Surface Finish Requirements (Ra 150) for Blasted Titanium Surfaces

[Ti QE]

I'm looking for help to resolve an issue with a blasted surface requirement (Ra 150) on a titanium surface. The customer is requiring Ra data for the surface but I believe Rz data will yield a more consistent surface finish.

[Stijloor]

In Reply to Parent Post by Ti QE

I'm looking for help to resolve an issue with a blasted surface requirement (Ra 150) on a titanium surface. The customer is requiring Ra data for the surface but I believe Rz data will yield a more consistent surface finish.

Hello Ti QE,

Welcome to The Cove!

May I ask you; what exactly does your customer want? What is the customer/engineering specification?

Could this article from MMS Online be of any help?

Stijloor.

[Ti QE]

Measurement is in mirco inches (sorry for the lack of detail) and the tolerance range is 80 minimum to 200 maximum. The surface finish will help adherence during a bonding operation. I'm unsure how they arrived at using Ra instead of Rz but I'm stuck with it. The repeatability of sampling is (ours versus theirs) is the current sticking point.

[Stijloor]

In Reply to Parent Post by Ti QE

Measurement is in mirco inches (sorry for the lack of detail) and the tolerance range is 80 minimum to 200 maximum. The surface finish will help adherence during a bonding operation. I'm unsure how they arrived at using Ra instead of Rz but I'm stuck with it. The repeatability of sampling is (ours versus theirs) is the current sticking point.

Hi Ti QE,

Is there a written agreement/specification stating how the inspection and frequency of inspection has to be performed and how the values should be expressed? Because if not, this situation will remain a "sticking point."

Many discussions here at The Cove Forums deal with issues that were never clearly defined and agreed upon between the customer and the supplier. Try to engage in a conversation with the stakeholders in this issue, and then try to create a win-win. Better for you, better for your Customer.

Stijloor.

[Phil Fields]

In Reply to Parent Post by Ti QE

Measurement is in mirco inches (sorry for the lack of detail) and the tolerance range is 80 minimum to 200 maximum. The surface finish will help adherence during a bonding operation. I'm unsure how they arrived at using Ra instead of Rz but I'm stuck with it. The repeatability of sampling is (ours versus theirs) is the current sticking point.

Is your company responsible for the bonding operation, or is that up to the customer?

[Ti QE]

My customer is responsible for the bonding operation; the surface roughness requirement helps the adhesion process.

[Ti QE]

All - I've been in contact with Mahr Federal and Mitutoyo (both profilometers were used to check surface finish and both had problems) and they have advised that their instruments are not the best method to measure surface finish on a grit blasted surface. Both instruments have issues with the surface irregularities (stylus gets caught on rough edges, stylus bounces, etc) which results in the diamond tip being ripped from the mountings thus causing the instrument to throw errors. Normal time between stylus replacement runs from one week to ? depending on usage. I've decided to use optical laser scanning (yes, it's expensive) to determine Ra values but it seems to be a definitive answer to the problem at hand.

Thanks to all for your comments and suggestions.

[Crash Not]

In Reply to Parent Post by Ti QE

Measurement is in mirco inches (sorry for the lack of detail) and the tolerance range is 80 minimum to 200 maximum. The surface finish will help adherence during a bonding operation. I'm unsure how they arrived at using Ra instead of Rz but I'm stuck with it. The repeatability of sampling is (ours versus theirs) is the current sticking point.

If it is an issue of "ours versus theirs" than maybe both profilometers should be calibrated to the same master. Or create a sample part and have them check it and indicate where the check(s) were made, in which direction, number of checks, ect., and keep that part for your reference.