Graphite mold engraving and milling machine
Graphite mold engraving and milling machine has developed greatly in the past few years in China. It is a special equipment for processing graphite molds. It can not only expand the production of complex shaped molds, but also greatly improve the processing precision and production speed. A good machine tool to recover the investment.
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 (HSCMACHINE).
Let us first figure out the difference between the three models:
1. – CNC milling and machining center for machining workpieces with large milling operations
2. – CNC graphite mold engraving and milling machine for 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.
I. – 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 – graphite mold 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 and has high processing precision. 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 φ10, and a depth of 0.75 for 45 steel (300) is good); 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 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 due to its excellent symmetry and excellent rigidity.
3. The difference between the moving part and the CNC milling is that the distance between the rail and the 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 having a significant rigidity. improve.
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 are 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 – Graphite mold engraving and milling machine requires high-speed CNC system, 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 on the programming software
From a software point of view, CNC milling machining centers, high-speed cutting machine tools, graphite mold 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 problem (followingError) makes the results and design graphics more in-depth. 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.
Fourth, the automatic tool change and automatic tool setting requirements of the tool magazine
The machining center is a decent term, 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 large number of holes and teeth, we must do the same every day (a minimum of 2 batches) More than one hundred) It is necessary to select 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 the 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 automatically pairs the knife, direct processing, the error is 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 large 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 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 (30~40%). 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 description of the tool has been fixed in the way of cutting the country. It means that increasing the speed without profit is equal to shortening the time.
High-speed cutting is determined by the current machine tool's own spindle and the limitations of the tools used. It is not always good. The current foreign practice is that the first equipment does not use high-speed cutting, while the second or third unit can be considered. This kind of equipment.
Successful practices such as:
One copy milling machine completes most of the cutting amount (heavy cutting) and has a machining allowance of 2~3mm, and the remaining cutting amount is quickly completed on the high-speed machine tool. This has many advantages:
1) – There are many heavy cutting machines and the processing cost is very low
2) - Large processing volume, low precision and easy to reach
3) – the tool is cheap
4) – After the high-speed cutting, the cutting distance of the first knife is uniform because the object is close to forming
5) – Forming fast and accurate
6) – avoid too much sanding, with precise dimensions
7) – Although the tool is expensive, the time is short, the cutting amount is small, and the performance price ratio is very good.
8) – Many nuances, such as small angle guides, etc., are meticulously processed once without the use of electric 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 baffles 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 graphite mold 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. of. For high-speed cutting equipment, the built-in electric spindle is required, and at a low speed, a certain torque is required to have a water-cooling machine to keep the spindle working temperature constant. The spindle power should be above 7.5~8KW, and the speed should exceed 25000RPM.