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In the domestic development of CNC engraving machine, it has only been developed in the last one or two years. Relevant processing factories and users have always stared at the trend of the manufacturers with a keen eye. This is also the main manufacturer of engraving and milling machine. The real reason for not relaxing.
As a user, of course, we must choose the right equipment. If the selection is not appropriate, not only can we not make money, but it will make us fall into the bitter situation of working for the machine. So what kind of machine tool is a good machine tool?
We believe that the definition of a good machine tool is this:
A machine tool that can recover the investment in a short period of time is a good machine tool.
The design life of CNC machine tools is generally 7 years, mainly based on the service life of CNC. The proportional relationship between spending money and earning money will directly affect your business. Therefore, careful analysis of functions for selection is a necessary condition for effective investment. .
The CNC engraving and milling machine is very early in the world. Strictly speaking, carving is part of milling. It is a question to ask yourself if you are buying an engraving machine or buying a CNC milling center. In addition, there are currently high-speed cutting machine tools (HSC MACHINE).
Let us first figure out the difference between the three models:
1. CNC milling and machining center processing equipment for workpieces with large milling capacity
2. CNC engraving and milling machine is used to complete small milling, or soft metal processing equipment
3. High-speed cutting machine for processing medium milling and minimizing the amount of grinding after milling
An in-depth analysis of the structure of the above equipment can help us make the right choice.
First, analysis and analysis from the mechanical point of view
The machine's machinery is divided into two parts, a moving part and a non-moving part. The work table, the skateboard, the cross flower stand, etc. are moving parts, and the bed base, the column and the like are non-moving parts.
1. CNC milling machining center
Non-mobile parts require very good steel properties
The moving part requires very good steel properties.
Advantages: capable of heavy cutting;
Disadvantages: Because the moving parts are equally large, the machine flexibility is sacrificed, and there is nothing that can be done for small parts and rapid feed.
2, CNC engraving and milling machine
Non-mobile parts require good rigidity
The moving part of the steel should be flexible, and as light as possible, while maintaining a certain degree of rigidity.
Advantages: It can carry out relatively small processing and has high processing precision. For high speed machining of soft metals;
Disadvantages: Heavy cutting is not possible due to poor steel properties.
3. High-speed cutting machine
Non-mobile parts require very good steel properties
The moving part has better steel requirements and is as light as possible.
Advantages: It can carry out small and medium-sized cutting (for example, a flat-bottom knives of generally φ10, and a depth of 0.75 for 45 steel (300) is better);
Disadvantages: It can be used efficiently and at low cost under proper use, so that the amount of grinding is extremely small. Improper use will immediately make the scrap of the tool pile up.
How to do the above requirements of light and rigid contradiction from the machine, the key is to work hard on the mechanical structure.
1. The bed body adopts a mesh structure with high and low ribs, and some directly adopt the hexagonal mesh structure of the honeycomb.
2, ultra-wide columns and beams, we know that the gantry-type structure has been the preferred structure by high-speed cutting equipment manufacturers due to its excellent symmetry and excellent rigidity.
3. The difference between the moving part and the numerical control milling is that the distance between the guide rail and the guide rail is widened to overcome the problem of bad torque.
4. In terms of materials, it is generally used in Mehana cast iron, which is to inoculate cast iron. When casting molten iron, a certain proportion of silicon (Si) is added to change the internal structure of iron, making it more resistant to stamping and significantly improving rigidity. .
5. The rigidity of the machine tool is mainly used to overcome the strong impact of the moving part on the non-moving part when moving at high speed, so the guide rail and the screw rod are required to be thicker, and the rigidity of the connecting part is strengthened.
Second, analysis and analysis from the perspective of numerical control
1. The CNC milling machining center requires a general speed for the numerical control system, and the spindle speed is about 0 to 8000 RPM.
2, engraving and milling machine. High-speed CNC system is required, and the spindle speed is about 3000~30000RPM.
3. High-speed cutting machine tools require high-speed CNC system and excellent servo motor characteristics. The spindle speed is about 1500~30000RPM.
Third, the analysis of programming software
From a software point of view, CNC milling machining centers, high-speed cutting machine engraving and milling machines can use standard CAD / CAM software such as: Mastercam Cimatron PE UG.
The milling machine usually thinks that the Cimatron tool path is better. The new version of the software fully examines the uniformity of the cutting amount of the tool at every moment, especially the speed and smoothness of the knife entering the moment of going out, and the following difference algorithm at the inflection point. The following error (Following Error) makes the results and design graphics more closely. The CAD part has just been used in a large number of intuitive 3D solid modeling such as Solidworks, and then transferred to CAM software through IGS.
But don't worry, the development speed of CAD/CAM is much higher than the development speed of CNC machine tools.
