The customer expects to receive a quality welded product on time. There are two ways for a supplier to achieve this – reactively or proactively. Reactively means not doing any preventative planning or analysis of what the true welding process capability is of each ship component welding system, be it man, machine or robot.
Proactive Intelligent Process Control
The proactive approach means one designs for manufacturing, employs capable processes and works with intelligent systems which again can be man, machine or robot based. The level of intelligent processing and pro-activeness is shown below.
- Level of intelligent automation Proactive/Reactive Level
- Manual welding Could be both
- Blind (no vision) machine or robot Reactive
- Automated pre-check of joint fit-up Proactive
- Real time seam tracking Proactive/Reactive
- Real time seam tracking with adaptive control Proactive-Adaptive Correction
- Laser vision system inspection Reactive but more accurate
- Weld Inspection Measurement System Proactive
- Closed loop control of process Proactive
- Repair based on automated weld inspection Proactive & Reactive
- Feed-forward ID of parts not to spec. from welding Proactive & Reactive
Let’s look at some specific applications of some of these systems starting with a manual portable weld inspection system (PWIMS).
Portable Weld Inspection Management System (PWIMS)
Presently there is a great deal of redundant and subjective inspection being done on all types of ship structures. It is not uncommon to see 400% inspection of some welds resulting in wasted time and unnecessary repairs.
An improvement to this situation is now possible to deploy for many applications.
The system consists of a portable handheld laser vision sensor combined with a database management tool. It provides objective weld feature measurements and SPC analysis tools.
Real Time Seam Tracking and Adaptive Processing
Typical stiffener welding machines consist of gantries, welding equipment and heavy duty clamping devices. Maintaining the wire position correctly in the joint has been done historically by manual jogging of the wire or using a probe seam follower. More intelligent welding can be done with a laser vision seam tracker capable of 1) qualifying the weld joint is within tolerance, 2) tracking the joint in real time and 3) adapting the weld process to optimize weld quality. To achieve precision welding results (minimum over welding) at maximum speed traditional methods will not work.
Closed Loop Control
The laser hybrid process consisting of a high power laser and Gas Metal Arc welding equipment is beginning to make inroads into ship component manufacturing. One of its big advantages is more precise welding resulting in reduced distortion. To achieve optimum control and quality, one manufacturer has deployed a closed loop control system that measures the weld shape just after the weld is solidified and then feeds this information back to give constant corrections. Travel speed and laser or GMAW parameters can be adjusted automatically as needed. See Figure 4 for an overview of this system.
How to get optimum welding performance, designing for manufacturing means considering the welding process to be used and its’ capability in the planning stage. In addition, design for automated process and inspection should also be considered. This will give you a good chance of achieving a job done right the first time.