Manipulators – Part 8 of 8 Articles
Robot Gun: Mounting the Gun and Operations Safety
In this final article in our series on manipulators, we will cover the mounting of the gun on an articulated robot and the safety of robotic operations. Some thermal spray operations may mount the gun in line with the last axis of the robot. While this may be the simplest approach, it is one of the least desirable. With the gun in line with an axis of the robot, the benefit of that axis is essentially lost. Rotation of the gun about its axis has little benefit. Also, mounting the gun straight out from the last axis results in the gun being cantilevered out from the robot, placing unnecessary loads on the robot.
| Robot Gun: Mounting the Gun and Operations Safety by Plasma Powder and Systems, Inc. In this final article in our series on manipulators, we will cover the mounting of the gun on an articulated robot and the safety of robotic operations. Some thermal spray operations may mount the gun in line with the last axis of the robot. While this may be the simplest approach, it is one of the least desirable. With the gun in line with an axis of the robot, the benefit of that axis is essentially lost. Rotation of the gun about its axis has little benefit. Also, mounting the gun straight out from the last axis results in the gun being cantilevered out from the robot, placing unnecessary loads on the robot. A superior gun mounting fixture is the type of fixture adopted by most of the welding industry. In robotic welding, the welding torch is mounted at an angle between 30 and 60 degrees to the last axis of the robot. It is also mounted close to the mounting face to minimize the cantilevered load from the gun, cables and hoses. A similar mount is typically used on robots provided by Plasma Powders & Systems, Inc. Some may be of the opinion that an angled fixture complicates the jogging of the robot during programming. However, when using a tool frame calibrated for the gun in use, positioning is actually easier than trying to move the gun using the world frame. The gun mounting fixture should also have alignment pins for accurate positioning of the fixture to the robot and mounting the gun to the fixture. This is important for the accuracy of the robot motion program. Safety is the final issue covered in this series. There are three parts to safety. In the typical order of priority, they are: 1. Safety of the operator and other personnel. 2. Safety of the thermal spray equipment. 3. Safety of the part being sprayed. There are the standard safety issues associated with thermal spray operations, whether manual or automatic. These include areas such as ear, eye and respiratory protection. Publications such as ANSI Z49.1, Safety in Welding, Cutting, and Allied Processes addresses most of the points of concern. However, little is said about safety issues with robots. For this, ANSI publication R15.06, Industrial Robots and Robot Systems – Safety Requirements is available. Equipment safety is generally concerned with “robot crashes” usually resulting in damage to the gun. The robot operator needs to be diligent regarding robot motions around objects in the spray booth. It is also important to keep the area around the robot clear of obstacles. The safety of the part is especially important when coating high-value parts such as landing gear struts. In such cases, the operator needs to be especially aware of any robot fault that could cause the robot to stall on the part, resulting in overheating and damaging the part. As noted in the first of this series, these articles were primarily oriented towards management to highlight issues that need to be considered. But, the information should also be of value to the thermal spray technician and the manipulator programmer when considering options for setting up and operating a manipulator. |