Question:
It uses a step of 0.2 ° that should mean that 1600 steps per revolution are the steps that are needed to complete full circle , which is actually the speed and at that speed motor has a moment of 4.5Nm without gearbox? Is this correct ?
Basically, i want to calculate how much time would i need to move robot head from position 0 to 1000 cm ( 1 meter ). At fast speed possible and with defined torque....
Robot is actually one big pick and replace machine that is used to sort materials from conveyor track.
This working model that am using now, has :
Upper arm --> 38 cm --> from motor shaft to joint
Lower arm --> 90 cm --> from upper joint to extruder
The system is rotary delta and it's controlled by one ready made 3d printer board.
Am sending data from our vision system to this board.
The 3d board is expanded with one additional board and i hooked stepper drivers to this extension.
In other words, at the moment, i can power motors up to 60V. Motor that am using right now is :
IMHO, problem is that i dont have option to hook up encoder to this 3d board.
When the robot is running ( move from position X to Y , pick up , return to start position ) it looks like its missing steps or power ( at highest speed, which would be 1 meter length in 1 second ).
After let's say 10 moves, extruder head is lowered down and robot starts to hit the conveyor belt, like it looses power.
Am not quite sure why is this happening because whole construction has only 1,5 kg and this should not be any problem for those motors.
1.5kg on a 90cm arm section is a lot of problem for a stepper motor! You need to calculate the required
torque and look this up in the torque/speed graphs of candidate motors - I can see now why you wanted
gearing.
Any backlash however is a big deal on arms with such a long throw, so this is normally the kind of
system that requires a servomotor and high resolution encoder, as accuracy of minutes of arc is
needed, beyond a stepper's abilities.
So either anti-backlash gears, or servomotor, would be the way to go for accurate control of such a
system.
Torque scales badly - doubling the size usually means the required torque goes up 8 fold or more due
to the moment of inertia becoming the limiting factor.
1.5 kg is the weight of all three arms so weight per motor would be around 500 grams.
I have added 1 additional kg directly to extruder head ( just for test ) and it works but only if
the motor is in constant motion. As soon as it stops and start again, extruder head drops down....
I was thinking about servo motor too but i dont know if this is supported by my 3d printer board.
But you mentioned zero backslash gear.....Do you have some link ?
Could this plus some encoder, solve the problem ?
500g at 90cm is still a lot of MoI. Have you done the calculations for torque needed to overcome
gravity forces and to provide angular acceleration? That's the first step to sizing motors and gears.