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CNC drilling machine and CNC milling machine are important equipment in PCB processing. The equipment is expensive. The selection of CNC machine tools is very important not only for operation, process setting and maintenance, but also for the quality of products.

As a technician, in consideration of pure technology and operation, the selection indicators of CNC machine tools generally start from the following aspects:

1. Rigidity and stability of machine tool table

In order to make the machine tool have enough stability, rigidity and avoid vibration, many manufacturers use marble as the bed material. Some Japanese manufacturers use steel as the bed. Because the deformation of steel at different temperatures is larger and unstable than marble, manufacturers will use compensation in the software to eliminate the accuracy loss caused by deformation.At present, most manufacturers use natural marble or artificial marble as the bed. It is recommended to use the equipment of marble bed. Marble is maintained with detergent and water at ordinary times, and alcohol is not allowed.After wiping, dry it with a dry cloth and wait until the water evaporates completely before it can work.

2. Rotating speed and stability of rotating shaft

At present, there are two kinds of rotating shafts, one is the rolling bearing with a maximum speed of 80000 revolutions, and the other is the air bearing with a maximum speed of 120000 revolutions.If it is a milling machine, rolling bearings should be used. Because its longitudinal bearing is better than air bearings, its drilling collets are also the focus of investigation. Some drilling collets are not easy to replace and maintenance is difficult. Some drilling collets wear quickly and become consumables, and the replacement cost is very expensive. Some require daily maintenance and waste time.The presser foot of the rotating shaft is another, and its unreasonable service life and design will also cause great trouble. For example, there is no seal between the shaft and the presser foot, resulting in a large power of the vacuum cleaner, resulting in a waste of funds for vacuum cleaner procurement or a waste of power of central dust collection, and may lead to poor chip removal in the hole of the circuit board.

3. Table movement accuracy and displacement repetition accuracy

This is the most important point when selecting, and it can not be seen through pictures or ordinary operation. It can be certified only after being tested after purchase. The current equipment can meet the design standard when it just leaves the factory.

4.Feed rate of. X, y and Z axes

Feed rate at present, the general screw stepping motor is used, and the speed is 25m / min. however, the new product has adopted servo motor. High feed rate can increase the production capacity by 20% – 40%. The speed of z-axis is affected by the drill bit and the drilling material, and the feed rate does not have a great impact on the production efficiency

5. Table movement and fixing device

In the past, many of the moving bearing of the table top were mainly guide rails, but also air floatation. The air floatation table top is flexible and easy to maintain, so it is the first choice when purchasing.The device for fixing the circuit board on the table is generally a pneumatic collet. The design of the collet has an important impact on the replacement of the equipment in the future. Generally, it is not easy to wear, because this place is one of the most seriously worn places in the equipment.Once worn, the replacement and commissioning shall be simple, including the commissioning of the positioning accuracy of the machine tool (for the template for milling machine).At present, many manufacturers provide automatic clamping devices. If you don’t have a good equipment maintenance engineer, you’d better not use them. Because the use of automatic loading and unloading devices has high requirements for maintenance engineers, and the current circuit board drilling sometimes takes more than one hour at a time, which is generally not necessary in China.

6. Maximum processing size

The maximum machining size is purchased according to needs. At present, most machine tools can meet your needs, except for some single axis or double axis machine tools for sample or test fixture.

7.Operating system and control system

At present, many machine tools use the general windows operating system, and the interface is very friendly. Some also use Chinese, which is easier to learn and operate. However, its disadvantages are that the stability of computer virus is slightly poor and management is difficult. Some use industrial system or UNIX system. This system has the advantages of good stability, not easy to failure and convenient management.However, the operation interface is in English, and the operation is a little slow.The latter is recommended from the perspective of process and equipment maintenance.

8. Tool management system

In the past, there were few machine tools, some had only 8 tool holders, and now most CNC machine tools can be equipped with hundreds of drill bits. Some systems also have automatic detection of broken drill and diameter detection length and radial runout systems. During model selection, it should be noted that most of the drill bits of CNC machine are placed at the front of the table, which has a disadvantage,If the circuit board processed during work jumps out due to fixing problems, it is easy to break all drill bits, including drill bit clamps.

9. Purchase of light ruler system

At present, most of the measurement systems of CNC machine tools use the light ruler as the position and accuracy measurement feedback system, and some use the magnetic ruler. The system stability and resolution of the light ruler are high. Because the reading head of the light ruler has no contact friction with the ruler body, it has a long service life, but the equipment should be kept clean at ordinary times to minimize dust pollution.

10. Dust collection system

If the company does not have a central dust collection system and uses an ordinary industrial vacuum cleaner as a supporting device, it should be noted that the power of the vacuum cleaner should be large, preferably 30-50% higher than the power required in the original design, because the power will be greatly reduced due to the blockage of the filter in the actual use process. Secondly, the powder bag of the vacuum cleaner should have sufficient capacity,If the capacity is too small, workers will often stop working to deal with dust, affecting production efficiency.

11. Protection system

It refers to the protection system designed to prevent accidental injury accidents and accidents on the equipment software and equipment itself, such as grating protection, infrared protection, air switch, etc. for example, infrared protection needs to be designed reasonably, and some protection designs are not very convenient for maintenance.Therefore, we should make a comprehensive balance.