Author Topic: Right motors, PSU for CNC mill  (Read 1182 times)

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Offline 3dgeo

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Right motors, PSU for CNC mill
« on: August 08, 2019, 05:57:09 pm »
Hello,

I know this is probably a bit out of topic but I'm making DIY CNC (100x100 modified WorkBee) and don't know what motors should I buy:
Nema23 23HS2430B 3A 112mm 1.7 Kg   OR   Nema23 23HS8430B 3A 76mm 1.2 Kg

Will TB6600 drivers be sufficient for those motors?

I probably will be using standard T8 2mm leadscrew. I want to mill thick aluminum with this CNC.

Thanks in advance.
« Last Edit: September 16, 2019, 03:11:07 pm by 3dgeo »
 

Offline jmelson

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Re: Right motors for CNC mill
« Reply #1 on: August 08, 2019, 07:04:07 pm »
The second motor has half the inductance, which means the same driver at the same DC supply voltage can spin it about twice as fast.
As to which motor provides the desired running torque at the speed you want, that is harder to extrapolate from the given data.  Note that steppers have WAY less running torque that their holding torque rating.  If you can find a graph of running torque for these motors with a specific driver and supply voltage, then you can make intelligent comparisons.

Jon
 

Offline 3dgeo

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Re: Right motors for CNC mill
« Reply #2 on: August 08, 2019, 07:18:42 pm »
As far as I know all similar CNC uses 2nd (smaller) motors, but motors prices are similar enough to consider bigger motors if it will give any additional benefits. I'm thinking that weight might be an issue if I'll go with bigger motors.
To be honest I think both motors have enough torque to do the job.
 

Offline patrick1

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Re: Right motors for CNC mill
« Reply #3 on: August 09, 2019, 08:57:42 am »
cool project,   so are you using the existing control board ?, and adding breakout board aftermarket drivers too accommodate for the larger motors, - if so, - how too you set a larger bed size for the board ?, or can this just be done in the slicer ?
 

Offline 3dgeo

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Re: Right motors for CNC mill
« Reply #4 on: August 09, 2019, 10:43:17 am »
It's not a 3D printer, it's a CNC mill. I'm also making Prusa MK3 clone, tho this is not it.
For now as a control board I'll use any compatible Arduino I have on hand and connect it directly to stepper drivers, later I want to make my own control/driver board with advanced drivers, like Prusas printer has, but beefier so they can drive Nema23.
Looks like there is no CNC mill board with advanced drivers like that, so this might be a good product to sell as well.
 

Offline larrybl

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Re: Right motors for CNC mill
« Reply #5 on: August 09, 2019, 01:23:27 pm »
Search YT for "This old Tony" He built a CNC from scratch and goes over a lot of the details involved.
 
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Online langwadt

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Re: Right motors for CNC mill
« Reply #6 on: August 09, 2019, 01:51:44 pm »
It's not a 3D printer, it's a CNC mill. I'm also making Prusa MK3 clone, tho this is not it.
For now as a control board I'll use any compatible Arduino I have on hand and connect it directly to stepper drivers, later I want to make my own control/driver board with advanced drivers, like Prusas printer has, but beefier so they can drive Nema23.
Looks like there is no CNC mill board with advanced drivers like that, so this might be a good product to sell as well.

I made this but I doubt many would pay a price for it that makes worth the effort of making and selling
 

Offline David Hess

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Re: Right motors for CNC mill
« Reply #7 on: August 09, 2019, 03:44:49 pm »
I would use the larger motor.  The supply voltage can always be raised if necessary to improve high speed torque.
 