Fourth, the tool magazine automatic tool change and automatic tool setting requirements
The machining center is a decent term. The machining center is a numerical control device for completing various processes in an automatic state. It is mainly for some fixed large-volume production operations. If we process a large number of holes and teeth, we must work every day. Do the same (a minimum of 200 batches), then you must choose the machining center. For the mold industry and small batch production units, don't move to the machining center, because you have seen too many manufacturers buy machining centers, when CNC milling The use of the tool magazine is very simple in terms of the cost of the CNC system, but the spindle and the tool magazine, the air compressor and various tool holders will increase the cost, so the difference for one device is more than 100,000 RMB, and the programmer Be clear-headed. Otherwise the tragedy will happen and the problem will increase quite a lot. What is the efficiency? For workpieces with less than one or two hundred copies of the same product, try not to use the machining center, and the efficiency is too low.
Is there any good way to improve efficiency, without using the tool magazine, and it will not cause artificial tool change error, only the automatic tool setting system, the knife is loaded upwards, one button, the machine tool is automatically tooled, direct processing, the error is 0.001~ Within 0.003μm, compared with the automatic change time, it is slower and less efficient. If it is a machining center and there is no automatic tool setting device and no tool magazine, the efficiency of the latter is much higher than that of the automatic tool setting machine. Fortunately, please pay attention to the price of the best brand of automatic tool setting instrument (Marposs), but it is about 10,000 yuan, and it is unlikely to be damaged. This analysis is for the domestic labor processing of large labor force and the processing of small batch industrial parts. If you fully consider the value of the use of funds, you should not use machining center equipment. In addition, there are still many problems in the tool magazines of domestic manufacturers. Imports are also quite expensive. (The BT40's 10 tool magazines will not be less than 100,000 RMB).
Five, the view of high-speed cutting equipment
A savvy processor will definitely spend a lot of time thinking about the damage caused by the machine's preparation time and human factors. We will never remember to remind them in this regard. What we should do is to give them higher processing efficiency from the machining time of the machine and to reduce their grinding time as much as possible. Even zero polished. The debut of high-speed cutting equipment is an event that makes processors feel at ease. Don't consider its expensive cost (about 1.5 million) first. I think it must be an old saying from the use: it is a fragrant meat for some people, and a poisonous poison for others. Japanese and Europeans have spared no effort to promote the benefits of high-speed cutting and let people use their equipment. Of course, some are not practical. In the 8 years of experience in the CNC machine tool industry, I told them that their cost should be around 60-700,000. Such a high profit rate is what makes me see their essence. The gross profit of domestic CNC machine tools should be between 30% and 40%. This is a reasonable, upright profit. If you are willing to maintain their high profits, I would like to make more money at the same time. More to consider after-sales service and so on. I can't believe that their service can solve all problems within 1-2 days. Because our existing technology can not achieve "solid fax".
From the perspective of revitalizing national industry, it should support the development of domestic machine tool factories. The essence of high-speed cutting is to walk the length of the tool in a short time. Everybody knows:
Distance = speed × time
The fixed cutting method of the tool determines that if it is long, it means no profit, and increasing the speed is equivalent to shortening the time.
High-speed cutting is not necessarily good due to the limitations of the current machine tool's own spindle and the tool used. At present, the common practice in foreign countries is that the first device does not use high-speed cutting, while the second or third device can consider this. equipment.
Successful practices such as:
A copy milling machine completes most of the cutting amount (heavy cutting) and has a machining allowance of 2 to 3 mm. The remaining cutting amount is quickly completed on a high-speed machine tool. This has many advantages:
1) Heavy cutting machine tools, processing costs are very low
2) The processing volume is large, the precision requirement is not high, and it is easy to reach
3) The tool is cheap
4) After the high-speed cutting, the cutting amount of the first knife is uniform because the object is close to forming.
5) Forming fast and accurate
6) Avoid too much grinding, with precise dimensions
7) Although the tool is expensive, the time is short, the cutting amount is not large, and the performance price ratio is very good.
8) Many nuances, such as small angle guides, etc., meticulously processing once without using sparks to help
9) Excellent surface finish (mirror effect)
From this point of view, the coordination of the equipment is the way to win, because its remaining amount is 2 to 3 mm, so two calibrated G54 on the XY on the workbench completes the problem of workpiece clamping, and for cutting The small amount of the workpiece is directly completed on the high speed machine.
Six, discuss the problem of the spindle
For CNC milling and machining centers, because of the low speed and high torque required, the reduction ratio of the spindle gearbox is required to increase the torque. The low speed and poor precision are inevitable, so it is unlikely that a small radius tool will be used.
For the engraving and milling machine, the spindle should work at 20,000 to 30,000 RPM, and the rotation accuracy is generally about 2 μ. Otherwise, the broken knife phenomenon is very serious, so the electric spindle must be used, that is, the motor and the main shaft are integrated. For high-speed cutting equipment, the built-in electric spindle is required, and at a low speed, a certain oil must be used to maintain the spindle working temperature. The spindle power should be above 7.5~8KW, and the speed should exceed 25000RPM.
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