Introduction to the Operation Process of CNC Machining Center

CNC machining centers are composed of mechanical equipment and CNC systems, which can achieve high-precision, high-efficiency, and high-quality parts processing.CNC machining center operation steps:

1. Preparation for startup

After starting or emergency stop reset, the machine tool needs to return to the reference zero position, that is, return to zero operation, to determine the reference position.

2. Clamping workpiece

Before clamping the workpiece, it is necessary to ensure that all surfaces of the workpiece are clean, free from oil, iron filings, and dust, and to use a file or oilstone to remove burrs from the surface of the workpiece.

Ensure that the used high-speed rail is ground flat on all surfaces by a grinding machine to make them smooth and flat.

The iron and nut must be firm and able to reliably clamp the workpiece. For some small workpieces that are difficult to clamp, they can be directly clamped on a vise.

The machine tool workbench should be kept clean and free from iron filings, dust, and oil stains.

Pad iron is generally placed at the four corners of the workpiece, and for workpieces with a larger span, an equal height pad iron needs to be placed in the middle.

Use a ruler to check whether the length, width, and height of the workpiece are qualified according to the drawing dimensions.

When clamping workpieces, according to the requirements of the programming operation manual, consider avoiding situations where the machining parts and tool heads may touch the fixture.

3. Workpiece collision number

Use a counting head to determine the machining reference zero position, which can be photoelectric or mechanical.

Dividing the middle and hitting the number is a method, and the steps are as follows:

The photoelectric probe remains stationary, while the mechanical probe rotates at 450-600rpm.

Manually move the X-axis of the workbench so that the counter touches one side of the workpiece.

When the counting head just touches the workpiece and turns on the red light, the relative coordinate value of the point is set to zero.

Manually move the X-axis of the workbench again, so that the counter touches the other side of the workpiece.

When the counting head first touches the workpiece, record the relative coordinate value at this time.

Subtract the diameter of the contact head (i.e. the length of the workpiece) from the relative value and check whether the length of the workpiece meets the requirements of the drawing.

Divide the relative coordinate number by 2 to obtain the middle value of the X-axis of the workpiece.

Move the workbench to the middle value on the X-axis and set the X-axis relative coordinate value of the point to zero, which is the zero position on the X-axis of the workpiece.

Record the mechanical coordinate value of the zero position on the X-axis of the workpiece at a position between G54 and G59, so that the machine tool can determine the zero position on the X-axis of the workpiece. Double check the accuracy of the data. The steps for setting the zero position of the Y-axis of the workpiece are the same as those for the X-axis.

4. Prepare all the tools

Replace the tool to be used according to the tool data in the programming operation manual.

Let the tool touch the height measuring device placed on the reference plane, and when the red light of the measuring device lights up, set the relative coordinate value of the point to zero.

Move the tool to a safe position, manually move the tool downwards by 50mm, and set the relative coordinate value of this point to zero, which is the zero position of the Z-axis.

Record the mechanical coordinate Z value of this point at a position between G54 and G59. This completes the zero setting of the X, Y, and Z axes of the workpiece. Double check the accuracy of the data.

The method of one-sided counting is similar to the above method, except that when touching one side of the X and Y axes of the workpiece, the relative coordinate values of the X and Y axes of the point are offset by the radius of the counting head to obtain the zero position of the X and Y axes. Finally, record the mechanical coordinate values of the X and Y axes at a position between G54 and G59, and carefully check the accuracy of the data again.

Check the accuracy of the zero point, move the X and Y axes to the edge of the workpiece, and visually inspect the accuracy of the zero point based on the size of the workpiece.

Copy the program files to the computer according to the file path in the programming homework guide.

5.Setting of processing parameters

Set appropriate machining parameters based on machining requirements, including spindle speed, cutting speed, feed rate for machining, cutting amount of the tool, etc.

6. Start processing

Before executing each program, it is necessary to carefully check whether the tool used matches the tool specified in the programming guide. At the beginning of processing, adjust the feed speed to the minimum and gradually execute, paying attention to the process of rapid positioning, cutting and feeding, while maintaining focus. Fingers should be placed on the stop button to stop immediately in case of problems. Pay attention to the direction of tool movement to ensure safe feed. Then gradually increase the feed speed to an appropriate level and apply coolant or cold air to the tool and workpiece.

When performing rough machining, do not leave the control panel too far. If any abnormalities occur, stop the machine immediately for inspection. After rough machining, measure the workpiece again to ensure that it is not loose. If there is looseness, it must be recalibrated and reworked.

During the machining process, continuously optimize the machining parameters to achieve the best machining effect. As this process is a critical one, after the workpiece is processed, it is necessary to measure whether the main dimension values are consistent with the drawing requirements. If there are any problems, immediately notify the team leader or programmer on duty for inspection and resolution. After passing the self inspection, the workpiece can only be removed and must be sent to the inspector for special inspection.

7. Processing type

Hole processing

Before drilling on the machining center, a center drill must be used for positioning, followed by drilling with a drill bit 0.5~2mm smaller than the drawing size, and finally finishing with an appropriate drill bit.

Reaming processing

When reaming the workpiece, it is also necessary to first use a center drill for positioning, then use a drill bit 0.5~0.3mm smaller than the drawing size to drill, and finally use a reamer for reaming. When reaming, it is important to control the spindle speed within 70-180rpm/min.

Boring processing

When boring the workpiece, first use a center drill for positioning, then use a drill bit 1-2 mm smaller than the drawing size to drill, then use a rough boring cutter (or milling cutter) to process until only about 0.3 mm of machining allowance is left, and finally use a pre adjusted size precision boring cutter for precision machining. The margin for the final precision boring should not be less than 0.1mm.

Direct Numerical Control (DNC) Operation

Before conducting DNC CNC machining, the workpiece must be clamped, the zero point must be determined, and the parameters must be set. Open the machining program to be transmitted in the computer and check it, then set the computer to DNC status and enter the correct machining program file name. Press the TAPE key and program start key on the machining machine, and the flashing LSK word will appear on the machine controller. Then press the Enter key key on the computer to perform DNC transmission processing.

8. Self inspection content and scope

Before processing, the processor must carefully read the content of the process card, have a clear understanding of the parts, shapes, and dimensions of the workpiece to be processed in the drawing, and understand the processing content of its subsequent processes.

Before clamping the workpiece, the size of the blank should be measured to see if it meets the requirements of the drawing. When clamping the workpiece, it is necessary to carefully check whether its placement is consistent with the programming operation manual.

After rough machining is completed, self inspection should be conducted in a timely manner to adjust data with errors in a timely manner. The content of self inspection mainly includes the position and size of the processing parts, such as whether the workpiece is loose, whether the workpiece is correctly centered, whether the size from the processing part to the reference edge (reference point) meets the drawing requirements, and the position and size between the processing parts. After checking the position dimensions, it is also necessary to measure the shape dimensions of rough machining (except for circular arcs).

After self inspection of rough machining, precision machining can only be carried out. After precision machining, workers should conduct self inspection on the shape and dimensions of the processing parts, such as detecting the basic length and width dimensions of the vertical processing parts, and measuring the base point dimensions marked on the drawings for the inclined processing parts.

Workers can only remove the workpiece and send it to the inspector for specialized inspection after completing the self inspection of the workpiece and confirming its compliance with the drawings and process requirements.