FEATURE FASTENING & JOINING
EVALUATING ROBOTIC TORCHES T
The difference between the optimum and an adequate robotic torch could mean the difference between hitting your quality and productivity goals and scrambling to ensure on-time delivery
o help you select the correct torch and maximise operational equipment
efficiency (OEE), quality and profitability consider 10 key points:
1. UNDERSTANDING TOOL CENTRE POINT Tool center point (TCP) is a point in space with a mathematical reference to the flange of a robot. For robotic GMAW welding this is essentially how the robot knows where the tip of the wire is. Robots are good at repeating the same
motion path. If the tip of the wire changes due to thermal or physical distortion the weld placement will change. In severe cases the torch will crash into the part or weld fixture. A change of the TCP over time means that the robot will deposit the weld bead somewhere other than the centre of the joint. When this happens operators may compensate for TCP drift by increasing bead width such as by slowing travel speed or programming a slight weave into the torch movement to ensure that the weld encompasses both plates and provides sufficient fusion. An incorrect TCP results in larger-than-
necessary weld beads increasing filler metal and gas costs, cycle time, heat input and total weld cost. Compensation kills profitability in automated welding and may compromise mechanical properties. Selecting a robotic torch with a consistent TCP can be the first step in improving welding and reducing filler metal usage.
2. TCP STABILITY IS THE MOST IMPORTANT FEATURE TCP is by far the most important attribute to consider when evaluating robotic torches. To ensure a consistent and repeatable TCP look for robust necks and mounting systems. ESAB machines the clamping flange of its Aristo RT torch link robotic torches from a solid piece of stainless steel. The necks have a wall thickness about three times that of a typical competitor’s product and as a result can withstand a collision and still maintain TCP. Further, they hold dimensional tolerances over time. They’re so robust that TCP alignment tools aren’t needed (and cannot even bend the neck). Comparatively less robust necks require
TCP neck alignment after a certain number of heating and cooling cycles and a much-needed alignment may not coincide with scheduled maintenance causing the OEE to reduce. In addition, the Aristo RT Torch doesn’t need to have the
2 MARCH 2017 | FACTORY EQUIPMENT 2
TCP recalibrated when changing the consumables or the same angle swan neck, minimising downtime.
3. EVALUATING MOUNT/NECK BEND COMBINATIONS While a 23°mount with a 22° torch basically offers the same amount of bend as a 0°mount with a 45° neck, the latter combination works better for welding small circles such as around an axle. With a 45° neck the torch can spin
around the 6th axis of the robot (where the torch mounts to the robot arm) in smaller circles. Conversely, a 0°mount with a 22° neck works well when you need to reach into a small opening. If you have one application best suited for a 45° neck and another application where a 22° neck works better select an Aristo torch bundle with a modular design. This lets you change the neck off the torch bundle (without tools) and insert the neck best suited for the application. For job shops this modular approach adds flexibility and reduces changeover time between parts.
4. INFINITE ROTATION TORCH V STANDARD TORCHES The external cables of a conventional torch limit arm rotation to +/- (leave as 240) degrees (ESAB Aristo RT standard torch rotation +/- 270°). After making a circular weld the next point in the program brings the torch to a safe space and unwinds the cable. With an infinitely turning media coupling of an Aristo RT Infiniturn torch (360° turning ) the arm can move directly to the next weld. Infiniturn torches reduce programming and unproductive air time. For parts with many circular welds an Infiniturn torch will reduce per-piece costs compared to a conventional one. Locating the media coupling inside the robot arm protects it from damage and extends cable life.
5. TEST TORCH CONFIGURATION Before part production begins take a 3D model of your part and test it in virtual reality. This will ensure correct torch selection prior to purchase.
6. CONSIDER PARTICLE JET CLEANING STATION Conventional mechanical reamers clamp the torch nozzle which may deform the nozzle and distort gas flow and affect TCP. The reamer wears the consumables faster and the process of mechanically scraping the nozzle and contact tip may have TCP implications. Reamers cannot remove
spatter from the gas baffle, potentially leading to gas flow interruptions and inconsistent weld quality. Conversely, the JetStream RT particle jet torch cleaning station cleans consumables with a high velocity blast of aluminium oxide particles. It cleans all torch components without
mechanically gripping the torch. As a result the JetStream extends consumables life, preserves TCP and maximises OEE.
7. NOZZLE STABILITY With threaded nozzles the threads become loose due to thermal changes in the constant heating and cooling cycles. A compression-fit nozzle slides over the
end of the torch but becomes loose over time with repeated removal and thermal changes and a fast air move could possibly throw the nozzle. The ESAB Aristo RT series combines threaded and compression-fit technologies, enabling the compression fitting to hold the nozzle in place even as the torch heats up and the threads loosen.
8. CONSIDER INTEGRATED BLOW OUT LINE An integrated blow out line is a second gas line (the first is the shielding line) that connects to the shop air supply. During air movement time the blow out
line enables using basically free shop air to cool the torch instead of expensive shielding gas. This can lengthen consumable life and improve TCP stability.
9. USE LONGEST LASTING CONSUMABLES POSSIBLE When analysing consumables you need to consider both the cost of downtime (OEE) and consumable cost difference. In most cases the former are significantly higher than the latter. ESAB recommends their CuCrCz Copper Chrome Zirconium long lasting contact tip and consumables; these will help prevent unplanned downtime and lower the weld cost.
10. DON’T LET CONDUIT LINERS BE A DRAG Frequent arm rotation combined with the heat of the weld puts constant pressure on automated MIG gun liners. To make the changing of the liner easier
the Aristo RT torch has been designed with a separate neck liner, minimising changeover time.
ESAB Group (UK) T: 0800 389 3152
www.esab.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57