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Offline patrick1

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Re: Right motors for CNC mill
« Reply #8 on: August 09, 2019, 04:11:27 pm »


I made this but I doubt many would pay a price for it that makes worth the effort of making and selling
[/quote]

Great Piece of work.    but your right, i would not want too buy one... or rather i would, but its like *i wont make my own drill or vacuum cleaner.... *      ... so little of the learning is widely applicable too what i do...  i would get more out of giving you my heart felt congratulations,     and continue with perpetual motion builds ;-D
 

Offline SparkyFX

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Re: Right motors for CNC mill
« Reply #9 on: August 09, 2019, 04:48:24 pm »
I probably will be using standard T8 2mm leadscrew. I want to mill thick aluminum with this CNC.
What shouldn´t be underestimated is that Aluminium (in general, there are several variants with vastly different properties) is "best" cut with a single flute cutter (given there is no flood cooling that washes chips out of the cutter and on a small machine), which results in higher cutting force per revolution should you aim for normal/higher feedrates. Depending on the cutter you also might need to cut deeper to actually get a working result, the rake angle for alu is steeper than e.g. steel, so experience from working with steel on bigger machines might not be comparable.

Which means for the positioning motors: as big as you can get and highest torque at lower speed. You need the high speed only for the rapid moves, where no cutting forces will slow the machine down. For deep cuts in alu you need a rigid machine or at least a closed loop control, losing steps ruins the experience and work otherwise (meaning you need to slow the feedrates significantly, where you need the torque)
Support your local planet.
 
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Offline 3dgeo

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Re: Right motors for CNC mill
« Reply #10 on: August 12, 2019, 11:49:10 am »
I made this but I doubt many would pay a price for it that makes worth the effort of making and selling

Pff, if you don't sell you will never know, put few on tindie and you will see.
I want to make commercial grade board with all the bells and whistles, but only time will tell if I do...

What drivers did You use?
Is that a "mega2560" chip? If so I don't understand why people still use that chip cos there are many way cheaper and way more powerful alternatives.

I would use the larger motor.  The supply voltage can always be raised if necessary to improve high speed torque.

OK, thanks, +1point goes for larger motors

What shouldn´t be underestimated is that Aluminium (in general, there are several variants with vastly different properties) is "best" cut with a single flute cutter (given there is no flood cooling that washes chips out of the cutter and on a small machine), which results in higher cutting force per revolution should you aim for normal/higher feedrates. Depending on the cutter you also might need to cut deeper to actually get a working result, the rake angle for alu is steeper than e.g. steel, so experience from working with steel on bigger machines might not be comparable.

Which means for the positioning motors: as big as you can get and highest torque at lower speed. You need the high speed only for the rapid moves, where no cutting forces will slow the machine down. For deep cuts in alu you need a rigid machine or at least a closed loop control, losing steps ruins the experience and work otherwise (meaning you need to slow the feedrates significantly, where you need the torque)

Well, I can get even bigger motors, but I thin that would be overkill for machine like this. Every workbee I've seen uses smaller motors.

+1point goes for larger motors

Well, I guess in the end bigger motors won :)
 

Online langwadt

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Re: Right motors for CNC mill
« Reply #11 on: August 12, 2019, 12:12:56 pm »
I made this but I doubt many would pay a price for it that makes worth the effort of making and selling

Pff, if you don't sell you will never know, put few on tindie and you will see.
I want to make commercial grade board with all the bells and whistles, but only time will tell if I do...

What drivers did You use?
Is that a "mega2560" chip? If so I don't understand why people still use that chip cos there are many way cheaper and way more powerful alternatives.

stm32f407 and powerstep01 drivers

 

Offline 3dgeo

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Re: Right motors for CNC mill
« Reply #12 on: August 12, 2019, 01:14:38 pm »
stm32f407 and powerstep01 drivers

Wow, those are really nice drivers.
At what current You are using them and do they become hot after a while with that current?
 

Offline Mechatrommer

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Re: Right motors for CNC mill
« Reply #13 on: August 12, 2019, 02:59:03 pm »
fwiw... 6040 frame is coming my way... the first bit of pieces i bought for this project was the 500W spindle with psu and few collets acc 2 years ago, and then few NEMA23 and TB6600 drivers. i wont know how they fair up or if they even working, because i never try, they just stayed in the storage all this years. others acc such towline, cables etc also ready, its only which control board that i'm going to use. did a research on the control SW, Mach3 needs payment to get full version license, so does the TeeksCNC? or what the name was, i think can find the free OSS version if i search harder. not really a big deal, i think can mod RepRAP workflow to work with a CNC. i thought i can build my own sturdy table for this, but thinking i dont have necessary tools and accuracy to build one, and i have to buy backlash free threads, bearings, heavy metals for table top or specialized grade A aluminium frame etc thats going to cost me money anyway, so after 2 years of dreaming i just bought the 6040 frame from aliexpress, now i think i've spent 80-90% of the cost, it should be near before i can complete my CNC project.. maybe in the next 1-2 years? ;D my incomplete gigantic 3d printer is there standing outside collecting collosal amount of dust for many more years waiting to be resumed :palm: with this post, this thread is now subscribed... ymmv.
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Online langwadt

