Roughness Rt Rzmax

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10-06-2015, 05:14 AM
cammarasana123

Roughness Rt Rzmax

Good morning everyone,

First time I post on this forum, I hope section is right and question is good :)

I've to dimension surface roughness and I've just got this reccomandation from supplier:
(Rt n, Rzmax 2.5n)

My point is: since Rt is maximum peak-valley height in evaluation length, it should be greater or equal then Rzmax (calculate on sampling length). Also assuming 16% rule for Rt, Rzmax should be at most 1.16n.

Are there other points to be considered in comparing these two roughness parameters?

Thanks for supporting,
10-06-2015, 07:48 AM
Kelly_Bramble

[QUOTE=cammarasana123;11426]
I've to dimension surface roughness and I've just got this reccomandation from supplier:
(Rt n, Rzmax 2.5n)

My point is: since Rt is maximum peak-valley height in evaluation length, it should be greater or equal then Rzmax (calculate on sampling length). Also assuming 16% rule for Rt, Rzmax should be at most 1.16n.[/QUOTE]

Yes, assuming ISO 4287 - Rt is the Total height of the roughness profile (peak to peak) and Rz is the maximum height of the roughness profile from the mean.

I suspect that your supplier simply got Rt and Rz reversed..

Going forward - the surface roughness requirements should be specified first by functional requirements and secondly if the functional requirements are not critical then specified by the target manufacturing process (economics does matter)..

For reference, see:

[U][B][URL="http://www.engineersedge.com/manufacturing/surface-roughness-conversion.htm"]Surface Roughness Conversion[/URL][/B][/U]
10-08-2015, 09:48 AM
cammarasana123

Re

[QUOTE=Kelly Bramble;11428]Yes, assuming ISO 4287 - Rt is the Total height of the roughness profile (peak to peak) and Rz is the maximum height of the roughness profile from the mean.

I suspect that your supplier simply got Rt and Rz reversed..

Going forward - the surface roughness requirements should be specified first by functional requirements and secondly if the functional requirements are not critical then specified by the target manufacturing process (economics does matter)..

For reference, see:

[U][B][URL="http://www.engineersedge.com/manufacturing/surface-roughness-conversion.htm"]Surface Roughness Conversion[/URL][/B][/U][/QUOTE]

Hi,

many thanks for supporting !!

Simone