Precision Fastening

Short of welding, the precise fastening of separate metal or plastic plates can best be achieved by threaded fasteners. Using semi-automated or fully automated precision fastening systems to install threaded screws, bolts, nuts and similar fasteners, metal plates can be securely fastened together. Not only can these systems attain extremely accurate torque and depth values, but they can also speed up overall production immensely thanks to robotic positioning, integral quality control instrumentation, automatic record document creation and many more options.

Sure can!  Automated screwdriving comes in two flavors: semi-automated and fully automated. Both solutions utilize motorized screwdriver spindles that drive fasteners to precise torque and depth specifications. Semi-automated screwdrivers are typically hand-guided by a human operator, whereas fully automated screwdrivers are positioned by multi-axis or linear robotics. You can even automate fastener feeding, bit change-out, quality control documentation and other support functions.

In the same way that an automated screwdriver installs threaded male fasteners using a driver bit, an automated nutrunner installs threaded female fasteners such as hex nuts using socket fittings. Most commonly, nut runners are used to place and torque down nuts over protruding screws, bolts and threaded studs during the assembly of manufactured parts. Nutrunners grip their fasteners around the outside head perimeter (by physical grippers or by vacuum), making them able to install capped screws by grabbing their heads as well. A fully automated nutrunner uses logic and motor controllers, robotic positioning, quality control instruments and safety protection devices to fasten nuts by machine. You might also know a nutrunner by another name:  automatic torque wrench.

Both an impact wrench and a nutrunner are motorized rotary tools used to thread hardware fasteners with minimal human effort. A nutrunner delivers smooth, high-speed rotation. It is used to install threaded nuts quickly up to a target torque value. An impact wrench is used to forcefully uninstall threaded nuts, using an internal hammer mechanism to repeatedly strike the drive end as it rotates in order to loosen torqued nuts from their studs. Said another way, a nutrunner looks to achieve a high torque value, and an impact wrench looks to overcome a high torque load.

Automated screw driving entails a few key steps: bit setting, fastener feeding, positioning, screw driving, torque checking and tool retraction. Once a bit is installed into the driver, it can drive multiple similar fasteners sequentially, or it can change bits and switch to driving a different style fastener, all automatically. Additional steps can be added to the process including precision multi-axis alignment using optical sensors, photo inspection and validation, and more.

Handheld screwdrivers require manual positioning, whereas a spindle screwdriver can be automatically positioned using robotic or actuated fixturing. So, the answer comes down to production requirements such as how often the driver is used, how difficult the part is to work with, required torque accuracy and how ergonomic the application is overall. Handheld powered screwdrivers are great for low-volume, bench-top work with nominal torque accuracy requirements, whereas automatic spindle screwdrivers are preferred for production-level manufacturing with tight-tolerance torque and positioning requirements.

We do! AMS is a premier manufacturer of automated precision fastening systems, serving the automotive, plastics, medical device, consumer goods, electronics and related industries. OEMs from all of these markets and more trust AMS to design, build, deploy and commission automated screwdriving and nutrunning assembly systems such as our PF-201 (semi-automated) and PF-401 (fully automated) platforms.

Automated nutrunning machines are industrial manufacturing systems that install threaded nuts over stud fasteners with minimal human effort. Nutrunner machines can position, screw down and torque nuts during the production of manufactured assemblies. A wide array of manufactured products depends on nutrunner machines, spanning medical device, automotive, electronic and many more applications. Human operators only need to load and unload the machine, and the automatic precision fastening system does the rest.

Automated fastening can be described as the installation of threaded fasteners using motorized screwdrivers and nutrunners, coupled with some level of electronic control over the position, torque, travel depth and RPM of the drivers. Single or multiple drivers can be operated within a single system, all of which can contour to different fastener locations, angles and positions around assemblies with complex shapes. Automated fastening also provides tangible safety, quality control and data acquisition features alongside the fastening process. Where semi-automated fastening involves a human operator to work the powered drivers, fully automated fastening needs no human operator as robotics handle the drivers directly.

In traditional manual screwdriving, torque wrenches with driver bit adaptors were used to tighten fasteners to a desired torque. Modern automatic screwdriving takes this same concept and puts the torque limiting function of the torque wrench directly into a powered screwdriver, allowing the screwdriver’s spindle to approach and brake within a very tight tolerance of the target torque rating. Several different technologies can achieve this type of torque control, all dependent on the screwdriver and level of automation selected. Simplistic screwdrivers may utilize a mechanical limiting clutch, and more advanced screwdrivers may use a DC electric controller powering a motor encoder. 

Selecting tools for an automated fastening system requires two main decisions: Is semi-automated or fully automated operation desired, and are bit-driven or grip-driven fasteners to be used? Semi-automated systems use human-operated drivers, so you’ll need that tool set plus fixture mounting, an electric drive controller and a tool suspension arm. Fully automated operation turns over driving to robotic positioners, calling for a more expansive equipment platform with multiple toolsets, automated bit change-out and fastener feeding, and multiple safety components. As for the fastener decision, screws that can be driven by a bit (Phillips, flat or Torx heads, for example) can use an automatic screwdriver tool. Nuts, hex cap bolts and other headed studs that must be contacted around their perimeter by grippers or by vacuum suction will instead call for a nutrunner tool.