Corrosion, Discoloration, and Contamination of Gears


Steps to take for avoidance of imperfections in the aesthetics and surface integrity of gearworks

Roscoe, IL - Forest City Gear recently disseminated the following tips to its employees and would like to share these ideas with the gearmaking community, as well as users and assemblers of gearworks. This information is provided for reference only and any further questions or comments should be directed to author Fred Young, CEO of Forest City Gear. He welcomes all feedback.

Recently and historically, we have had issues with gears that suffered from the above conditions, after heat treat. These issues can also appear during hot and humid times, as well. We previously had a sand/vapor blast unit that was used to clean off debris and contamination from gears, prior to further processing.

My suggestions for future handling, based on experience and a reading of the current technology, include the following:

1. We should change the routings to include a hand blasting (not tumble blasting) by
our heat treaters.

2. We should stipulate the further provision to our vendors that this is initiated only for cosmetic cleaning purposes and that they are enjoined from too extensive a blasting, which could cause dimensional changes or damage to our parts.

3. We are looking for a uniform and clean surface on all areas that are not ground and this would include gear root diameters, where appropriate. If we do not have high confidence in the individual heat treaters to perform this critical task, we should try to use the Comco blast unit we have in-house or investigate the purchase of a unit similar to the old one we had. I know that the main objections to that equipment were the excessive dust and grit surrounding it and the extra processing time required. However, the returns we have experienced from time to time over these issues demand that we take some aggressive preventative steps. Please note that this is not limited to parts that are only heat treated.

4. When we use our ultrasonic cleaner or parts washers with soap and hot water, water
spots and/or soap contamination may be objectionable to some very particular and
discerning customers. Changing of the final cleaning solution may be necessary, in such cases.

5. If it is feasible, we should use any of the currently available vacuum heat treating processes to assist us in maintaining cleanliness and an optimally professional visual appearance, which can help minimize objections by outside inspectors.

I welcome all your suggestions to further our desire for achieving "Excellence without Exception." (This is the company motto at Forest City Gear.) I think that if all hands are on the lookout to address the corrosion, discoloration, contamination and pitting issues and address corrective procedures prior to further processing-gear grinding, cylindrical grinding or other machine operations- this will help minimize our overall cost. It is very difficult to address these issues after grinding has occurred, as you all know.

The September/October (2009) issue of Gear Technology had an article starting on page 60 entitled, "Gear Corrosion During the Manufacturing Process," which focused on issues of pitting caused by corrosion, which can be very serious and ultimately lead to gear failure in operation.

While the article discussed the REM Chemical process of isotropic superfinishing in particular, much of the information is germane to the points above and will contribute to your understanding and resolution of these problems. I encourage you to read it. The watchword at Forest City Gear is that all of us are responsible to be on the lookout and take steps to prevent this situation from future occurrence, to the greatest degree possible. It will be prudent to gather some examples and point out exactly what we are trying to prevent from going out the door, by reviewing it with all hobbing/secondary, shaping and grinding department personnel, at the earliest opportunity.

For more information on this announcement, please contact:

FOREST CITY GEAR CO., INC.

11715 Main Street

Roscoe, IL 61073-0080

Phone: 815-623-2168

Fax: 815-623-6620

Web: www.forestcitygear.com

Email: sales@forestcitygear.com

Attention: Fred Young

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