Riveting in Sheet Metal Fabrication Using CNC Technology(types of fits Miranda)
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How Rivets Work
Rivets are mechanical fasteners that join materials by expanding when the tail of the rivet is upset, flared, bucked or driven by a riveting gun. The rivet shank fits into pre-drilled holes in the materials being joined. As the tail of the rivet is deformed, the rivet expands, causing the shank to swell and grip the sides of the hole. This creates a solid joint.
Rivets come in many styles, shapes and materials. Some common types include blind rivets, tubular rivets, drive rivets and structural rivets. They are used to join sheet metals, plastics, composites and other materials in countless industries and applications.
Traditional Manual Riveting
In traditional manual riveting, holes are first drilled or punched into the materials at precise marked locations. A rivet is inserted into each hole, and the tail is then flared using a hammer or rivet gun, upsetting the rivet and causing it to expand within the hole. This process requires physical strength and skill. Workers must be able to precisely match the force and strike the rivets accurately to avoid damage.
Manual riveting has several downsides. It is relatively slow, leading to low production rates. Operator fatigue can reduce quality over time. And because it is performed by humans, there can be inconsistencies between rivets and products. However, for low volume production, manual riveting may still be the most cost-effective option.
CNC Riveting Machines
For high-volume manufacturing, CNC riveting machines improve consistency and throughput. CNC systems enable precise computer control of the riveting process by automating the drilling of holes, insertion of rivets and upsetting of the rivet tails.
Here are some of the benefits of CNC riveting:
- Speed and efficiency. CNC machines can dramatically increase riveting production rates compared to manual methods. Riveting heads can upset multiple rivets per second based on the design specifications. This also reduces worker fatigue.
- Consistency and precision. CNC equipment ensures each rivet is placed and upset with exactly the same programmed force and location across the production run. This level of consistency is almost impossible to achieve with manual riveting.
- Flexibility. CNC machines can be programmed to rivet many product variations. Quick changeover between programs allows flexible production.
- Integration. Many CNC riveting systems are designed to integrate with other fabrication processes like cutting, forming and drilling. This automates the full fabrication process flow.
- Monitoring. Modern CNC controllers collect production data that can be analyzed to find improvements and issues. This facilitates continual optimization of the riveting process.
- Ergonomics. Automating riveting with CNC equipment reduces hard labor and repetitive actions by workers. This improves worker health, safety and satisfaction.
CNC Riveting Process
The basic CNC riveting process involves three stages: hole drilling, rivet insertion and tail upsetting. However, different machine configurations suit different production flows and volumes. Here are some of the most common CNC riveting machines:
- Single-station presses: A riveting head is mounted over a CNC-controlled drill head on a hydraulic press. The materials are loaded and holes are first drilled. Rivets are then fed into the holes and upset.
- Multi-station dial machines: Materials are fixtured on platens arranged radially around an indexing dial. As the dial rotates, drilling, rivet insertion and upsetting are performed at sequential stations.
- Inline machines: Straight inline machines use conveyors to move materials between discrete process modules. Flexible manufacturing systems align various CNC modules including drills, inserters and upsetters.
- Robotic cells: Industrial robots armed with riveting end effectors can be programmed to handle riveting. Robots add flexibility and can service multiple stations.
- Specialized systems: Custom CNC machines are designed for niche applications and high volumes like aerospace riveting. They incorporate industry-specific processes and quality controls.
Every CNC machine requires fixtures to hold and locate the parts. Programmable logic controllers coordinate the staging, clamping, drilling, inserting, upsetting, unloading and all other automated motions. Operators oversee the machines, supply materials, make adjustments and handle quality checks.
Programming Rivet Patterns
CNC riveting programs specify the locations of every rivet to be drilled and inserted in each part. Programmers analyze the part design and required rivet pitch, spacing and sequence. Riveting programs are coded in G-code, which provides coordinates for hole drilling and instructions for controlling drills, inserters and upsetters at each hole.
Modern CAM (computer-aided manufacturing) software can automatically generate riveting programs from 3D CAD models. Engineers simply specify rivet parameters like diameter and pitch. Simulation features also let programmers visualize the machine motions and riveting sequence before running production. This helps in avoiding collisions and errors.
Engineers must account for several factors when programming CNC riveting patterns:
- Rivet type and specifications like diameter, grip range and material. These impact the hole size and upset force.
- Spacing between rivets based on joint strength needs.
- Order and direction of riveting to avoid deformation.
- Collision avoidance between rivet gun and formed flanges.
- Clamping points to secure the materials while drilling and riveting.
- Precision hole locations and angles, especially for awkward intersections.
- Approach angles so rivet guns can access every hole.
- Multiple riveting steps for staggered rivet rows or multilayer materials.
Quality Control
Because rivets hold critical airplane and automobile parts together, quality control is crucial. Programmers input allowable tolerances for hole diameter, rivet length, grip and tail dimensions. In-process sensors track measures like rivet setting force. If dimensions shift out of spec, the machine automatically stops and flags the error.
Post-process inspections are also common. Operators may pull random samples to measure rivet length and ensure the tails are fully formed. Automated vision systems can also scan for defects like cracks or poor upset shape. Tagging each sample makes any issues traceable back to the specific machine, fixture and program. Continuous quality data helps adjust processes to prevent future defects.
Applications of CNC Riveting
From aircraft and autos to bridges and appliances, CNC riveting automated production across many industries.
Aerospace: Aircraft bodies and wings involve thousands of rivets joining aluminum skins to stringers and ribs. CNC machines expertly drill the many overlapping holes and upset the flush rivets.
Transportation: Cars, trucks, railcars, ships and more all use rivets in body panels and frames. Multi-shift automated lines rivet mass volumes cost-effectively.
Metal building: Steel I-beams, girders, roofs and cladding all get riveted on large CNC beds. Mechanical fasteners assemble structures quickly.
HVAC: Boilers, ducts, vents and other sheet metal components use rivets at seams and joints. Inline machines rivet at high speeds.
Appliances: Washing machines, dryers, ovens, microwaves and more rely on tough rivets at chassis and casing seams. CNC provides precision.
Electronics: Computers, tablets and gadgets have stamped and riveted metal enclosures.Automated cells make millions of the same consumer products.
Many products combine riveting with other processes like punching, bending, welding and hardware insertion in mixed CNC fabrication lines. Programming software optimizes the flows between work stations. This maximizes throughput, quality and consistency.
The Future of CNC Riveting
CNC riveting technology will continue advancing alongside other smart manufacturing trends.
More automation, sensors and data analytics will streamline changeovers, speed defect detection and prevent downtime. Vision-guided robots may handle loading and unloading. Machines with internet connectivity can monitor production remotely.
New riveting techniques like self-piercing rivets promise faster, lower-cost assembly. Improved alloys and coatings will resist corrosion and fatigue. Stronger composite materials allow lighter, reliable designs.
Custom CNC machines Purpose-built for niche tasks will enter smaller workshops. User-friendly programming software will be accessible to more manufacturers. Higher speeds and precision will boost mass production quality.
While rivets have been used since ancient times, today's CNC automation applies this classic fastening solution for the high-tech demands of modern manufacturing. Continued advances promise to unlock even greater performance and versatility into the future. CNC Milling CNC Machining