Suggestion for servo motor --> big delta robot

Arnix · 27 Jan 2019, 22:45

after gearbox. But that is exactly the thing i would like to discuss. Please look at text below..
@Edkirk
Great info. Thank you. I will contact them tomorrow.
There is one thing that i dont understand with this servomotors...
e.g. if i set 10:1 gearbox and if i get let's say 15Nm on my gearbox shaft, how can i calculate needed RPM and power ? I was looking at calculator that 691175002 suggested but there is bunch of options and i dont know will this work in real time.
;-------------------------------------
Most of the industry motors used for such applications use 500 - 1Kw motors which is a lot , so i can not understand the purposes for such power. As far as i know, pickup speed is "regulated" with servo motor speed and power ? But do i really need so much motor power ? There must be some catch why they are using such strong motors.
;----------------------------------
Btw. yes they are expensive and that's why i would like to find some motor in lower/middle price range, that will do the job.
;---------------------------------
@Edkirk
When we define motor and when i buy them i will open new topic on how to hook them to duet. I hope you can help me out with that, i dont wont to burn something

Arnix

Edkirk · 27 Jan 2019, 23:10

What are you building a pick and place robot or a 3D Printer?

Arnix · 27 Jan 2019, 23:18

It's pick and place robot. 1,5 meter working radius with optimal 60 pickups per minute. Container is on both sides of the conveyor track and vision system is set to drop to nearest one.

This part is working and at the time, am using steppers for this,
but i would like to implement servos from clearpath.

A.

Edkirk · 27 Jan 2019, 23:47

What type of controller/software are you using? There are various options when using Clearpath Servos, step and direction are well suited for a 3D printer or a cnc router with a controller running a predetermined program using predefined GCode.

RCarlyle · 28 Jan 2019, 03:10

@arnix the reason no one is answering your specific size/power/speed questions is that nobody knows how “picks per minute” translates into speed/acceleration for your system. A pick is not a well-defined load, it’s a performance target. We all have no idea what you need because we don’t know enough about your machine, working loads, tolerance for slower picks when crossing the whole working volume, etc.

The required motor power comes from the max value of (torque * angular speed). You can probably get this from your simulation based on the worst case of picks in many different locations around the working area. Torque in Nm multiplied by speed in rad/sec gives power in watts. If you have the exact ideal gearbox for your application, this wattage is how much motor power you will need. But the farther your gearbox ratio is from ideal, the more you need to oversize the motor to make sure the desired speed/torque point lies within the performance curve for the motor.

Arnix · 28 Jan 2019, 09:50

Good morning..

@Edkirk

at the moment am using stepper motors that are connected directly to duet3d board. So just duet board + 24V power supply + motors. Anyhow, this was just for test. Based on your suggestions (when we switch to servo) I will buy what you think it's necessary to make this project work. Please look at text below where i have described project goals. If i understand correctly, every SD model has all in one ( encoder, controller, driver ) or do i need to buy controller separately ? How did you connect your DUET to servo motors ?

@RCarlyle
That was exact our thinking. Thank you for confirmation !.
Let me run some additional tests so I can discus about this, in more details..

Regarding robot job:

robot will sort colored plastic material (similar as the robot from my first post, but with different material ).
colored object are placed on conveyour track at random order and position
weight of the object is under 100 grams
vision system is done and it's tracking objects in realtime so there is no delay. Objects will be spotted and tracked and if the robot can follow 1 pickup per second routine, everything should work.
tracking diameter is 100 cm.
please look at the robot on my first post. Goal is the same but with different materials and maybe 10% lower speed.

Arnix

dc42 · 28 Jan 2019, 11:39

@arnix said in Suggestion for servo motor --> big delta robot:

@691175002

after gearbox. But that is exactly the thing i would like to discuss. Please look at text below..
@Edkirk
Great info. Thank you. I will contact them tomorrow.
There is one thing that i dont understand with this servomotors...
e.g. if i set 10:1 gearbox and if i get let's say 15Nm on my gearbox shaft, how can i calculate needed RPM and power ? I was looking at calculator that 691175002 suggested but there is bunch of options and i dont know will this work in real time.
;-------------------------------------
Most of the industry motors used for such applications use 500 - 1Kw motors which is a lot , so i can not understand the purposes for such power. As far as i know, pickup speed is "regulated" with servo motor speed and power ? But do i really need so much motor power ? There must be some catch why they are using such strong motors.
;----------------------------------
Btw. yes they are expensive and that's why i would like to find some motor in lower/middle price range, that will do the job.
;---------------------------------
@Edkirk
When we define motor and when i buy them i will open new topic on how to hook them to duet. I hope you can help me out with that, i dont wont to burn something

Arnix

@Arnix, you should avoid putting a gearbox on the output shaft of a servo, because then gearbox backlash will matter. Instead, look for a servo that provides the right combination of output torque (high) and RPM (low), perhaps using a built-in gearbox.

Are you sure you need 15Nm output torque? That's a huge amount of torque, equivalent to accelerating a mass of 1.5kg on the end of an arm 1m long. What is the mass of your effector?

Looking through the Clearpath listing, this one is close to your specifications https://www.teknic.com/model-info/CPM-MCVC-3441S-RLN/. It has 13Nm peak torque at low speeds (you don't need high output shaft speeds in your application). But it's Nema 34 size, so you will have to do some redesign to accommodate it. There is the possibility that it might overheat if you demand high torque from it for too much of the time, although I think that's unlikely unless the effector is massive.

dc42 · 28 Jan 2019, 11:40

PS:

If you do end up needing low backlash gearboxes, I found this company http://www.apexdyna.nl/en/products/.
Does your simulation tell you the peak revs/second for the arms?

Arnix · 28 Jan 2019, 13:14

@dc42
Are you sure you need 15Nm output torque? That's a huge amount of torque, equivalent to accelerating a mass of 1.5kg on the end of an arm 1m long. What is the mass of your effector?

*** we have added additional weight for "just in case" scenario but extruder with vacuum system and load will have at least 1KG. Beside, everything is set for high speed movement and as you know , there is a big difference between moving 1kg load in 10 or in 1 or 0.5 seconds. I hope i am on the right track with this... What do you think ?

Does your simulation tell you the peak revs/second for the arms?
*** max speed is 1 turn per second. Tested working area was 850mm.

A.

dc42 · 28 Jan 2019, 13:20

@arnix said in Suggestion for servo motor --> big delta robot:

max speed is 1 turn per second

So that's 10 turns/sec at the input side of your x10 gearbox. So the step pulse rate at x16 microstepping is 10 * 200 * 16 = 32kHz. Knowing that, you can use the calculator at reprapfirmware.org to determine whether 24V is sufficient to maintain torque at that speed using your current stepper motors.