The sector of automated and robotic welding and accessories was worth $1.9 billion in 2017.
Welding is used as a fabrication process in every industry large or small, and is a principal means of fabricating and repairing metal products. The process is an efficient, economical, and dependable means of joining metals. However the manual welding process has it’s downsides – welding by hand requires man power, and with that the room for human error. Plus there is no capability for repeatability or high volume.
Enter automated welding equipment, used and refurbished robotic welding equipment of these popular brands are supplied include ABB, Motoman, Fanuc, Cloos, OTC, Kuka, Panasonic, Miller and Lincoln. We can also fit any welding application – MIG, TIG, Plasma cutting, Plasma welding on to the welding robot.
It finds application in the automobile industry, and in the construction of buildings, bridges and ships, submarines, pressure vessels, offshore structures, storage tanks, oil, gas and water pipelines, girders, press frames, and water turbines. The welding equipment market is very mature, however, with the growing trend toward welding automation and the increase in demand from end-user industries, higher growth is expected.
The remarkable success of welding-intensive, end-user sectors, such as the shipbuilding and automotive industries, has galvanized the welding equipment and consumables market. An increasing number of industries are automating their production to a large extent and robotic welding is becoming a standard feature of such automation. The market for welding robots is growing at a higher rate than any other type of industrial robot.
Robotic Welding Equipment
There are two popular types of industrial welding robots. The two are articulating robots and rectilinear robots. Robotics control the movement of a rotating wrist in space. A description of some of these welding robots are described below:
Rectilinear robots move in line in any of three axes (X, Y, Z). In addition to linear movement of the robot along axes there is a wrist attached to the robot to allow rotational movement. This creates a robotic working zone that is box shaped.
Articulating robots employ arms and rotating joints. These robots move like a human arm with a rotating wrist at the end. This creates an irregularly shaped robotic working zone
There are many factors that need to be considered when setting up a robotic welding facility. Robotic welding needs to be engineered differently than manual welding. Some of the consideration for a robotic welding facility are listed below:
Accuracy and Repeatability
- Number of axes
- Seam Tracking systems
- Weld monitors
- Arc welding equipment
- Part Transfer
A robotic welding system may perform more repeatably than a manual welder because of the monotony of the task. However, robots may necessitate regular recalibration or reprogramming.
Robots should have the number of axes necessary to permit the proper range of motion. The robot arm should be able to approach the work from multiple angles.
Robotic welding systems are able to operate continuously, provided appropriate maintenance procedures are adhered to. Continuous production line interruptions can be minimized with proper robotic system design. Planning for the following contingencies needs to be completed:
- Rapid substitution of the inoperable robots.
- Installing backup robots in the production line
- Redistributing the welding of broken robots to functioning robots close by
ROBOTICS welding videos. Some supplied by Westermans others for information only
How important an application is robot welding?
Robotic spot and MIG welding are important applications for robotic automation representing about 60% of the world’s robot population. As the production of robots has increased over the years, the unit cost has decreased and this allowed companies in the general industry sector (as opposed to automotive) to consider robot welding for medium to high production needs. Robots reduce labour costs and itis a misconception to think that robots take away jobs.
Areas where robotic welding is implemented
Typical assemblies in the automotive industry suitable for robot based welding automation are: exhaust systems, seats, cross members, steering hanger brackets, engine mountings, tow bars, suspension parts. In general industry: furniture, gates, stoves, bridge sections, wind turbines. Items for the yellow goods industry (earth moving vehicles) include: buckets, cabs, loader arms and back hoes. In fact anything that is produced in reasonable volumes can be made by robots.
How the technology has changed over the years
Although the principle of robot welding has not changed since its introduction in the seventies, suppliers are constantly developing new features that make it easier to implement this technology with improved performance and lower investment levels. Many of the images show Motoman robots as they could be used without copyright. However the information on this site is of a general nature and applies to most robot suppliers.
Benefits of robotic welding
A robot typically works between two or more work stations. This means that during the robot welding cycle the operator is unloading a welded assembly and then loads new components to a welding fixture. Because there is less handling compared to a manual weld cycle the robot achieves much higher levels of arc-on time. The robot also moves very quickly between the joints and this yields a further saving in cycle time. Typically a robot system will increase output by a factor of two to four. This depends on the nature of welding. An assembly with lots of short welds can be produced with the most time savings. The cost savings that robot welding brings, can help companies to be more competitive and beat off competition from low cost manufacturing countries in Eastern Europe or China. In order to assess what sort of productivity improvements can be achieved it would be appropriate to compare manual welding times with robot welding times.
