Hello -

I'd like to injection mold a set of spiral bevel gears for use in a new product. I've been told the tooling for this is extremely difficult. I understand that the geometry of this type of gear is much more involved than a straight cut bevel gear and am wondering if this type of gear is ever injection molded. I would appreciate your thoughts. Also, if you could point me to examples of plastic molded spiral gears that would be great.

Best regards,
Jason

I haven't made a tool for a bevel gear for a long time. The common method in the sixties was to hard nickel chrome on to a master which because the grain had to be very fine took weeks. Now a good quality cnc edm machine can do the job. The tooth form is contained in a ring which is free to rotate as the part is ejected. A good toolroom with the right equipment should be able to do the job.

Unless you are a molded gear engineer I would not waste your time trying to make gears on your own. There are very few real gear engineers that can engineer quality plastic gears and fewer molders who can make them. If you are after low quality gears, more like cogs, then your options open up. However, you mention specifically spiral bevel gears and I am assuming you want a high class tooth form, therefore your best course of action is to search for a gear engineer. BE CAREFUL many people say they understand gears and don't.

BTW I have done many products with all levels of gear classes, machined and molded. I offer this advice because I understand the issues around gear designs, such as my work on the XBOX Kinect.

Ed I understand your concern you will note I said tool room not precision machinists. Any good tool maker with the right equipment can make a good quality gear mold if he is a good tool maker and does not have the right equipment he will reject the job. Unfortunately today many so called tool rooms are only precision machinists. I have worked mainly in precision molding so molding gears in the past was not a big issue. supplying gears for meters and instruments. However again there are many moulders that are little more than plastic squirters. which an audit can easily sort out.