Hello to everybody,
I'm new to this forum, and except for 2 or 3 posts made on the Nicholas Seward Simpson thread, this will be my first real contribution.
I certainly think Nicholas' design is brilliant and I feel inspired to improve it, although there is not much you can do. Annirak drive is great and I have to confess that I couldn't understand it at first, until I realized that with Annirak geometry you do not control an angle anymore, but a distance, thus, eliminating many non linearity problems. That's a great design!
Then I thought: what is the downside of it? Well, now the non linearity gets swaped to the force, so you can apply less force (or generate more torque to turn the arm) the closer to 180 deg upper and lower arm are, and more force the closer to 90 deg they are(simplifying, I understand there are more things to consider). That really is not a downside, considering the printer doesn't need too much force and that there are 3 arms that very seldomly all will be close to 180 deg. position.
But...I wanted to design something different, closer to the original design of Simpson, by using a rotation driven mechanism and not the Annirak drive (which is great), just for the sake of it.
My idea, at this point, considers using gears to increase torque and translate the mechanical power from the motor to the driven axis. Problem is the non linearity (which N. Seward warned me about with something like: going away from Annirak drive will increase the complexity of the firmware, which is true), but I have an idea to solve that issue:
Using non circular gears at the last reduction step, I mean, gears that can have a variable torque/speed around and can be designed to compensate for the non linearity, working in fact like the Annirak drive but with gears, so I would expect to use the same firmware.
I attached a [very unfinished] image of the design and a sketch of the non circular gears.
What do you think? Of course, all of the gears should to be printed, getting closer to the dream of a completely printed machine. Oh, and the gears may not need to be elliptical. I have to calculate, but probably some excentric circular gears are all I need.
Ahh, backlash. I know that is the main issue with gears, but I am considering preloading the transmission with a rotating spring. I know that this is very likely to work as the arm needs to turn much less that 180 deg. The spring will make the gears touch only on one side of the theet, unless the motor is too quick and the spring couldn't react. I hope I can use it.
Ps: This is just a concept. Details of sizes, positions, bearings and more have to be carrefuly designed.
I'm new to this forum, and except for 2 or 3 posts made on the Nicholas Seward Simpson thread, this will be my first real contribution.
I certainly think Nicholas' design is brilliant and I feel inspired to improve it, although there is not much you can do. Annirak drive is great and I have to confess that I couldn't understand it at first, until I realized that with Annirak geometry you do not control an angle anymore, but a distance, thus, eliminating many non linearity problems. That's a great design!
Then I thought: what is the downside of it? Well, now the non linearity gets swaped to the force, so you can apply less force (or generate more torque to turn the arm) the closer to 180 deg upper and lower arm are, and more force the closer to 90 deg they are(simplifying, I understand there are more things to consider). That really is not a downside, considering the printer doesn't need too much force and that there are 3 arms that very seldomly all will be close to 180 deg. position.
But...I wanted to design something different, closer to the original design of Simpson, by using a rotation driven mechanism and not the Annirak drive (which is great), just for the sake of it.
My idea, at this point, considers using gears to increase torque and translate the mechanical power from the motor to the driven axis. Problem is the non linearity (which N. Seward warned me about with something like: going away from Annirak drive will increase the complexity of the firmware, which is true), but I have an idea to solve that issue:
Using non circular gears at the last reduction step, I mean, gears that can have a variable torque/speed around and can be designed to compensate for the non linearity, working in fact like the Annirak drive but with gears, so I would expect to use the same firmware.
I attached a [very unfinished] image of the design and a sketch of the non circular gears.
What do you think? Of course, all of the gears should to be printed, getting closer to the dream of a completely printed machine. Oh, and the gears may not need to be elliptical. I have to calculate, but probably some excentric circular gears are all I need.
Ahh, backlash. I know that is the main issue with gears, but I am considering preloading the transmission with a rotating spring. I know that this is very likely to work as the arm needs to turn much less that 180 deg. The spring will make the gears touch only on one side of the theet, unless the motor is too quick and the spring couldn't react. I hope I can use it.
Ps: This is just a concept. Details of sizes, positions, bearings and more have to be carrefuly designed.