The CNC engraving machine has achieved great development in China. It is only a matter of 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 the engraving and milling machine. The real reason for slackness.
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, which is 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 function selection is necessary for effective investment. condition.
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. The CNC milling and machining center is used to complete the processing equipment of the workpiece with large milling amount;
2,--CNC engraving and milling machine is used for finishing or clearing of more complex parts, its milling is small but fine but also very fast, and can replace some EDM;
3,--High-speed cutting machine is used to complete the medium milling amount and reduce the grinding amount after milling to the lowest processing equipment
An in-depth analysis of the structure of the above equipment can help us make the right choice.
First, from a mechanical point of view
The machine tool is divided into two parts, the moving part and the non-moving part: the work table, the skateboard, the cross flower table, etc. are moving parts, the bed base, the column, etc. are non-moving parts.
1, - CNC milling machining center:
The non-moving part requires very good steel properties. The moving part requires very good steel.
Advantages: Heavy cutting can be performed; Disadvantages: Because the moving parts are equally large, the flexibility of the machine is sacrificed, and there is no power for small parts and rapid feed.
2,--CNC engraving and milling machine
The non-moving part of the steel requires a good moving part of the steel to be flexible, as light as possible, while maintaining a certain degree of rigidity.
Advantages: It can carry out relatively small processing, high processing precision, and can replace part of EDM. High-speed machining for soft metals; Disadvantages: Heavy cutting is not possible due to poor steel properties.
3, --- high speed cutting machine
The non-moving part requires 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 the correct 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 from the mechanical, light, rigid and contradictory, the key lies in 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 because of 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. From the material, the Mehana cast iron is generally used, that is, the cast iron is cast. When the molten iron is poured, a certain proportion of silicon (Si) is added to change the internal structure of the iron, making it more resistant to stamping and rigid. Significantly increased;
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, 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 0-8000RPM.
2,--The engraving and milling machine requires high-speed CNC system, the spindle speed is about 3000-30000RPM
3, high-speed cutting machine tools require high-speed CNC system and excellent servo motor characteristics, spindle speed 1500-30000RPM or so
Third, analysis on the 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, PRO / E, UG and so on.
Milling machines usually think 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 of work, and the following 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 far faster than the development speed of CNC machine tools.
The engraving process is controlled by a relatively small angle due to the particularity of the tool. It is better to use TYPE3 or engraving software.
Fourth, the automatic tool change and automatic tool setting requirements
The machining center is a decent term, and it is called a machining center because it is equipped with an automatic tool changer. But I think the requirements for the tool magazine must be combined with reality.
The machining center is a numerical control equipment for completing various processes in an automatic state. It is mainly for some fixed large-volume production operations. If we process a box with many holes and teeth, we must do the same every day (one batch minimum 2 More than one hundred) It is necessary to choose the machining center. For the mold industry and small batch production units, do not move to the machining center, because too many manufacturers have bought the machining center, when CNC milling is used, the tool magazine is used for CNC. The cost of the system is very simple, but the spindle and tool magazine, air compressor and various tool holders will increase the cost, so the difference for one device is more than 100,000 yuan, and the programmers must 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, and the direct processing is performed with an error of 0.001- Within .0003 μm, compared with the automatic change time, it is slower than efficiency. 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) is only about 10,000 yuan, and it is unlikely to be damaged. This analysis is for the domestic labor processing of labor force and the processing of small batch industrial parts. Full consideration of the value of the use of funds must not use processing center equipment, in addition, the domestic manufacturers of the tool magazine basically have many problems. 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 processing time of the machine, and to reduce their grinding time. 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 point of view: 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 margin is what makes me see their essence. The gross profit of domestic CNC machine tools should be between (30-40%). 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 the 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 description of the tool has been fixed. The way it is determined to be long means that unprofitable speed increase is equivalent to shortening the time.
High-speed cutting is determined by the current spindle of the machine tool itself and the limitations of the tool used. It is not always good. The current foreign practice is that the first device does not use high-speed cutting, while the second or third device can be considered. This kind of equipment.
Successful practices such as:
One copy milling machine completes most of the cutting amount (heavy cutting) with a machining allowance of 2-3 mm, and 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)--tools are cheap
4)-- After turning into high-speed cutting, the cutting amount of the first knife is uniform because the object to be processed is close to forming.
5)--Forming fast and accurate
6)--Do not wear too much, with accurate size
7)--The tool is expensive, but 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., meticulous processing is completed once without using sparks
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 2-3 mm, so the two calibrated G54 on the XY on the workbench complete the problem of workpiece clamping, and for cutting The small amount of the workpiece is directly completed on the high speed machine.
Sixth, there is still a problem to discuss is 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 must work at 1-2 million RPM, and the rotation accuracy is generally about 2 μ. Otherwise, the broken knife phenomenon will be very serious, so the electric spindle must be used, that is, the motor and the main shaft are integrated. For high-speed cutting equipment, a built-in electric spindle is required, and at a low speed, a certain oil pressure is required to maintain the spindle operating temperature.
