Producing High Quality Rivets with CNC Machining(metal surface finish chart Cheryl)
- source:BAGANZ CNC Machining
What is a Rivet?
A rivet is a mechanical fastener that consists of two main parts - a smooth cylindrical shaft and a head. The shaft is inserted into pre-drilled holes in the materials being joined. The rivet head is then hammered or pressed, deforming the tail and clamping the materials together. Rivets are available in many materials, sizes, and head styles to accommodate different applications.
Benefits of Rivets:
- Simple, economical fastening method
- Permanent, vibrations resistant connections
- Wide material compatibility including metals, plastics, composites
- Variety of head styles for accessibility
- Allows for movement from thermal expansion
Why CNC Machining for Rivet Production?
Computer numerical control (CNC) machining utilizes programmed automation to precisely machine parts. This offers important advantages for rivet manufacturing:
- High Degree of Accuracy and Consistency: CNC machines can repeatedly produce rivet shafts and heads to tight dimensional tolerances. This level of consistency is difficult to achieve with manual machining.
- Flexible Production: CNC programs can be rapidly adapted to produce different rivet designs, diameters, and lengths. Setup time is minimized compared to traditional equipment.
- Cost Effective for Large Volumes: The programmed automation of CNC machining enables high production rates and economy of scale. Machining costs per part are reduced.
- Ability to Machine Exotic Materials: CNC machines can effectively cut, drill, and shape hardened metals, alloys, and engineered materials that could be challenging with manual methods.
- Automated Quality Control: Modern CNC machines often include integrated inspection systems to automatically verify critical dimensions and continuously monitor process performance.
CNC Rivet Machining Process
The typical CNC machining process for rivets involves two main steps:
1. Shaft Production: CNC turning centers use rotating cutters to precisely cut rivet shanks from bar stock. The machines can produce small diameter shafts with fine surface finishes and tight length tolerances. Secondary operations like drilling and threading can also be integrated.
2. Head Forming: Second CNC operations form the rivet heads. Heading machines utilize punches to deform the shaft end into the desired domed, flat, or countersunk head shape. Multiple die sets allow flexible head styling. Precision servo electric drives actuate the heading ram for accuracy.
Other CNC operations like cleaning, inspection, sorting, and packaging may also be automated. This complete production line enables the volume production of rivets to meet requirements.
Optimizing Rivet CNC Machining
To consistently produce quality rivets, CNC programs and processes must be optimized:
- Utilize rigid, vibration damping machine structures and precision spindles to minimize chatter and distortion during turning, drilling, and heading operations.
- Select optimum tooling geometries and coatings based on rivet materials. Use sharp, high-quality carbide inserts.
- Program optimal feed rates and cutting speeds to balance productivity, tool life, and finished rivet quality.
- Schedule regular machine maintenance and calibration to maintain tight tolerances.
- Adopt reliable tool monitoring and broken tool detection to minimize scrap.
- Implement statistical process control (SPC) and quality management methods to minimize variability.
- Carefully design rivet handling mechanisms to avoid jams and damage.
- Train machine operators on proper program loading, setups, and quality checks.
By combining robust CNC machinery with optimized programming and quality control techniques, manufacturers can reliably produce large volumes of high precision rivets for critical applications.
Inspection and Testing
To confirm that rivet quality meets specifications, manufacturers perform several inspection and testing procedures:
- Dimensional Inspection: Sample rivet shafts and heads are measured to verify conformance to prints. Attributes like diameters, lengths, head height, and straightness are checked.
- Mechanical Testing: Hardness and tensile tests confirm rivet strength and ductility. Shear and pullout testing validates rivet performance in the assembled joint.
- Visual and Microscopic Examination: Rivets are visually examined under magnification to check for surface defects. The quality of head forming and other features is evaluated.
- Process Audits: Manufacturers audit the entire CNC machining process to make sure machines are calibrated, processes are controlled, and operators are trained.
By combining robust quality assurance practices with the capabilities of CNC machining, rivet producers can deliver the tight tolerance, high strength, and consistent quality fasteners that today's designs demand. CNC Milling