The Importance of Quality Rivets in CNC Machining(difference between 316 and 316l Jane)
- source:GAENOR CNC Machining
What are Rivets?
A rivet is a mechanical fastener that joins two or more materials by inserting its cylindrical shaft through pre-drilled holes in the parts to be assembled. The rivet shaft has a head on one end and a tail on the other. Once inserted, the tail end is upset, or deformed, to create a second head that secures the rivet in place. This creates a permanent mechanical connection.
Rivets come in a wide range of styles, sizes, materials and head shapes to accommodate different applications and assembly requirements. Some common types include:
- Solid rivets - made of a single material like steel, aluminum, titanium or monel. The most universally used rivet type.
- Blind rivets - designed to be installed where access is only available to one side of a part. The mandrel stem is pulled to deform the tail.
- Drive rivets - contain pre-assembled drive pins that are hammered or squeezed to flair the tail. Often used where an air hammer isn't available.
- Self-piercing rivets - pierce and join sheet materials without pre-drilling. Used extensively in auto manufacturing.
- Structural rivets - extra-large rivets designed for critical structural connections.
Why Rivet Quality Matters in CNC
For companies using CNC machining for high-volume manufacturing and fabrication, rivets are often inserted by automated riveting machines integrated into the overall assembly process. In these scenarios, rivet quality and consistency is imperative for several reasons:
Precision Tolerances - CNC machining and fabrication relies on tight tolerances between parts and fasteners. Quality rivets meet exact specifications for shaft diameter, head/tail dimensions, chamfer style and more. Rivets out of spec can prevent proper insertion or upset.
Strength - Rivets hold materials together in finished products, so their strength directly impacts the part's structural integrity. Low quality rivets are more likely to shear or malform during installation and use.
Reliability - A broken or failed rivet can mean an entire product fails. Consistent quality results in reliable connections over the product lifetime. Bad rivets lead to errors and rework.
Automation Accuracy - Modern riveting machines detect hole locations and rapidly insert thousands of rivets per hour. Inferior rivets with differences in size, shape or chamfer can cause misfeeds, jams and machine wear.
Speed - With automated CNC, rivets must be inserted precisely and quickly. Variable rivet quality forces adjustments to equipment, slowing cycle times.
How Are Quality Rivets Produced?
Industrial rivet manufacturers utilize advanced techniques and tight quality control to produce consistent, high-performance rivets optimized for automated CNC processes:
- CNC heading machines - Computer-controlled cold forming machines create rivet heads through high pressure indentation. Precision programmed tooling ensures exact head dimensions.
- Heat treating - Extensive heat treatment hardens and strengthens the rivet shaft material for maximum toughness and shear strength.
- Plating/coating - Many rivets receive surface treatments like zinc plating to resist corrosion and improve machinability. Coatings cut friction during insertion.
- Chamfering - The rivet hole chamfer is critical for location and insertion. Chamfers are machined to consistent angles and depths.
- Dimensional sorting - Sophisticated sorting equipment grades rivets by length, diameter and other attributes to guarantee dimensional uniformity required for CNC equipment.
- Statistical process control - Throughout manufacturing, quality metrics like diameter variance, tensile strength and head roundness are measured continuously to identify and correct any process deviations.
Key Rivet Material Options
CNC shops can select rivet materials matched to their specific application and strength needs:
- Aluminum - Lightweight, with good corrosion resistance. Choice for aircraft and other transportation.
- Steel - Very high shear strength. Used in heavy machinery and structural applications. Can be heat-treated.
- Stainless Steel - Best corrosion resistance. Ideal for harsh environments. Provides good shear strength.
- Monel - Nickel alloy with strength resembling steel but excellent corrosion resistance. Common in marine and chemical installations.
- Titanium - Extremely strong but lightweight. Used in aerospace applications. Resists corrosion and fatigue cracking.
- Brass - Decorative appearance along with good corrosion protection. Used for consumer goods. Lower strength than steel or aluminum.
Optimizing Your CNC Riveting Process
To get the best performance and efficiency from CNC-installed rivets:
- Consult with your rivet supplier to select the optimal rivet style, materials and treatments for your specific application.
- Adhere to recommended hole sizes for proper rivet fit. Use hole deburring tools maintain clean edges.
- Make sure your automated feed systems include screens to remove debris and defective rivets that could jam equipment.
- Set machines to the proper insertion force and upset pressure. Make minor adjustments as needed to get a good flow with no jams.
- Perform regular maintenance on insertion mechanisms, anvils, separators and feeding devices. Replace worn tooling.
- Implement statistical process control tracking for rivet quality, especially diameter and grip range.
With close attention to rivet selection and process control, manufacturers can achieve fast, error-free automated CNC riveting that meets product quality and performance objectives. The right rivets plus dialed-in equipment equal strong, reliable end products. CNC Milling CNC Machining