Many manufacturing and process lines feature handheld fastening tools, typically driven by compressed air. While these tools are perfectly adept at boosting productivity, ensuring repeatability and reducing fatigue, how about going a step further, to semi-automation? This concept sees workers feed a piece part into a machine that performs the process, riveting for example. Another form of semi-automation involves rivets or screws fed automatically to the handheld tool for fastening by an operator.
So, what are the signs that might prompt a shift to semi-automation? Well, perhaps the task is taking too long or is too fiddly. Are workers on the line complaining? Maybe consistency or quality is falling, or the job is becoming a production bottleneck.
MAKING THE CHANGE
The transition to semi-automation cannot take place at the flick of a switch. There are many engineering challenges to overcome and define. Firstly, what type of assembly automation best suits the application? Further influencing factors will likely include the required lead time for deployment and the available resources to help implement the system, such as in-house expertise, time and space.
Budget is arguably the ‘elephant in the room’, something that Richard Avery, sales and marketing director at Zygology, a specialist in technical fastening requirements for industry, says is holding back many who want to automate further.
“I used to work for a company that developed automated riveting systems, but beyond the large OEMs, there seems little willingness in the UK to invest in systems of this type,” he says. “However, if we were having this conversation in Germany, the outcome would likely be different. They do their calculations a different way, taking into account the productivity gains available.”
He adds: “The automatic feeding of rivets to the gun is a smaller and more cost-effective step towards semi-automation. We sell a number Z-AR auto-feed riveting systems (pictured, left) every year. This type of system can accelerate assembly, improve quality and reduce manufacturing lead times.”
The Z-AR utilises specially adapted Stanley XT1 (pictured above) or XT2 tools attached to the bowl feeder and control unit, with rivets fed to the nose tip of the tool at the rate of 60 or more per minute. The bowl feeder will hold up to 1,000 rivets, eliminating the handling of rivets by the tool operator.
Another established solution in this area is the Gesipa GAV 8000 Eco and Electronic machines (the latter features integrated setting process monitoring) for blind riveting. The console comprises a vibratory rivet feeder, pneumatic-hydraulic power unit and electronic control system. A pistol-type tool head provides manual operation, or users can take advantage of a robotic or in-line tool head. Operators simply activate the gun trigger to blow-feed a rivet into position in the tool. At the same the time, the mandrel from the previously installed rivet returns to the console via a vacuum-assisted collection system. A receptacle within the console houses spent mandrels, while sensors with indicator lights on the control panel alert the operator when it is time to empty the spent-mandrel receptacle, replenish rivets or attend to a service matter.
CARRY THE LOAD
For those seeking semi-automated systems where operators simply load the workpiece, what does such a machine look like in terms of configuration? In truth, there are numerous examples across industry, such as the PF-401 from AMS Automated Machine Systems. This machine features up to 10 automatic screwdrivers or nutrunners mounted vertically on a single actuator over a work bed. The worker simply loads a workpiece into a fixture and inserts the required screwdriver/nutrunner bits. A PLC control monitors torque and angle during operation, while programmable I/Os and data collection meets product traceability requirements. Historical data functions include fastening results, torque curves and system errors.
This is just one example. As with all investments, calculating the ROI is critical to support the business case for semi-automation. Here, throughput and productivity may well increase, while reject parts and scrap could diminish, all of which provide a positive contribution. On the flip side, energy costs may rise, as there is more automation involved, which could prove pivotal in an era of high energy prices.
One way to cut the energy costs associated with fastening operations is to shift from pneumatic to electric (battery-powered) tools, such as pictured below. This move negates the high cost of generating compressed air, not to mention any associated leaks. In addition, many workers enjoy the feeling of being free from an airline. Of course, other factors are at work here, which must be included in the investment calculation.
“If a manufacturing plant already has compressed air capabilities, our advice is typically to retain their current strategy of using pneumatic tools,” says Avery. “It makes commercial sense as everything is in place for this methodology. However, for smaller companies or start-up operations, battery-operated fastening tools can offer the opportunity to reduce energy costs.” To provide an idea of the potential savings available, a recent report by Stanley Engineered Fastening called ‘Battery vs Pneumatic Tools’ says: “A 2018 University of Minnesota study determined that pneumatic power tools use around seven to 13 times more energy than electric motor-driven power tools – and motor-driven tools have become even more efficient since then.”
CALL TO ARMS
If a robot is the preferred technology for migrating to a semi-automated process, then a collaborative robot (cobot) will likely provide the optimal solution, thanks to its ability to work safely with humans. While a human operator loads workpieces, fills a hopper with fasteners, and changes tooling and fixtures, the cobot will provide the fastening operation, bringing tireless reliability and productivity to the task.
According to system integrator Reeco, cobots are capable of fastening bolts on assembly lines in a very similar way to humans, operating and manipulating within tight space scenarios. The company says that the rationale for traditional industrial robots such as speed, repeatability, consistency and accuracy, are also true for cobots. Reeco reports that cobots are filling the gap in automation where flexibility is of importance, being capable of integration around existing equipment, operators and processes (pictured above).
Mark Gray, UK sales manager at Universal Robots, reports on one of many semi-automated fastening operations he has seen involving cobots: “One of our customers relies on human operators to manufacture motorcycle panniers. They place assemblies into fixtures, building two assemblies side by side. When they finish the first assembly, a cobot with an attached screwdriver swings into position and fastens the screws. While the robot is doing that, the operator finishes the second assembly. By the time the robot has fastened the screws on the second assembly, the operator has unloaded the first assembly and prepared another. And so it goes on.”
He adds: “The cobot is a tool to increase productivity, reliability, and health and safety. Research suggests that human-robot collaboration is up to 85% more productive than humans or robots alone. If you think about work balancing a semi-automated fastening task, the cobot can work in the dead time when operatives are performing preparatory assembly. Cobots help human workers to achieve higher productivity; and low productivity is what we what suffer from in the UK.”
