Producing High Quality Rivets with CNC Machining(remove chrome plating Ina)
- source:BAGANZ CNC Machining
What are Rivets?
A rivet is a mechanical fastener that consists of two main parts - a smooth cylindrical shaft and a head. The shaft is inserted into holes drilled or punched into the materials being joined. The rivet head is then flattened using specialized tools, creating a tight joint that holds the materials together.
Rivets come in a wide range of styles, sizes and materials. Some common types include blind rivets, tubular rivets, semi-tubular rivets, split rivets, and drive rivets. The material is typically steel, aluminum, titanium, or specialty alloys.
Why Use CNC for Rivet Machining?
CNC machining offers numerous advantages for producing high quality rivets with precision and efficiency. Here are some of the key reasons CNC is ideal for rivet manufacturing:
- Accuracy and Consistency - CNC machines can repeatedly produce rivet shafts and heads to tight tolerances of +/- 0.005 inches or better. This level of accuracy ensures rivets conform to specifications.
- Flexibility - With CNC, the rivet manufacturing process can easily switch between different rivet sizes and designs. The CNC program just needs to change, allowing fast transitions.
- Volume Production - CNC machining has very high throughput capabilities, enabling mass production of rivets to keep up with demand. Complex parts can also be automated.
- Materials Capabilities - CNC machines can work with all standard rivet materials including steel alloys, aluminum, titanium and more. Advanced CNC tools allow machining hard materials like stainless steel.
- Lower Costs - CNC boosts efficiency and minimizes material waste, resulting in lower per part costs compared to manual machining processes. The automated nature of CNC also reduces labor expenses.
CNC Rivet Machining Processes
Producing rivets via CNC machining generally involves two main processes - machining the rivet shafts and forming the rivet heads. Here is an overview of how it works:
Rivet Shaft Machining
The rivet shafts are machined from rod stock fed into the CNC machine. Common materials include aluminum, steel, stainless steel, copper, and more. The automated CNC program controls the machining operations to create the precision shaft dimensions including the diameter and length.
Typical machining processes for the rivet shafts include:
- Turning - Precisely rotating the rod stock while a cutting tool shapes the profile. Highly accurate diameters can be achieved.
- Facing - Machining the ends of the rods to exact lengths for the rivet shafts.
- Chamfering - Cutting angled edges on the rivet shaft ends to aid rivet head forming.
- Threading - Imparting threads on the rivet shaft if needed for threaded rivets.
The CNC machine can perform all these operations in sequence without human intervention via its programmed instructions. The cut rivet shafts then proceed to rivet heading.
Rivet Head Formation
The pre-cut rivet shafts now have the rivet head formed on one end. Heading produces the flange that rivets against the workpiece when installed. CNC offers a few approaches to rivet heading:
- Spinning - The rivet tips are placed in a high speed spinning head die. The friction and pressure forms the head.
- Peening - The shaft tip is hammered or squeezed to flare out the metal into a rivet head.
- Upsetting - The rivet tip is compressed between a die and force applied by a punch to flare the head.
For high volume production, specialized CNC rivet heading machines are used. They combine feeding of pre-cut rivet shafts with integrated tooling to form the heads via spinning, peening or upsetting in a smooth automated process.
The CNC machine electronically synchronizes the head formation tooling with the rivet shaft feed for precision control of the riveting sequence. Rivet heads can be accurately and consistently produced at rates exceeding 100 rivets per minute.
Machine Tools for CNC Rivet Production
There are several CNC machine tools well-suited for efficient rivet manufacturing:
- CNC Lathe - Performs turning, facing, chamfering, threading, and other OD (outside diameter) operations on rivet shafts. Multispindle CNC lathes can machine multiple rivets in parallel.
- CNC Screw Machine - Specialized CNC lathe designed for high volume screw machining. Efficient for mass producing threaded or unthreaded rivet shafts.
- CNC Upsetter - Forms rivet heads via upsetting process with high force ram and die. Can be integrated with feeding system.
- CNC Riveting Machine - Full work cell that handles rivet feeding, cutting, and heading in an automated sequence. Ideal for mass production.
- Swiss-Type CNC Lathe - Unique CNC lathe with guide bushing and rotary cutter head. Permits complete inline rivet machining in one setup.
The modular nature of CNC allows tailoring the machining solution specifically for the rivet design, materials, volumes and production requirements.
Optimizing Rivet Quality
To consistently achieve excellent rivet quality, CNC programs should be designed to optimize these key factors:
- Tight Tolerances - Hold rivet dimensions to tight +/- 0.005 inch or better tolerances. CNC is capable of much higher precision.
- Surface Finish - Use appropriate tooling, feeds and speeds for an ideal smooth surface finish free of defects.
- Dimensional Accuracy - Verify CNC program is producing rivets precisely matched to the design prints. Perform periodic quality checks.
- Material Integrity - Select tooling material and machining parameters to avoid heat damage, tears or cracks in the rivet material.
- Head Formation - Dial in optimal head shape, diameter, thickness and concentricity relative to the shaft.
- Deburring - Remove all sharp edges or burrs from rivet machining that could cause issues during installation or operation.
By combining a well-designed CNC machining process with quality assurance procedures, manufacturers can churn out perfect quality rivets at high volumes with CNC capabilities. CNC Milling