How can the acceleration and deceleration curves of an automatic glue injection robot's dispensing path be optimized to avoid defects such as stringing or accumulation during start-stop transitions?
Publish Time: 2025-09-16
In automated processes for precision manufacturing, an automatic glue injection robot is not only a robotic arm that performs glue application but also an intelligent terminal that precisely controls fluid behavior in both time and space. One of the core challenges is maintaining consistent glue delivery during complex motion, particularly at the start and end points of the path—the start-stop transitions. Two typical defects are most likely to occur during this phase: stringing, where the glue is stretched into thin strands during needle withdrawal, breaking off and remaining on the product surface. Accumulation, where the automatic glue injection robot experiences a sudden drop in speed at corners or stops, allowing the glue to continue to be extruded due to inertia, resulting in localized excess accumulation. These defects not only affect appearance but can also cause electrical shorts, sealing failure, or assembly interference. Therefore, optimizing the acceleration and deceleration curves of the dispensing path is crucial for process quality.Traditional constant-speed or abrupt-speed control methods struggle to cope with the inertia and viscoelastic properties of fluids. Glue flow in pipes has mass and viscous resistance. When an automatic glue injection robot suddenly starts, mechanical motion begins, but glue flow is delayed due to lag, resulting in insufficient glue at the beginning. Conversely, during an abrupt stop, even after motion has ceased, glue continues to be squeezed out due to inertia, causing accumulation at the end. Furthermore, high-viscosity glue responds slowly to pressure changes, further exacerbating dynamic inconsistencies. Relying solely on fixed-parameter acceleration and deceleration patterns cannot adapt to variations in glue properties, needle size, or trajectory curvature, resulting in a very narrow process window.Modern automatic glue injection systems use intelligent acceleration and deceleration profile planning to coordinate mechanical motion with fluid dynamics. Key to this is the use of smooth, continuous speed change strategies, such as S-shaped acceleration and deceleration profiles, to gradually transition the rate of velocity change (jerk) and avoid sharp shocks. At the beginning of the trajectory, the automatic glue injection robot starts with a very low initial velocity and gradually accelerates to the set value, allowing the glue pressure to build smoothly, achieving a "soft start" and avoiding initial glue breakage. At the end point, the system enters a deceleration phase early, bringing the speed asymptotically to zero. Fine-tuning the timing of glue dispensing shutoff ensures that the glue extrusion terminates before movement comes to a complete stop, preventing stringing.For corners or tight-radius turns, the system employs a look-ahead control algorithm to anticipate changes in path curvature. It proactively reduces speed before entering the curve, maintains a minimum stable speed at the point of maximum curvature, and accelerates smoothly after exiting the curve. This process involves more than simply reducing speed; rather, it dynamically calculates the optimal speed profile based on the curvature radius, glue rheological properties, and glue dispensing rate. This ensures stable glue flow even at low speeds, avoiding glue breakage caused by slowing down or deviation caused by speeding up.Going a step further, some high-end systems incorporate a pressure feedforward compensation mechanism. During the acceleration phase, the control system anticipates pressure lag and preemptively increases glue supply pressure. During the deceleration phase, it preemptively reduces pressure to offset inertia. This coordinated "motion-pressure" control ensures true synchronization between glue output and spatial trajectory, achieving the ideal "where you go, what you get."In addition, the lifting trajectory of the needle tip as it leaves the workpiece surface has been specifically optimized. At the end of dispensing, the automated glue injection robot rapidly rises vertically, synchronizing with a glue-cutting air pressure pulse to quickly sever the glue strands and minimize residual material. The lifting height and speed are set based on the viscosity of the glue to avoid excessive height affecting timing or low speed causing contact.As the automated glue injection robot traverses tiny solder pads, every millimeter of its trajectory bears the ultimate pursuit of precision. The acceleration and deceleration curves are no longer cold mathematical functions, but rather the result of a deep understanding of the fluid's characteristics and gentle guidance. They create a tacit understanding between the rigidity of the machine and the flexibility of the fluid, ensuring each start and stop is clean and precise, and each drop of glue is precisely placed. This represents the essential leap forward in automation, from "being able to do" to "doing it well."
