suspicious friction coefficient for anodized die extrusion profile

[cervantes]

Hello,

strange situation - anyone can help me
I have a profile, drawing stated as follows:
material Aluminum 6063F22, Aging T6, natural anodizing 10my


now, two different batches from the same supplier have difference in friction coefficient (against homogenous polyurethane material) around 40% !!!

does anyone know how the hell they manage to achieve such unstability?....
I discovered this today and I got stuck - is it other type of alloy, maybe something with anodizing?....

 

[tbuelna]

Since it's the anodize coating that is in contact with the urethane material, that is what you need to look at. Was the same anodize process used for both batches? Surface texture can also have a large effect on friction values. A variation of 40% in measured friction coefficient between single samples tested at different times is not that unusual.

Can you provide more information regarding processing of the test samples, how the testing was conducted, and the results of the testing.

 

[cervantes]

ok, we made a profilograph test for both profiles (this is a die extrusion profile), made in all possible directions - value of "Ra" parameter is almost the same (0,005 difference is max.)

I clean one of the samples 12 hrs in aceton (the one which has definitely lower friction coefficient), because I thought it will remove invisible oil film - no bigger effect

I will estimate friction coefficient today, but organleptic there is no doubt that there is a diffference

honestly - I do not know what is the reason, I was hoping that profilography test will give an answer, but it creates more questions

 

[tbuelna]

What are the units of that "0.005" difference in Ra surface roughness? A difference of 0.005 inch in surface roughness would be huge, but a difference of 0.005 micrometer is quite modest.

 

[cervantes]

we have measured angle when sample starts to slide
17 deg vs 25 deg which is 0,3 v 0,46

I also attached results and screenshots - maybe I wrongly interpreter results (honestly I hope so)

 

[cervantes]

we are operating in metric system, nopt inches

 

[cervantes]

this case was just solved
I haven't explained exactly that both of them were machined.
Now we checked friction coefficient before and after machining, even if it is cleaned with alcohols etc. you can not completely remove invisible thin oil film.

Does anyone has experience with cleaning systems etc?

 

[tbuelna]

Didn't your OP state the surface was anodized?

 

[Duwe6]

One of the steps in anodizing is a cleaning in hot, alkaline soap. Try using dishwasher detergent for your laboratory cleaning.