Need a material with extremely high friction but no adhesion.

[Pulsar]

I am in the process of building a tracked vehicle with an extensible gripper arm to handle... delicate... materials.

The gripper itself is a three finger "pinch" gripper. The problem at hand is that the objects we are picking up are fragile. To put a rather fine point on it, if you squeeze them too hard they can explode. Unfortunately they are non-rigid materials. Think something like an innertube.

Our problem is this: at the maximum force our gripper can safely output, the objects slip out of our grasp. We have already increased the surface area we are gripping to the maximum amount.

Since the 3 things that affect friction are normal force, surface area, and surface property of the two interfacing materials, the last thing we can do is add some type of material to the gripper to increase friction.

The object itself has a thin extremely smooth plastic extrerior.

Can anyone give some suggestions of materials that are EXTREMELY tacky, can be cleaned for repeated use, but do not have adhesive properties? I don't want any pine tar on this thing - it wouldn't be good for our environment. I was thinking a thin layer of extremely soft silicone material - but I don't know where to even search for a good source of something like that.

This is a real world problem - our gripper is already fabbed out aluminum and powdercoated so it is non-reactive. Now we need something we can glue, bolt, or rivet to the gripper surfaces to make them more tacky.

 

[Matthias99]

I would have suggested that maybe using a pinch-style gripper is not the way to go, but it sounds like you already have some significant investment here. It might be easier to 'scoop up' the object rather than to try to 'grab' it with minimal force.

Some kind of soft silicone gel or foam rubber might be your best bets. If you just want something quick and dirty to try out -- you could get silicone gel by cutting up one of those silicone oven mitts, and grippy foam rubber is basically what mouse pads are made out of. I don't know much about sourcing custom-made stuff, though.

 

[PottedMeat]

---edit
^^^ yeah what he said, go to a local Target/WalMart/HomeDepot whatever and walk around and see if you can find something that would work.
---


You know those soft rubber/sillicone sweepers? They've got ~3" long sillicone rods arranged like a broom that pick up dirt - would that work? I'm sure you could buy a few and find a way to bolt it on and try it out, then maybe find a custom manufacturer.

 

[bobsmith1492]

Rubber?

 

[TuxDave]

If you're looking for a soft silicon material, just go to any kitchen store and pick up a couple and cut it up.

 

[KMurphy]

EPR (Ethylene Propylene Rubber)

 

[SagaLore]

Add a vacuum and suction it, while cradling it in some soft foam.

 

[imported_Tick]

Super fine grit sand paper may be the best choice if you are dealing with something not vulnerable to abrasion. Also, what about sintered rubber? Some of the grippies stuff available. But again abrasion may be a problem.

EDIT: Oh, and divinci's second law of friction says that surface area has only a very small effect on static frictional force... so gripper size shouldn't matter too much.

 

[SmoiL]

Two ideas. Maybe try using a balloon or examination glove wrapped around the gripper. Also if you get ahold of some foam (say about 1/2 in thick and have a pad on each gripper), if it gives very easily it should contour(?) slightly to the shape of what you are trying to pick up and help grip it delicately. An extreme case might use aerogel as the foam pads.

Just ideas.

 

[grant2]

I think the idea is a larger area allows more force to be exerted without damaging the object.

 

[cheesehead]

Foam-rubber. It's used for shock-mounting R/C airplane recievers.

 

[imported_Tick]

So? What did you guys decide on?

 

[DrPizza]

Originally posted by: SagaLore
Add a vacuum and suction it, while cradling it in some soft foam.

First thing I thought of as well.

 

[irishScott]

Originally posted by: DrPizza

Originally posted by: SagaLore
Add a vacuum and suction it, while cradling it in some soft foam.

First thing I thought of as well.

Then he'd have to add an air compressor and tubing, increasing power usage/complexity/cost. If he can get a reliable friction-based grip that does the job, that requires almost no maintenance, huge efficiency bonus. Remember KISM (Keep it simple morons!)

 

[irishScott]

I can't get the exact material, but those mp3 pads for car Dashboards are insane.

http://www.handstands.com/retail/automotive-accessories/sticky-pad.php

 

[irishScott]

Also OP: if the objects you have to move are of the approximate same size, couldn't you just make a "chamber" of sorts when the fingers come together? IE if the objects are cylindrical, Put pads on the fingers (bent metal) to form a cylinder when they close, thus completely enclosing the object? Could take some metalworking, but could work.

 

[DrPizza]

Originally posted by: irishScott

Originally posted by: DrPizza

Originally posted by: SagaLore
Add a vacuum and suction it, while cradling it in some soft foam.

First thing I thought of as well.

Then he'd have to add an air compressor and tubing, increasing power usage/complexity/cost. If he can get a reliable friction-based grip that does the job, that requires almost no maintenance, huge efficiency bonus. Remember KISM (Keep it simple morons!)

A small impeller and some cheap tubing might do the trick.

 

[WoodButcher]

I bought blue rubber gloves at the lumberyard because of their gripping qualities. I was installing very large windows recently and those gloves did the trick. Check the Depot and lowes, I think they were actually called "Grippers"

 

[dealseaker]

some place mats at our kitchen table are made of some material you are looking for, my wife probably got them at walmart, or what about those things u put under area rugs?

 

[Pwnbroker]

I don't know the weight of what you are trying to hold, but with plastic, static electricity comes to mind. Also, I don't know the volatility of the item in question.

 

[oynaz]

Try latex, the kind used for goalkeeper's gloves (a soccer goalkeeper, that is).

 

[Kreon]

At the ACE store where I work we have these gloves called Garden Go (I think that's the name) Gloves.

They're pretty gripping.
I dunno if they're like the lumbermill gloves previously mentioned

 

[jagec]

latex, cling-wrap, a precisely machined and very slightly wet (or oily) surface, styrofoam+pressure, those gooey worm-things that kids swing around, silly putty...

Or just hack off your partner's hand and use that, skin has some pretty remarkable properties.

 

[HVAC]

A glue that adheres to the grippers but not the object you want to pick up.
How about acrylic in very small spheres. Same kind of thing used on Post-it notes. I think you can buy spray forms of it.

 

[Matt1970]

I would thing surgical latex glove material would give you great grip provided it stays dry.