Welding Digest

Playing in the dirt has never been so high tech! A far cry from the metal Tonka trucks of our youth, today’s excavating equipment is massive and specialized from the electronics that power them to the buckets that scoop tons of earth in each fell swoop. Constructed of a special alloy steel, these buckets are divided into the backhoe bucket and front shovel bucket depending on the type of materials being scooped.

The most common bucket in operation is the Crawler excavator. These heavy components must be able to hold tons of dirt, rock, clay, etc., without cracking or breaking down. The strength of the welds holding the bucket’s various components – bottom, wall, hanging ear, ear, tooth and side plates, bucket and side teeth, and various other parts – is of the utmost importance in guaranteeing performance. The key to ensuring an inherently strong bucket with long service life involves the implementation of an automated welding process developed around manufacturer specifications.

Automation

Excavation buckets feature steel plates, or strips, that protect the bigger plate from wear and tear. These strips are typically welded to the bigger piece using gas metal arc welding (GMAW) techniques to tolerances within +/- 100 of an inch. According to Mika Nihti, area sales manager, Eastern Europe, of welding automation solutions expert Pemamek (located in Loimaa, Finland and Mason, Ohio), investment in a CNC plasma or laser cutting machine is a must for ensuring these plates are cut to fit perfectly together.

“When a customer moves to robotic welding, they need to consider prefabrication,” said Nihti. “Cutting these steel components must be accurate. That means no air gaps or spaces. Assembly personnel must also be trained in automation once the decision has been made.” Plasma cutting machines are engineered to cut according to CAD specifications accurately, eliminating the guesswork as to whether parts fit together properly, fitting them tightly together, reducing weld volume, and allowing for an inherently stronger weld piece.

Analyze This

An automated system can’t be installed in a day. Nihti pointed out a feasibility study of the customer’s workpiece is a good place to start. From there, they work to determine the correct welding processes and optimal welding parameters as well as workflow and timing. Shop floor considerations must also be taken as well as a solutions partner’s ability to provide assistance even after the line has gone live. He referred to a customer in Estonia, Harry Metal OÜ, where the recommended system for welding a 22000-lb bucket for a mining loader included one welding robot with varying setups and two manual welding 3-axis workpiece positioners with programming, and the capability of welding using all major processes. Pemamek offered weld quality testing prior to installation. Recommendations included a PEMA XYZ robot gantry with a longer Y axis of travel for reachability from both sides of the workpiece and easier programming; one PEMA Skyhook SH2R-100000, 22000-lb, 2-axis workpiece positioner; one Yaskawa AR 1440 robot arm with a YRC1000 controller; one Fronius TPS 600i single GMAW equipment; one PEMA safety system with light curtains, a fume extraction system, and a laser seam searching sensor; two PEMA APSi 15000 3-axis wireless programmable positioners; and the center behind the entire system, WeldControl 300 Offline programming software.

Developed for 3D CAD-based offline programming, this software enables welders to download CAD files then edit welds and robot configurations as necessary. Operators and manual welders can further manipulate individual welds and access a library of weld functions and weld slicing options all on one panel.

“Offline programming is the key,” said Nihti. “The customer is producing several different workpieces, sometimes thousands . . . In many cases, the manual welder becomes the operator who is programming somewhere else in the facility while the robot continues to weld all of the time.” The ability to configure robotic positions and welds offline allows welding operators to move from job to job more efficiently. Multiple welds can be programmed into the software ahead of time then implemented when needed. Multipass welding operations can be programmed for large and heavy steel structures.

Nihti also emphasized the importance of automated welding positioners. The Harry Metal system features a Skyhook PRO SH2R-10000 2-axis positioner offering +/- 185-deg turning range at 2 rpm and a Skyhook PRO APSi 15000 3-axis positioner with wireless programming, maximum tilt torque of 51600 lb ft, and maximum load cap of 33000 lb.

A Solution for Continuous Throughput

The system detailed is one example of the types of automated welding solutions available. Nihti stressed no matter which configuration a shop decides, it needs to be flexible and designed for that shop’s individual needs. A one-size-fits-all approach doesn’t work.

Overall, the ability to automate an entire system goes beyond a specific industry. In Harry Metal’s case, they have been able to increase productivity by 400 to 500% and have set themselves up for growth. Automated welding technologies are offering solutions to manufacturers that need to keep production moving with little to no error in the fastest way possible.

This article was written by Michael Bell (director of sales North America, Pemamek) for the American Welding Society.