Specifying the average slope of a profile

[MechEnjoyer]

Hi all,

I have a component that will have a sliding surface and it is important that the surface quality is good to reduce the frictional forces as much as possible. I used this document: Link, to get some more information on how the surface roughness affects the coefficient of friction and one of the things that they conclude is that the average slope of a profile affected the coefficient of friction the most.

To my question, I was wondering if it is possible to define the average slope of the profile in a drawing under a surface texture symbol or should I just use standard GD&T symbols to control such a feature? I have never faced a problem like this one before and I am not quite sure if I can specify this or if I should just keep to the normal ways to specify surface texture. Your help and insight is greatly appreciated!

Best regards

 

[Burunduk]

According to ASME B46.1-2019, there is a parameter called "Average absolute slope, RΔa".
I would suggest checking in the manual of the device that will be used to evaluate the surface texture if an output value of this parameter can be generated.

You can call it out on the drawing just like any other parameter that is not Ra, per the ASME Y14.36 rules (if you need help with that too - ask).

Some info on it from the standard:

Z(x) is the roughness profile's height function (X is along the evaluation length).

 

[MechEnjoyer]

Hi Burunduk

Thank you very much for your response. The equations you sent are familiar to me so that feels good. I'll have to first contact the manufacturing company to see what device they are using. Anyway, thank you again for your response, I really appreciate it and hope you have a great midsummer!

Best regards

 

[Burunduk]

MechEnjoyer,
Happy to help! Good luck, and I'd love to hear any updates.