The processing performance of the CNC machining center is very powerful, and it has a wide range of applications. However, in the use of CNC machining centers, there is some detailed knowledge that we need to master. The editor summarizes a lot of information and analyzes the use of CNC machining in detail. The eight steps that the center needs to be familiar with, let’s see if you have overlooked these:
1. Preparation Before Starting The Machine
Every time the machine is turned on or after the feed is stopped or reset, the machine reference should be reset to zero first so that the machine has a reference position for future operations.
2. Workpiece Clamping
Before the workpiece is clamped, each surface needs to be cleaned. It should not be stained with iron filings, dust, and oil. Use a file or oil stone to remove the burrs on the surface of the workpiece. The high-speed iron used for clamping must be smoothed by a grinder. Make it smooth and credible. The code iron and nut must be fixed to be able to reliably clamp the machined parts. When dealing with some difficult clamping parts, they can be directly clamped on the vise. The machine table must be kept clean and free of iron filings, oil, and dust. Iron pads are generally placed at the four corners of the workpiece, and high-speed rails must be placed in the middle for parts with a too large span.
According to the size of the drawing, use the drawing ruler to check whether the length, width, and height of the workpiece are qualified. When clamping the workpiece, follow the clamping and placement method of the programming operation guide to avoid the failure of processing and the presence of tool heads during processing. The fixture may be touched. After the workpiece is placed on the iron pad, the reference surface of the workpiece should be drawn according to the requirements of the drawing. For the kind of workpiece that has been ground, the verticality of the workpiece needs to be tested and the workpiece is drawn. Afterward, be sure to tighten the nut to prevent the workpiece from being unreliably clamped and the only phenomenon in the processing of the workpiece, pull the table again to make sure that the error does not exceed the specified value after the clamping is completed.
3. The Number of Workpiece Touch
For the clamped parts, you can use the touch head to set the reference zero position of the touch number, and the touch head can use photoelectric and mechanical methods. There are two methods: the middle touch number and the single side touch number. The middle touch number step is rough as follows:
Photoelectric static, mechanical rotation 450-600ipm, the X-axis of the worktable is manually moved by the middle touch so that the touch head touches the side of the workpiece, when the touch head just touches the workpiece and the red light is on, set this The relative coordinate value of the point is 0, and then manually move the X-axis of the worktable to make the touch sensor touch the other side of the workpiece. When the touch sensor touches the workpiece, record the relative coordinates at this time, and subtract the touch according to the relative value. The diameter of the number head, check whether the length of the workpiece is as required by the composite drawing.
Divide this relative coordinate number by 2, the value obtained is the middle value of the workpiece X-axis, and then move the worktable to the middle value of the X-axis, so that the relative coordinate value of the X-axis of this point is set to 0, this point It is the zero point on the X-axis of the workpiece. Carefully record the mechanical coordinate value of the zero points of the X-axis of the workpiece in one of the G54-G59, let the machine tool determine the zero point on the workpiece, and check the correctness of the data again, the Y-axis of the workpiece 0 The steps of point setting are the same as the operation mode of X-axis.
4. Workpiece CAM Software Programming
Programmers select the parts to be processed, program them through the CAM software UG, generate the tool path, conduct interference checking through the UG simulation module, and process after the interference check to generate safe and stable NC codes, which are transmitted to the workshop and then on the machine.
5. Prepare All Tools According To The Programming Instructions
According to the tool data in the programming operation guide, replace the tool to be processed, let the tool touch the height measuring instrument placed on the reference surface, and set the relative coordinate value of this point to zero when the measuring instrument is red. 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 machine coordinate Z value of this point in one of the G54~G59. This completes the zero settings of the workpiece X, Y, and Z axes. Check the correctness of the data again.
The one-side touch count is to touch one side of the X and Y-axis of the workpiece according to the above method. The relative coordinate value of the X and Y axis of this point is offset. The mechanical coordinates of the X and Y axis are in one of the G54~G59. Once again, carefully check the correctness of the data.
Check the correctness of the zero points, move the X, Y-axis to the side suspension of the workpiece, and visually check the correctness of the zero points according to the size of the workpiece. Copy the program file to the computer according to the file path of the programming operation guide.
