The role of an optimized NC program can be summarized as: optimization of processing time, optimization of machining paths, optimization of cutting conditions, and the like. Processing time optimization is the most encountered in production. For example, use the φ12 mm end mill to mill the part shown in Figure 1. As can be seen from Figure 1, the material removal rate is not the same for the length of processing and the short edge. That is, if a cutting feed speed is given, the cutting load of the cutter shaft is different. When milling the short edge, the material removal rate is high, and the cutting load of the tool is large. When milling the long edge, the material removal rate is low and the cutting load of the tool is small. Since the cutter shaft can normally mill off the material of the short side (setting the cutting load of the cutter shaft at this time is 100%), the cutter shaft does not exert full power when milling the long side, and there is room for improving the production efficiency.
In order to increase the machining efficiency, the programmer can take into account that the cutting load of the cutter shaft at the time of milling is maintained at a high level. If you set the feedrate for short-edge milling to 120mm/min and the feedrate for long-edge milling to 160mm/min, this can reduce the milling time.
Simple two-dimensional contour processing, in order to make the material equal volume removal rate as good as possible, can be manually programmed in different line feed rate. However, in the more complex two-dimensional processing, the programmer considers how to allocate the feedrate. Its workload is very large. Even if different feedrates are edited in the NC program respectively, the actual cutter cutting load will also be There are major fluctuations. It is very difficult to manually assign different feedrates for each cutting block in the NC program of the 3D part.
The machining process of CNC machine tools is limited by the shape of the machining and the cutting conditions. In this way, the programmed speed and feed rate must be used at each stage of the process, and there is not enough flexibility to adapt to the dynamic changes during processing. In fact, cutting conditions tend to change dynamically due to the following reasons. These reasons include: (1) The surface of the workpiece is often uneven, regardless of billet, bar, forging, or casting. (2) The tool gradually wears during machining. (3) The material is different between the workpieces and the hardness of the material in the workpiece is not uniform, resulting in hard spots and soft spots. (4) The shape and size of the workpiece change. (5) The effect of different cooling effects during processing results in surface hardness changes. The purpose of optimizing the cutting parameters and machining tool trajectory is to make the CNC machine tool play an optimal processing efficiency, so that the product has the best processing quality. Cutting parameters are related to factors such as tool life, machine parameters (spindle speed, power, and torque). Taking into account the above reasons, in order to ensure the safety of processing, programmers have no choice but to adopt the most conservative cutting parameters, which leads to a reduction in processing efficiency. On the contrary, in order to shorten the processing time, the programmer has to set larger processing parameters, which will result in damage to the tool workpiece and the machine tool. No matter how optimized the numerical control program, they can not take into account the dynamic changes in processing, far from meeting the need for real-time adjustment of cutting parameters based on actual cutting conditions.2. OMAT machine tool adaptive system
Increasing market competition requires drastically lower costs, which requires producers to reduce unnecessary cost consumption, including: processing time, machine maintenance, maintenance costs, tooling costs, and long lead times. Real-time optimization techniques used in adaptive systems are indispensable in solving these economic problems. The highly efficient adaptive control system is based on continuously detected cutting parameters, realizing complete real-time optimization of the machining process, allowing the CNC machine tool to exert its maximum potential and reaching the highest tool life.
In the early 1990s, the 0MAT company began to apply adaptive control technology to the CNC machining process by combining adaptive control technology with the metal processing expert system summarized by the 0MAT company. The biggest feature of the O-Mach machine tool's adaptive system is that it can realize real-time optimal feed according to most parameters of the specific spindle and workpiece material. These parameters can be input or can be imported from external tool directories. The operator does not need to know the specific At the load limit, the internal expert system has determined its load limit for each tool. If the 0MAT adaptive controller (OptiMil-XL, OptiMrill-XL, and OptiDrill-XL) is directly installed on the CNC machine, the cutting conditions are monitored in real time and each step is taken. The feed rate is automatically adjusted to the most suitable value, which ensures a constant cutting load. This constant load is obtained taking into account changes in the cutting conditions, thus ensuring the shortest processing time and the maximum capacity that the tool and the machine allow. jobs. O-MAT's OptiMonitor-XL monitors the cutting process continuously and only operates under overload conditions (stops and alarms).
In addition, the 0MAT machine tool adaptation system also allows NC programmers to be more daring and to set the feed rate as if a new tool were used. The feed rate is adjusted accordingly based on the degree of tool wear, so that the system can automatically perform tool monitoring during machining. Apply monitoring results to feeds. At the same time, the system also gives the operator timely replacement of the worn tool, so that no tool breakage or premature tool change will occur. 0MAT machine tool adaptive system can not only detect tool wear, but also through the monitoring of the spindle load and the corresponding adjustment of the feed rate, to protect the tool, reduce waste and reduce the repeated work time. When a sudden overload occurs in the cutting, the alarm system issues an alarm and automatically stops the machine if necessary.
3.OptiMil-XL milling cutter function
The following uses the OptiMil-XL Optimizer as an example to illustrate the working principle and usage of the OptiMil-XL Optimizer.
(1) Operating principle of the OptiMil-XL Optimizer The OptiMil-XL Optimizer (hereinafter referred to as the Optimizer) stores the machining parameters for each step. These cutting parameters are identified by a unique machining code. Cutting parameters are grouped by process. For each tool that will be controlled or monitored by the optimizer, prepare the parameters that need to be set for the machining operation. These parameters can be entered in the memory of the optimizer through the keyboard on the router and correspond to the NC program, setting up new processes or selecting existing processes. Allow the router to enter automatic mode and run the NC sequence on the machine. In this mode, the router is ready to accept commands from the NC sequence to start its adaptive control function or monitoring characteristics.
