Predicting wear of metal folding board on flexible film packaging line

[Life is a bowl of problems]

The machine in question manufacturers flexible packaging using various films one example being polyethylene. Part of the process pulls the film over a triangular folding board whose edges can be made from various metals, such as stainless steel or aluminum. We have used various treatments and coatings to minimize friction and reduce wear along these edges, but significant wear still occurs.

We are now trying to find a way to estimate the life expectancy of these folding boards based on the different materials and treatments we use. I have looked at the Archard-Child equation, but it requires knowing the Wear Coefficients for the material pair in question which I have not been able to find.

Considering the many applications in the packing industry that include plastic film, under tension and at speed, sliding over rollers, thru guides and along other surfaces I would think analytical and empirical methods to estimate wear would abound, but I am having a hard time finding anything.

Any help would be appreciated.

 

[IRstuff]

A picture of the process would help

What is the number of cycles before wear is unacceptable? Is it a cost issue? Did it ever meet expectations for wear?

I think that wear is inevitable. There was a post here many years ago about cotton thread wearing through SS guide rollers; it's simply a matter of time.

Seems to me there are two options:
> make the edges infinitely hard, and infinitely expensive
> make the edges somewhat hard, but cheaply, and replace as needed.

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[3DDave]

There won't be sliding over rollers - the rollers are turning. I would consider putting an air supply with small holes or a shallow channel to provide an air film to keep the plastic from touching but still retain close control.

Cotton (cellulose) is notoriously abrasive, but I would not expect polyethylene to cause wear. Is it possible there is dust contamination in the area that is getting between the polyethylene and the metal and that is the abrasive? Is there cardboard processing in the same plant?

 

[IRstuff]

Yeah, probably just rubbing; it wasn't necessarily clear in this thread: thread367-92753

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[Life is a bowl of problems]

I have attached a couple of images for clarity.

The polyethylene web is continuously pulled through this portion of the packaging line. As the web is pulled over the folding board, the web is folded in half and turned horizontal. The edges of the folding board wear from the continuous sliding of the polyethylene web over it.

We see wear in the field over time and don't expect to prevent it. We do however want to optimize our material selection to minimize this wear and also want to estimate the expected time these folder edges will last before requiring replacement.

The machines can run in excess of 100 fpm 3 shifts a day 7 days a week. We would like to be able to give our customers an estimate of how often these edges need to be replaced.

We do not want to set up a physical testing rig to empirically determine wear rate, at least not at this time. Hoping for an analytical approximation.

 

[Life is a bowl of problems]

Here is second image that did not upload with my previous post.

 

[IRstuff]

OP's images

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[IRstuff]

Some random things on the internet. The last one might be interesting, but I didn't read in detail. Again, you have a choice of hardened steel, something even more exotic, or possibly PE itself, the latter might be in an insert that can be readily and inexpensively replaced.

https://www.sciencedaily.com/releas...m has,nature's most wear-resistant materials.

https://www.ceramicsrefractories.sa...ials such as,to meet changing market demands.

https://blog.thepipingmart.com/metals/what-is-the-most-abrasion-resistant-material/

https://www.leecosteel.com/news/pos...eel plate,and hardness, but reduces strength.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2391012/pdf/nihms33353.pdf

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[EdStainless]

You can't take theory and then use your own service data to arrive at factors to use?
What materials have you tried?
SS means almost nothing it is so vague.
Rollers and air knives are both great options.
If you are looking for materials then nothing will touch ceramics.
You just have to figure out how to mount them.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[SWComposites]

if its a wear issue, why not put rollers on those angled folding edges?

 

[Compositepro]

This type of process function is often done with "turning bars" or similar. The edges should have very carefully controlled radius so that a layer of air gets trapped between the plastic film and the stationary surface, which acts as a lubricant to create very low friction. A sharp edge acts as a scraper, eliminates the air film, and collects dirt. The contact pressure at the turning surface will be proportional to the web tension and inversely proportional to the turning radius. Air bars fed by a blower can be used where very low friction is desired

 

[Compositepro]

Rollers cannot be used because the material is not moving in the same direction as the surface of the roller. This process requires sliding contact.

 

[Life is a bowl of problems]

I appreciate all the helpful feedback. I think I now have multiple directions to pursue in reducing wear in my application. I'll try to reply back with any results that may be of interest.