The robot has a very high repeatable accuracy (± 0.08 mm) and excellent path following accuracy. The robot presents the welding gun at the correct welding angle, welding speed and distance. The high level of integration to the welding equipment ensures that optimum welding conditions can be used for each and every joint. The end result is consistent high quality output, day in day out, year in year with reduced cost for rework, scrap or removal of weld splatter.
It is up to the judgment of a manual welder to weld to the correct standard, but often the weld is oversize. A robot however, always welds to the correct length and size of weld that it has been programmed to produce. This means that some potential savings in wire consumption can be made. If for example a manual welder welds a 5 mm fillet, where only a 4 mm fillet is required, the savings in welding wire alone will be a staggering 36%!
In recent years it has become increasingly difficult to employ manual welders. There tends to be a certain amount of staff turnover and this of course carries a cost for recruitment and training. When labour is an issue companies often find themselves working overtime or having to employ additional contract labour to meet demands and this can have a serious impact on production costs. If products cannot be supplied to the end customer, penalties may be incurred or future business may be at risk. Whilst there will always be a requirement for manual welding, companies that invest in robotic automation are much less dependent on manual welding.
A robot welding system addresses health and safety issues associated with dangerous welding fumes and exposure to arc-flash. Companies can reduce the risk of their employees claiming compensation if they are affected by the hazardous working environment.
The robot can be used to weld many different products and allows companies to consider Just In Time production. By reducing work in progress and stock levels, savings can be made due to fact that less value is added to stock levels in terms of labour, transport and storage costs.
- Compared to the same output from manual welding bays the robot requires less floor space.
- robots carry out work in areas that would be unsafe for humans
- robots carry out work that would not be economically viable in a high wage economy
- robots carry out work that would be impossible for humans.
Robots specifically designed for arc welding
In 2003 the world saw the launch of a Motoman robot specifically designed for arc welding. The upper arm of this robot consists of two sections through which the welding hose bundle is guided. This arrangement offers higher protection to wear and tear compared to the traditional dressing method where the hose bundle runs over the top of the upper arm. In addition it facilitates robot programming since the programmer does not need to consider the hose bundle which could otherwise get snagged up in the assembly or fixture. A fringe benefit is also that the Tool Centre Point (the reference point for programming, in this case the end of the welding wire) is more consistent due the better guided and shorter hose bundle. This in turn can give a quality improvement when welding conditions are critical.
Inside the cabinet is a power supply, a computer, servo amplifiers and communication boards. These can be simple I/O boards or field bus boards. For welding sometimes an analogue interface card is required to control the speed of the wire feeder of the welding equipment, but this can also be done via a field bus board, or the Ethernet or even the serial connection of the computer. As part of the robot system is also a teach pendant.
The working envelope of a robot is shaped like a fist and when it is floor mounted the maximum reach is usually in line with the motor for the lower arm joint. For this reason the robot may be placed on a base frame. The envelope of the robot will extent in a circular motion and the work piece will be placed inside the working envelope. You can also see that the area at the top is wider and this is the reason to invert the robot if it has to weld an assembly that is too wide to fit into the envelope in front of the robot and if a larger robot cannot be used either.
The articulated arm of the robot has 6 degrees of freedom or axes, which are driven by electric, brushless AC motors from the robot controller. Most robot manufacturers refer to these axes as 1 to 3 for the major axes and 4 to 6 as the minor axes. Motoman Robotics refers to these axes by their logical names; “swing”, “lower”,”upper” and then “upper”, “rotate” and “bend”. On the teach pendant you will find six toggle keys and these are clearly marked so it easy to find you way round if you are new to robot programming.
Robot manufacturers will specify the relevant speeds for each of their robot axes. In an arc welding robot program there are often very small moves between welds and these do not allow the robot to reach maximum speed. The most important factor is for the robot to accelerate as fast as possible, reach its maximum speed and then decelerate to the next welding position as quickly as possible. This kind of control is taken care of within the dynamic model that is part of the the motion control software. The software also considers the weight of the tool at the end of the robot arm, and additional loading such as the wire feeder, friction in the joints and any other external forces that act upon the robot such as gravity. This dynamic model also ensures that all the motors work in harmony with each other resulting in good path following accuracy and very high positional accuracy.
Generally the speed of the robot is restricted to its slowest axis and for that reason it is a good idea to select “joint moves” for air moves between welds. In this mode the robot will move to its programmed position in the fastest possible way, irrespective of path.
The industry standard is a machine with about 1.4 m reach from the centre of the base to the point P, which is the centre of the knuckle joint near the wrist. It is however very useful to have the option of a robot that has a larger reach. The choice of robot depends on the assembly that needs to be welded.
