just not appropriate to attempt with the spindle you have. It's a whole nother ball of wax.

[A_Camera]

I believe it was 120 mm/min but looking at the screen I think I boosted it at 350mm/min. You can hear how the motor is dying when it goes full cut.
https://youtu.be/b07LcBoAqEY

I will check the VFD manual to see if there is a setting to boost the torque at low speeds.

Thanks !

Three more things...

I noticed that you don't use any lubricant. I don't think that's a good idea at all. Try at least to spray it with some soap water.
Use a vacuum cleaner to remove chips. It is not a good idea to mill chips over an over again.
I think that with a four flute end mill you will need more RPM. 6k is not enough, so I'd try to increase the RPM. Once you can comfortably cut with that speed, increase the feed rate and adjust the RPM again to get better results.

I think that if you spray with soap water and vacuum clean the surface you will notice dramatic improvements, even without doing anything else.

[ely862me]

Hi guys,

On the first job I used 12000rpm and a faster feedrate. The chips were a lot smaller I mean almost like wool. I thought, well this doesn't look good. I used some soap water mixed with some oil and it didn't seem to matter much. The problem arised at some cuts where I used a V bit and the material melted behind it(low feedrate or high rpm). Also the finish was a bit porous as of melting.
On the second job, the one you saw on youtube, I used 6000 rpm, and boy what a difference !! The chips were nice and the noise was lower and acceptable, I tried with the soap mixture but didn't seem to care much. On the V bit pass I put some oil on the surface and I also cleaned the areas of chips. When I cut it though I didn't clean it because the sides were clean due to the air from the spindle, but indeed in the full cuts were some chips left.

In the future I will try to see about the VFD torque boost, I will try at least 8000rpm and also a better feedrate. At the moment I don't have a vacuum cleaner for it but it's on the shopping list. Would a 6mm one flute endmill work for cutting aluminum ? I have one that I use on wood. It also make a lot of high noise, as it is quite long-about 50mm active cut. Since these are my first attempts I assume that in time I will learn about how's and what's ..
Thank you !

[Andreiir]

For a 1 flute u need more rpm from spindle , i mean about 16000 or 20000 rpm , and there gone be a nice finish .
With 4 flute u cut steel and other low rpm metals , with 1 , 2 or 3 flutes u can cut wood , plastic , aluminium , the more flute u have the slow rpm u go and more torque u need .
In aluminium u need to be careful because if the bit get too hot then aluminium melts on it and u can't cut more , u need colant or air blower fot that to chill out the bit and material .

[G59]

ely,

here is a link toa free online Feed and Speed Calculator.

FSWizard - Advanced Online CNC Speed and Feed Calculator

Now instead of guessing at things, learn the terminologies and plug the number into the calc. Then implement them into your program.

Have fun.

[ely862me]

For my 6mm 4flutes endmill wants 10000rpm and 3500mm/min with a DOC of 1mm and a WOC of 1.2mm.. WOW I barely cut wood like that .. I will try that although my setup might not be sturdy enough for it!!

Cheers for the Calculator !

Thanks for the info Andreiir !

[ely862me]

The motor has 12k rpm at 220v at 200hz, and 18k rpm at 330v at 300hz, my house doesn"t have 3 phase 380v, only 220v. Can i increase only the frequency?
I tried increasing voltage at 240v output the vfd accepted the value but was not constant going 219-239v, tried with 240hz as well.

If I increase frequency to 300hz y will have about 15000 rpm, but no torque because i am not keeping v/hz ratio, correct?

"Correction added from 400v to 330v and 400Hz to 300Hz. "

[mactec54]

The motor has 12k rpm at 220v at 200hz, and 18000 rpm at 400v at 400hz, my house doesn"t have 3 fase 380v, only 220v. Can i increase only the frequency?
Tried increasing voltage at 240v output the vfd accepted the value but was not constant going 219-239v, tried with 240hz as well.

If i increase frequency to 300hz y will have about 15000 rpm, but no torque because i am not keeping v/hz ratio, correct?

You can only use the Frequency that is rated for your motor, there are may different, spindle motors, and they all have there own spec's that you have to use, or you will smoke your spindle motor, so what is the max spec's of your motor

[ely862me]

Please see the image attached to my previous post. Thank you !