Every fastening decision can impact the early stages of appliance design through to assembly and, ultimately, end-product performance. Design decisions include which hardware to specify and which equipment can best promote efficient, safe, and cost-effective installation.
Self-clinching fasteners will often be specified at various locations in appliances to attach components such as housings, service doors, plates, and internal electronics and circuitry. These fasteners (dozens of types in thousands of variations) install permanently in thin metal sheets to provide permanent threads for mating hardware. Installation of these types of fasteners is most often performed during assembly instead of during final production. (Those in the metalworking industry serving appliance manufacturers are some of the largest users of the hardware.) A properly selected press supported by complementary technology and operating options can make all the difference in the installation.
While all presses to install self-clinching fasteners will provide necessary squeezing force to enable the fastener to become an integral part of an assembly, press similarities end there. Some presses are relatively basic for smaller jobs; others for high-volume applications are highly advanced with programmable electronics and user-friendly controls. Robotics can be integrated and safety features have become standard.
Some of the typical considerations in deciding which type of press to utilize include overall job volume; fastener sizes and how many different types of fasteners will be installed per application; center-to-edge distance of the installation point (which will suggest required throat depth); necessary insertion force for installation; workpiece size and configuration; and budgetary parameters.
The simplest presses are portable hand tools, which typically weigh only 10 lbs./4.6kg and can achieve ram forces of up to 6,000 lbs./26.7kN. These hand presses will install self-clinching nuts and studs in unified and metric sizes and can utilize appropriate punches and anvils, which can be snapped into place.
Larger stand-alone manual press systems are equipped with adjustable stroke lengths to speed operation and can deliver a ram force of 500 lbs./2.2kN to 12,000 lbs./53.3 kN. Rapid tooling changeover can accomplish short production runs efficiently.
On the higher end of the scale, automated presses deliver rapid high-volume fastener installations. Feeding rates are typically five or six times faster than those obtained with manual insertions, and squeezing action is adjustable to compensate for variations in thickness and hardness of a sheet and in fastener heights. These presses can perform at cycle rates up to 2,750 strokes/hour while delivering a ram force of 400 lbs./2.7kN to 16,000 lbs./71.2kN.
All presses for installing self-clinching fasteners can be placed at the most advantageous locations in an automated production line for appliance assembly. Depending on production scope, some users determine that a combination of automated and manual presses in a work cell instead of one model alone can better serve their fastener-installation needs.
Several new innovations in press technology and operating software have arrived to optimize the fastener-installation process. Among them:
• Robotics. The incorporation of robotics is relatively new in fastening applications. Their adaptation for use with fastener-installation press equipment achieves the goal of total automation and streamlining of the entire process with virtual hands-off operation.
Computer-driven and teachable for any application, the latest generation of robotics can be synchronized with a press to present the workpiece to the point of fastener installation. Standard robotic arms can offer maximum flexibility with six axes of movement and 40″ reach. In addition, any appliance application requirement can be accommodated. Advanced units come equipped with touch-screen controls for easy operation.
• Safety Systems. These generally are standard in most automatic or fully automated fastener-installation presses, but their design and effectiveness can vary. The newer safety systems are designed to reduce potential accidents and injuries, optimize operator confidence, and avoid workpiece damage, while ensuring rapid and accurate self-clinching fastener installation. A reliable safety system is one that is designed as an integral part of a press (not as an “afterthought” or add-on feature.)
In particular, users should be wary of “safety systems” employing a conductive approach, where the tooling becomes part of the safety circuit. In this equipment, the press goes into high boost to install the fastener when it contacts the conductive workpiece and completes the safety circuit. If the conductive part contacted is a ring or sweaty hand/arm of the operator, the press will go into high boost, quite possibly resulting in injury. If a non-metallic workpiece is utilized, the safety must be completely turned off (and rendered inoperable) to protect the workpiece. As a result the press must be operated in a double-step mode, which negatively affects productivity.
An effective integrated safety system will activate in all modes of operation (with the first step established as the safety stroke) and feature a single-fault tolerance design, whereby no single fault will compromise the operation of the system. Other system elements should include double safety valves, synchronized safety sensors, transducer feedback with double inputs, and system reset.
• Operating Software. Fully automated press systems continue to evolve with software engineered for enhanced job productivity, safety, and quality.
The latest examples include Fastener Length Monitoring (FLM) to flag and reject fasteners identified by the system as too short or too long; Smart-Dwell/Force Verification to ensure consistent, reliable, and secure low-force fastener installations; Soft-Touch, which offers unprecedented ram-speed control combined with gentle workpiece contact to provide added workpiece protection, and reduced noise; Setup Access Codes with three “fail-safe” levels to maintain desired installation parameters; and upgraded Maintenance Diagnostics to aid in troubleshooting and service.
• Specialized Tooling. Workpieces with unusual installation requirements, such as back flanges or recesses have traditionally precluded use of automated presses to install self-clinching fasteners due to limited access. New developments in tooling, such as bottom-feed clinch-nut tooling for “inside-out installation,” has turned the tables and allowed users to forego manual equipment in favor of automatic presses when the volume of fasteners is significant enough to warrant.
• In-Die Fastener Feeding. Portable systems are now available to work in tandem with a stamping press (and properly tooled die) to feed and install self-clinching nuts, studs, and standoffs during the process of stamping appliance components. This provides an unprecedented capability to perform two operations (stamping and fastener-installation) simultaneously in a die. Users report increased productivity, quality, and savings.
Our Die-Feeding System is virtually “plug and play” by utilizing multi-pin twist lock connectors to interface with the die and stamping press. (Only a standard 110V receptacle and shop air are required for operation.) Recognizing an industry need for flexibility, the system can be configured for multiple or single insertions, generally matching the rate of the stamping press.
Operators are guided by a touch-screen (for set-up and operation) and an online library of fault/help screens. Standard (remove and change to) In-press removable tooling can handle complex workpieces and offers considerable adaptability capable of reaching into areas generally considered inaccessible. Customized tooling can be engineered to meet particular application needs.
The Die-Feeding System consists of die tooling, fastener-feeding system, and die-sensing system. Customers are fully supported from die design through installation and in-house training.
More innovations can be expected as the industry strives to develop equipment that is safer, quicker, and engineered to do more than ever before. As advancements in press technology quicken, it can prove helpful to consult with an experienced manufacturer to ensure that fastener installation will be performed with the most appropriate machines to maximize production efficiencies and economies.