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Drilling is an important part of the PCB shape processing technology. Many people mistakenly believe that drilling must be done at low feed rates and low speeds. This was true in the past, but today's cemented carbide drills are different. In fact, users who choose the right drill bit can greatly increase productivity and reduce overall cost per hole.
Do you know which PCB circuit board shape processing drilling technology
For end users, there are four basic types of drills with carbide cutting edges to choose from: solid carbide, indexable inserts, welded carbide tips and interchangeable carbide tips. Each has its advantages in specific applications.
The first solid carbide drill was used in modern machining centers. It is made of fine-grained cemented carbide and has a TiAlN coating to increase tool life. These self-centering drills achieve excellent chip control and chip removal in most workpiece materials due to their specially designed cutting edges. . The self-centering geometric angle and good accuracy of the solid carbide drill bit ensure that high-quality holes without any further processing are obtained.
The holes processed by the welding drill have a fairly high surface finish, high dimensional accuracy and good position accuracy, and no further finishing is required. Due to the cooling through holes, the welding point drill bit can be used in machining centers, CNC lathes or other
A machine with sufficient stability and speed.
The indexable insert drill bit covers a large diameter range when the drilling depth is from 2XD to 5XD. They can be used in rotating applications as well as in lathes. For most workpiece materials, these drills use a self-centering geometric angle to reduce cutting forces and provide good chip control.
The last type of drill bit combines a steel body with a replaceable solid carbide drill tip called a crown. This kind of drill bit can obtain higher productivity with lower processing cost under the premise of providing the same accuracy as the welding drill bit. This new-generation drill bit with a cemented carbide crown provides precise dimensional increments and has a self-centering geometric angle that ensures high machining dimensional accuracy.
Careful consideration of tolerances and machine stability
The PCB factory should select the drill bit according to the specific tolerances on the processing. Usually the tolerances of small diameter holes are tighter. Therefore, drill bit manufacturers classify drill bits by specifying nominal hole diameters and upper tolerances. Among all the drill bit types, the solid carbide group drill bit has the tightest tolerance. This makes them the best choice for drilling extremely tight tolerance holes. The factory can use a solid carbide drill with a diameter of 10mm. The tolerance is from 0 to +0.03mm.
In one aspect, the indexable insert drill bit tends to deflect. These drills are equipped with two blades-an inner blade in the center and a blade extending from the inner blade to the edge-initially only one blade participates in the cutting. This creates an unstable situation that causes the bit body to deflect. And the more the month length of the bit deviates. Therefore, when factories use indexable insert drills of 4XD and above, they should consider reducing the feed rate during the first millimeter of processing and then increasing it to the normal feed rate. The welded bit and the interchangeable crown bit are designed with two symmetrical cutting edges forming a self-centering geometric angle. This stable cutting design allows the drill to enter the workpiece at full speed. The only exception is when the drill bit is not perpendicular to the machined surface, it is recommended to reduce the feed by 30% to 50% when cutting in and cutting out.
On the other hand, welding drills or Seco drills with interchangeable hard alloy crowns have a tolerance of 0 to +0.07mm. These drill bits are often a good choice for PCB circuit board drilling production processing. The indexable insert drill bit is the hard work drill bit in the industry. Although their upfront cost is usually lower than other drills, they also have the largest tolerances, which can range from 0 to +0.3mm depending on the diameter/hole depth ratio. This means that end users can use indexable insert drills when they require large hole tolerances, otherwise they must prepare to use a boring tool for hole finishing. Together with the hole tolerance, PCB circuit board factories need to consider the stability of the machine tool during the selection process. Because of stability to ensure tool life and drilling accuracy. The OCB circuit board factory should verify the status of the machine spindle, fixtures and accessories. They should also consider the inherent stability of the drill bit. For example, solid carbide drill bits provide the best rigidity, which makes it possible to obtain high accuracy.
The latest drill bits with interchangeable solid carbide tips provide superior economic efficiency. Instead of replacing the entire drill bit body, the end user only buys a cemented carbide bit whose price is equivalent to regrinding a welded drill bit or a solid cemented carbide drill bit. These crowns are easy and accurate to replace. The factory can use multiple crowns on a drill body to drill several holes of different specifications. This modular drilling system reduces the inventory cost of drill bits from 12mm to 20mm in diameter.
In addition, it eliminates the cost of back-up drill bits when welding drill bits or solid carbide drill bits are reground. When reviewing the cost per hole, the factory should also take the total tool life into consideration. Generally, for a PCB circuit board factory, a solid carbide drill bit can support regrinding 7 to 10 times, while a soldering drill bit can only regrind 3 to 4 times. On the other hand, the steel body of the crown type drill bit can be replaced with at least 20 to 30 crowns when machining steel parts.
There is also a productivity issue here. Welded drill bits or solid carbide drill bits must be reground; therefore, factories tend to reduce the speed to avoid chip sticking. But the drill bit with the interchangeable tool bit does not need to be reground, so the PCB circuit board factory can use sufficient feed and speed during processing without worrying about the sticky chip of the cemented carbide material.
