Welcome to our Newsletter. In this issue we will analyze the possibility of regrouping products through the 4th axis, spacing and joining together moving parts within the gripper. More topics will follow with the next Newsletters. Please feel free to send us a feedback or to contact us to discuss more in deep any topic relevant for you.
Regrouping with 4th axis
In Delta Robots kinematics, translation of an object from A to B is completely independent of rotation. The main three axes translate the TCP (Tool Center Point) while the 4th axis typically serves to rotate the product around its vertical axis. Since the 4th axis is completely independent, it can be removed if no rotation is required (3 axis version), or it can be modified to support an alternative movement. A common and often very helpful alternative use is grouping or spacing products. Using rack-and-pinion or tooth belts, the rotation of the 4th axis is used to change the pitch between products picked. Using the 4th axis allows making use of the servo control.
The traditional approach for regrouping and similar additional movements is through a system of pneumatic cylinders. The main issue with cylinders is there is no control of the motion parameters and a gentle movement comes at compromises of speed. Despite the use of dampener, there is typically an impact at the end of the movement, shaking the robot structure and the product on the suction cup.
In contrast, servo control allows well controlled movements including jerk* limited acceleration and deceleration. This allows much gentler product handling and limits the impacts on the hardware. It also allows for format changeover without changing parts, often making these solutions particularly robust and yet versatile.
As with any solutions, also this comes at a cost. For simple grouping with just one or two moving parts, the simplicity and lower cost of pneumatic solutions is very attractive. The advantage of gentler movements typically involves more moving and engineered parts. Compared to more traditional devices, special attention should be paid to the still relatively dynamic movements, which also the gripper must follow. The design must take into consideration the gripper will be deformed under dynamic load. A careful analysis of the degree of freedom is critical. Typical issues otherwise include self-locking of bearings. However, in situations with more flexibility required to adjust the spacing, even depending on format, or in complex regrouping tasks with more than two products involved, the advantages of using the servo control by far outweighs the additional engineering.
About VELTRU
VELTRU provides components and logistics software for pick-and-place applications to machine manufacturers and system integrators. We offer Delta robots, Soft PLC controls, machine vision support and multi-robot applications. We can support you "hands on" with training, engineering and project assistance as required. Our Application Template allows to configure standard applications and to program additional functionality for special project demands.