The Motoman MH50-20 in the tower welding system above is an example of a robot with an extremely long reach. It would be very unusual to use such a machine, but in this case is it more economical to use this robot, rather than a standard robot on a track or inverted robot that is suspended from a gantry system. An inverted robot will use the top area of the robot’s working envelope and this can be useful if an assembly is otherwise too wide or to deep to reach the joints with a floor mounted robot.
Almost all modern robots feature AC servo motors rather than DC motors and these have the advantage that the control system will remember the relevant position of the robot, even after a power cut. These motors are capable of driving the robot very quickly and accurately and stop where required without undesirable vibration or backlash. The servo motors are controlled from servo drive units inside the robot controller. They control the speed in relation to the distance from the desired point which requires the use of tachometers to monitor the velocity and encoders to monitor the the position. The programmer does not get involved in the detail of how the robot does this and merely uses a teach pendant to instruct the robot what to do.
The computer inside the robot controller does not only run the motion control software, but also the welding software that provides the robot with a flexible interface to the welding power source. In order to achieve high quality welding it is important that the robot can accommodate different welding conditions. Without this software it would, for instance, be very easy to burn through thin materials or have a cold weld on heavy welding applications when starting the weld. Hence the software can mimic the skills of a manual welder and is extremely comprehensive. Once the welding parameters have been fine tuned, they are stored and called up for that particular joint condition inside the robot program. Generally the parameters are stored as data that divide the weld into tree sections: start data, main data and end data. The number of parameters that can be selected are extensive and include the following:
Gas pre-flow and post flow,· Start & end voltage with time,· Main seam voltage or trim if in synergic mode,· Main seam wire feed speed,·
Start & end wire feed speed,· Weaving patterns,· Re-start function,,· Pulse patterns trim· Crater fill,· Burn back control,· Automatic re strike
It is also possible to rely on the comprehensive welding software that is resident in the power source and most customers prefer this kind of interface since it makes robot programming simpler. In addition it is less likely that the operator will corrupt any welding programs. One of the advantages of this kind of interface is that it is easier to identify any faults since the responsibilities are clearly identified with the robot being responsible for moving the torch and the power source being responsible for the process. This principle of interface works as follows:
At the start of the joint the robot controller sends a digital output to the power source to select a particular weld schedule (start, main and end conditions).
The robot controller then initiates a signal for the power source to switch on the welding process via the welding interface board.
The robot power source returns a signal to the robot controller that an arc has been established.
The robot controller then initiates the movement of the robot.
At the end of the joint the robot sends a signal to the power source to stop the process and extinguish the arc.
- The robot moves to the next position in its program, etc.
- Positioners for robotic welding
· When a joint cannot be addressed in the correct welding position, it will be necessary to rotate the assembly so that the robot can weld the joint in the horizontal-vertical position, vertical down hand position (for materials up to 3 mm thick) or gravity position. Overhead welding is perfectly OK for a manual process, but should be avoided with a robot since weld spatter can get lodged onto the tip with the result that the system stops due to a weld error.
· Interface into the robot controller
· Positioners, sometimes called manipulators, tend to be servo controlled and are driven from the robot controller and programmed from the robot teach pendant. The movement of the positioner is integrated with the robot, which means that the robot can move to the joint, whilst the positioner is bringing the joint in position. Alternatively if the assembly has an orbital weld (e.g. an exhaust system), the positioner can rotate the assembly whilst the robot remains stationary or moves along with the joint if the orbital weld is eccentric.
· Handling capacity
· Positioners will be specified to a certain handling capacity and this depends on the weight of the assembly plus the fixture. The Motoman range of positioners tend to be modular in construction with handling capacities from 250 kg to a massive 20,000 kg. Other manufacturers may also have a standard range of positioners or may be able to manufacture bespoke units.
· Types of positioners
· There are many types of positioners designed to suit the exact requirements of the assembly that needs to be welded. The positioners can be a single axis or twin axes, single station or twin station. Below are some examples of the most common types.
· Twin station positioners
· A twin station positioner has a positioner on each end of an indexing mechanism so that the robot can weld an assembly, whilst the operator is tending the fixture. The indexing mechanism is usually servo controlled and can either be vertical or horizontal. A vertical index is like a haymaker wheel. This type of positioner has the advantage that the index movement requires less space and is therefore the best choice for longer assemblies.
· A limiting factor for twin station positioners is the width of the assembly or fixture. This should fall within the specified swing diameter or else there will be interference with the central beam or floor.
