With the continuous development and popularization of 3D printing technology, more and more parts and prototype designs begin to adopt this flexible and efficient manufacturing method. However, in practical application, 3D printed parts often need secondary processing, such as drilling and tapping (that is, machining threads in holes) to meet the requirements of assembly and connection. This paper will introduce how to drill and tap on 3D printed parts, and provide some practical skills and precautions.

First, the basic steps of drilling

1. Choose the right drill bit
Because there are many kinds of 3D printing materials, such as PLA, ABS, PETG, nylon and photosensitive resin, their hardness and toughness are different. Therefore, a suitable drill bit should be selected according to the material characteristics. For common materials such as PLA, ordinary high-speed steel (HSS) bit can meet the requirements; For high-strength or fiber-filled materials, it is suggested to use tungsten carbide bit to improve wear resistance and service life.

2. Mark the drilling position
Before drilling, mark the accurate drilling center point on the surface of the part with a marking tool or a center punch to prevent the bit from slipping and ensure the accurate hole position.

3. Control the rotating speed and feed speed
When drilling, the rotating speed of drilling machine or electric drill should be controlled to avoid material melting or deformation caused by too high rotating speed. Generally, it is recommended to control the rotating speed between 500 and 2000 rpm, depending on the material and the size of the drill bit. When feeding, it should be kept at a constant speed, so as to avoid hole wall fracture or drill bit fracture caused by excessive force.

4. Cooling and chip removal
In the process of drilling, proper use of cooling liquid or compressed air can help to remove chips and reduce temperature, especially for thermoplastic materials, which can effectively prevent deformation or material melting caused by overheating.

Second, the key points of tapping process

1. Select the appropriate tap.
Before tapping, the corresponding tap should be selected according to the required thread specifications (such as M3, M4, etc.), and the drilling diameter should be matched with the tap. For example, a threaded hole of M3 usually needs to drill a bottom hole with a diameter of 2.5mm first.

2. Lubricate the tap
Adding proper amount of lubricating oil or tapping paste during tapping can reduce friction, prolong tap life and improve thread quality.

3. Adopt step-by-step tapping method.
For hard or thick 3D printed materials, it is suggested to do it in two steps: first, use the initial cone to drill, and then use the middle cone or fine cone to finish thread forming. This can reduce the torque and prevent the tap from breaking.

4. Pay attention to cleaning and deburring
After tapping is completed, it is suggested to use a brush or an air gun to remove the residual debris in the hole, and use a chamfering drill to remove the burr of the hole to ensure the smoothness and stability of the threaded connection.

Third, common problems and solutions

-Cracking of hole wall: It may be caused by brittleness of material or too fast drilling speed, so it is suggested to slow down the feed speed.
-Thread sliding: It is common in 3D printed materials with low strength, so it is considered to use embedded metal screw sleeve (such as Helicoil) to enhance the thread bearing capacity.
-hole position deviation: use fixture or positioning template to fix parts to ensure drilling accuracy.

IV. Conclusion

Although 3D printing has obvious advantages in manufacturing complex structures, it still needs to cooperate with traditional processing methods in actual assembly. Drilling and tapping are common post-processing technologies of 3D printed parts. Mastering its key points can not only improve the practicability and assembly efficiency of parts, but also expand the application scope of 3D printing technology in engineering field. As long as the tools, control parameters and operation details are reasonably selected, even novices can achieve high-quality drilling and tapping operations on 3D printed parts.