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Re: Right motors for CNC mill
« Reply #14 on: August 12, 2019, 04:47:19 pm »
stm32f407 and powerstep01 drivers

Wow, those are really nice drivers.
At what current You are using them and do they become hot after a while with that current?

as far as I remember 4-5A, they get no hotter than you can keep a finger on them so maybe 60'C
 

Offline 3dgeo

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Re: Right motors for CNC mill
« Reply #15 on: August 12, 2019, 05:37:24 pm »
... with this post, this thread is now subscribed... ymmv.

 :-DD That's the way to subscribe to thread...  :-DD
I really hope I'll build it faster, I have mine designed with 3D, so all I need to do is buy/cut parts and add them together...
I contacted bigger motor seller and asked if he can sell outside of Ebay, Ebay collects way more money then original price is stating and there is no one to ask why – I've had enough with that cap, I'm not buying directly from Ebay anymore...
C and other beams I'll buy from Greece, they sell them cheaper than China and ships them way cheaper and faster.
I'm considering These Ball screws instead of regular lead screws, but I doubt I can fit them without changing the design.
Also I haven't decided on software yet, and for a mill I think 500W will be a bit weak, I'll probably go with 1.5KW.

as far as I remember 4-5A, they get no hotter than you can keep a finger on them so maybe 60'C
I'll probably go with them as well, they look really good on paper.
Mind sharing Your board design?  ::)
« Last Edit: August 12, 2019, 05:41:56 pm by 3dgeo »
 

Online langwadt

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Re: Right motors for CNC mill
« Reply #16 on: August 12, 2019, 08:17:31 pm »
... with this post, this thread is now subscribed... ymmv.

 :-DD That's the way to subscribe to thread...  :-DD
I really hope I'll build it faster, I have mine designed with 3D, so all I need to do is buy/cut parts and add them together...
I contacted bigger motor seller and asked if he can sell outside of Ebay, Ebay collects way more money then original price is stating and there is no one to ask why – I've had enough with that cap, I'm not buying directly from Ebay anymore...
C and other beams I'll buy from Greece, they sell them cheaper than China and ships them way cheaper and faster.
I'm considering These Ball screws instead of regular lead screws, but I doubt I can fit them without changing the design.
Also I haven't decided on software yet, and for a mill I think 500W will be a bit weak, I'll probably go with 1.5KW.

as far as I remember 4-5A, they get no hotter than you can keep a finger on them so maybe 60'C
I'll probably go with them as well, they look really good on paper.
Mind sharing Your board design?  ::)

not really, but you are looking at +$100 worth of parts, a 4 layer board, you will also need a stencil
and because of some quirks in how the drivers are controlled it only works with my port of GRBL

So I don't think it would be very useful
 

Offline 3dgeo

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Re: Right motors for CNC mill
« Reply #17 on: August 12, 2019, 11:22:59 pm »
not really, but you are looking at +$100 worth of parts, a 4 layer board, you will also need a stencil
and because of some quirks in how the drivers are controlled it only works with my port of GRBL

So I don't think it would be very useful

Over 100?  ??? What is so expensive?  :o Driver chips – 9 buks a pop, 4layer PCB like 10-15buks a pop, MCU 5/pop, so far  60. Passives and connectors are not that expensive, or I'm missing something? You don't need stencil, can hotair it without it easily.

Tell me more why you picked that MCU, 82 IO 512K mem, 192K ram, 168Mhz seems a bit overkill if you ask me... Why simple STM32F103 is not enough? P.S. dam, LCSC cranked price on those, sad times.....