· Single axis positioner
· Also known as a head and tail stock positioners. The distance between fixture discs may vary dependant on the length of the assembly. One end is driven by an electric servo motor whilst the other end is a freely rotating tail stock. Between the fixture discs will be a frame work, known as a strong back, that will support the fixture. It is common to have two of these positioners in a robot cell in order to obtain the benefits of the multi-station approach.
· Twin station single axis positioner
· The principle is the same as for two single axis positioners expect that the two units are mounted on a station index mechanism, which means that all unloading and loading operations can be done from a single area. This is often an advantage to save floor space and save the operator from having to walk round the system. The station index can be horizontal or vertical. The purpose of the central screen in the centre is to prevent the operator receiving arc flash.
· Single station twin axes positioner
· This type of positioner has two degrees of freedom. The face plate can rotate and tilt. It will be possible to locate the joint in a gravity position, which is useful when welding conditions are critical for e.g. the welding of boilers or excavator buckets. Welding in the gravity position also has the added bonus that the welding process can be slightly faster.
· Twin station twin axes positioner
· Two twin axes positioner mounted from a station index mechanism. This type of unit may or may not have tail stocks depending on the type of assembly that is held. The advantages of the twin station approach are the same as for the single axis twin station positioner.
· Linear tracks
· If the joints to be welded are outside the working envelope of the robot,the robot can be mounted on a linear track, which will extend the reach of the robot. Short tracks tend to be two position pneumatic, whilst longer track will be servo controlled. Linear tracks are also used when two workstations are positioned in an in-line layout.
· A gantry system dramatically extends the working envelope of the robot. The robot is inverted and carried in the Y direction along the work piece, if required in the X direction across the work piece and it is also possible to have a Z direction that moves the robot up and down. The Y axis of the gantry can be long enough to create two separate workstations in order to increase the system’s productivity. The additional axes are fully servo controlled and are controlled and programmed from the same robot control system. It is also possible to have additional carriers to have multiple robots.
Robots in the automotive industry
Robots have been keeping things moving in the automotive industry for 30 years: the cost-intensive models of the past have meanwhile made way for versatile and reliable high-tech robots. With the development of each new model, robots have gradually become more profitable. Today, they pay for themselves faster than ever before. And because KUKA is continuously breaking new ground with its research and development, KUKA robots are not only among the most innovative and powerful machines on the market, they are also true all-rounders. No matter what the task – welding, foundry operations, laser applications or palletizing – these multi-talents improve the entire production chain, from operation in press shops to paintshops and final assembly. It is no wonder, then, that they are meanwhile considered indispensable in all areas of the automotive industry.
Areas of Application for Robotic welding….. No matter how hard the task, KUKA robots make light work of it: they are robust and resistant when working with foundry machines. They exhibit great reliability and endurance when carrying out the complex handling of heavy weld guns. Pin-point accuracy and high performance in preciselaser applications. Specialists on the one hand, these robots can be employed almost universally. They can be integrated flexibly and virtually without risk into almost any work process. At the same time, they create the ideal conditions for future production expansions or changeovers. Short-term increase in productivity or securing the future long term – KUKA robots manage both
Automation in the metal industry…. Their modular structure, flexible controller and ready-made application packages make KUKA robots indispensable for the manufacture of metal products. Their main areas of application are machining operations, such as drilling, milling or cutting, as well as bending and stamping. They also improve cycle times and productivity in welding, assembly, loading and unloading operations. Even in foundry environments, specially equipped KUKA Foundry robots are characterized by their long service life and resistance against heat, water and dirt. And last, but not least, KUKA robots make an important contribution to efficient quality management, with independently executed inspection operations such as surface inspections.
Robots in the metal industry…… More productivity, cost-effectiveness and quality – the demands of the metal industry are becoming ever greater. With modern robotics from KUKA, it is always possible to stay one step ahead. With flexible applications and the latest control technology, KUKA robots take over numerous work steps in multiple-shift operation, even in harsh production settings – thus increasing the profitability of the manufacturing operations. Robust Foundry robots function as a reliable link between individual production islands, for example, in environments with high temperatures and a high degree of fouling. Thanks to their enormous payload capacity and positioning ability, KUKA robots are meanwhile also indispensable for the transfer of heavy loads.
From steel to cast iron: the metal industry….. Light metals, non-ferrous heavy metals, precious metals and special metals or steel – without foundry operations and steelworking/metalworking, there would be no metal industry. And without multiple-shift operation and automation, there would be no manufacturing to ensure cost-effectiveness and competitiveness while relieving human workers of unnecessary burdens. For this reason, KUKA offers the ideal solution for every production process: from casting to welding, from forging to cutting, and from loading and unloading to assembly.
As a company we do not buy and sell Robotic welders every day of the week, however we are here to help if you need any information either buying or selling. Give us a call.