Today, welding is one of the most important processes used by the manufacturing and fabrication industries, producing a wide range of products starting from nano components and assemblies to giant ships, bridges, tunnels etc. involving a wide range of materials. Keeping with the varied range of demands, there is now a proliferation of welding processes, techniques, machinery, equipment, consumables and operators available in the market.
As far as the manufacturers are concerned, what counts the most is the growth of demand and cost of production. Thus ensuring that, customer satisfaction for quality products is met, coupled with instant delivery and a financially stable bottom line.
The areas of Fabrication, Gas Metal Arc Welding (GMAW) / Metal Inert Gas Welding (MIG), Gas Tungsten Arc Welding (GTAW)/ Tungsten Inert Gas Welding (TIG) and Spot Welding are the most sought after welding processes. Such a demand has resulted in variations in Spot, MIG and TIG processes, equipment, consumables, use of inert gases or combinations and operators trained at different levels with different skills. Moreover, introduction of Robotic Welding has added sophistication to the manufacturing processes.
The best practice in SPOT, MIG and TIG welding can be simply defined as the most effective and efficient method to weld a joint by MIG or TIG or Spot Welding process with continuous improvement. The term “effective” refers to the method which utilizes the resources to the optimum extent and the term “efficient” refers to the method of minimum wastage. In addition an approach for continuous improvement will pave the way for adopting the BEST PRACTICE in MIG / TIG/Spot Welding.
The GOAL of best practice in Spot / MIG / TIG Welding is to produce what the customers want, when they want it, while exceeding their quality expectations, and being productive, profitable and safe.
The Best Practice in Welding starts with the Product Design and the following points should be examined thoroughly for review and may be seeking for alternate design:
- Material of content
- Joint type – tension, compression, shear or combination
- Weld size
- Positional approach
- Inspection and Testing requirement
Once the Design is finalised, the immediate next step is to prepare the Welding Procedure Specification (WPS). All the welding parameters are to include:
- Welding position, weld size, current, voltage, welding speed, number of passes, consumables, joint preparation, pre-heating and post weld heat treatment etc
- At this stage the welding engineer tends to follow a pattern set in the previous joint/past experience in order to play safe
- Past experience, coupled with updated knowledge of shop floor practices and problems and the end results obtained earlier must be used now
The next step is to finalise the procedure qualification record:
- The joints must be tested as per specifications/codes to consolidate and validate the parameters and the process set in WPS to form the Procedure Qualification Record (PQR)
- This PQR must be followed in totality for the best practice we are discussing from the start
- PQR is not just a document; it should be used in operational practice religiously
- WPS must be displayed at the shop floor locations where the welding will be done
- Supervisors, welders, inspectors must be thoroughly acquainted with WPS and PQR
A number of Positive actions must be initiated for implementation in Planning and Management Systems:
- Production planning, scheduling, material planning – Application of Supply Chain Management is wanted.
- Material Management involving material purchase and inventory management must be technical knowledge oriented, rather than vendor influenced.
- Systems Management and Control adhere to the ISO 3834, ISO-9000, ISO 14000 standards as Operational Support Systems.
The co ordination among the operational team plays a pretty important role too:
- The most important part of best practice in welding is played by Operational Team at the workplace
- This starts with the machinery and equipment to be used. The selection of the machinery and equipment for welding is to be done effectively and efficiently and it should not be made on the basis of the most sophisticated or expensive machinery and equipment available, instead the decision should be made on their appropriateness of the application to meet the requirement. It is not always necessary to deploy Synergic Pulse MIG or Robotic Welding in all types of welding for Fabrication or Manufacturing Operations
The best of equipment might not be instrumental in producing the Best Practice. It needs:
- Periodical calibration
- Beginning of shift inspection
- Protection from weather and vandalism
- Proper provisions for earthing with respect to all types of power resources
- Stable Power Supply at correct frequency
- Immediate repair and maintenance on detection of faults.
- Upgradation/replacement according to requirement
In order to derive the best results:
- The best welding results are derived from best inspection before and during welding
- Before welding, inspection will ensure proper joint preparation and fitment, correct use of clamps in jigs and fixtures, specified positional welding, pre-heating if prescribed, correct setting of gas inflow, electrode tip shape and size, etc
- During welding inspection, ascertain use of correct/specified current, voltage speed, weaving, gas pressure and flow, maintaining welding position, filler rod feeding rate, inter-pass temperature, inter-pass weld cleaning etc
For the development of Best Welding Practice, one of the most important and essential steps is the development of skills of the supervisors and welders. Both are complementary in work situations and as such both are to be developed in terms of:
- Mental and Manual Skills
- Skill Development is a continuous process both on and off the job along with regular assessment and performance evaluation of both
An important and effective step to achieve best welding practice is Quality Control and Inspection. The targets of QC & Inspection should be:
- Defect identification and advise measures for rectification.
- Apply statistical methods in repetitive welding processes especially in Spot Welding.
- Generate KPIs for Weld Quality Performance and circulate to all the concerned stakeholders in the job for target achievement.
- Propagate Quality as an uncompromising factor in the work culture.
This article has been reproduced from the information provided by National Welding Research & Training Institute (NWRTI)