Research On Mathematical Modeling And Control Method Of Adhesive Dispensing Volume Based On Contact Force

With the rapid development of precision micro-manufacturing technology,higher demands are placed on the dispensing volume and repetition accuracy of the adhesive.In the joining and assembly process of ultra-precision parts,the adhesive dispensing volume needs to be controlled at the f L-p L level in order to ensure the bonding quality and assembly accuracy of micro parts.Accurate control of the dispensing volume of ultra-micro adhesive is crucial to the quality of encapsulation,but most of the current control methods have some problems,such as timeconsuming parameter adjustment,low measurement accuracy and poor consistency.Therefore,it is critical to find a suitable method for controlling the dispensing volume of ultra-micro adhesive.This thesis proposes a contact force-based control method for the adhesive dispensing volume of needle transfer type based on the analysis of the composition and action mechanism of contact force,and this method can control the adhesive dispensing volume at the p L level by adjusting the contact force threshold.By analyzing the change of liquid bridge profile in the extrusion stage,a mathematical model describing the change of contact force is established,and provides a theoretical basis for revealing the change relationship between contact force and adhesive dispensing volume.The mathematical description of the adhesive volume and transfer rate was completed to better study the adhesive distribution.Based on this,a mechanism and method to control the dispensing volume by triggering the liquid bridge pull-off action through contact force control was developed.According to the critical contact force detected in real time,the change state of the contact process of the adhesive droplet was judged,and this was used as the basis to trigger the tensile stage of the liquid bridge,so as to realize the prediction and control of the adhesive dispensing volume.The adhesive dispensing control system was designed and developed,and the software program was developed to control the reciprocating motion of pipetting needle by the threshold of contact force.The micro pressure sensor with a resolution of0.001 m N was connected to the dispensing system,and the experimental platform for ultra-micro adhesive dispensing that can achieve online monitoring of contact force was established.Through system commissioning,closed-loop control based on contact force for adhesive dispensing was achieved.A series of experimental studies were conducted on the method of controlling the adhesive dispensing volume based on contact force.Experiments were conducted with a critical contact force in the range of 0.5 m N to 4.5 m N,and the results of the study showed that the adhesive dispensing volume increased approximately linearly with the increase of the critical contact force.In the automatic control experiment,the deviation rate of dispensing volume under the same contact force was less than 1.7%,and the average deviation rate of adhesive dispensing volume was 0.6%,the smallest dispensing volume was 105.1 p L,and the deviation value was 0.8 p L.