BTW, how hard would be to integrate ESP32 as an MCU? I'm talking about software side, hardware wise shouldn't be hard at all. That BT or WIFI in CNC would be very cool....
 

Online langwadt

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Re: Right motors for CNC mill
« Reply #18 on: August 13, 2019, 12:29:32 pm »
not really, but you are looking at +$100 worth of parts, a 4 layer board, you will also need a stencil
and because of some quirks in how the drivers are controlled it only works with my port of GRBL

So I don't think it would be very useful

Over 100?  ??? What is so expensive?  :o Driver chips – 9 buks a pop, 4layer PCB like 10-15buks a pop, MCU 5/pop, so far  60. Passives and connectors are not that expensive, or I'm missing something? You don't need stencil, can hotair it without it easily.

Tell me more why you picked that MCU, 82 IO 512K mem, 192K ram, 168Mhz seems a bit overkill if you ask me... Why simple STM32F103 is not enough? P.S. dam, LCSC cranked price on those, sad times.....

BTW, how hard would be to integrate ESP32 as an MCU? I'm talking about software side, hardware wise shouldn't be hard at all. That BT or WIFI in CNC would be very cool....

if you are not buying china specials and only building one connectors/passives and enclosure adds up, even from jlpcb etc. PCBs is double that since you can't get less than 5 and if you don't want to wait add the same for shipping

sure you can hot air almost anything, but the powerstep is not a your average package and if you screw it up the board is junk

I used the mcu because I use it in other projects and on a one-of it would be pointless trying so save a few dollars on the mcu

there's a connector for an esp-01, considering all the other things that can go wrong on a CNC I wouldn't want  to share cpu with a wifi stack, I'm not even sure I'd want wifi

 

Offline 3dgeo

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Re: Right motors for CNC mill
« Reply #19 on: August 13, 2019, 02:02:36 pm »
if you are not buying china specials and only building one connectors/passives and enclosure adds up, even from jlpcb etc. PCBs is double that since you can't get less than 5 and if you don't want to wait add the same for shipping
Maybe, not gonna argue with that. But if You would make them in bulk price is way less than 100, one offs is always very expensive.

sure you can hot air almost anything, but the powerstep is not a your average package and if you screw it up the board is junk
Can't imagine how bad you should screw it up to make board useless :) Just watch Lous Rossmann, that dude do crazy stuff with boards and don't screw them up, the secret is to use enough flux  :-DD

I used the mcu because I use it in other projects and on a one-of it would be pointless trying so save a few dollars on the mcu

there's a connector for an esp-01, considering all the other things that can go wrong on a CNC I wouldn't want  to share cpu with a wifi stack, I'm not even sure I'd want wifi
EPS32 has two cores, on for WIFI stuff other for user code, so it should be a variable option.
Anyway, it's a bit too early to talk about control board, first I have to make frame itself :) Tho I'm very thankful for letting me know about those awesome drivers. I was gonna use 3A ones, was't happy about their amperage, but they also had SPI, stall detection and other fancy features.
 

Offline 3dgeo

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Re: Right motors, PSU for CNC mill
« Reply #20 on: September 16, 2019, 03:56:49 pm »
I'm back again to nag more  :-DD this time abut PSU.

According to this stepper PSU guide I made some calculations and got these numbers:
Bigger motors 83V, smaller 60V @8A

I can make my own PSU from thransformer, but looks like making it will be more expensive than just to buy something like this puppy: HRPG-1000-48 (21A).
I know this is a way overkill, but it's still cheaper than to build my own PSU from transformers (prove me wrong).
I can overvoltage this PSU to 56V and drive smaller motors very close to their limits or bigger motors still far from heirs, tho should I worry about back EMF with this PSU?

Using this voltage it looks like cheap drivers will not cut it – TB6600 only up to 45V...  :-\

Do numbers above look OK or I missed something? What is recommended "distance" from max voltage (I'll probably go with bigger motors)?

