Midwest Engineered Systems built a robotic welding with large positioner system for large part manufacturing for a power management company.
Prior to the installation of the Robot Automation System, this was entirely a manual process. All welding was manual, and a crane did all part positioning. This did not allow for proper in-position welding and created ergonomic issues for the operators.
MWES was asked to design a robotic welding solution that is integrated into a conveyance system that automatically removes tack-welded pieces from the conveyor. The system would need to interface with the customer’s SAP system to gather needed information and automatically use parametric programming to weld specified “leak-proof” welds without operator intervention.
The product dimensions could vary infinitely between maximum and minimum sizes. A work envelope of 17” x 35” x 47” for the smallest unit and 60” x 105” x 98” for the largest would need to be accommodated. The maximum weight for the assembly would be 4000 lbs.
System justification was to improve first pass quality and increase production.
A Robotic Weld Cell, which operates in automatic mode in the following manner:
The weld cell would communicate with the welding line conveyor system which is intended to shuttle product from station to station during the fabrication process. The PLC operating the conveyor system will communicate to the weld cell the pertinent information of the product coming into the weld cell. The weld cell will receive the information and adjust its weld program and tooling to accommodate the incoming tank.
If the incoming product requires the weld process to change due to material type the robot will dock its current weld torch and pick up the correct one for mild steel and stainless steel. The stainless steel weld package will also be used for bi-metallic welds (mild steel to stainless steel). As the unit enters the weld cell, sensors will indicate its presence. The conveyor transfer system will then shuttle the unit into a section of the cell to present it to the positioner for automatic loading, load onto the positioner, and the tooling will automatically clamp it into place. The weld cycle will begin executing the parametric program and the weld routines. Upon completion, the conveyor transfer system will remove the completed unit from the positioner and return it to the conveyor system and communicate to the conveyor the unit is ready to continue to the next fabrication phase.
Midwest Engineered Systems Inc. fully automated solution included:
- Conveyance System
- Chain Driven Live Roller Conveyor
- Turntable with Chain Driven Live Roller Conveyor
- 3 Strand Chain Conveyor
- ABB Robots
- 4 ABB Robots with IRC5 Controller
- 4 ABB Servo TrackMotion integrated to IRC5 Controller
- 3 External Servo Axis per Robot for MWES Positioner control
- 4 MWES Three 3- Axis SkyHook positioners integrated to the IRC5 Controller
- 1 MWES Three 3-Axis SkyHook Smart Positioner Integrated to an Allen Bradley PLC and driven by Kinetix Servo Drives.
- Positioner EOAT
- Each positioner was equipped with a 6 axis servo gripper which has the ability to adapt to the infinite number of part designs.
- Product Tracking Software
- Product tracking is done using Turck RFID technology. The operator loads a part onto the conveyor system, then the operator scans a barcode on the work order and associates the work order to a RFID puck. The operator mounts the RFID puck to the unit and it is released into the production system. As the unit travels down the conveyance system, RFID readers mounted at the entrance of the weld cells read the puck and decide where to direct the unit. If it is sent into a weld cell, the PLC requests manufacturing data from a SQL database via an OLDI Module which ties the PLC to SQL database. The SQL database will reply with the requested data and the PLC then sends the manufacturing data to the robot and the Weld Cell begins production.
- Tool Changing Station
- Each welding robot is equipped with an ATI tool changer to allow the robot to change torches as need. There is a torch dedicated to mild steel and a torch dedicated to stainless steel. In the case we are welding a bi-metallic, with both mild and stainless components, the stainless torch configuration is used. When a torch is not in use it is stored in a dedicated Torch Holder.
- Tactile Sensing
- This system uses two different types of tactile sensing, standard SmarTac that is built into the Fronius TPS5000 Weld Power Source in which the robot uses the torch gas cup or the welding wire to touch off on the product to locate the weld start point. Or the MWES Laser SmarTac in which the robot uses a Laser to search the part without actually touching the part to locate the weld start point.
- Active Weld Tracking
- This system uses two different types of Active Weld Tracking. One method is using the ABB Weldguide III product. Weldguide III is a thru the arc method of tracking, in which the weld Current and Voltage are monitored during the welding process by the Weldguide III board. The Weldguide III board sends data to the robot which is used to make path corrections and to maintain the proper weld wire stick out. The other method is the Servo Robots Power-Trak seam tracker. The Power-Trak uses a Laser and a Camera to find the contour of the part and sends real-time data back to the robot which the robot uses for path correction during the weld process.
- Parametric Robot Programming
- This system needed to handle an infinite number of different sizes and feature locations. To manage this task, MWES used a technique known as parametric programming. Parametric Programming is a type of mathematical optimization, where the optimization problem is solved as a function of one or multiple parameters. MWES worked with the end user to develop manufacturing rules. These rules allowed MWES to know what features would be on the unit, and where the features would be located. The unit data information array was sent to MWES via the customer’s ERP system. Once the robot received the data array, the data was parsed and stored in different register positions. The robot program used the data to locate the unit and all its features. MWES then used the tactile searching to find the weld start positions and the weld tracking methods to ensure the weld was laid consistently into the joint.
- This programming technique will allowed the end user to create new part styles that will not require robot programming as long as the part designs adhere to the manufacturing rules
- ABB Robot Studio
- The robot programs were created off line in a Software Package. This software allows for robot program creation without causing interruption to robot production. As well this software package will allow the end user to test their new tank designs off line in the virtual world and identify any possible issues before send the new design into production.
Impact to the Customer
The final robotic welding and positioner system provided the customer with the following benefits:
- Reduced Rework/Increased First Pass Quality
- Increased Throughput
- Improved Part Traceability