In the past, the old-fashioned, low-speed C620 lathe spindle was fitted with a plain bearing. Although the sliding bearing has the advantages of simple structure, convenient manufacture, low cost, stable operation, and insensitivity to shock and vibration, it is far from meeting modern cutting machine tools. High speed, high precision, high efficiency, and it is difficult to repair after wear. The surface roughness and precision of the machined parts are poor and the productivity is low. To this end, the C620 lathe spindle front end sliding bearing has been modified, the specific steps are as follows (see the attached drawing)
The modification of the front end bearing hole of the headstock 1 is to machine the front end bearing hole of the headstock 1 into Ø150K6. In order to facilitate the loading and unloading of the bearing, a hole of Ø151mm and a length of 55mm is machined at the left end of the bearing hole. In addition, a Ø16mm hole is drilled for easy operation of the fastening screw 5.
1. 2. headstock spindle adjusting nut 3. 4. 5. locking nut fastening screw movable bearing pad 6.3182120 7. 8. The pressure ring bearing cap bearing a schematic front spindle lathe C620 <br> <br> improve the bearing cap
Modification of the main shaft 3 A M100 x 1.5 mm thread is machined on the main shaft 3 in accordance with the size and position shown in the drawing, and an adjustment nut 2, a nut stop pad 4, and a fastening screw 5 are disposed. 2 The 1:12 taper is machined on the main shaft 3 according to the position and size shown in the figure to match the inner taper hole of the bearing 6.
Machining of the bearing cap 8 and the bearing cap pressing ring 7 The original sliding bearing adjusting nut internal threading car is machined into the size of the bearing cap 8 as shown (the unlabeled dimensions are existing in the original part). 2 The original bearing cap pressure ring is machined to the size of the bearing cap pressure ring 7 as shown.
The axial movement of the main shaft 3 and the adjustment of the radial clearance 1 The axial movement of the main shaft is adjusted by the adjusting nut at the rear end of the main shaft. The measured amount of the bearing surface of the main shaft shoulder should be 0.015 mm. 2 The radial runout of the spindle centering journal is adjusted by adjusting the nut 2 to obtain a slight radial clearance of the bearing 6. The radial runout of the spindle centering shaft head should be 0.02 mm.
The accuracy of the machine tool after the modification is as follows:
The radial runout of the spindle centering shaft head is 0.01~0.03mm
The axial movement of the spindle is 0.015mm
The parallelism of the spindle axis and the movement of the slide is 0.02 mm over 300 mm (in the plane perpendicular to the horizontal plane)
The lateral movement of the horizontal turret to the spindle axis is 0.02 mm (concave) at 3000 mm.
The height deviation between the head and the tailstock is 0.03mm
On the 300mm long shaft, the outer circle of the finished car is measured: roundness is 0.02mm, cylindricity is 0.03mm
The flatness of the end face of the finished car on a 300 mm diameter is 0.02 mm (concave)
The surface roughness of the machined surface is Ra 6.3 to 3.2 mm.
The above data is in line with JB2670-82 "General Rules for Precision Inspection of Metal Cutting Machine Tools". The quality of the product has been significantly improved compared to machine tools that have not been modified with spindle bearings.
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