Achieving Optimal Rivet Quality with CNC Machines(rms finish chart Herman)

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Rivets play an integral role in manufacturing and construction, providing a strong mechanical fastener to join two or more components together. With the advent of computer numerical control (CNC) machines, the riveting process has been automated and streamlined for higher productivity and precision. However, achieving consistent, high-quality rivets requires careful programming, setup and maintenance of CNC riveting equipment.
This article provides guidance on optimizing CNC machine parameters, tooling and processes to obtain the best rivet quality for your application. Proper rivet specifications, feed systems, installation pressures and inspection procedures will be covered. Adhering to these best practices will result in enhanced joint integrity, lower defect rates and improved end-product performance.
Understanding Rivet Quality Standards
Before programming a CNC riveting operation, manufacturers must understand the key metrics that define a quality rivet:
- Head Height/Diameter - The rivet head height and diameter must meet design specifications, which governs the clamping force.
- Head Shape - Rivet heads should have the appropriate shape (dome, countersunk, flat, etc) without excessive flashing.
- Shank Conformity - The rivet shank should completely fill the prep hole without cracks or leaks.
- Locking Collar/Tail Form - The tail end should flare outward and lock the rivet in place.
- Pulling Force - Sufficient force must be applied to plastically deform the rivet tails.
- Stress Distribution - The clamping force should be evenly distributed for joint stability.
These parameters need to be validated through statistical process control tracking and quality assurance procedures. Operators can reference standards such as ISO 15977, ASME B18.1.6 or DIN 7337 for further guidance on proper rivet quality.
Programming Considerations for CNC Riveting
CNC programmers need to carefully determine the appropriate operating parameters and code commands to achieve high-quality rivet installation. Here are some key considerations:
- Feed System – Use a bowl, tape or stick feeder suited for the rivet size and throughput rate. Proper feeder angle, chute length and vibration settings are critical.
- Tooling – Select suitable rivet insertion heads, anvils and nosepieces. Carbide or tool steel construction with refined geometry prevents premature wear.
- Clamping – Program adequate clamping pressure and dwell time to hold parts firmly in place during riveting. Avoid distortion.
- Hole Alignment – Precisely align riveting gun axis with component holes via accurate fixturing and CNC program coordinates.
- Ram Stroke – Optimize ram stroke length, dwell time and speed for complete rivet setting without excess force.
- Installed Height – Control inserted rivet height above the top surface as needed for flash removal.
- Automated Inspection – Incorporate in-process inspection for key measurements like rivet height and pull force.
Optimizing these parameters requires consulting machinery manuals, material specifications, engineering drawings and extensive prototyping.
Riveting Process Considerations
In additional to CNC programming, shops need to address key factors in their overall riveting process:
- Operator Training – Skilled technicians should be educated on properly setting up and running the equipment.
- Maintenance Routines – Follow all OEM preventative maintenance schedules and procedures.
- Tooling Management – Establish tool inventory systems, usage tracking and replacement protocols.
- Raw Materials Handling – Store and deliver rivet stock to machines in a manner that avoids contamination or damage.
- Fixture Layouts – Design fixtures to provide sufficient access for rivet installation while minimizing part deformation.
- Quality Control – Perform test runs on all new or revised programs and conduct spot inspections on production runs.
- Parameter Logging – Monitor and record machine settings, cycle times, rivet batch numbers and QC data.
- Corrective Action – Analyze any out-of-spec conditions and adjust processes accordingly.
Adhering to proven manufacturing principles and CNC best practices will help shops achieve the highest and most consistent rivet quality over time.
Inspection and Testing Procedures
To guarantee rivet joint integrity in the finished product, manufacturers must conduct thorough inspection and testing:

- Dimensional Checks – Use gauges or instruments to validate rivet head and shank dimensions against specs.
- Head Profiles – Visually inspect for proper shape, circumferential concentricity, cracks, chips and flashing.
- Pull Tests – Confirm adequate clamping force by pulling on rivet head with a tension tester.
- Microscopic Examination – Review interfacial regions, joint gaps and evidence of radial cracking at high magnifications.
- Leak Tests – For fluid sealing applications, pressurize riveted joints and check for leaks.
- Vibration Testing – Perform riveted assembly vibration tests to check for loosening.
- Destructive Testing – Conduct shear, tensile or peel testing to failure to assess joint strength.
- Non-destructive Testing – X-ray or ultrasonic inspection can identify internal flaws like porous seams.
- Statistical Validation – Monitor key measurements with statistical process control charts to identify deviations.
By making quality riveting an organizational priority and implementing robust inspection procedures, manufacturers can achieve the highest reliability in their riveted products.
Rivets produced using CNC technology can elevate quality and throughput for high-demand manufacturing applications. However, optimal rivet installation requires careful selection and programming of feed systems, tooling and machine parameters along with a disciplined focus on maintenance, training, fixturing, quality control and continuous improvement. Engineers should reference industry specifications and standards to define proper rivet attributes and inspection methods. By adopting modern CNC best practices and testing protocols, manufacturers can gain confidence that their riveted assemblies will deliver maximum performance and safety. CNC Milling CNC Machining