Figure 1. Dual Scara Robot assembly machine. Source: Visumatic.While automation technology has evolved from waterpower and steam engines to the proliferation of electric cars, internet of things (IoT) technologies and the advanced computational abilities needed to run them, screws are still widely used to hold the world together. These twisted inclined planes come in many forms, from tiny watch screws meant for intricate work, to more rough-and-ready helix-cylinders that secure wooden decks. While the basic screw concept has stayed the same for hundreds of years, drive technology has advanced from simple flathead recesses, to hex and torx driving models, to specialty screws manufactured with tamper resistance in mind.

Advances aside, the process used to insert screws is normally left to the consumer’s imagination — if they so choose to think about it at all — but the cost and quality of a product is a direct result of how fasteners are attached. Consider an operator working in a factory with a simple handheld screwdriver. The screw is inserted and torqued to a “value” that feels right to the person driving it. If a different operator takes over, more or less tight screws may be the result, and even products made by the same person can vary throughout the day.

Screw automation benefits

Figure 2. Torque value can vary considerably if factories aren’t automating their processes. Source: Gorodenkoff/AdobeBeyond manual screw insertion, implementation of a “semi-automatic” system where the operator manually positions a powered driver can not only improve repeatability but also processing speed and can mitigate repetitive stress injuries (RSIs). This can be a dramatic improvement, but as discussed here, such automation is only taking a process from what one might term “Level 0” automation to “Level 1.” In the linked article, four levels of automation are discussed, all the way up to a “Level 4/lights out” assembly line featuring Visumatic’s Viper fastening robot. The article even outlines a Visumatic screw driving implementation that increased productivity by a factor of 15.

Versatile collaborative robot fastening

Full Level 4 automation is not appropriate for all operations, and engineers and management will need to consider how far to take a process. One alternative is using a cobot setup, and Visumatic can help integrate their screw fastening systems with customer-provided robotics to augment human labor.

For instance, an electronics manufacturer was rolling out an updated product design and wanted to prove out a new form of process automation at the same time. Because of the to-be-assembled part’s compound angles, they chose to use a flexible cobot — otherwise known as a collaborative robot —mounting a Visumatic screw feeder. This proved to be perfect for the given application. As it utilized a fastener that was common in the facility, the implementation would help to prove out the use of this technology combination for future applications as well.

Here, Visumatic worked with the customer to develop a collaborative work cell platform that would be nearly universal for most product assemblies. This was done to allow simple, cost-effective changeover to new products, and quick implementation of future process improvements. It also reduced support and maintenance training requirements.

In this case, the customer brought their own cobot system, and Visumatic provided the specialized screw fastening equipment to unleash its screw driving potential.

Automation tracking benefits

As noted earlier, an automated or semi-automated system can improve speed and repeatability. Such a setup can also improve how well a process is tracked. So, after making the leap from unpredictable human torque driving to well-specified driver values, engineers can drill down between settings, or even into the differences that may crop up in order to make process improvements. Having this data on-hand allows one to take a process from good — even very good — to excellent and provide a reference in the case of customer returns.

Overall process considerations

Figure 3. Handheld pin insertion. Source: Visumatic

While increased speed capability is generally a very good thing, one must also consider that screw automation does not happen in a vacuum. As one part of an assembly line’s processing speed ramps up, upstream processes will need to be able to supply parts, while downstream operations will need to accommodate for the potentially increased load.

Rather than (or in addition to) looking at an existing assembly line process and selecting the best available tool for screw fastening in a factory’s current state, it can be helpful to step back and envision the best future situation. With this whole-process vision in mind, engineers can then find the tools to make this a reality. One might also consider design changes to the product itself to better facilitate automation. While certain improvements may be impractical in the immediate future, do not be afraid to consider longer-term planning opportunities, and what one might be able to control for the next product iteration.

How much automation is appropriate?

When thinking about what level of automation to implement in the short- or medium-term, one has to consider how mature a product is, its customization needs and how much longer a product will realistically be produced. A high-volume product that never changes (and will be around for many years) may be an excellent candidate for a highly developed lights-out automation solution. A product that changes over time may be a better fit for a human controlled semi-automatic screw feeder, while something in the middle, perhaps with difficult to reach holes, or several versions, may be better suited for a cobot workstation.

One must also consider that not all products are designed well for automation. To address and head off potential difficulties, Visumatic is happy to offer their expertise to create assemblies that screw together smoothly with minimal operator intervention. Poorly “automatable” assemblies can suffer from quality problems through their lifetime and incur extra labor expenses that might have been averted with a few simple tweaks.

Success example: Flexible tabletop assembly machine tackles tight on-center spacing

When considering screw automation, one might logically assume that such machinery requires either wide screw spacing to accommodate static tooling, or expensive robotics to move screw insertion equipment in place sequentially. In fact, Visumatic equipment can be tailored to accommodate very tight spacing, even in semi-automatic installations.

In one successful installation, an electrical products manufacturer was struggling to maintain production numbers without adding labor. This application required two screws to be driven to depth in a metal electrical connector. Screw installation points were less than an inch apart (7/8 inch), creating a challenge for automated fastening.

Per customer workflow demands, Visumatic provided a flexible tabletop approach which can be moved anywhere on the factory floor as needed. This features a two-spindle VPD power driver, tied together by a weldment and base plate. A separate feeder unit is connected to the spindle assembly by hoses and cabling.

To use the device, an operator places a single part in the fixture, allowing the Visumatic screw fastening device to take care of feeding screws and driving to the required depth. It features a straightforward control platform with a simple PLC and basic operator interface, and the modular design keeps the customer in control of their process flow. A Visumatic tabletop assembly machine is a very affordable option for high-volume, flexible assembly, which can be appropriate in many situations.

Visumatic: A partner in screw automation

Visumatic is ready to help with all aspects of screw automation. This may involve advice on whether a product is a good fit for automation — and how to make it better — leading to screw insertion equipment that is designed from the ground up for smooth operation. Visumatic can also help augment existing assembly lines for better screw fastening, whether that is an operator-driven semi-automatic screw fastening station, a full lights-out assembly operation or something in-between.

Visumatic is a specialty engineering firm located in Lexington, Kentucky, whose mission is to deliver easily recognizable value in every fastening solution they create. Their engineers have over 90 years of combined experience, and average employee tenure is 14 years. This expertise allows them to build and deliver most screw fastening systems in three to six weeks.

Visumatic’s expertise, use of high-quality components and extensive testing before final implementation results in high reliability and reduced time, leading to a low total cost of ownership. When help is needed, support is available via on-call staff, and they can be at a customer site within 24 hours. Many Visumatic systems have been in operation for years, and they stand ready to design, build and support cutting-edge screw automation products now and well into the future. Visit the Visumatic website for more information.