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Right motors, PSU for CNC mill
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3dgeo:
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.
Mechatrommer:

--- Quote from: 3dgeo on September 16, 2019, 03:56:49 pm ---or I missed something?

--- End quote ---
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.


--- Quote from: 3dgeo on September 16, 2019, 03:56:49 pm ---Share your PSU and motors specs please.

--- End quote ---
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...
3dgeo:
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.


--- Quote from: Mechatrommer on September 16, 2019, 08:44:14 pm ---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?

--- End quote ---

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  ::)


--- Quote from: Mechatrommer on September 16, 2019, 08:44:14 pm ---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...

--- End quote ---

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.
Mechatrommer:

--- Quote from: 3dgeo 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...? :-//

--- End quote ---
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.


--- Quote from: 3dgeo on September 17, 2019, 01:36:44 am ---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.

--- End quote ---
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).


--- Quote from: 3dgeo on September 17, 2019, 01:36:44 am ---Sadly, I have no knowledge on 4 or 5 axis milling, solid 3 axis mashine will be plenty for me for a while  ::)

--- End quote ---
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.


--- Quote from: 3dgeo on September 17, 2019, 01:36:44 am ---Looks solid machine, tho that mill looks way underpowered?  :horse:

--- End quote ---
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.
langwadt:

--- Quote from: Mechatrommer on September 17, 2019, 05:07:37 am ---
--- Quote from: 3dgeo 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...? :-//

--- End quote ---
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?

--- End quote ---

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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