The Importance of Quality Rivets in CNC Manufacturing(working of spring Marshall)
- source:ESKRIDGE CNC Machining
What are Rivets?
A rivet is a mechanical fastener used to join multiple layers of material by inserting a metal shaft through aligned holes in the layers and deforming the protruding end to secure it in place. The deformed end is called the rivet head, while the pre-inserted end is called the shank or tail. When installed correctly, the rivet head and shank bind the materials together.
Rivets come in various head shapes, shank lengths and diameters, and materials. Common rivet materials include aluminum, steel, copper, and titanium. The choice of rivet depends on the materials being joined, strength requirements, and environmental factors.
Benefits of Rivets in CNC Manufacturing
Rivets offer several advantages that make them a staple in CNC manufacturing:
- Strength - Properly installed rivets form a tight connection that distributes stress evenly. This makes components more resistant to shock, vibration, and fatigue.
- Durability - High quality rivets withstand years of use without loosening or corroding. Aluminum and stainless steel rivets provide excellent longevity.
- Weight savings - Rivets are lighter than welds or bolts. This helps reduce component weight in aircraft, vehicles, and other applications where lightness is critical.
- Quick installation - Automated riveting with CNC machines enables fast mass production. Hand riveting also allows rapid assembly.
- Flexibility - Unlike welding, riveting can join dissimilar metals. Rivets can also connect layers of different thicknesses.
- No heat - Rivet installation doesn't require heat like welding or brazing. This prevents part warpage or damage to heat-sensitive materials.
- Cost effectiveness - Mechanical fasteners like rivets are inexpensive, especially compared to the equipment and effort needed for welding.
For these reasons, CNC-manufactured products prominently feature rivets to assemble sheet metal structures, hardware, enclosures, and more.
CNC Riveting Machines and Tooling
Installing rivets manually is labor-intensive and inconsistent. For efficient, high-volume production, CNC machines automate the riveting process for accuracy and speed.
Modern CNC riveting machines use advanced pressure, impact, or swaging techniques to insert and deform rivets in one automated cycle. Different tools are available for blind rivets, solid rivets, and specialty rivet types.
- Nose assemblies - The riveting nose contacts the workpiece and contains the rivet setting tools. Nose design affects accessibility in complex assemblies.
- Anvils - Anvils support the rivet tail during heading. Concave, flat, and custom anvil shapes are available.
- Feeder systems - Vibratory bowl, rails, or robotic feeders supply rivets to the nose for consistent fastening.
- Pressure foot - This clamping foot counteracts the rivet setting force to keep parts firmly aligned. Pressure feet optimize rivet quality.
- Controls - Programmable controllers set riveting parameters like force, stroke, and cycle times. Integration with the overall CNC system enables riveting automation.
Proper maintenance and calibration of these machine components is necessary to produce high-quality riveted assemblies.
Rivet Quality Considerations
In CNC applications, rivet quality directly impacts the durability, appearance, and safety of the finished product. Here are key factors to consider when selecting rivets:
- Strength - Rivet strength must suit the application loads and service conditions. This includes shear and tensile strength.
- Ductility - Ductile rivets can undergo deformation during installation without damage. Ductility reduces the risk of rivet cracking.
- Hardness - Harder rivets are more resistant to loosening and wear over time. Hardness must be balanced with ductility.
- Materials - Choose rivet materials compatible with the workpiece and environment. Factors are corrosion resistance, temperature limits, and galvanic corrosion.
- Plating - Plating like zinc improves corrosion resistance and lubricity. This avoids seizing during insertion.
- Dimensional accuracy - Precisely machined rivet dimensions allow consistent installation and optimum performance.
- Testing - Extensively tested rivets guarantee reliable quality. Common tests assess shear/tensile strength, vibration resistance, and inserts/removals.
- Certifications - Look for rivets meeting important quality standards like AS9100, ISO 9001, and those required by your industry.
By selecting top-grade rivets and diligently managing CNC machine maintenance, manufacturers can produce secure and enduring riveted assemblies. The upfront investment in quality pays dividends through boosted production efficiency, reduced defects, and improved product longevity.
Inspection and Testing
To guarantee rivet quality, manufacturers should perform several inspections and tests:
- Dimensional inspection - Sample rivets must meet design specifications forparameters like head and shank diameter, length, groove dimensions, etc.
- Material certification - Chemical analysis and material tests validate proper composition and mechanical properties like tensile strength.
- Plating thickness - For plated rivets, plating thickness should be measured to ensure adequate corrosion protection.
- Installation tests - Test installations assess insertion force, rivet seating, head formation, and pull-out resistance.
- Microscopic inspection - Examine rivets under a microscope to check for surface defects like cracks or porosity.
- Destructive testing - Shear and tensile testing verifies rivet strength. Analysis of failed rivets validates ductility and quality.
- Salt spray testing - This accelerated corrosion test detects flaws in plated/coated rivets.
- Process audits - Audit rivet supplier's manufacturing process for adherence to protocols that ensure consistency.
By combining statistical sampling with 100% automated inspection of critical parameters, manufacturers can cost-effectively confirm rivets satisfy all quality requirements before CNC installation.
From tiny consumer electronics to massive aircraft, quality rivets are the unsung hero holding many CNC-manufactured products together. With automated installation and strict quality control, rivets provide a reliable, lightweight fastening solution perfect for high-volume manufacturing. By selecting reputable suppliers, proper machine maintenance, inspection testing, and process oversight, manufacturers can achieve consistent, high-quality riveting results and deliver exceptional products to their customers. The upfront effort toward rivet quality control is a savvy investment that pays dividends for years down the road. CNC Milling CNC Machining