This view is also important:
[attachment 17113 Armassembly5.jpg]
On the math side, as you know, the relationship between the lengt of the arm (the distance of the variable side of the triangle) and the angle we control is not linear, so, every turn of the motor changes the lenght at a different rate according to the angle at the moment, being 90 degres the "worst" case for resolution and the best for speed and 180 degrees being the opposite. How are you dealing with that? I'm using a final gearing of 3 to 1 that seems too low to overcome the loss of resolution at 90 degrees, where a 1.8 degree step changes the lenght more than 1mm!
Here is a graph (length change on the vertical axis and angle of the arm on horizontal axis):
[attachment 17114 Linearity.png]
What is your final pulley reduction? Is there any modification to the firmware to addres this issue? I also figured out the inverse kinematics of my model in MS Excel and learned that if I increase the gearing the resolution will be higher, but aproaching 180 and 0 the speed will be very very low. Do you plan to work your printer on certain restricted volume? I plan to add a 4th degree of freedom in the form of a variable height printing surface, so I can work the robot arms on an optimal angle.
I was dreaming, what if you could decouple the arms from the motors at the extended position and simultaneously coupling them to the base, so it can be lowered with no extra motors? I will probably start a new thread on that.
Keep the good work!
[attachment 17113 Armassembly5.jpg]
On the math side, as you know, the relationship between the lengt of the arm (the distance of the variable side of the triangle) and the angle we control is not linear, so, every turn of the motor changes the lenght at a different rate according to the angle at the moment, being 90 degres the "worst" case for resolution and the best for speed and 180 degrees being the opposite. How are you dealing with that? I'm using a final gearing of 3 to 1 that seems too low to overcome the loss of resolution at 90 degrees, where a 1.8 degree step changes the lenght more than 1mm!
Here is a graph (length change on the vertical axis and angle of the arm on horizontal axis):
[attachment 17114 Linearity.png]
What is your final pulley reduction? Is there any modification to the firmware to addres this issue? I also figured out the inverse kinematics of my model in MS Excel and learned that if I increase the gearing the resolution will be higher, but aproaching 180 and 0 the speed will be very very low. Do you plan to work your printer on certain restricted volume? I plan to add a 4th degree of freedom in the form of a variable height printing surface, so I can work the robot arms on an optimal angle.
I was dreaming, what if you could decouple the arms from the motors at the extended position and simultaneously coupling them to the base, so it can be lowered with no extra motors? I will probably start a new thread on that.
Keep the good work!