The term Positioner is an industry name given to an electro-mechanical device designed to manipulate weldments into an optimized orientation for weld seam accessibility best suited for welding parts in-position i.e. 1F, 1G, etc.. Positioners may be controlled manually with hand controls or automatically in a robotic weld cell for example or a combination thereof. Positioners generally have between 1 and 4 axes of motion including rotary and linear axes or combinations of both. By definition according to the ISO 8373 standard, some positioners are actually considered robots because several designs are “automatically controlled, reprogrammable, multipurpose manipulator programmable in three or more axes”.
1.) Size & Weight Matter
Many welding positioners are available with a standard range of size and weight capacities however, custom solutions are often required to cope with large and heavy parts. In some cases, the size and weight are so great that drop-center positioners are required to overcome the tremendous movement involved with overhung loads. When designing a robotic welding system, we start the entire process with the part or range of parts in mind and build the system around it.
2.) Part Load & Unload
Weldments are generally clamped into customized fixtures that are attached to the positioner platter or they may be placed into a common base fixture capable of accepting multiple fixtures of various shapes and sizes. This approach greatly increases the flexibility of the positioner as the applied fixtures that clamp directly to the parts can be quickly loaded and unloaded in and out of the common base on the positioner. High variability low volume system generally require quick change applied fixtures like this to accommodate the wide range of parts to be welded. It is important to keep the welding system busy by quickly exchanging parts for the robot to weld to maximize throughput and return on investment.
4.) Positioner Options
Numerous types and styles of positioners are used for welding automation:
- Head and tailstock
- Tilt-Rotate (not common for automated systems)
- Dual Headstock with horizontal interchange axis
- Dual Headstock with Ferris wheel style interchange axis
- SkyHook dual axis arm and platter
- SkyHook dual axis arm and platter with tailstock
- SkyHoist three axis arm with vertical lift, arm, and platter
- Two axis Drop center with platter and support from both ends
- Three axis Drop center with vertical lift with platter and support from both ends
- Large capacity articulated robots (hold and weld
The beauty of the SkyHook, SkyHoist, and drop-center positioner design is the fact these units keep the weldments centric to the robot work envelope, whereas a tilt-rotate positioner moves the part throughout a much greater area in space. This leads to the concept of a robot positioner, or Robot Transport Unit (RTU). A welding robot is sometimes anchored in a fixed location with a positioner in close proximity to it. This does not always allow the robot to reach all of the welds on a given part if at all, depending on the size of the part being welded. We expand the work envelope of the robot by including additional linear and rotational axes such as slides or rotating columns or both. Examples of RTUs are:
- Horizontal linear track
- Vertical linear track
- Gantry (inverted linear track)
- Rotating robot boom
- Any combination of the above
- Large robot holding small robot, i.e. ABBs IRB800
5.) Constant Welding Production
Many automated welding systems are made up of two or more workstations or interchange axes as with the dual headstock/tailstock or SkyHook style positioners. This not only increases production flexibility, it can increase system arc-on time because it eliminates the need to stop the robot to unload hot welded parts and load cold parts into the positioner fixtures.
Midwest Engineering Systems offers standardized and custom robotic positioners based on your welding specifications. We offer many advanced positioner features such as: integration with a number of robot arms and controllers, automatic lubricant to slewing ring, auto adjust counter weights, motor control isolation, and spring-loaded pins. Contact us today to learn more about how our positioners can enhance your welding production.
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