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- source:GAENOR CNC Machining
Riveting has traditionally been done manually using hand tools. However, with advancements in computer numerical control (CNC) technology, automated riveting machines are now commonly used, especially in high production environments like aerospace and automobile manufacturing. CNC riveting maximizes efficiency, precision and consistency compared to manual riveting.
This article will provide an overview of CNC riveting in sheet metal fabrication. It will cover the basics of the riveting process, the advantages of CNC automation, and the common CNC riveting machines and tools used.
The Riveting Process
Rivets are tubular or solid cylindrical shafts with heads on one or both ends. The head on one end is larger than the hole diameter while the other end is inserted through the materials being joined. Once in place, the plain end is mechanically deformed to form the second head. This locks the rivet in place, clamping the materials together.
There are several types of rivets used including blind, tubular and semi-tubular. Blind rivets have a pre-formed head on one end and are deformed on the inserted end. Tubular rivets require access to both sides of the material to form heads on each end. Semi-tubular rivets have a partial pre-formed head and are deformed on the insertion end.
The riveting process consists of three main steps:
1. Drilling or punching holes in the materials to be joined. Hole size and spacing is precisely determined.
2. Inserting the rivets through the holes and fitting them flush against the material.
3. Using a rivet gun or other tool to mechanically deform the plain rivet end to form the second head. This expands the rivet, filling the hole and clamping the materials together.
For structural integrity, multiple rows of rivets are used with precise spacing between rivets and rows. Proper hole alignment is critical for the rivets to fit correctly.
Advantages of CNC Riveting
CNC or computer numerical control uses programmed automation to control tools and machinery. CNC riveting machines utilize advanced software and robotics to automate the riveting process for high volume production environments. This offers many advantages over manual riveting including:
- Increased Speed and Efficiency - CNC machines can rivet much faster than manual work, speeding up production times significantly. They can install hundreds of rivets per hour compared to dozens by hand.
- Improved Consistency and Quality - Automated precision helps eliminate human error and fatigue for more uniform results. CNC ensures consistently positioned holes, proper rivet placement and optimal force when deforming rivets.
- Lower Labor Costs - Less manual labor is needed to operate CNC machines, reducing production costs. One machine can replace many workers riveting by hand.
- Flexible Production - CNC programs can be easily adapted to handle product design changes and variations. Different rivet patterns and spacings can be accommodated with software changes rather than reconfiguring tools.
- Worker Safety - Automation reduces the need for workers to handle repetitive and physically strenuous riveting tasks that can lead to injury. CNC improves overall working conditions and safety.
- Reduced Material Waste - Automated precision drilling and alignment helps avoid cost overruns from improperly drilled holes and mistakes.
CNC Riveting Machines and Tools
There are many types of CNC machines that can perform automated riveting. Common configurations include:
- Gantry Style - These C-frame units suspend riveting tools above the work material to provide access from above. Parts can be moved under the gantry for flexible production.
- Robotic Arms - Articulated robotic arms allow a wide range of motion to position riveting tools. Multiple arms can be coordinated together.
- Specialized Machines - Custom CNC units can be built to rivet specific aerospace or automobile components. Rotary indexing tables and multiple heads are used.
- Multi-Spindle Heads - Riveting heads containing multiple spindles are commonly used to simultaneously drive multiple rivets for high volume output.
- Drilling Units - High speed CNC drilling machines are used to produce the precisely aligned rivet holes. Coordination with riveting units allows smooth workflow.
- Tool Changers - Quick changing tool systems let one CNC machine automatically switch between drilling and riveting operations.
- Robotic Crawlers - Magnetic crawlers can move along large aerospace structures to bring riveting systems right to the work area.
- Vision Systems - Cameras and sensors provide closed-loop feedback to precisely guide CNC riveting systems and verify rivet placement.
Common CNC riveting tools include squeezers to flatten deformable rivets, impact rivet guns to quickly upset solid rivets, presses to insert flush rivets, and drilling units to produce holes. Tool heads can be interchanged on a machine to suit different applications.
Programming and Codes
CNC riveting machines are programmed with detailed code containing specific instructions controlling the equipment. Code defines the locations to drill holes, robot motions, rivet selection, force parameters, tooling changes and all other automated tasks.
Code is written by skilled programmers using CAD models and product specifications. Different manufacturers have proprietary programming languages, but G-code is the most common numerical control programming language used.
Riveting codes specify hole coordinates, spindle speeds, rivet feed rates, insertion depth, hammer force or squeeze pressure, dwell times and other variables. Optimal code programs the process for maximum quality, speed, safety and efficiency.
Code can also be generated using computer aided manufacturing (CAM) software. CAD models are imported and programmers use the CAM interface to define toolpaths and operating logic which is converted into machine code.
Quality control sensors and vision systems may provide live feedback during the riveting process to optimize results. This allows adaptive control by having the CNC machine automatically adjust parameters based on real-time variances.
Applications and Best Practices
CNC riveting is commonly used in metal fabrication industries such as:
- Aerospace - Aircraft frames and skins are heavily riveted, often with specialty flush rivets. CNC enables drilling and driving thousands of rivets to precise specifications.
- Automotive - Auto bodies rely on CNC riveting for mass production of frames, panels and chassis components. Multi-spindle heads efficiently install many rivets concurrently.
- Electronics - Small precision parts like computer cases and control boxes use CNC machines for consistent quality riveting.
- Appliances - Household appliances that use sheet metal enclosures and wraps take advantage of automated riveting.
- Metal Building Products - CNC produces solid and consistent riveting results during fabrication of building products like roofing, siding, railings, and more.
- Infrastructure - Bridges, towers, railway cars, and similar structures leverage CNC to rivet strong yet lightweight metal components.
To utilize CNC riveting effectively, here are some best practices:
- Validate code programs on sample materials first before full production runs.
- Use strict tooling setups and precise calibration to avoid alignment issues.
- Apply lubrication to moving components for smooth automated operation.
- Inspect rivets, holes and finished products regularly for quality control.
- Select optimal rivet material and coatings to prevent corrosion.
- Consider secondary finishing steps like grinding or smoothing if needed.
- Adjust force parameters to avoid damaging or deforming materials.
With its precision, speed and consistency, CNC riveting is a transformative fabrication process for mass producing riveted assemblies. Automation increases throughput and reduces labor costs significantly compared to traditional manual methods. This allows manufacturers to improve profitability and competitiveness, especially critical industries like aerospace and automotive. Continued advancement in robotics, computer vision and adaptive control will drive further improvements making CNC riveting an even more dominant mass production technique. CNC Milling CNC Machining