1. Precision control techniques and methods for PCB board milling are essential for ensuring high-quality outcomes.
2. The milling process requires careful attention to detail to achieve accurate dimensions and surface finishes.
3. Various techniques, including feed rate adjustments and spindle speed optimization, play a crucial role in precision control.
4. Utilizing advanced CNC machinery enhances the precision of the milling process significantly.
5. Additionally, implementing proper tooling strategies is vital for achieving desired tolerances.
6. Monitoring the milling parameters in real-time can help identify potential issues early in the process.
7. Regular maintenance of milling equipment ensures optimal performance and longevity.
8. Ultimately, combining these techniques will lead to superior PCB milling results.
9. Continuous improvement and adaptation of methods are necessary to meet evolving industry standards.
10. As technology advances, staying updated with the latest innovations is critical for PCB manufacturing success.
1. The milling technology of Printed Circuit Board (PCB) NC milling machines encompasses several critical factors, including the choice of cutting direction, compensation methods, positioning techniques, frame structure, and cutting points, all of which are vital for achieving milling precision.
2. Below are the accuracy control techniques and methods for PCB milling, compiled by Jieduobang PCB.
1. **Cutting direction and compensation method:**
When the milling cutter engages with the board, one side always faces the cutting edge, while the other side is positioned against it. The former results in a smooth machined surface and high dimensional accuracy. With the spindle consistently rotating clockwise, an NC milling machine with a fixed spindle and worktable should utilize counterclockwise cutting when milling the printed board’s external contour.
2. This technique is commonly known as reverse milling. For milling frames or grooves within the circuit board, the forward milling method is employed. Milling plate compensation involves the machine tool automatically setting the milling cutter to offset half of its diameter from the center of the milling line—effectively, the radius—ensuring that the milling shape aligns with the programmed settings. If the machine tool includes a compensation function, attention must be given to the compensation direction and the program commands, as errors in using compensation commands can alter the circuit board’s dimensions to match the milling cutter diameter.
3. **Positioning method and cutting point:**
There are two main positioning methods: internal and external. Positioning is crucial for process developers, and typically, the positioning scheme is established prior to circuit board manufacturing. Internal positioning involves selecting mounting holes, plug-in holes, or other non-metallic holes on the printed board as positioning holes. The relative position of these holes should ideally be on the diagonal, with larger diameter holes preferred. Avoid using metallized holes, as plating thickness discrepancies can impact the consistency of the selected positioning hole and may also risk damaging the plating during handling. It’s advisable to minimize the number of pins, enhancing positioning accuracy and reducing plate deformation.
4. Generally, two pins suffice for small boards, while three are preferred for larger ones, offering accurate positioning, minimal shape deformation, and efficient milling speed. The downside is the need for various pin diameters based on the numerous hole types in the board. If suitable positioning holes are absent, discussions with customers about adding them during early production can be cumbersome. Additionally, differing milling templates for each board type complicate management and increase costs.
5. External positioning involves adding positioning holes outside the plate for milling. This method is easier to manage and can standardize production across approximately 15 milling board templates. However, if the board is milled all at once, it risks damage, particularly to the panel, as the milling cutter and dust suction device may inadvertently pull the board, causing breakage.
6. The segmented milling method is utilized to maintain joint points. First, mill the plate; once milling is complete, pause the program, secure the board with adhesive tape, execute the next program section, and drill out the joint point with a 3mm-4mm drill bit. This method offers fewer templates, lower costs, and simpler management, allowing all circuit boards to be milled without installation or positioning holes. It simplifies early production processes while optimizing substrate utilization. However, the use of drill bits can leave 2-3 protrusions in the circuit board shape, which may be aesthetically unpleasing and could fail to meet customer expectations, alongside longer milling times and slightly increased labor intensity.
7. **Frame and cutting point:**
The fabrication of the frame occurs during the initial stages of circuit board production. Frame design influences not only electroplating uniformity but also the milling process. Poor design can lead to frame deformation or small waste blocks during milling, obstructing dust extraction or damaging high-speed milling cutters. Notably, frame deformation—especially with external milling positioning—can result in finished board distortion. Optimal selection of cutting points and processing sequences is essential to maintain maximum frame strength and speed, while poor choices may lead to deformation and scrap of the printed board.
8. **Process parameters of milling:**
1. The shape of the printed circuit board is machined using a cemented carbide milling cutter, with typical cutting speeds ranging from 180 to 270 m/min.
2. The calculation formula is as follows (for reference only):
3. S = pdn/1000 (m/min)
4. Where: P: π (3.1415927)
5. d: Diameter of the milling cutter in mm
6. n: Speed of the milling cutter in RPM