Share your PSU and motors specs please.
« Last Edit: September 16, 2019, 03:58:35 pm by 3dgeo »
 

Offline Mechatrommer

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Re: Right motors, PSU for CNC mill
« Reply #21 on: September 16, 2019, 08:44:14 pm »
or I missed something?
you probably missed that most people in google build CNC with TB6600 and NEMA23.. unless you want to cut high speed steel, then you'll need a lot larger stepper and driver and PSU, good luck building frame for it. ymmv.

Share your PSU and motors specs please.
i also missed that most people use 24V PSU to power NEMA23 through the TB6600 (40V max), i have few 12V PSU unit bought earlier for the giant 3d printer project, but forgot that i have no 24V PSU in stock, so i'm ordering just few days ago from aliexpress, the 41A version, $40+ cheap i hope i'll get better than what i paid for :P am also ordering this, just in case it will do any good?



i always been meaning to have a proper lathe, maybe this should do the trick? i'm aiming for maximum 5 axis utilization, now i have more nema23 and tb6600 than needed (spare parts) just need to figure out later what fw-sw controller-cam toolchain that i'm going to use, diy gcode scripter comes to mind, dreaming and dreaming. i'm planning to utilize old marlin fw that was designed for 3d printer, so i have to make a converter or emulator board to turn spindle RPM close loop control into a plastic squirter's nozzle's heater's temperature feedback, highly experimental, highly unprovable, not yet. pcb already sent to seeedstudio yesterday, after days of laying out traces until the eyes blurred due to lack of sleep, no word from swmbo she got used to it i guess. thought i have to put this project upfront since many other projects will require this. without this i have to do the hardwork again of handsaw cut and backpain, with this machine working, the rest should be alot easier, i hope.

some of the parts gathered so far, after 2 years or more of dreaming.... maybe the better place for discussion and collecting intel is cnczone or reprap cnc...
« Last Edit: September 16, 2019, 08:48:56 pm by Mechatrommer »
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Offline 3dgeo

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Re: Right motors, PSU for CNC mill
« Reply #22 on: September 17, 2019, 01:36:44 am »
I'm aware that most people uses TB6600 and NEMA23, that was my plan as well. Tho I want to do it "properly", but as usual – my knowledge on the matter is not sufficient.
Those calculations looked kinda strange – bigger motors rated for 1.6 Ohms/phase, so 3A * 1.6 Ohms is 4.8V, so whats the point to use high voltage PSUs? 12V with 3A current limit should be fine...? :-//
I don't want to cut steel, tho it should be able to cut aluminum.

i'm ordering just few days ago from aliexpress, the 41A version, $40+ cheap i hope i'll get better than what i paid for :P am also ordering this, just in case it will do any good?

What comes to PSU purchase – this is the only part I'm not brave enough to buy from Aliexpess, I rather go with well known brand purchased  from well known distributor. I'm not trusting my shop or home to a cheap PSU knockoff from Ali even if I'll have to pay 10 times more.
I've seen "AVE" used similar "lathe" – if it's good for him it should be good for everyone  ;D Actually this is 4 axis (not a lathe) – it's purpose to make precise "slow" movements (that's why stepper is used). Lathe purpose is to spin fast, relatively speaking rotation precision doesn't matter for lathe.
Sadly, I have no knowledge on 4 or 5 axis milling, solid 3 axis mashine will be plenty for me for a while  ::)

some of the parts gathered so far, after 2 years or more of dreaming.... maybe the better place for discussion and collecting intel is cnczone or reprap cnc...

Looks solid machine, tho that mill looks way underpowered?  :horse:
And no, I think this is a better place, cos I have questions on electrical part, not so much on a mechanical.
« Last Edit: September 17, 2019, 01:42:00 am by 3dgeo »
 

