Material that won't scratch/leave residue on glass

[Kinsrow]

Hi,

I'm researching material that will be not leave marks/scratches or residue when pressed against the glass with, say 5 lbf. I can think of plastics and polymers but not sure of which ones.

From this material, I'm going to make pins that will be spring loaded. The window glass will touch and press the pins with, say 5 lbf.

Thanks

 

[dik]

Almost any plastic material. Your end useage should determine the type of plastic. Acrylics, neoprene, polycarbonates, etc.

Dik

 

[dimjim]

Find out what car wiper blades are made of and use
the same.

 

[dik]

Wiper blades are commonly made using EPDM "ethylene propylene diene monomer" and silicon.

Dik

 

[dik]

forgot to add, most glazing gaskets use butyl rubber.

 

[CoryPad]

dik means SILICONE (polydimethylsiloxane), not elemental silicon.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dik]

thanks Cory, was a typo... sand can scratch glass... and thanks for the chemical name... I didn't know it was a siloxane...

Dik

 

[unclesyd]

If you will look over this site I think you will find what you need. This material is used with glass in both dynamic and static applications.
When I was involved with this material their technical and sales force were always very helpful.

http://www.santoprene.com/home.html

 

[dvd]

Felt works well. Those little green sticky felt pads can be obtained in different sizes.

 

[IRstuff]

How often and for how long? Previous threads have shown that even cotton thread is abrasive against steel if the conditions are maintained sufficiently long.

TTFN

 

[Kinsrow]

Thanks for input.

IRstuff

It's 200-300 times/day and 2-5 second per cycle.

 

[IRstuff]

If it's the same piece of glass, then I would suspect that you'd want something that does not deform, since the deformation will cause a lateral motion of the pad surface relative to the glass.

How big is this pad? How does the system ensure that the pad hits the glass squarely? Any angular displacement will also cause the pad material to move against the glass.

What's the criticality of the non-abrasion? Perhaps the glass portion should be made replaceable.


As a further example, albeit somewhat poor, most copy machine glasstops get abraded where the roller wheels touch the paper during the copying process. It's the restarting of the paper motion after the copying that does it, since there's no longer the air film to buffer the paper from the glass.

TTFN

 

[Kinsrow]

IRstuff,

Basically, I have a fixture that locate and press a glass window to a tape. The tape is adhesive backed and will be located using slot and a hole on a vacuumed plate that has 2 spring loaded locating pins. These pins will be riding on bushing or linear bearings. Since the window need to be pressed to the tape and the the locating features are inside the tape geometry, I'm planning to use either plastic or hard rubber pad mounted on the spring loaded locating pins so that the window will not scratch and more importantly leave no marking. Right now, either I use FDA grade polyurethane or PTFE. The window is 6" square and the pad will be 3/8".

Non-marking is the critical issue here.

The pressing actuation can be either manual or pneumatic driven.

 

[IRstuff]

Oh, OK. It's essentially a one-time operation, w.r.t. the glass. I'd be more worried about the pad wearing, then.

Since your pin is spring-loaded, the pad doesn't need to be. I'd be concerned that the urethane might acquire a "set." Likewise, certain PTFE's will flow under pressure.

Have you considered some sort of nylon-derivative like Delrin?

TTFN

 

[Kinsrow]

Delrin would be another choice. This material is scratch resistant also. Misumi also sells a lift pin that is made out of PEEK or UHMW. What do you think about these two?

Thanks

 

[IRstuff]

I don't know enough about them, but they seem to be reasonable candidates, although they'e both noticeably harder than Delrin.

TTFN