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Eight operation steps of CNC machining center

Jan 03, 2020

1 Preparation for startup

After the machine tool is turned on or reset according to the emergency stop, the machine tool is first returned to the reference zero position (that is, to zero), so that the machine tool has a reference position for its subsequent operations.

2.Clamping Workpiece

Before clamping the workpiece, clean the surfaces first. It should be free of oil, iron filings and dust, and use a file (or oil stone) to remove burrs on the surface of the workpiece. The height iron used for clamping must be smoothed by a grinder to make it smooth and flat. The iron and nut must be solid, which can clamp the workpiece reliably, and clamp some small workpieces that are difficult to clamp directly on the tiger. The machine tool workbench should be clean and free of iron filings, dust, and oil. At the four corners of the workpiece, a contour horn should be placed in the middle for a workpiece with a large span. According to the size of the drawing, use a pull ruler to check whether the length, width and height of the workpiece are acceptable.

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When setting up the workpiece, according to the setting method of the programming work instruction, you should consider avoiding the processing part and the situation where the cutter head may hit the fixture during processing. After the workpiece is placed on the horn, it is necessary to pull the reference surface of the workpiece according to the requirements of the drawing. For the workpiece that has been ground on all six sides, check whether the perpendicularity is acceptable. After the workpiece is pulled, the nut must be tightened to prevent the workpiece from being displaced during processing when the clamping is not firm; pull the table again to ensure that the error is not excessive after clamping.

3. Number of workpiece hits

For the clamped workpiece, the touch reference can be used to set the reference position for touch counting. The touch count can be used in both photoelectric and mechanical types. There are two methods for dividing the number of hits in the middle and one-sided hitting. The steps for dividing the number of hits in the middle are as follows: photoelectric type static, mechanical rotation 450 ~ 600rpm. Manually move the X axis of the worktable to make the touch head touch one side of the workpiece. When the touch head touches the workpiece and the red light is on, set the relative coordinate value of this point to zero; then move the work manually The X axis of the table makes the touch head touch the other side of the workpiece. When the touch head just touches the workpiece, note down the relative coordinates at this time. According to its relative value minus the diameter of the touch head (ie the length of the workpiece), check whether the length of the workpiece meets the requirements of the drawing. Divide this relative coordinate number by 2. The resulting value is the middle value of the X axis of the workpiece, and then move the table to the middle value on the X axis. Set the X coordinate relative value at this point to zero, which is the workpiece. Zero position on the X axis. Carefully record the mechanical coordinate value of the zero position on the workpiece X axis in one of G54 ~ G59, and let the machine tool determine the zero position on the workpiece X axis. Once again carefully check the correctness of the data. The steps for setting the zero position of the workpiece Y axis are the same as those of the X axis.

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4.CAM software programming

The programmer selects the workpiece to be processed, and programs it through the CAM software WorkNC to generate a tool path. The interference is checked on the tool path by the WorkNC simulation module. After the interference check, post-processing is performed to generate a safe and stable NC code and transmitted to the workshop. 

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5.Prepare all tools according to the programming work instructions

According to the tool data in the programming work instruction, replace the tool to be processed, and let the tool touch the height measuring device placed on the reference surface. When the red light of the measuring device is on, set the relative coordinate value of this point to zero. Move the tool to a safe place, manually move the tool down 50mm, and set the relative coordinate value of this point to zero again. This point is the zero position of the Z axis.

Record the mechanical coordinate Z value of this point in one of G54 ~ G59. This completes the zero setting of the X, Y, and Z axes of the workpiece. Once again carefully check the correctness of the data. The one-sided touch is also to touch one side of the X and Y axes of the workpiece according to the above method. Offset the relative coordinate values of the X and Y axes at this point. The radius of the touch counter is the zero position of the X and Y axes. The X and Y axes are mechanically seated in one of G54 ~ G59. Once again carefully check the correctness of the data. Check the correctness of the zero point, move the X and Y axes to the side of the workpiece, and visually check the correctness of the zero point according to the size of the workpiece. Copy the program file to the computer according to the file path of the programming work instruction book.


