How to avoid or reduce downtimes with welding robots

Posted by Prof. Emil Schubert on Jun 3, 2022 11:06:54 AM
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When it comes to high quantities, cost and time pressure, welding robots provide valuable assistance. With them, consistent quality can be achieved in the shortest possible time. However, productivity in automation or robotics also depends significantly on how often and how long a welding robot is at a standstill because it has to be reloaded, set up again after a crash or generally maintained. Every second of downtime counts and costs money. And it cannot be generalised who is more affected by downtimes in production: the group with large robot production lines or the small medium-sized company that only has one welding robot in operation. A welding robot in industry must function trouble-free as much as possible – and having the right equipment in production or in the company helps with this. Find out here how to reduce downtimes for welding robots.

Reasons for downtimes with welding robots

First of all, the causes of downtimes in robot welding must be considered on a case-by-case basis and from the individual situation. The necessary measures must also be decided accordingly. Each robot cell in industrial production must be considered as an independent system and sources of error are everywhere.

Already when selecting the equipment, one of three essential cornerstones is laid for whether there will be frequent downtimes with welding robots or whether the process will run for longer periods without interruptions. These include:

  1. Selection of the robot welding torch according to the application
  2. Selection of wear parts such as contact tip, gas nozzle, gas distributor and liner
  3. Cable assembly and cable assembly guide
  4. Robot torch mount and switch-off protection
  5. Torch cleaning station

A must: "clean" robot programming

While the selection of the right welding equipment represents the hardware of a welding robot, the area of robot programming forms the second cornerstone that guarantees a trouble-free process. "Clean" programming is literally the alpha and omega for ensuring that the weld seam is set as prescribed, that the high-quality wear parts can also fulfil their good service lives and that the switch-off takes place reliably in the event of a crash. Without proper programming of the robot, even the best equipment is of no use. If the programming is not correct at just one point, the welding process will not run smoothly or accurately and can have serious consequences for equipment and products. In this sense, robot programming is the "heartbeat" that ensures that the welding process runs smoothly.

Preventive maintenance is the third cornerstone for reducing unplanned downtime.

We will take a close look at each of the above mentioned five topics in this and two further blogs and show precautionary measures as well as solutions.

1. Selection of the robot welding torch according to the application

Robot welding is not only a hot business, but it can also be quite rough. A robot torch has to withstand quite a lot in its daily routine: high currents, extreme heat, flying welding spatter and occasionally a more or less hard crash. It must be built for these daily stresses - and there are big differences between the robot welding torches in the industry.

 

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Welding power

As a general rule, the welding torch system must be selected to match the welding power. We recommend:

  • Power range ≤ 250–300 A = gas cooled
  • Power range > 300 A = liquid cooled

It is possible, but not advisable, to try to weld components with a 400 amps gas cooled torch system at 80 percent duty cycle. With high process heat and long duty cycles, the robot torch system must be actively cooled. Cooling the torch with suitable coolant reduces the heating of wear parts such as the contact tip and gas nozzle, which thus have a longer service life and need to be replaced less frequently. The fact that downtimes occur in the example mentioned is almost pre-programmed.

Torch geometry

The torch geometry is selected to fit the welding task. Standard robot welding torches have bending angles of 22°, 35° and 45°. Straight robot torch necks – i. e. 0° bending – should not be used if possible. The reason: A welding wire always has a natural spin when it is guided through the welding torch, the so-called pre-dressage. This is caused by winding the wire onto a spool or into a barrel as delivered.

Abbildung_DrahtspuleK300 wire spool with pre-dressage L=approx. 600 mm

The larger the pre-dressage, the more directionally the wire is fed into the contact tip. Therefore, the number of wire contact points in the contact tip is correspondingly small.

Fewer contact points for current transmission mean a higher current density per point. This results in greater heating. With straight torch necks, as is often used in automatic operation, wires with a large pre-dressage – i. e. diameters of 900 to 1,200 mm – are very difficult to weld. This can be solved by so-called wire straighteners, which give the wire a certain dressage, as well as by longer contact tips or narrower bores in the contact tips.

For some applications, special torch geometries are necessary, which are then referred to as special torches. It is important for the torch geometry that the robot welding torch ensures good accessibility to the workpiece. It should be avoided by all means that the robot has to be set up or positioned unfavourably to be able to reach the product to be welded easily. This could affect the service life of the cable assembly if it becomes twisted, jammed or stuck.

Exchangeable torch necks

A lot of time can be saved when using exchangeable torch necks. In case of maintenance or malfunction, exchangeable torch necks can be replaced very quickly. The maintenance is carried out outside the robot welding cell so that the welding robot can continue welding. With the help of a setting gauge, the TCP should be checked and corrected if necessary. After that, the torch neck is ready for the next change. The torch neck can be changed manually by the system operator, but also automatically with the help of torch exchange systems such as the ATS Rotor or the TES system from ABICOR BINZEL.

Useful tips

  • When selecting the equipment for the robot welding torch, be sure to look for quality.
  • Ensure "clean" programming of the robot.
  • Select the torch system to match the welding power.
  • Select the torch geometry according to the welding task (preferred bending angles are 22°, 35° and 45°).
  • With straight torch necks, more attention must be paid to the contact points in the contact tip for current transmission. In this case, wires with a small pre-dressage (>900 mm), suitable wire straighteners, longer contact tips or narrower bores in the contact tips can help.
  • Make sure that the robot welding torch can easily reach the workpiece.
  • Avoid strong twisting and hitting of the cable assembly.
  • Exchangeable torch necks save additional time and reduce the downtimes of welding robots.

ABICOR BINZEL offers suitable welding torch solutions for industrial robots for all requirements:

  • Reliable air cooled and liquid cooled MIG/MAG robot welding torches:
    • with exchangeable neck system for frequently changing welding tasks and to significantly reduce maintenance times on the welding robot
    • with different torch neck geometries and lengths
    • reliable and highly flexible up to 600 amps
    • extra robust and crash-resistant
    • particularly powerful for extra long duty cycles
    • as tandem welding torch systems for highest demands
    • as entry-level robot welding torches for the high-performance range
  • TIG robotic torch system for almost all automated TIG applications.
  • Efficient TIG all-rounder systems for welding components with simple geometry
  • Plasma robotic welding torches for very high quality welds

If you have any comments or questions about robotic welding torches with regard to downtimes for welding robots specifically for your company or applications, please feel free to leave a message in the comments field.

In the next blog on how to reduce downtime with welding robots, we will focus on the choice of wear parts. Here we will take a close look at the contact tip, gas nozzle, gas distributor and liners.

See you and …

Happy welding!

Topics: Robotic Welding