The spindle box is a key component of the China CNC vertical machining center, adopts a symmetrical design, and reasonable reinforcement design based on dynamic analysis to ensure good anti-torsion, anti-bending ability and stability accuracy. The spindle box plays a positioning support and prolonging the spindle on the machine tool structure, so the manufacturing precision is required to be high.
Take the vertical machining center spindle box as an example, through the analysis of the spindle box structure and machining requirements, the key points and difficulties that need to be particularly paid attention to during the machining process are determined, and a reasonable manufacturing process plan is formulated to ensure the machining quality of the spindle box and improve production efficiency.
The raw material of the spindle box is HT300, and the casting is made of resin sand molding. The movement between the column and the spindle box is combined with a rolling linear guide. Its main requirements are as follows:
There shall be no casting defects such as sand holes, air holes, shrinkage cavities, and cracks in the casting, and the casting shall be subjected to aging treatment, and the hardness shall not be lower than 190HBW.
The straightness of the two guide rail surfaces is 0.005mm, the straightness of the two guide rail surfaces is 0.01mm, and the flatness of the guide rail surface is 0.01mm.
The parallelism of the large surface of the screw seat and the two guide rail surfaces is 0.01mm, and the parallelism of the vertical surface and the guide rail vertical surface is 0.01mm.
The parallelism of the ϕ140H5 spindle hole and the guide rail large surface and vertical surface is 0.005mm.
The surface roughness values of all important surfaces are Ra=1.6μm.
Through the analysis of the structure and machining requirements of the spindle box parts, the machining key points and difficulties are as follows:
The guide rail surface is the benchmark of the screw seat and the spindle hole. How to ensure the high position and tolerance requirements of the two guide rail surfaces is a difficult point in the machining process.
The ϕ140H5 spindle hole is the key part of the spindle box. How to ensure the dimensional tolerance and positional accuracy is also a difficult point in the machining process, which needs to be given priority in the process plan.
Since the precision of the spindle box directly affects the precision of the machine tool, ensuring the stability of the spindle box accuracy is also the focus of the process plan.
The principle of determining the process plan is:
Reasonable layout of aging process to eliminate various stresses of the spindle box and ensure the stability of the spindle box accuracy.
Correct arrangement of rough and finishing processes, and make the error caused by rough processing corrected as much as possible through semi-finish processing and finish processing.
Make full use of the machining performance of the horizontal machining center to minimize the turnover of the workpiece and improve efficiency.
Reasonably arrange the finishing process to ensure the stability of the dimensional and positional accuracy of the workpiece after machining.
During the machining process of the spindle box, two vibration aging processes are arranged to fully eliminate the stress generated during casting and the residual stress generated during processing. It can prevent the deformation and cracking of the casting and ensure the stability of the dimensional and positional accuracy of the spindle box after machining.
During rough processing, due to the small deformation caused by the vibration aging, considering that the machining of the spindle box belongs to batch production, multiple workpieces are installed for rough machining on a gantry milling machine or gantry planer. The tolerance of 3mm is left around the roughing, the tolerance of 3mm is left on one side of the spindle hole rough boring on a horizontal boring machine.
Semi-finish machining further removes the allowance. A tolerance of 0.5mm is left around the four sides, guide rail surface and screw seat installation surface on a CNC horizontal milling and boring machine, and a tolerance of 0.5mm is left on one side of the spindle hole. The other non-important surfaces are machined to the design requirements, fully eliminating the residual stress generated during the machining process.
The finishing process is completed on the horizontal machining center of Japan's Matsuura. First, the guide rail surface and the screw seat mounting surface are machined, and the parallelism and perpendicularity of each surface are ≤0.01mm, and guide rail surface mounting holes are machined out. Then, the spindle hole is precisely bored based on the C surface of the guide rail vertical surface as the benchmark, and the remaining unprocessed surfaces are processed by rotating the workbench. In order to ensure the parallelism and perpendicularity requirements of the spindle hole and guide rail surface, a special boring tool needs to be designed.
Deed CNC offers different vertical machining center for custom solutions, we have 5 axis CNC vertical machining center and VMC vertical machining center, CNC vertical turning lathe machine. Through the above analysis, the feasibility of the spindle box process plan is clarified and the correctness of the machining process flow is confirmed. By following the above process flow, it can meet the precision requirements of the vertical machining center for the spindle box.