Mechanical Knowledge

How to Operate A CNC Milling Machine?

Before understanding the operation of the milling machine, lets first understand the milling machine. The milling machine is a widely used machine tool. It can process planes (horizontal planes, vertical planes), grooves (keyways, T-slots, dovetail grooves, etc.), and split teeth. Parts (gears, spline shafts, sprockets), spiral surfaces (threads, spiral grooves) and various curved surfaces. The CNC milling machine is an automatic processing equipment developed on the basis of general milling machines. The processing technology of the two is basically the same, and the structure is somewhat similar. CNC milling machines are divided into two categories: without tool magazine and with tool magazine. Among them, the CNC milling machine with a tool magazine is also called CNC milling center. Let's take a look at how to operate a CNC milling machine.

General steps of operating a CNC milling machine

1) Before writing or programming, you should first compile the processing program of the workpiece. If the processing program of the workpiece is longer and more complicated, it is best not to program on the machine tool. Instead, use a programming machine or computer programming to avoid occupying the machine. For short programs, it should also be written on the program list.

2) Generally, the machine is turned on first, and then the system is turned on. In some designs, the two are interlocked, and the machine cannot display information on the CRT without powering on.

3) Reference point return For machine tools with incremental control systems (using incremental position detection components), this step must be performed first to establish the movement reference of each coordinate of the machine tool.

4) According to the storage medium of the program (paper tape or magnetic tape, disk), the processing program can be input by paper tape reader, cassette tape machine, programming machine or serial communication. If it is a simple program, it can be input directly on the CNC control panel using the keyboard. If the program is very simple and only one piece is processed, there is no need to save the program. The MDI method can be used to input and process section by section. In addition, the workpiece origin, tool parameters, offsets, and various compensations used in the program must also be input before processing.

5) Editing of the program If the inputted program needs to be modified, it must be edited. At this time, place the mode selection switch in the edit position, and use the edit keys to add, delete, and change. For the editing method, see the corresponding manual.

6) The machine is locked and running the program. This step is to check the program. If there is an error, you need to edit it again.

7) Workpiece loading, aligning and tool setting adopt manual incremental movement, continuous movement or use hand wheel to move the machine tool. Align the starting point to the beginning of the program, and set the tool reference.

8) Starting coordinate feed for continuous processing generally uses programs in the memory for processing. This method has a lower failure rate than the program on paper tape. The feed rate during processing can be adjusted by the feedrate override switch. During processing, you can press the feed hold button to pause the feed movement, observe the processing situation or perform manual measurement. Press the cycle start button again to resume processing. To ensure that the program is correct, it should be rechecked before processing. In the milling process, for flat curve workpieces, a pencil can be used to replace the cutter on the contour of the workpiece on the paper, which is more intuitive. If the system has a tool path simulation function, it can be used to check the correctness of the program.

9) The operation display uses the various screens of the CRT to display the position of the workbench or the tool, the program and the state of the machine tool, so that the operator can monitor the processing situation.

10) After the program output processing is completed, if the program is necessary to be saved, it can be left in the CNC memory. If the program is too long, the program in the memory can be output to an external device (such as a punching machine etc.).

11) Generally, the machine tool should be shut down before the system is shut down.

7 precautions when operating a CNC milling machine

(1) Before starting each time, check whether the lubricating oil in the lubricating oil pump behind the milling machine is sufficient, whether the air compressor is turned on, and whether the mechanical oil used for the cutting fluid is sufficient.

(2) When turning on the machine, first turn on the main power supply, then press the start button in the CNC power supply, turn the emergency stop button clockwise, and wait for the milling machine to detect all functions (the row of red indicators on the lower operation panel goes out), press The machine button resets the milling machine and is on standby.

(3) In manual operation, you must always pay attention to that before moving in the X and Y directions, the Z axis must be at the knife-raising position. During the movement, you can't just watch the change of the coordinate position on the CRT screen, but observe the movement of the tool. After the tool moves to the position, look at the CRT screen to make fine adjustments.

(4) In the process of programming, for beginners, try to use the G00 instruction as little as possible, especially in the X, Y, Z three-axis linkage, you should pay more attention. When emptying the knife, the movement of the Z axis should be carried out separately from the movement of the X and Y axes, that is, the tool is lifted more and the tool is inserted less obliquely. Sometimes due to oblique insertion, the tool will hit the workpiece and the tool will be damaged.

(5) When using a computer for serial communication, you must first turn on the milling machine, then turn on the computer; turn off the computer first, then turn off the milling machine. Avoid impacting the computer due to the instantaneous change of current when the milling machine is switched on and off.

(6) When using the DNC (program transfer between computer and milling machine) function, pay attention to the memory capacity of the milling machine. Generally, the total number of bytes of the program transferred from the computer to the milling machine should be less than 23kB. If the program is relatively long, it must be processed by the computer while transmitting, but the program segment number must not exceed N9999. If the number of blocks exceeds 10,000, the block number can be cancelled with the help of the program editing function in MASTERCAM.

(7) When an alarm occurs on the machine tool, the cause should be found according to the alarm number, and the alarm should be cleared in time. Do not shut down the machine, otherwise it will still be in the alarm state after the machine is turned on.

After reading this article, you should have a general understanding of how to operate a CNC milling machine. The precautions for operation are summarized from our daily work. We hope these experiences are helpful to you.

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