The CNC machining center is a fully automatic machine tool that can be processed automatically. It has the characteristics of high processing efficiency, strong cutting force and high precision. With automatic tool change function, multiple processes can be processed through one clamping of the workpiece. In terms of flexibility, the CNC machining center can process various parts with complex shapes, and the adaptability of parts processing is very strong. This article mainly tells about the processing technology of CNC machining center processing cover plate parts.
Cover plate processing requires steps such as milling, drilling, reaming, boring, reaming, and tapping.
1. Part process analysis
The material of the cover plate is cast iron, and the blank is a casting. The content of the cover plate to be processed is that the plane, holes and threads are concentrated on the A and B surfaces. The four sides on the side do not need to be processed, and the highest accuracy must reach IT7 level. Then we can use the A surface as the positioning reference, and process it in the previous process, and select the B surface and the working hole on the B surface to process on the machining center.
2. Choose a machining center
Since all the holes on the B surface can be processed in a single station, a vertical machining center can be selected. The processing content of the parts includes rough milling, finishing milling, rough boring, semi-finishing boring, fine boring, drilling, expanding, countersinking, reaming and tapping. The required tools are not more than 20, so I choose ESLY-850 CNC machining center can meet the above requirements.
The X-axis stroke of the machine tool is 800, the Y-axis stroke is 500, the Z-axis stroke is 500, the table size is 1000×500, the distance from the spindle end to the table surface is 110-610mm, and the positioning accuracy and repeat positioning accuracy are 0.01mm. The storage capacity is 24, and the above-mentioned content processing can be automatically completed after the workpiece is clamped once.
3. Design process
(1) Choose the processing method
Surface B can be rough milled and fine milled: Φ60H7 hole size accuracy requirement is IT7, roughness is Ra0.8um, rough hole has been cast, so it can be rough boring + semi-finish boring + fine boring: Φ12H8 hole dimensional accuracy requirement is IT8 Grade, roughness is Ra0.8um, in order to prevent drilling deviation, we can drill the center hole-drilling-reaming-reaming: Φ16 hole on the basis of Φ12 hole countersink to size is enough; threaded hole in M6 Between M20 and M20, then we can drill the bottom hole first and then tap the thread.
(2) Determine the processing sequence
In order to reduce the number of tool changes and according to the principle of first roughing and finishing, face first and hole first, the processing route is: roughing and finishing milling B surface-roughing, semi-finishing, finishing boring Φ60H7-drilling the center hole of each smooth hole and threaded hole —Drilling, expanding 4×Φ2H8 holes—counterface 4×Φ16 holes—stranding 4×Φ12H8 holes—M16 tapped holes for drilling bottom holes, chamfering and tapping.
(3) How to install and select fixtures
According to the characteristics of the cover plate’s simple shape, small size, and smoothness on all sides, we can choose a vise, which is positioned on the bottom surface A of the cover plate and two sides, and the jaws can be clamped from the side.
(4) Selection of tools
In terms of processing content, the tools that need to be used include milling cutters, boring cutters, center drills, twist drills, reamers, end mills (counterface Φ16 holes) and taps, etc. The specifications need to be selected according to the processing size.
(5) Determine the feed route
The feed route for rough and finish milling of the B surface is determined according to the diameter of the milling cutter, with two feeds in the X direction (see Figure 5-40). Since the position of the hole requires accuracy within the range that the machine tool’s positioning accuracy can guarantee, all the hole processing feed routes are determined according to the shortest route. Figure 5-41 and Figure 5-45 show the progress of each hole processing. Give the route.
(6) Selection of cutting parameters
Determine the cutting tolerance and feed rate according to Table 5-11, and then calculate the feed rate of the machine tool spindle at light speed.