Our team is struggling to come to an agreement on the method of moving the intake arms for the power cubes. Snow Problem from Ri3D is a good example of the pistons moving the intake arms and Greenhorns from Ri3D is a good example of the springs moving the intake arms. Does anyone have strong preference or experience when using either pistons or springs? Thank you!
Do you plan to use pneumatics anywhere else on your robot?
-Use Springs, but do it in a well thought out robust way so you get consistent “springy” results.
Will you already have pneumatics on your robot?
-Use Cylinders, most cylinders won’t need much PSI to get a good springy result that will interface well with cubes. This method will be more repeatable but is more complex to put on a robot if you have little experience working with pneumatics.
It doesn’t make much sense to put pneumatics on your robot for one function so try the best you can to save weight by not adding pneumatics.
This. For pneumatic cylinders, you may want to consider the spring loaded cylinders, which only require air pressure to move in one direction. So pressure would be applied to extend the piston, but the spring would retract it upon ventilation of the pressure, eliminating the need for opposing air pressure.
Although that solves his issue, that method doesn’t allow you to change your spring tension, since pistons with springs have only 1 spring option. You can play with the angle I guess but it will never be as good as a replaceable spring.
Air Cylinders (a piston is just part of an air cylinder) are springs, nicely damped constant-force springs. You can adjust gripping force by adjusting your working pressure and deployment/gripping speed with flow control valves. You can adjust stroke coarsely by changing cylinder size, or finely by installing shims on the air cylinder shaft to limit retraction. You can choose to power the gripper open, closed, or both.
I’d be awfully tempted to use air cylinders because of their flexibility. FWIW we had 13 air cylinders on our robot last year, double-acting and spring-loaded flavors, and weighed in at 95lbs, so don’t buy into the notion that ‘pneumatics will make you heavy.’