I fixed a 15g weight on a 40cm aluminum bar. This bar is fixed perpendicular to the axis of my Nema 17 stepper motor and my weight rotates very well, with good acceleration and at high speed.
I would like to add a reducer to rotate a mass of 80 g or, 120 g if possible, thanks to a reducer, without my NEMA17 stalling and keeping its acceleration (2.5 turns-2) and speed (2.5 turns. ) The last two parameters being managed by a Teensy (Arduino with a much faster clock), it should not be a problem of any multiplier by 5, if I have a reduction of 5: 1.
My nema 17 does 200 steps / turn, I manage my motor in 6400 step / round (i.e. 32 * 200 to have less vibration and more coupling). But whatever.
Do you think these reducers are easily mountable and will do the trick? Which reduction to choose?
The motor axis of my nema 17 is 5 mm, I would like to be able to couple a reducer which also has its 5 mm motor axis.
The motor shaft is connected to the end of the bar. Motor shaft is horizontal.
I need the good power, thus to know the ratio of reduction in order to change the weight from 15g to 80 or 120g .Also I would like to have a motor axis of the reducer of 5mm or find an idea to transform the motor axis of the reducer from 8mm to 5 mm for example
Well, my maths (questionable) says about 53Ncm for a 30g bar with a 120g mass 40cm from the shaft center, so you would need at least 1.5:1 torque increase / speed decrease. But remember, stepper motor torque falls off as speed increases. Find the speed / torque curve for your motor.
Not sure it can be done - the requirement to retain the speed and acceleration, but increase the mass means more power is needed, you can't increase power with a reduction gear. However perhaps the setup is already over-powered enough?
Those aren't angular accelerations or speeds, which are measured in rad/s/s and rad/s (or rpm).
Keep in mind that reducer is not precise like stepper motor is, error is around 1 degree usually by documentation. Higher precision are much more costly. Dimentions and weight of reducer make me think nema 23 stepper could be better option for you (if have a driver which have enough current). I tried several stepper motors and their holding torque in datasheet were always 2.5-3 times higher than measured on practice, for example when i expected 18 kgcm (1.8 Nm) it was just around 6 kgcm measured with scales at very low rpm. Some bad steppers were even worst. Anyway back to reducer gears - they can be connected differently tot he shaft of stepper, some steppers are designed to work with reducer, so they need specific reducers, but in your case reducer should be compatible with BLDC motors (or for the servo motors if nema 57 dimentions), so for usual cylindrical shaft. If reducer is correctly picked up, then it's easy to mount, don't worry.
Those motors can be controlled with a PID aren't they?
Does it exist BDLC motors with good Holding Torque (N.cm Min) and Detent Torque (N.cm Max) for 30$ max?
I mentioned BLDC motors to choose reducer properly, not cause you have to choose BLDC instead of stepper. Yes, BLDC can be very powerful, but they more costly than steppers and need another driver with three phases and closed loop to be precise as steppers (but i just used driver for three phase steppers 3DM683). Also BLDC are for torque at high rotation speeds, while steppers for low speeds. So most likely BLDC is not for you, unless you try to spin stepper motor very fast, like 500 rpm and more but to keep high torque.
Here is how generic reductor looks like https://aliexpress.ru/item/32836244524.html?sku_id=65029031742&spm=a2g2w.productlist.0.0.b6fa5b87lWW995
The hole for shaft connects tightly with the screw. If description says reducer compatible with servo or bldc then it must be right for you. If just with steppers, must check that back side of it.
And here is stepper for cylindrical (much cheaper reducer type) and as you can see it's shaft is not standard, so if you buy wrong reducer for such stepper, will not be able to connect it: https://imgur.com/a/2Woac5A
The price of reductor is high enough, cheaper to get nema 23 stepper, even 30 kgcm torque one will cost around the same as planetary reducer gears or less.
it is like 7 times more Holding Torque. So I can theoretically put a weight 7 times more heavy?
I'm a bit hurry, and I don't have time to change all my setup because I have ten motors to change and the system to attach the light on the bar, and the bar on the motor.
That why I would like to try this model of reducer very cheap.
Do you think it is suitable to my nema 17?
Not exactly. As i mentioned earlier those numbers from the datasheet are incorrect for real things, so the motor with 30 kgcm holding torque on practice should give only 10-12 kgcm usable torque, so for your 40cm bar it's just 0.2-0.3 kg weight to rotate at low speed.
Anyway, if you have many motors, replacing them is not an option.
Reducer from that link don't have good picture of back side, so i can't tell for sure. Especially confusing small gear on the main picture in the corner and pink arrows point to text that 3 and 5 mm diameter shafts used, so i suppose that small gear is an adapter mounted on the shaft of stepper motor. I didn't see such reductors and can't tell how they work. Try to find youtube videos where people show similar or other products which looks the same but do have good picture of the back side of it.
I'm saying with more mass you need more torque and thus power. Torque to overcome rotational inertia scales with MoI (moment of inertia) and angular acceleration, increasing mass increases MoI, so torque will go up.
That formula you give is wrong:
power = torque x angular velocity, SI units: watts, newton-metres and rad/s respectively. The conversion factor between rpm and rad/s is 30/pi, which is about 10, the 9550 is 100 times too large.
Tip: use SI units throughout and you won't make crazy scale errors like this.
Hi Mister.
Stepper motor torque falls off as speed increases. If my motor goes to 2.5 round/s, is this planetary gearbox will keep enough power to make turn a 120g mass 40cm?
I have a got a nema 17 with a torque of 40Ncm.
Do you have the speed / torque curve of this planetary gearbox ?
