How to weld and repair the broken shaft of the servo planetary reducer

Broken shaft is a common failure of the servo planetary reducer. Many users do not know how to deal with the broken shaft. After a large number of practical cases, the broken shaft of the servo planetary reducer can be repaired by welding. Today I will show you how to weld.The welding is divided into three stages: pre-weld preparation, welding and post-weld treatment. The specific operations are as follows:

1. Preparation before welding

1. Welding groove and gap design.The fractured part of the servo planetary reducer should be processed and leveled before welding, and corresponding measures should be taken for the design of the welding groove to reduce the stress.The U-shaped groove is designed according to the fracture condition and the diameter of the part. The upper width of the groove is 20 mm and the depth is 37 mm.After the end surface of the fracture is processed flat, the end surface of the fracture is cut with a formed turning tool to make it consistent in shape.In order to avoid stress concentration, all parts of the groove should be rounded to reduce the proportion of the base metal melted into the weld metal and prevent cracks.The welding gap also has an important impact on the quality of the weld. If the gap is too small, defects such as incomplete penetration or excessive weld accumulation may occur, and if the gap is too large, it is easy to burn through.

2. Clean up before welding.Before welding, the rust, oil stain, moisture and oxide skin on the groove and blunt edge surface of the shaft welding part of the servo planetary reducer must be removed. First use flame baking to remove water and oil, and then use manual emery cloth or grinder to polish to remove rust. deal with.The oxide skin can be directly removed by grinding with a grinder, and for some difficult-to-clean oil stains, it can be cleaned with acetone or ethanol.

2. Welding

In the welding process of the servo planetary reducer, in order to prevent welding deformation, positioning blocks should be added at the groove to ensure equal spacing welding.The positioning point welding position is selected on both sides of the positioning block to avoid welding deformation of the axis.At the same time, the cooling rate of the entire welding area is reduced to prevent cracks.The weld seam should be welded evenly with the rotation of the shaft. Each layer of weld seam should be completed once. The appearance of the weld seam should be visually inspected. If there are pores, slag inclusions, cracks, etc., the weld seam defects should be removed by carbon arc gouging. Welding can then be continued.When the welding seam cooling temperature is not lower than 200°C, weld to the height of the positioning block, knock off the positioning block, and continue welding.The surfacing height should be greater than the diameter of the original shaft in order to leave enough machining allowance.

3. Post-welding treatment and machining

After welding, it is covered with asbestos for heat preservation to reduce hardenability and avoid brittle cracks.In order to eliminate the welding stress, the weld area can be heated to 350~550°C with a flame, buried in hot sand or white ash and slowly cooled until the temperature is normal.The appearance of the solder joints of the servo planetary reducer is required to be neat and beautiful, the weld seam is uniform, and there are no pores, slag inclusions, poor melting, splashes and undercuts.After the appearance inspection is qualified, re-turn the outer circle and end face of the welding part of the output shaft according to the required size.