Satellite welding at the Indian Space Research Organisation (ISRO).
PW Resistance Welding Products has been designing and making high quality spot welders for automotive and aerospace applications for over 40 years. With a range from full robot cells to spare electrode tips, the company’s welding guns hitherto used hydraulic or pneumatic actuation for electrodes to close circuit for the weld.
For the past four decades, ISRO has launched more than 65 satellites for various scientific and technological applications like mobile communications, direct-to-home services, meteorological observations, telemedicine, tele-education, disaster warning, radio networking, search and rescue operations, remote sensing and scientific studies of space.
“We have dealt with ISRO for a number of years, providing small handheld push welding machines,” explains Ian Brent-Smith, managing director of PW Resistance Welding Products.
Motor driven ball screw actuators had been used but the company was not happy with their durability. Therefore, when PW Resistance Welding Products won a new order from the Indian Space Research Organisation (ISRO), it approached Olsen Engineering for an alternative technology.
“This time ISRO came up with a project involving a rocket nozzle on the outside of which they wanted to weld wires in a way that was controllable, because welding wires to flat metal sheets is difficult.
“We wrote a draft specification for them suggesting what they would want, and they used that specification for the tender which we then won. We made a special one-off machine using an Exlar Tritex integrated motor actuator, which has a control system built into it.”
Olsen has supplied a touch screen HMI solution complete with micro PLC connected to a Tritex linear actuator for satellite welding at the Indian Space Research Organisation (ISRO). This allows the operator to enter and adjust the required force in kilograms for each stage of the production process to test and optimise the weld quality depending on the thickness and type of material.
Exlar's Tritex Series actuators combine three technologies to deliver for the first time a truly simple and low cost electric alternative for fluid power actuators. Tritex actuators with built-in mechanical converters also replace electric drive systems employing ball screw or gear reducer mechanisms for a complete actuation solution.
Tritex actuators represent an all-electric solution for moving and/or positioning mechanical devices in a large variety of industrial or military grade applications. Tritex actuators eliminate the need for pneumatic and hydraulic cylinders while improving position performance, reducing cycle times and eliminating the maintenance associated with fluid power devices. Ball screw mechanisms, and separately mounted gear reducers are also a thing of the past because rotary to linear converters or mechanical reducers are designed in.
Integrated Drive Electronics
The unit was pre-commissioned at PW Resistance Welding Products premises in Bicester, Oxfordshire before being despatched to India. When the Space Research Institute in India took delivery, Olsen Engineering provided its own dedicated encrypted remote technical support to check the unit was operating satisfactorily. By using remote support software, Olsen was able to detect problems early on, for example when the installation team in India had overlooked the neutral connection from the transformer to the unit.
Another key feature available was to alter the weld gap off set distance and speed of the weld to reduce production times. Three foot pedals were connected to the system using digital inputs to the Tritex, which was connected over mod-bus RS485 to the HMI. The rig was shipped in 2009 and on arrival there was a technical issue which was solved using Olsen Remote support software. In fact it turned out the neutral mains power had not been connected.
Once up and running, the operator in India would input the product thickness and the offset distance from the weld, as well as the force and speed at which he wants to weld a component. The homing routine was also incorporated into the micro PLC of the Gefran HMI.
PW Resistance Welding Products has since deployed Exlar actuators from Olsen Engineering for a number of other projects. ISRO purchased a complete weld gun and controller for welding components to satellite frames. Olsen Engineering supplied a fully integrated Exlar Tritex actuator together with a Gefran HMI.
This included programming to allow an operator to enter the force required for the weld on the HMI, distance from the offset of the weld and speed of weld. Gefran designs and manufactures automation control systems offering machine constructors a wide range of specific components including control panels, operator interfaces and input/output systems, as well as programmable logic controllers and industrial PLCs.
The Tritex actuator has a built-in servo drive which controls the motion to the initial welding position, then applies force at a certain speed to the component being welded before being retracted back to the initial position, all under the control of foot pedals. Communicating over Modbus RS485 the Gefran controller incorporates a micro PLC.