(2) Main Features of the Optimizer Figure 2 illustrates the milling process controlled by the optimizer. In the milling process controlled by the router, when the cutting state exceeds the normal range, the cutting feedrate is reduced below the setting value of the machining program, and if necessary, the machine is stopped to avoid cutting tools and workpieces. And machine tool damage. When the cutting status allows saving time, the router increases the feed override to be higher than the machining program setting. The final result is equivalent to an optimal average feedrate override, which is more efficient than the feedrate set by the machining program. In the case of a multi-axis machine, the optimizer continuously detects the load on each spindle and then adjusts the feed rate based on the spindle with the highest applied load.
(3) Two methods of operation of the optimizer 1 Pre-setting method (default method). When this method is used, the expert system inside the optimizer uses the user-entered operating parameters to calculate the maximum allowable load value for each pass, and achieve this by continuously optimizing the actual feed rate for the entire pass. A load. 2 Training method This method includes two stages of "learning" and "re-learning" to prepare for special situations, including fixture problems, special tools, application of old tools, and special workpieces not included in the material library of the router. material.
During the learning phase of each pass, the optimization router does not perform adaptive feed rate control. According to the programmed feed rate, the system only monitors the load changes and notes the maximum load that can be achieved in this pass. This learned maximum load value is then applied to the "re-learning" phase (see Figure 3), so that where the maximum load is detected, the feed rate under adaptive control in this place is equal to the programmed setting. Feed rate is 100%. As a result, the cutting speed is higher than the programmed feed rate when the load is relatively light. At the maximum load point, the router will cut at the programmed feed rate.
4. Experimental conclusion
In recent years, we have carried out cutting tests on different parts, and we have proved through test data that: in the rough machining, the removal of workpiece blanks is relatively large, the accuracy requirements of the parts are generally relatively low, and the optimization effect of using the optimization router is better; In addition, because the requirements for the accuracy of parts have been taken into account, the remaining machining allowance is relatively uniform, and the cutting load changes little, so the optimization effect is not necessarily obvious. In general, in roughing and semi-finishing, adaptive control is very effective when the material cutting amount changes, the material hardness changes, or the workpiece surface has large changes. Under typical cutting conditions, the processing cycle can be shortened by 10% to 40% depending on the processing conditions.
When using the router, we think that we should also pay attention to the following points:
(1) First of all, it is necessary to select the tool from the tool, and it is recommended to use advanced tools such as carbide tools as much as possible. Because the same specifications of high-speed steel tools and hard alloy tool, the allowable cutting speed difference of several times, the spindle speed is also a lot of difference. From the perspective of tool life, HSS tools have a low life expectancy. It is very difficult to use high-speed steel tools to improve the machining efficiency of the machine.
(2) In general, the parameter value recommended by the tool supplier is an upper limit value. Exceeding the recommended parameter value will shorten the tool life and increase the tool cost; if it is less than the recommended value, the tool performance will not be fully utilized.
(3) CNC machine tool spindle has power torque characteristics. Under a certain speed, the machine tool is a constant torque output, and the output power is gradually increased. After reaching this speed, the machine tool is a constant power output. When using the router, once the tool cutting parameters are determined, it must be verified whether the cutting parameters are within the range of power and torque that the machine can output. The power torque characteristics of the optimizer output should be matched to the optimized spindle motor characteristics to prevent overload.
An outdoor barbeque grill is a grilling tool that is composed of a cooking surface typically made of parallel metal bars and porcelain covered metal grid. These bars of grid are mounted over a fuel source that is capable of generating intense heat with a temperature ranging from 500 degrees Fahrenheit to more than that. It is this heat actually that makes the grilling successful.
There are several types of outdoor barbequegrill. Two of the most common are charcoal and gas grill . They highly differ not only in sizes and shapes, but more to their features and functions. These types are now marketed throughout the word that you can find models of them in mails, shopping stores, and even in your neighorhood stores.
Charcoal Barbecue Grills
The charcoal outdoor barbecue grills are by far the least pricey option available. They come in different sizes and style, but the standard models are said to be difficult to install and are not readily available for cooking. You still need to take some time preparing for it, so if you are the type of person who is after promptness, then the charcoal type of outdoor barbecue grill may be the best option for you to consider.
Aside from that, the charcoal outdoor barbecue grills may create only a fair amount of smoke when lit. They also have the tendency to flare up, the reason that most households who are considering this grill type typically consider the area that they`re going to cook in. And, just like the other type of outdoor barbecue grill, the charcoal provides heat hat can`t easily be controlled, plus the cleaning up can be messy at times provided that you are using charcoal as a fuel source.
Gas Barbecue Grills
As the name implies, the gas outdoor barbecue grills use gas as the source of power. Unlike the charcoal type, this is pricier, but the fuel that they use is as readily available as the charcoal outdoor barbecue grills. Also, what`s nice to know about this type is that it can easily be assembled and installed. You can even cook your favorite meat just after lighting it up. And, they don`t create a smoke, but they tend to flare up just like in charcoal grills. Because of this fact, it is also important to consider the area you are going to cook in. In addition, the gas outdoor barbecue grill can be cleaned up easily and quickly as it is not messy as charcoal. The heat is even controllable, which means less effort and less hassle.
There are alternatives to the above mentioned types of outdoor barbecue grills. Whatever your final choice is, it is important to make sure that the grill you are considering can meet your specific requirements.
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