Detailed CNC engraving and milling machine

Engraving and milling machines are CNC milling machines using small tools, high power and high speed spindle motors. Machining dies They are based on milling in the machining center, especially when machining small dies with small tools, and they are very expensive and costly. The advantage of engraving machines is that if they are hardened, the processing materials will be too hard to be strong. The emergence of engraving and milling machine can be said to fill the gap between Lee.

CNC engraving and milling machines and engraving machines and machining centers (computers) are all very similar in appearance and structure. The following are comparative analysis of the three:

Conceptually speaking:

Machining center: Hong Kong, Taiwan and Guangdong are called computer gongs. It is a highly automated multi-function CNC machine tool with a magazine and automatic tool changer. The first machining center appeared in the United States in 1958. It can realize the centralized processing of multiple processes such as milling, drilling, boring, reaming and tapping after the workpiece is clamped once. The function emphasizes “milling” in particular.

Engraving machine: Its high spindle speed is suitable for the processing of small tools, and the torque is relatively small. It focuses on the "sculpting" function, such as the wood (specially processed wood called wood carving machine), two-color board, acrylic plate and other low hardness plate, not Too suitable for large cutting workpieces. Currently, most of the products on the market that are under the banner of the engraving machine are mainly processed and handicrafts. The cost is low. Because the accuracy is not high, it is not suitable for the development of molds. However, there are exceptions such as wafer engraving machines.

CNC engraving and milling machine (: As the name implies. It can be carved, but also milling, engraving machine based on the increase of the spindle, servo motor power, bed tolerance, while maintaining the spindle's high speed, more importantly, high precision. The milling machine also develops to a high speed, generally called a high-speed machine, which has a stronger cutting ability and a very high machining accuracy. It can also directly process materials with a hardness higher than HRC60 and can be molded once.

From the appearance of volume:

The machining center has the largest volume, the large 1690 type machine has a volume of 4m*3m, the small 850 type machine also has a 2.5m*2.5m, followed by the engraving and milling machine, and the relatively large 750 type machine is generally 2.2m*2m. The smallest.

From the mechanical structure:

The machining center generally adopts the cantilever type. The engraving and milling machine and the engraving machine generally use the gantry type structure. The gantry type is divided into the beam type and the fixed beam type. Currently, most of the engraving and milling machines use the fixed beam type. From the indicator data:

Spindle maximum speed (r/min): machining center 8000; carving and milling machine most common 30,000, high speed machines are all higher than 30,000; engraving machine is generally the same as engraving and milling machine, engraving machine for high light processing can reach 80000, but that use It is not the general motor spindle but the air spindle.

Spindle power: the largest machining center, from a few kilowatts to several tens of kilowatts; followed by carving and milling machines, generally within 10 kilowatts; the smallest engraving machine.

Cutting capacity: the largest machining center, especially for heavy cutting, roughing; followed by engraving and milling machines, suitable for finishing; engraving machine minimum.

Speed: Because the engraving and milling machine and engraving machine are relatively light, their moving speed and feed speed are faster than the machining center, especially the high-speed machine equipped with a linear motor can reach a maximum speed of 120m/min.

Accuracy: mainly depends on the cost and quality, and on the quality of the processing center to achieve the accuracy required to be higher than the other two.

From the processing dimensions: the table area can be a better response to this. The smallest worktable area (in mm, the same below) of the domestic machining center (computer 锣) is 830*500 (850 machines); the largest worktable area of ​​the sculpting and milling machine is 700*620 (750 machines), the smallest is 450 * 450 (400 machines); engraving machine generally does not exceed 450 * 450, the common is 45 * 270 (250 machines).

Speaking from the application object: The machining center is used to complete the machining of large-milled workpieces, large-scale molds, hardness-compared materials, and also suitable for roughing of common molds; engraving and milling machines are used to complete smaller milling operations, and are small-sized. The precision machining of the mold is suitable for the processing of copper and graphite, etc. The low-end engraving machine is biased towards the processing of boards with low hardness such as wood, two-color board, and acrylic board, and the high-end wafers and metal housings are polished and polished.

