Common causes of errors in gear hobbing

Writer： admin Time：2024-11-05 15:45:52 Browse：12℃

Reasons related to machine tools

The precision of parts in the machine tool transmission chain, such as the tool spindle and worktable spindle, has been lost or worn, 

and the gap between transmission parts has increased, resulting in looseness and impact during cutting;

The contact between the spindle of the worktable and the conical guide surface of the worktable is hard, and the worktable is driven heavily, 

resulting in frictional heating and vibration during rotation; Or it may come into contact with looseness, causing the workbench to shake during operation;

The two indexing worm gears of the tool holder body and worktable move too much in the axial direction during operation,

 or the meshing clearance between the worm gear and the worm wheel is too large, causing jumping during operation;

The cutting mechanism of the machine tool is not working properly, causing scratches on the machined surface of the workpiece during the return of the gear hobbing tool.  

Solution:

Identify parts with lost accuracy for repair, correction, or replacement;

Scratch the surface of the conical guide rail to maintain even contact and no heaviness within one rotation;

After grinding and adjusting the gasket and replacing the bearing, ensure that its axial displacement is within 0.005 and maintain a reasonable meshing clearance between the worm gear pair;

Readjust the tool mechanism, especially when the machining modulus is greater than 4 or smaller, this phenomenon occurs more frequently.  

Reasons related to cutting tools

1. The cutting edge of the gear has been worn down, causing tearing and other issues on the tooth surface of the inserted gear;

2. During the cutting process, the gear hobbing tool generates chip deposits and adheres to the blade edge.

 The adhesive part of the blade is not worn off during grinding, which improves the surface roughness of the teeth;

3. The rake angle of the gear hobbing tool should be adapted to the material of the gear being hobbing. 

If a gear hobbing tool with a rake angle of 5 ° is still used for hobbing alloy materials after quenching and tempering treatment, it is easy to produce chip deposits during hobbing;

4. The gear hobbing cutter is not securely fastened after installation, resulting in displacement and vibration during cutting.  

Solution:

Re sharpen the gear hobbing cutter to make the blade sharp, and fully cool it during sharpening to improve the grinding quality of the front blade surface;

Appropriately increase the reciprocating stroke of the gear hobbing cutter to prevent the formation of chip lumps;

Appropriately increase the rake angle of the gear hobbing cutter;

Reinstall and tighten the gear cutter.

Reasons related to installation, cooling, workpiece materials, and heat treatment

Improper or too dirty selection of cutting fluid;

The installation of the gear blank is not firm, resulting in displacement and vibration during cutting;

The material hardness is too high, causing defects such as tearing and fish scales on the tooth surface.  

Solution:

1. Reasonably choose cutting fluid, and replace too dirty cutting fluid in a timely manner;

2. Check if the gear blank is securely fastened;

3. Pre heat treatment of gear blanks