Types of Robot Transporters

• Linear Floor Tracks

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  Usually the least expensive robot transport option, linear floor tracks allow the robot to reach welds on very long parts.

  Tracks can be as long as 30 meters (98.4 ft.). Length is limited by the manipulator cables.

  One or more robots can be mounted on a carriage that either indexes between two or more fixed positions along the track length or is servo-controlled by the robot controller. Using a servo-controller allows continuous positioning of the robot anywhere along the length of the track.

  If the robot needs to move to more than a few positions along the track, a servo-controlled track typically is less expensive.

  Servo-controlled tracks also provide more programming flexibility. With a servo-controlled track, the robot can weld a continuous bead the length of the track. If coordinated motion control is included, the robot can be programmed to weld the part while it is turning.

  A robot on a linear track can only access the part from a single side, so the width and depth of parts that can be processed are limited to the reach of the robot arm. However, robots often are mounted on risers on the track carriage to increase their elevation and depth of reach.

  Floor tracks take up a significant amount of space but, with an opposing work station configuration, parts can be processed on both sides of the track.

  Work flow is flexible. The cell layout can be configured to allow parts to enter from both sides of the track or to move in and out in a straight line from multiple — parallel — work stations on one side of a longer-length track.

  Anti-collision software enables multiple carriages to travel on the same track without interference.

  Carriages also can be expanded to allow two robots to be mounted on a single platform.

  Separate carriages are advantageous when relatively few welds are spread out along the length of the part. The robots can operate independently and work on opposite ends of the part or can be used to simultaneously weld along the same seam.

  Two robots on a single carriage save the cost of an additional axis, and are suitable for applications in which multiple welds are grouped together. The carriage can be moved to a fixed position and the robots then can sequence the welds within their reach.

  For welding applications, the carriage should be large and heavy enough to support a bulk wire drum. That greatly reduces wire feed issues. Trying to feed wire through conduit in a cable tray is less reliable, and generally requires an assist feeder at the drum. That increases system complexity, cost, and maintenance issues.

  Safeguarding a linear track is not difficult if the manufacturer has provisions for mounting switches and cams to monitor the carriage position along the track. Such monitoring could include continuous position sensing or segmenting the travel into zones, depending on the risk assessment.

  Floor tracks require leveling when they are installed, but work with modest concrete floor requirements and have minimal height requirements.

• Wall-mounted tracks
  

  Linear tracks mounted in an elevated position on a wall allow robots to works from overhead. (Photo 2.)

  Mounting a linear track in an elevated vertical position allows a robot to work from overhead. (See Photo 2).

  This configuration can give the robot a wider reach and allows them to reach down into part cavities. This design is different from floor tracks, and support columns for wall-mounting add expense.

  A robot on a wall-mounted track can only process parts directly in front of it, so this configuration lends itself to an inline part flow.

  The wall-mounted track creates a narrower workcell because parts are processed from one side and equipment can be located under the support structure. Care must be taken to allow for overhead clearance for the track and the rear of the robot on the carriage.

  Welding electrode delivery is more difficult with a wall-mounted track because it is harder to mount a wire spool on the carriage on an elevated rail. However, as with floor tracks, multiple carriages can be located on a single wall-mounted rail.

  Limiting devices can be mounted to the robot arm to mute safeguards while the robot is overhead and become active when it moves down into a workstation. As with floor tracks, safeguarding switches also can be added to monitor the carriage position.