The processing scope recognizes: machining center, engraving and milling machines can be made of non-metal can also be made of metal, and even can do the hardness of the mold, engraving machine can only do ordinary acrylic products and non-metallic products, generally direct supplies, such as crafts , circuit boards, etc.

supplement:

In foreign countries, there has been a CNC engraving and milling machine for a long time. Strictly speaking, engraving is a part of milling. It is a question that often needs to be asked about whether to purchase an engraving machine or purchase a CNC milling machining center. High-speed cutting machine (HSCMACHINE).

Or let us first find out the difference between the three models:

1.--CNC Milling and Machining Centers Machines for Larger Milling Workpieces 2.--CNC Engraving and Milling Machines for Smaller Milling, or Soft Metal Processing Equipment 3.--High Speed ​​Cutting Machines Machining equipment for medium-sized milling and minimizing the amount of grinding after milling The in-depth analysis of the structure of the above equipment can help us to make the right choice. First, the machine's machinery is divided into two parts from a mechanical point of view. Moving parts and non-moving parts: Tables, skateboards, crossovers, etc. are moving parts, bed bases, columns, etc. are non-moving parts. 1. - Non-moving parts of CNC milling machining center. Steel requirements are very good. Good advantages: Heavy cutting can be performed; Disadvantages: Due to the same large moving parts, the flexibility of the machine tool is sacrificed, and the small part and rapid feed are ineffective.

2.--The numerical requirements of the non-moving part of the CNC engraving and milling machine are good. The mobile part of the steel should be flexible under the premise of being as light as possible, while maintaining a certain degree of rigidity.

Advantages: Can be processed with finer processing and high precision. High-speed machining is possible for soft metals; Disadvantages: Heavy cutting is not possible due to poor steel properties.

3, - high-speed cutting machine tools in the non-moving part of the steel requirements are very good mobile part of the steel requirements are better, and as light as possible.

Advantages: It can carry out medium and small amount of cutting (for example, generally φ10 flat bedknife, for 45 steel (300) depth of cut is 0.75 is good); Disadvantages: It can be used under the correct use, high efficiency, low cost, so that the amount of grinding becomes very small. Improper use will immediately pile up the scrap of the tool.

How to mechanically accomplish the above requirements of lightness, rigidity, and good contradiction lies in the mechanical structure.

1.-- The bed adopts a mesh structure with high and low ribs, some directly use the hexagonal mesh structure of the honeycomb, 2 - extra-wide columns and beams, and everyone knows that the structure of the gantry is excellent. Symmetry and excellent steel properties have been the preferred structure for high speed cutting equipment manufacturers.

3, - The difference between the moving part and the CNC 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 generally speaking, the use of Meehanite cast iron, which is the birth of cast iron, in the pouring of molten iron when a certain proportion of silicon (Si) to change the internal structure of the iron, making it more resistant to punching, 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 during high-speed movement, so the guide rail, screw rod requirements are rougher, and the rigidity of the connection part is reinforced. II. - Numerically-controlled milling machine center requires high speed for CNC system. Spindle rotation speed is 0~8000 RPM. 2. High-speed CNC system is required for engraving and milling machines. Spindle rotation speed is 3000 to 30000 RPM Left 3. High-speed cutting machine requires high-speed CNC system and excellent The characteristics of the servo motor, spindle speed 1500 ~ 30000RPM three, - programming software analysis From the software point of view, CNC milling center, high-speed cutting machine milling machine can use standard CAD / CAM software such as: MasterCamCimatronPEUG, etc. . The milling machine usually thinks that Cimatron has a better tool path. The new version of the software fully considers the uniformity of the cutting amount at every moment of the cutting tool, especially the speed and roundness of the knife as it enters the work, and the follow-up difference algorithm at the inflection point. The following error (FollowingError) makes the results and design graphics more closely. The CAD part has just been used in a lot of intuitive three-dimensional solid modeling such as Solidworks and then transferred to CAM software through IGS for processing.

But don't worry, the development speed of CAD/CAM is much faster than the development speed of the CNC of the machine tool. The engraving process has considerable fine angle control due to the special nature of the tool, and TYPE3 is preferable. Fourth, the automatic tool change and automatic tool setting of the tool magazine is a decent term, but I think the demand for the tool magazine must be combined with the actual situation.

