Trial cutting method
That is, first cut a small part of the processing surface, measure the size obtained by the trial cut, and adjust the position of the tool cutting edge relative to the workpiece appropriately according to the processing requirements , then try cutting again. then measure. After two or three attempts of cutting and measuring, when the machine is processing, once the size meets the requirements, the entire surface to be processed is cut.
The trial cutting method is repeated by “trial cut – measure – adjust – trial cut again” until the required dimensional accuracy is achieved. For example, bore processing test of box hole system.
The precision achieved by the trial cutting method can be very high and does not require complicated devices. However, this method is time consuming (requiring multiple adjustments, trial cuts, measurements and calculations), is inefficient and relies on the trial cutting method. Technical level of workers and precision of measuring instruments, quality is unstable, so it is only used for the production of single parts and small batches.
As a type of trial cutting method – matching, it is a method of processing another workpiece that matches it based on the workpiece being processed, or a method of combining two (or more) pieces together for processing. The requirements for the final dimensions processed in the production process are based on the requirements corresponding to the parts processed.
adjustment method
The precise relative positions of machine tools, fixtures, cutting tools and parts are adjusted in advance with prototypes or standard parts to ensure the dimensional accuracy of the part. Since the size is adjusted in advance, there is no need to try cutting again during processing. The size is automatically obtained and remains unchanged during processing of a batch of parts. For example, when using a milling machine fixture, the tool position is determined by the tool setting block. The essence of the setting method is to use the setting device or tool setting device on the pre-assembled machine tool or tool holder to make the tool achieve a certain position accuracy relative to at the machine tool or assembly, then processing a batch of workpieces.
Feeding the tool according to the dial of the machine tool and then cutting is also a type of setting method. This method first requires determining the scale on the dial by a cutting test. In mass production, tool setting devices such as fixed range stops, prototypes and models are often used for setting.
Compared with the trial cutting method, the adjustment method has better machining precision stability and higher productivity. It does not have high requirements for machine tool operators, but it does have high requirements for machine tool fitters. It is often used in batch production and mass production. .
sizing method
The method of using the corresponding size of the tool to ensure the size of the processed part of the workpiece is called sizing method. It is processed using standard size tools and the size of the processing surface is determined by the size of the tool. That is, tools with a certain dimensional accuracy (such as reamers, reamers, drills, etc.) are used to ensure the accuracy of the processed parts of the workpiece (such as holes).
The sizing method is easy to operate, has high productivity, and the processing accuracy is relatively stable. It has almost nothing to do with the technical level of the worker. It has high productivity and is widely used in various types of production. Such as drilling, reaming, etc.
active measurement method
During the machining process, the machining dimensions are measured during machining, and after comparing the measured results with the dimensions required by the design, the machine tool is either allowed to continue working or stopped. This is the active measurement method.
Currently, active measurement values can be displayed digitally. The active measurement method adds the measuring device to the process system (i.e. the unit of machine tools, tools, fixtures and parts) as a fifth factor.
The active measurement method has stable quality and high productivity, which is the development direction.
automatic control method
This method is composed of a measuring device, a power supply device and a control system. It combines the measurement, feeding device and control system into an automatic processing system, and the processing process is automatically completed by the system.
A series of tasks such as dimensional measurement, tool compensation adjustment, cutting processing and machine tool parking are automatically carried out to automatically achieve the required dimensional accuracy. For example, when processing on a CNC machine tool, the processing sequence and processing accuracy of parts are controlled through various program instructions.
There are two specific methods of automatic control:
1. Automatic measurement, that is, the machine tool has a device that automatically measures the size of the workpiece. When the workpiece reaches the required size, the measuring device issues an instruction for the machine tool to automatically retract and stop working.
2. Numerical control, that is, the machine tool has a servo motor, a pair of rolling screw nuts and a complete set of numerical control devices that control the precise movement of the tool holder or workbench. Acquisition of size (movement of the tool holder). or established) is programmed in advance. The program is automatically controlled by a computer numerical control device.
The initial automatic control method was carried out using active measurement and mechanical or hydraulic control systems. At present, pre-arranged programs according to treatment requirements have been widely used. adapt to changes in processing conditions during processing, automatically adjust the processing amount, and automatically control processing with adaptive control machine tools that optimize the processing process according to specified conditions.
The automatic control method has stable quality, high productivity, good processing flexibility, and can adapt to multi-variety production. It is the current development direction of mechanical manufacturing and the basis of computer-aided manufacturing (CAM).
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