Methods for Repairing Bald Plastic Gear: Seeking Suggestions

Hot_Amir wrote:

If the plastic gear is bald, how to fix it

Ah, dealing with a worn-out plastic gear can be a bit of a challenge. When you say the gear is "bald," I assume you mean that the teeth of the gear have been worn down or stripped to the point where they no longer mesh effectively with the corresponding gear.

Here are a few approaches to fix or address a worn plastic gear:

1. Gear Replacement: The most straightforward solution is to replace the damaged gear with a new one. This ensures proper meshing and operation. If it's a standard gear, you may be able to find a replacement easily. If it's a custom part, you might need to contact the original manufacturer or have a new gear fabricated.

2. Build Up and Reshape: For a temporary fix, you could use a putty or epoxy designed for plastic repair to build up the worn teeth and then file or cut them back into the correct shape. This is a delicate process and might not provide a long-term solution, especially under high load or speed.

3. Reinforcement: If the gear operates under low stress, adding a sleeve or a coating to the gear's shaft might reduce slippage and extend the gear's life.

4. 3D Printing: If you have access to a 3D printer capable of printing with durable materials, you could 3D print a new gear. This is especially useful if the original gear is no longer available.

5. Professional Repair Service: Some companies specialize in repairing gears, including plastic ones. They may have techniques and materials that are not commonly available.

It would be helpful to know more about the application of the gear and the specific problems you're encountering. Can you provide more details such as the type of plastic, the load the gear is under, and the importance of the gear's precision? This information could help in suggesting the most appropriate repair method or potential alternatives.

Hot_Amir wrote:

(...) utes]:

Plastic gear whose circle and circumference is 8 cm. About one centimeter of the protrusion that is involved with the gear of the drive motor has been removed and straightened. When it reaches that point, it becomes junk and does not transmit power. How to repair the missing and shortened gears?

Given the specifics you've provided, it seems like you have a particular section of the gear's teeth that have been worn down significantly. To repair this, you have a few options, although each comes with its own set of challenges and considerations:

1. Epoxy Repair: You could use a moldable epoxy putty that adheres to plastic. This method involves forming the putty to recreate the missing teeth, letting it cure, and then refining the shape. Once it's fully cured, you can carefully file or cut it to match the profile of the existing teeth. It's a delicate process and may not withstand high loads or speeds, but it could serve as a temporary fix.

2. Professional Remanufacturing: Some companies provide services to rebuild or remanufacture plastic gears. They can often add new material and re-machine the teeth to the original specifications. This option can be rather costly but is likely to provide a more durable and long-lasting repair.

3. 3D Printing: If you have a model or precise dimensions of the original gear, you could 3D print a new section or even an entire new gear. This would involve using a strong plastic like ABS or PETG that can withstand the forces involved. The printed part could be used on its own, or it could potentially be used to create a mold for casting a new gear in a more durable plastic.

4. Custom Fabrication: If you have access to a machine shop, you might be able to have a new gear fabricated. Depending on the complexity and size of the gear, this might involve CNC machining or another form of precision manufacturing.

5. Reinforcement with a Metal Gear: If the plastic gear keeps failing and it's a critical component, you might consider replacing it with a metal gear. This would likely involve finding a compatible metal gear or having one custom-made. Metal gears are more durable and can handle greater loads, but they can also introduce new challenges such as increased wear on adjacent plastic gears, the need for lubrication, and potential alignment issues.

6. Adjustment of the Drive System: If possible, you could adjust the position of the motor or the mating gear to skip the damaged section, provided the gear has enough intact teeth to function properly. This is more of a workaround and not a repair per se, but it might get the system running temporarily.

The appropriate method largely depends on the load the gear needs to withstand, the critical nature of the application, and whether you’re looking for a temporary or a long-lasting solution. Before proceeding, consider the gear's role in the mechanism and the feasibility of each repair method. If this is a frequently occurring issue, it may be worth investigating the cause of the wear to prevent future failures, such as misalignment, inappropriate material selection, or inadequate lubrication.

Do you have the capability to fabricate or 3D print a new gear, or would you prefer to attempt a repair with materials such as epoxy? Also, is this a high-load application or something less critical?