The machining center is a numerical control device that completes a variety of processes in an automatic state, mainly for some fixed high-volume production operations, if we process a lot of holes, the teeth of the box, but also to do almost every day (a batch of minimum 2 More than a hundred) that must be selected processing center, for the mold industry and small batch production units do not always on the processing center, because seen too many manufacturers buy machining center, when CNC milling to use, use the knife library on CNC The cost of the system is simple, but the spindle and the magazine, the air compressor, and the various handles increase the cost, so the difference for one device is more than 100,000 yuan, and the programmer must be clear-headed. Otherwise, the tragedy will happen, and the problems will be increased a lot. In terms of efficiency, the use of machining centers should not be used for parts with a production volume of less than one or two hundred of the same type, and the efficiency is too low.

What is a good way to improve efficiency, do not use the tool magazine, and will not cause artificial tool change errors, only automatic tool setting system, a knife to the last one, a button, the machine tool automatic tooling, direct processing, error in 0.001~ Within .0003μm, compared with the automatic change of time, it can't be a little slower. If it is a machining center, there is no automatic tool setting machine tool and no tool magazine, but compared with the automatic tool setting tool, the efficiency in the latter is much higher than the former. Please note that the price of the best brand of the automatic tool setting tool is not more than 10,000 yuan (Marposs), and it is unlikely to be damaged. This way, it analyzes the processing of domestic molds for labor and the processing of small batches of industrial parts. Considering the use value of funds must not use the processing center equipment. In addition, the domestic manufacturers' magazines still have many problems. Imports are also quite expensive. (The BT40's 10 magazines will not be less than RMB 100,000).

Fifth, the view of high-speed cutting equipment Smart processors will certainly take a lot of time to consider the machine preparation time and human factors caused by the loss, we always remember not to remind them in this regard. What we should do is how to give them higher processing efficiency from the machine's processing time, and possibly reduce their grinding time. Even polished. The debut of high-speed cutting equipment is an event that stuns processors. Don’t think about its expensive cost (about 1.5 million yuan). From the use of it alone, I think it must be the old saying: It is a fragrant meat for some people and a poison for other people. , Japanese and Europeans spared no effort to promote the benefits of high-speed cutting and let people use their equipment. Of course, some are not practical. The actual experience in the CNC machine tool industry in the past eight years told me that their cost should be around 600-700,000. Such a high rate of profit 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 not be able to earn 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 to 2 days. Because our existing technology can not achieve "solid fax."

From the perspective of revitalizing national industries, we 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. We all know that the distance = speed × time tool description has fixed the way the country's cutting is determined by long means that increasing profit without speed is equivalent to shortening the time.

High-speed cutting is determined by the limitations of the current machine tool's own spindle and the tool used. It is not a good idea to use high-speed cutting. At present, the general practice in foreign countries is that the first device does not use high-speed cutting, while the second or third device can be considered. This equipment.

Successful practices such as:

One copy milling machine finishes most of the cutting amount (heavy cutting) while leaving a machining allowance of 2~3mm, and quickly completes the remaining cutting amount on a high-speed machine tool. This has many advantages:

1)--Heavy-cutting machine tools are many, and the processing fee is very low. 2)--The processing volume is large and the precision is not high enough. 3)--The tool is cheap 4)--After switching to high-speed cutting, because the processing object is close to forming. , so the first knife cutting is very uniform 5) - forming fast and accurate 6) - too much grinding, with accurate size 7) - The tool is expensive, but the time is short, the cutting amount is not large, the price ratio is very Good 8)--A lot of subtleties, such as small-angle conduction, etc., careful processing once completed without sparks, 9)--excellent surface finish (mirror effect)

From this point of view, the coordination of the equipment is the way to win, because the remaining amount of it is 2~3 mm, so two calibration G54 baffles on the work table to complete the problem of workpiece clamping, and for cutting A small amount of work is done directly on the high-speed machine.

6, there is a problem to be discussed is the spindle problem for CNC milling and machining centers because of the need for low-speed large twist data, so it is necessary to reduce the torque ratio from the spindle gearbox to improve the torque speed is low and the accuracy is inevitable, So it is unlikely to use a small radius cutter. For the engraving and milling machine (for the spindle to work in 2 ~ 30,000 RPM can work, rotation accuracy is generally about 2 μ, otherwise the phenomenon of broken knife is very serious, so we must use the motor spindle, that is, the motor and the spindle is one For high-speed cutting equipment, it is required that the built-in electric spindle, but also at a low speed must use a certain torque to have a water cooler to maintain a constant spindle temperature spindle power to be above 7.5 ~ 8KW, speed should exceed 25000RPM .