Achieving High Quality Rivets with CNC Machines(4 axis cnc Isabel)
- source:GAENOR CNC Machining
Rivets are a crucial fastening component in many manufacturing applications. While traditionally installed by hand, computer numerical control (CNC) machines enable riveting to be automated for higher efficiency and consistency. However, like any manufacturing process, there are several factors that contribute to achieving a quality riveted joint using CNC equipment. In this article, we'll explore considerations around rivet material selection, CNC programming, machine setup and processes to consistently produce strong, reliable rivet connections with a CNC machine.
Rivet Material Selection
The characteristics of the rivet material itself are foundational to joint integrity. Steel, aluminum, copper, Monel and titanium alloys are all common rivet materials, each with their own strengths and limitations. Key factors to evaluate include:
- Shear and tensile strength: The rivet must be strong enough to handle expected load levels without failing. High strength materials like certain steel alloys are preferable for heavy duty connections.
- Ductility: More ductile materials like aluminum can deform and flow better during riveting to create a tighter joint. Brittle materials may be more prone to cracking.
- Corrosion resistance: Materials like stainless steel or Monel resist corrosion in wet environments. Unprotected steel is prone to rusting which can compromise joint strength over time.
- Cost: Material cost differences can be a factor for high volume production runs. Steel rivets are generally most economical.
The intended application should guide which material properties are most important to optimize for maximum service life and reliability. Consulting with rivet suppliers is recommended to select the best option.
CNC Programming Considerations
Well-programmed CNC code is essential to achieve consistent, high quality riveted joints. Here are some best practices to follow:
- Precisely control feed rates and position stops for hole alignment. Riveting requires very accurate hole alignment between parts, usually within a few thousandths of an inch. Programmed sequences must enable repeatable precision.
- Incorporate specific pressures, duration and extension for rivet setting. Most CNC controllers allow programming rivet cycles with these parameters. Optimal settings depend on rivet size and material and should be validated through testing.
- Include automation for inserting rivets in holes. Devices like auto feed rivet heads, vacuum pickup or robotic arms can be programmed to orient and deliver each rivet to the joint point for improved efficiency.
- Develop sequences to access tight spaces. CNC automation enables riveting angles and locations that may be difficult by hand. Multi-axis movements, special tooling and creative step sequences can rivet hard to reach areas.
Thorough CNC programming is key to quality and efficiency in automated riveting. Taking advantage of the controllability and flexibility of CNC systems allows consistently achieving tight, strong joints.
CNC Machine Setup
Proper physical setup of the CNC system is also critical for quality rivet connections:
- Select suitable riveting heads for head style, diameter and material. Sets are available for flat head, countersunk head, large flanged head and other styles to match application needs. Precision ground tooling helps optimize pressure dispersion for uniform setting.
- Use rigid, vibration dampening base structures. Riveting develops significant forces which can distort lesser frames and foundations leading to misalignment. Massive bases or active isolation systems are ideal for best results.
- Incorporate adequate workholding. Fixtures should firmly fix parts in precise alignment and withstand riveting forces without movement. Dedicated fixtures ensure accuracy and reduce variability.
- Provide sufficient access for rivet insertion. Multi-axis rotary tables or robotic arms may be needed to orient parts for easy rivet loading into tight spaces in complex assemblies.
- Use proper drilling before riveting. Accurate hole sizes are critical for joint strength. CNC drilling operations should be process controlled and incorporate pecking cycles, high helix drills and carbide tooling to avoid excessive tool pressure, heat and hole damage.
A CNC machine set up specifically for quality riveting will repeatedly deliver precision joints. Taking steps to manage vibration, alignment and access makes consistent results more attainable.
CNC Riveting Processes
The actual automated riveting process can also be optimized to achieve quality results:
- Perform test rivets on samples to dial-in equipment settings and parameters. Different joint materials and designs will respond differently. Testing determines ideal pressures, durations and depths.
- Incorporate in-process inspection. Sensors can help monitor each rivet setting event for any potential defects. Stopping bad rivets immediately avoids propagating issues.
- Implement effective chip and shaving control. Drilling and riveting produce debris which can scratch finished surfaces or clog machine systems. Good chip management via vacuum systems, brushing and air blasts preserves quality.
- Automate rivet insertion. Mechanized feeding of rivets into each hole eliminates handling variability for more uniform joints. Systems avoid jamming through controlled vibratory, centrifugal or robotic loading.
- Control heat buildup. Extended automated riveting shifts generate significant heat which can affect tolerances. Coolants or reduced cycle times may be required for thermal stability.
- Perform final inspection of joints. Automated or manual checks of joint fit, rivet flushness, material cracking and proper clinch confirms the process consistently produces quality.
A well-managed CNC riveting process leverages automation while implementing key quality checkpoints to achieve repeatable success.
Getting top notch riveted joints from a CNC machine requires careful coordination of material selection, programming, machine setup and process control. With attention to each element, manufacturers can achieve automated riveting that reliably produces precise, high strength connections efficiently. While initial validation and testing is required, the long term benefits of quality and consistency make CNC riveting an ideal solution for many applications. Consultation with experts in rivets, CNC machinery and production engineering ensures implementing the best combination for maximum results. The rewarded efforts are joints that repeatedly withstand demands over time. CNC Milling CNC Machining