6. Setting of Processing Parameters
Spindle speed setting during processing: N=1000×V/(3.14×D)
N: Spindle speed (rpm/min)
V: Cutting speed (m/min)
D: Tool diameter (mm)
Processing feed rate setting: F=N×M×Fn
F: Feed speed (mm/min)
M: Number of cutting edges
Fn: The cutting amount of the tool (mm/revolution)
Cutting amount per blade setting: Fn=Z×Fz
Z: The number of blades of the tool
Fz: The cutting amount of each edge of the tool (mm/revolution)
7. Start Processing
At the beginning of each program, it is necessary to carefully check whether the tool used is the tool specified in the programming guide. When starting processing, adjust the feed speed to the minimum. When executing fast positioning and cutting in a single block You need to concentrate, your hands should be placed on the stop button. If an abnormality occurs, stop immediately. You need to observe the direction of the tool movement to ensure safe feed, and then slowly increase the feed speed to a suitable position. At the same time, you need to add coolant to the tool and the workpiece, or cold wind. Do not leave the control panel too far away from the control panel when roughing. If there is any abnormality, stop and check immediately. Pull the meter once after roughing to make sure that the workpiece is not loose. If any, you need to re-calibrate the follow-up count. Optimize the processing parameters to achieve better processing results.
Because this process is a key process, it is said that after the workpiece is processed, it is necessary to measure whether the main dimensions of the workpiece are consistent with the requirements of the drawing. If there is a problem, it should be reported to the on-duty leader or the program editor for inspection and resolution. After passing the self-inspection, it can be unloaded and must be sent to the inspector for special inspection.
Processing type
Hole Machining: Before drilling holes on the machining center, be sure to use a center drill for positioning, then use a drill that is 0.5 to 2 mm smaller than the drawing size for drilling, and then use a suitable drill for finishing.
Boring processing: The workpiece should be bored with the center drill for positioning before drilling with a drill bit 1 to 2mm smaller than the drawing size, then use a rough boring tool (or milling tool) to process until only about 0.3mm machining allowance is left on one side, and finally use a pre-sized fine boring tool for fine boring, with the last fine boring allowance not less than 0.1mm.
Reaming processing: When reaming the workpiece, you must first use a center drill to locate, then use a drill that is 0.5~0.3mm smaller than the drawing size to drill, and finally use a reamer to ream. Pay attention to control the spindle speed during reaming. Within 70~180rpm/min.
Direct numerical control (DNC) operation: Before DNC numerical control processing, the workpiece should be clamped, the zero position should be set, and the parameters should be set. Open the processing program to be transferred to the computer to check, then let the computer enter the DNC state, and enter the file name of the correct processing program. Press the TAPE key and the program start key on the processing machine tool, and then the machine tool controller will flash with the word LSK. Press the Enter keyboard on the computer to perform DNC data transmission processing.
8. Self-Checking Scope and Content for Processors
The processing personnel must read the content on the process card before processing, know the part and shape of the workpiece to be processed, and the dimensions marked on the drawing, and know the processing content of the next step.
Before the workpiece is clamped, it is necessary to measure whether the size of the blank material meets the requirements of the drawing. When the workpiece is clamped, it is necessary to check whether the placement is consistent with the programming operation instruction.
Perform self-check after roughing is completed so that the data with errors can be adjusted in time. The content of self-check is mainly the position and size of processing compensation.
After the rough machining self-inspection, the precision machining can be carried out. After the precision machining, the operator should perform self-inspection on the shape and size of the processing compensation, and check the basic length and width dimensions of the vertical surface processing compensation. For the processing compensation of the inclined surface, Check the several dimensions marked on the drawings. After the processing personnel complete the self-inspection, they can unload the workpiece and send it to the inspector for special inspection after confirming that it meets the drawings and process requirements.
The above are the eight basic steps used by CNC machining centers. Let’s summarize them together. They mainly include preparation before starting up, workpiece clamping, workpiece touch number, workpiece CAM software programming, preparation of related tools according to the operation instructions, setting of processing parameters, start-up processing, and self-inspection work after processing is completed, hope it can be helpful to you.