Electronics Protection - September/October 2012 - (Page 8)

Feature Key Drivers When Turning to Captive Panel Screws LillyAnna Penn, Global Product Manager-Assembled Products PennEngineering Whenever designers must consider how to best equip panels, covers, drawers, racks and other access points with fastening hardware, panel fastener assemblies integrating captive screws often will turn out to be ideal solutions – and for good reasons. In addition to providing secure attachment and controlled access, these types of fasteners are designed to keep parts to a minimum for easy and efficient handling and installation. Captive screw assemblies also mount permanently, eliminating the risks associated with loose hardware that could fall out, get lost or misplaced, potentially causing damage to other components. While all panel fastener assemblies with captive screws offer these universal benefits, narrowing the field from among dozens of potential candidates and options may initially seem daunting. But the selection process can be made easier by first focusing on this central question, which mounting style is best suited for the application and what features would be appropriate to specify? Ultimately, the answers will help guide designers to proper choices. Some applications may be inappropriate for self-clinching hardware, especially when stainless steel panels are involved, due to the relative fastener/panel hardness issue. But compatible solutions exist. An example is a captive panel fastener with a retainer made from 400 series stainless, which will install reliably into a stainless sheet. Flare-mounted panel fasteners with captive screws will usually be one of the types recommended for stainless applications, and for most any thin material of any hardness. Unlike self-clinching versions, a flare-mounted fastener’s shank deforms (instead of the panel) during installation and will require minimal installation force. These likewise will install flush on the backside of a panel and, unlike self-clinching fasteners, will be appropriate for close centerline-to-edge applications and for use in painted panels, since the paint thickness will not hinder attachment (unlike the self-clinching process) and no marring will occur during installation. One tradeoff, an extra step will be required for panel preparation, since the mounting hole will require a countersink. Floating/flaring style fasteners can install into stainless and into any thin panel material (including PC boards), regardless of panel hardness. These are similar to flare-mounted types in that they deform during installation, require minimal squeezing force with punch and anvil (to flare their retainer) and serve as practical hardware for close centerline-to-edge applications. An added advantage, they can compensate for mating thread misalignment, offering up to 0.81 inches/2.06 mm of float within the mounting hole. Key Driver: Mounting Style Standard mounting styles of captive panel screws may employ self-clinching, flare or float/flare mounted technologies. Selfclinching types will install flush (when using shortest screw length) on the backside of a panel, no protrusions on the side of the sheet opposite installation, and will require minimal panel preparation. No secondary operations will be necessary, which can help maximize productivity along the line. The fastener is inserted into a properly sized hole in the mounting sheet, and by applying sufficient squeezing force from a press, becomes a permanent part of the assembly. As a result, the sheet material surrounding the hole is forced into the fastener’s undercut, securing against axial movement and against rotation by a displacer. For any self-clinching fastener the relationship between fastener and sheet material is critical and three basic requirements will be necessary for successful outcomes: • Metal sheets into which the captive panel fastener will be installed must have adequate ductility to allow the displaced sheet material to cold flow into the undercut. • Metal sheets into which the fastener will be installed must be sufficiently softer than the fastener so that the fastener itself does not deform during the installation process. • Sheets must meet the minimum sheet thickness required by the particular fastener. As an example, one basic type of captive panel screw assembly requires a minimum sheet thickness of 0.036 inches/0.92 mm. Typically, there is no specified maximum thickness required for clinching into sheets. Sheet thickness may become a consideration, however, depending on the fastener’s screw length. 8 Key Driver: Features and Functions After a suitable mounting style of the fastener has been selected, its inherent features and functions will open a window into potential best picks. The availability of standard and optional capabilities equips designers with many potential solutions that can resolve potential application issues or otherwise advance objectives. Following are some commonly expressed concerns and/or requirements and how they can be handled: • How can potentially off-angle thread engagement and potential thread damage be avoided during assembly? Self-clinching, flare-mounted and floating captive panel screws can be engineered with patented anti-cross threading technology, which easily corrects off-angle installations, aligns components, and slides through clogged internal threads. Specification of this feature can save time and money by eliminating failures, repairs, scrap and downtime associated with thread damage. Here’s how the technology works. During initial engagement when threads come into contact, the anti-cross threading feature begins to cam over the female thread. The two thread helixes then align perfectly and fasteners will drive normally with reduced effort. September/October 2012 www.ElectronicsProtectionMagazine.com http://www.ElectronicsProtectionMagazine.com

Table of Contents for the Digital Edition of Electronics Protection - September/October 2012

Electronics Protection - September/October 2012
Table of Contents
HP Intelligent Series Racks Offer Monitoring Capabilities for Data Centers
The Unknown Problem with Airtight Enclosures
Key Drivers When Turning to Captive Panel Screws
Emerging Trends in Field Equipment Enclosures
JV Industrial Solves Power Outage Issues with Battery-Free Flywheel
The Green Data Center Opportunity
The Power-Grid and Protecting Electronic Devices
Maximizing Availability, Capacity and Efficiency with Rising Data Center Temperatures
Canyonwest Cases Releases new Enclosures for Flat-Screen TV Transportation
Ohmite Manufacturing Releases Radial-Fin Heat Sink Extrusions
Rogers Introduces Condux Plus Conductive Foams
FIP Gasketing Resin Offers Advantages over Gasketing Materials
Minmax Power Releases MSGWI06 Series of DC/DC Power Modules
New E-Line Locking Systems Reduce Security Costs and Enhance Locking Solutions
Industry News
Calendar of Events

Electronics Protection - September/October 2012