There are no singularities in the build volume. Depending on their geometry there might be a singularity when the effector is over a shoulder bolt.
A singularity is a position where a move away from it is unpredictable. (Obviously there is more to it but that is mostly it.) Simpson/GDR have a real bad singularuty when the hub attachment point and the shoulder joints are coplanar. Any stepper rotation could result in the effector going up or down depending on gravity. Luckily the effector has to go through the build platform to get to that singularity.
This is the beauty of driving the elbow. In this case it removes singularities and allows the bot to be more compact.
A singularity is a position where a move away from it is unpredictable. (Obviously there is more to it but that is mostly it.) Simpson/GDR have a real bad singularuty when the hub attachment point and the shoulder joints are coplanar. Any stepper rotation could result in the effector going up or down depending on gravity. Luckily the effector has to go through the build platform to get to that singularity.
This is the beauty of driving the elbow. In this case it removes singularities and allows the bot to be more compact.