Offline Mechatrommer

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Re: Right motors, PSU for CNC mill
« Reply #23 on: September 17, 2019, 05:07:37 am »
I'm aware that most people uses TB6600 and NEMA23, that was my plan as well. Tho I want to do it "properly", but as usual – my knowledge on the matter is not sufficient.
Those calculations looked kinda strange – bigger motors rated for 1.6 Ohms/phase, so 3A * 1.6 Ohms is 4.8V, so whats the point to use high voltage PSUs? 12V with 3A current limit should be fine...? :-//
i think your calculation is for stall condition, and ignoring the wiring resistance, mosfet Vds loss in the driver circuit, and other losses here and there in the whole system. i wont bet 5V PSU will give me enough juice to deal with the losses. you may try 12V but since everybody in the net is going the 24V route, so getting it at $40 part will not hurt much, it can be a good investment for later project if it turned out not suitable for this job. i already have few 12V PSU to play with, and its also easily available in form of PC ATX PSU sold everywhere locally. mosfets in the stepper driver maybe happy with higher voltage, who knows? about trusting the china design, well maybe there's few caps and mosfets need replacement in case of smoke comes out, but i'm not going to trust brand name either. i had Gigabyte brand ATX PSU that failed much earlier than no name brand PSU, i have HP (USA?) Z800 server PC workstation coming this way with PSU issues discussed everywhere in the net, so even USA brand is not a bulletproof product. but everybody is free to choose what they like.

Actually this is 4 axis (not a lathe) – it's purpose to make precise "slow" movements (that's why stepper is used). Lathe purpose is to spin fast, relatively speaking rotation precision doesn't matter for lathe.
yes thats why i'm planning to mod it to be connected to a dc or bldc motor later to become a lathe, and also thats why i have to go to the hassle to build a converter circuit to read its rpm to thermistor voltage (close loop rpm control) to make it reprap/marlin compatible, a stepper motor wont need such converter. at first i was eyeing on the "5th axis cnc" in aliexpress, the cheapest version is like this... its wonderful how cheap it is nowadays, if its from USA, its going to be 10X cost more, but with higher quality of course, but whats good it is to hobbiest if its not affordable? but further meditation made me come with a conclusion that it will be more difficult to mod "4th and 5th axis jig" like that to become 4th axis turn machine or lathe. so the vote went to the 4th axis turn machine, should be easier to mod to lathe or add a 5th axis later (after i build some metal rig with 3 or 4 axis CNC).

Sadly, I have no knowledge on 4 or 5 axis milling, solid 3 axis mashine will be plenty for me for a while  ::)
yes its understandable. in fact most people will do great with 3 axis, but i want to do all possibility that i think i will be going to get later while i am at this matter right now.

Looks solid machine, tho that mill looks way underpowered?  :horse:
yes probably so, thats why this is going to be try and error myself, iirc 1.5KW spindle was too expensive for me 2 years ago. at least it should be good cutting or drilling some wood or plastics. the 6040Z frame came with 65mm dia spindle holder, that should be able to hold larger spindle motor, but for now, it is for spare part as i've mounted the 52mm spindle holder that came with the 500W motor earlier.

cheers and best regards,
The Mechatrommer.
« Last Edit: September 17, 2019, 05:09:48 am by Mechatrommer »
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Re: Right motors, PSU for CNC mill
« Reply #24 on: September 17, 2019, 09:07:43 am »
I'm aware that most people uses TB6600 and NEMA23, that was my plan as well. Tho I want to do it "properly", but as usual – my knowledge on the matter is not sufficient.
Those calculations looked kinda strange – bigger motors rated for 1.6 Ohms/phase, so 3A * 1.6 Ohms is 4.8V, so whats the point to use high voltage PSUs? 12V with 3A current limit should be fine...? :-//
i think your calculation is for stall condition, and ignoring the wiring resistance, mosfet Vds loss in the driver circuit, and other losses here and there in the whole system. i wont bet 5V PSU will give me enough juice to deal with the losses. you may try 12V but since everybody in the net is going the 24V route, so getting it at $40 part will not hurt much, it can be a good investment for later project if it turned out not suitable for this job. i already have few 12V PSU to play with, and its also easily available in form of PC ATX PSU sold everywhere locally. mosfets in the stepper driver maybe happy with higher voltage, who knows?

that's fundamental to how stepper drivers work. Steppers are big inductors so the higher the driver voltage the faster you can reach max current, iow the higher the voltage
the faster you can step without losing all your torque. I'd say 24V is a bare minimum

https://www.electrocraft.com/img/products/stepper/torque_TPP23-90A10.png


 
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