Glebar Centerless Grinding toubles- .0098" Nitinol to .0025"

[daily_grind]

Hi All,

To preface, I am very new to grinding and just started this position about a month ago, so please forgive me if I get any nomenclature wrong.

I have been tasked with getting our two grinders running production capacity, which has been quite the challenge.

My current issue is the Nitinol wire. From what I've come to understand, Nitinol sucks to grind. Glebar had completed part samples to prove it could be done (in house) and had shipped the very same machine they did the R&D on, to us.

This is the current setup:

Diamond Wheel-400 grit-resin core, Diamond Rotary Dresser, Mineral Oil Coolant

Once everything was set on the machine, I was maybe able to make about 10 parts before my tolerances starting drifting out, like the diameters were getting smaller across the entire profile. I'm not sure what the cause was for that.

I reached out to Norton, and a sales rep came in and told me I had the wrong setup for trying to run Nitinol. He suggested using a CBN wheel. He also pointed out that I wasn't dressing the wheel, which could cause issues. We're definitely not in production mode, so I haven't keeping an accurate part count. I guess my question is this, am I using the right wheel/coolant, and how often should I be dressing (silicon stick) the grind wheel.

 

[michiganbuck]

Here find an older PM thread on the subject.
Centerless grinding nitinol

For some materials, one may back off on the fineness of the wheel grit, by using the wheel that will still give the surface finish needed.

Sounds like heat may cause some of your problem, sometimes a dwell in feed can help for that..but I'm not the centerless guy so don't know how you might dwell the feed.

In vitrified wheels sticking you try a pattern of every certain number of parts. The stick is to reduce the height on the bond so to let the diamonds be above the wheel body, which helps to make space for chips and coolant.

A broken medium hardness green wheel makes a very good diamond wheel stick.

You might call Radic wheels and ask their wheel guy about that material...see if he supports the Norton guy / or has more to add.

 

[daily_grind]

Thank you for the response.

After having the head of R&D come and see what the issue was, we were able to make 100 consistent wires, with maybe 2-3 adjustments.

For starters, our wheel wasn't dressed properly, and as I'm finding out, not having that crisp edge on the exit side was killing us.

Once we actually had the correct profile dressed in, we were able to get the .02" transition on the back end of the wire.

From there, it was just a matter of letting the wheel getting up to temperature, making minor adjustments to the funnel angle, rinse repeat.