6.Setting of processing parameters

Setting of spindle speed during processing: N = 1000 × V / (3.14 × D) N: spindle speed (rpm / min) V: cutting speed (m / min) D: tool feed speed (mm) processing feed rate Settings: F = N × M × FnF: Feed rate (mm / min) M: Number of tool edges Fn: Cutting amount of the tool (mm / rev) Setting of cutting amount per edge: Fn = Z × FzZ: Tool's Number of edges Fz: Cutting amount of each edge of the tool (mm / rev)


7.Start-up processing

At the beginning of executing each program, you must carefully check whether the tool used is the one specified in the programming guide. When starting the processing, the feed speed should be adjusted to the minimum, and the single block should be executed. Focus on the rapid positioning, falling, and feeding. When the hand is on the stop button, stop immediately if there is a problem. Pay attention to the direction of the tool to ensure safe feeding. Knife, and then slowly increase the feed rate to an appropriate level, and at the same time, add coolant or cold air to the tool and the workpiece. When roughing, do not be too far away from the control panel, if there is an abnormal phenomenon, shut down and check in time. After roughing, pull the watch again to make sure that the workpiece is not loose. If necessary, you must recalibrate and count. Continuously optimize the processing parameters during the processing to achieve the best processing results. Because this process is a critical process, after the workpiece is processed, its main dimensions should be measured to be consistent with the requirements of the drawing. If there is a problem, immediately notify the team leader or programmer to check and solve it. It can be removed after passing the self-inspection. Must be sent to the inspector for special inspection. Processing type: Hole processing: Before drilling on the machining center, you must use a center drill to locate the hole, then use a drill bit smaller than the drawing size of 0.5 ~ 2mm, and finally use a suitable drill bit to finish the machining. Reaming processing: To ream the workpiece, you must first locate it with a center drill, then drill with a drill bit 0.5 ~ 0.3mm smaller than the size of the drawing, and then use a reamer to ream the hole. When reaming, pay attention to controlling the spindle speed at Within 70 ~ 180rpm / min. Boring processing: To perform boring processing on the workpiece, first use a center drill to locate the hole, then use a drill bit smaller than the drawing size by 1 ~ 2mm, and then use a rough boring tool (or milling cutter) to process only 0.3mm on one side. Left and right machining allowances, and finally fine boring with a fine boring knife adjusted in advance, the last fine boring allowance must not be less than 0.1mm. Direct numerical control (DNC) operation: Before DNC numerical control processing, the workpiece must be clamped, the zero position must be set, and the parameters must be set. Open the processing program to be counted in the computer for inspection, then let the computer enter the DNC state, and enter the file name of the correct processing program. On the processing machine, press the TAPE key and the program start key. At this time, the machine controller appears flashing LSK. Press the Enter keypad on the computer to perform DNC data processing.

8.Contents and scope of workers' self-inspection

Before processing, the processor must read the contents of the process card clearly, know the parts to be processed, the shape, the dimensions of the drawings, and the processing 8.Content of the next steps.

Before the workpiece is clamped, it should be measured whether the blank size meets the requirements of the drawing. When the workpiece is clamped, it must be carefully checked whether its placement is consistent with the programming operation instruction. After the roughing is completed, a self-inspection should be performed in time to adjust the error data in a timely manner. The content of the self-test is mainly the position and size of the processing part. Such as: whether the workpiece is loose; whether the workpiece is correctly divided; whether the size of the processing part to the reference edge (reference point) meets the requirements of the drawing; After checking the size of the position, measure the rough shape rule (except for arc). Finishing is performed only after roughing self-inspection. After finishing, the workers should conduct self-inspection on the shape and size of the processed parts: the basic length and width of the processed parts on the vertical plane are measured; the dimensions of the base points marked on the drawing are measured on the processed parts on the inclined plane. After completing the self-inspection of the workpiece, the worker can remove the workpiece and send it to the inspector for special inspection after confirming that it meets the requirements of the drawings and processes.

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