Dynamic Clamping Control for Laser Welding Thermoplastics
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Solution Overview
Problem
Conventional laser welding apparatuses for thermoplastic resin members experience strength deficiencies and variations due to inadequate clamping pressure, which drops after laser irradiation, leading to volume contraction issues.
Innovation Solution
A method and apparatus for laser welding thermoplastic resin members that adjust the pressing force during and after laser irradiation to maintain consistent contact pressure, using feedback control based on temperature or pressure detection to prevent separation and air gap formation, ensuring uniform welding and increased strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If constant clamping pressure is applied during laser welding, then the welding process is simple to control, but welding strength is insufficient and variations occur due to volume contraction
Solution Approach 1:
The clamping pressure is changed from constant to dynamic, varying in three stages: initial pressure before irradiation, increased pressure during irradiation to compensate for volume expansion, and maintained pressure during cooling to compensate for volume contraction. This dynamic adjustment ensures consistent contact between welded surfaces throughout the process, improving welding strength while maintaining operational simplicity.
Solution Approach 2:
The clamping pressure parameter is modified throughout the welding process based on the thermal state of the material. By detecting temperature or pressure changes and adjusting the clamping force accordingly, the system optimizes welding quality without complex mechanical structures.
2Strength
If pressure is applied strongly from the beginning to prevent separation, then welding strength improves, but the melted portion cannot expand properly during heating causing defects
Solution Approach 1:
Initial clamping pressure is applied at a moderate level before laser irradiation to ensure contact between surfaces but not so strong as to prevent thermal expansion. The pressure is then increased during irradiation to compensate for expansion, and maintained during cooling. This staged approach prevents both separation and expansion restrictions.
Solution Approach 2:
The clamping pressure is applied in periodic stages corresponding to the welding process phases: pre-irradiation contact, irradiation with volume change compensation, and cooling with contraction compensation. This periodic adjustment optimizes both strength and quality.
3Ease of operation
If clamping pressure drops after laser irradiation, then the system is simple to operate, but air gaps form and welding strength varies
Solution Approach 1:
The system uses feedback control by detecting temperature or pressure changes during and after irradiation, then adjusting the clamping pressure accordingly. This ensures continuous contact between welded surfaces during cooling, preventing air gap formation and ensuring uniform welding quality without complex manual intervention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves high welding strength with reduced variations by dynamically adjusting the pressing force, preventing air gaps and enhancing the density of the welded portion, thereby improving the quality and consistency of the weld.
Implementation Method 1
irradiating the contact surfaces of the two members with a laser beam shone from the first member side
Implementation Method 2
absorptive thermoplastic resin that absorbs the laser beam
Implementation Method 3
pressing the two members... adjusting the pressing force applied to the first member and the second member
Implementation Method 4
volume contraction... preventing separation and air gap formation
Implementation Method 5
melting at least one of the contact surfaces of the two members... gently pressing the members when heated, gradually increasing the pressing force when the resin at the joining surfaces is melted
Data Source
AI summary
A method and apparatus for welding members formed of thermoplastic resin material, with high welding strength and small strength variations. A laser welding apparatus 1 brings a first member 2 formed of a transmissive thermoplastic resin that transmits a laser beam into contact with a second member 3 formed of an absorptive thermoplastic resin that absorbs the laser beam, and joins the thermoplastic resin members by melting their contact surfaces 4 with the laser beam. The laser welding apparatus 1 further comprises a laser beam generator 10 for irradiating the contact surfaces with the laser beam shone from the side of the first member 3 so as to melt at least one of the contact surfaces of the first member and the second member. The apparatus also comprises a clamp mechanism 20 for pressing the first member and the second member together, a temperature sensor 31 as an adjusting means for adjusting the pressing force applied to the first member and the second member, and a personal computer 32 for calculating the pressing force based on the output of the temperature sensor. The clamp mechanism is controlled with the calculated pressing force.