How to choose CNC milling machine and CNC grinding machine correctly?

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

As a craftsman for pure technical and operational considerations, the selection objectives of CNC machine tools generally start from the following aspects:

1. Rigidity and stability of machine tool table

In order to make machine tools have satisfactory stability and rigidity to avoid vibration, many manufacturers choose marble as the bedding material. Some Japanese manufacturers choose steel as the bedding material. Because the deformation of steel at different temperatures is larger and unstable than marble, manufacturers will choose compensation in software to eliminate the loss of accuracy caused by deformation. At present, most manufacturers choose natural marble or artificial marble as bedding. It is recommended to choose marble bedding equipment. Marble is maintained and wiped with detergent and water in normal maintenance, and alcohol is not used. After wiping, dry it with a dry cloth and wait for the moisture to evaporate thoroughly before it can work.

2. Rotation speed and stability of rotating shaft

At present, there are two kinds of rotating shafts, one is rolling bearing speed up to 80,000 revolutions, the other is air bearing speed up to 120,000 revolutions. If it is a milling machine, rolling bearings should be selected, because their longitudinal load is better than air bearings, and their drill chucks are also the investigation scale of acquisition. Some drill chucks are not easy to replace and maintain, some drill chucks wear quickly and become consumables and replacement costs are very expensive, and some need daily maintenance wasted time. The presser foot of the rotating shaft is another one. The unreasonable life and planning of the presser foot will cause a lot of trouble. For example, the absence of seal between the shaft and the presser foot to form a vacuum cleaner requires a great deal of power to form the waste of funds purchased by the vacuum cleaner or the power of central vacuum cleaner, and may result in bad debris discharge in the circuit board hole.

3. Moving accuracy and displacement repetition accuracy of mesa

This is the most important point when choosing, but also can not be seen by pictures or general operation, as long as the purchase of future tests can be certified, the current equipment can reach the planning standards when it first leaves the factory, the key is whether the accuracy of operation in the next one to two years is very stable, in this regard, the machines produced in Europe do better.

Feed Rate of 4.X, Y and Z Axis

Feed rate is now commonly used with a screw stepper motor, the drilling machine speed is 25 meters per minute, and the new product has been selected servo motor, high feed rate can improve productivity by 20% - 40%, Z-axis speed is affected by the bit and drilling data feed rate, the impact on output power is not very large.

5. Mobile and Fixed Equipment of Desk

In the past, many of the mobile bearing capacity of the mesa were mainly guideways, but also air flotation was used as the bearing capacity of the mesa movement. Air flotation mesa was selected as the first choice because of its sensitive movement and convenient maintenance. Pneumatic chuck is usually used for fixing PCB on the table. The planning of chuck has an important influence on the replacement of equipment in the future. It is not easy to wear, because the wear is one of the most severe places in the equipment. Once wear and tear is replaced and debugged, it should be concise, including debugging about the positioning accuracy of machine tools (about making templates for milling machines). Now many manufacturers supply automatic clamping equipment, if you do not have a good equipment maintenance engineer, it is better not to choose, because the selection of automatic feeding and unloading equipment for maintenance engineers is very high requirements, and now the circuit board drilling sometimes takes more than an hour, generally there is no need to choose in China.

6. Maximum Machining Scale

The largest processing scale is purchased according to the demand. Most machine tools can satisfy your demand now, except for some single-axis or double-axis machine tools for sample or test fixture manufacturing.

7. Operational and control systems

Nowadays, many machine tools choose general windows operating system with friendly interface. Some choose Chinese language, which is easy to learn and operate. However, the security of computer virus is slightly poor and difficult to handle. Some choose industrial system or Unix system. The advantages of this system are good stability, not easy to break down, and easy to handle. But the operation interface is in English, and the operation is a little slow. The latter is recommended from the point of view of process and equipment maintenance.

8. Tool management system

There used to be only 8 clamps for machine tools, but now most of the CNC machine tools can be equipped with hundreds of drills. Some systems also have automatic detection of broken drills, diameter detection of length and radial runout system. When choosing the type, we should pay attention to the item that most of the CNC machine tools are placed at the front of the table. This planning method has a defect, if it is added in the operation. The circuit board of the worker jumped out because of the problem of fixing. It was very simple to break all the drill bits including drill jigs. Some drill jigs are planned on top of the machine tools. For example, some Swiss machines do not have this problem. The sensitivity of detection organization is too high and too low for the machine tools. Generally, it is better to be on the low side.

9. Optical ruler system selection

At present, most of the measurement systems of CNC machine tools use optical ruler as feedback system for measuring orientation and accuracy, and magnetic ruler as well. The optical ruler has high stability and resolution. Because the reading head of the optical ruler does not touch the ruler body, it has a long life, but usually insists on cleaning the equipment to minimize dust pollution.

10. Vacuum Cleaning System

If the company does not have a central vacuum system and chooses the general industrial vacuum cleaner as the supporting equipment, we should pay attention to the high power of the vacuum cleaner, for example, the power required by the original plan is 30%-50%, because the blocking power of the filter will decrease a lot in the practical application process, followed by the vacuum cleaner.