Bearing Press Force Data Management Help Needed

[JeffZim]

We have manufactured a Bearing Press for a production part we are manufacturing for a transmission case. The assembly part print calls out the bearing press in force to be 675 lb. MIN to 1,800 lb. MAX. We currently begin capturing force data after we have engaged and entered the bore with the bearing by 3/16". We then take a force reading every .038 in. until we complete 10 readings. If any one of the ten samples is outside of the force range we fail the part. Our average reading of the 10 data points so far has always been within the acceptable range.
Is there a standard method or specification for determining how to test the production process for pressing a bearing into a part. We can't find anything defined by our customer, (Big Three). Would the current method be to rigid? We are scraping more parts than we anticipated.

 

[handleman]

You might get in touch with Scimetric (I think that's the name). They make data acquisition and analysis equipment for industrial automation integration, and they have a module that is designed to monitor press force vs. distance curve. They also have some pretty good experience with different pressing parameters and failure modes.

-handleman, CSWP (The new, easy test)

 

[gnausley]

Jeff,

It is very common for part prints to call out force requirements like this that are not specific enough or that are not adequate to really ensure the quality of the assembly.

If a print calls out "bearing press force to be 675 lb. MIN to 1,800 lb" the question should be "at what point in the press move?".

During the press cycle the press force will climb from zero to some value as more of the surface area of the bearing is engaged into the bore, with the force leveling out somewhat once you have full engagement, then spiking when the bearing shoulders.

Many people will check the press force at one location, at a fixed distanced before the bearing shoulders. This provides some information but is realing not adequate to ensure a high quality assembly. Your attempt to check the force at various points along the press force curve is a better approach to ensure a good assembly, however checking every point to the same force limits will lead to false failures.

The best approach is to (This approach is accepted by the Automotive industry) is to monitor the force signature over the entire press fit process setting ramping limits (taught-in possibly) around this curve and pulling out and monitoring some critical points of the curve.

-Where did the bearing first contact (Touch Point) the bore?
-What was the final depth the bearing was pressed too?
-What is the distance from Touch Point to Final depth?
-What was the force prior to shouldering?
-What was the shouldering force?

The force signature along with the answers to these questions tell you if the assembly is good or not.

A system that collects this information allowing you to build a history is also very helpful in determining what is typical for your production parts.

The company I work for (Promess Inc out of Brighton, Mi. (810)229-9334) provides a variety of test systems including systems to monitor press fit processes. I would be happy to discuss this in more detail with you if you have any questions.

Glenn