Machineable Polymer With Excellent Impact Absorption Properties

[Correy]

Hi All,
I am an electrical engineer by discipline faced with a materials problem for which I was hoping to get some expert advise ; )

I am trying to improve the design of the infeed portion of our packaging line. The purpose of the infeed system is to convey cylindrical rolls traveling parallel to a conveyors direction of motion onto a cleated conveyor with the rolls traveling perpendicular to conveyors direction of motion. This is accomplished by means of a sweep wheel / star wheel arrangement where the sweep wheel kicks the rolls off of the first conveyor onto the star wheel, and the star wheel drops the roll into the cleated conveyor. Both the sweep wheel and the star wheel are made of UHMW. The star wheel is roughly shaped like a roman cross, 10” in Diameter, 1 “ thick with 4, 2” diameter half circle pockets.

The conveying process is quite fast (75 rolls/min) which is where my problem arises. The sweep wheels must kick an incoming roll into the star wheel with great force in order to meet the throughput requirements of the system. Often because of the impact of the roll on the star wheel, the roll hops up off the star wheel as in an elastic collision. Frequently this “hop” will cause the roll to be in an orientation that ultimately jams the star wheel and crushes the roll.

So …. drum roll please … my question is, is there a material available to machine a star wheel out of that can absorb this impact much better then my current UHMW star wheel.

Any help would be greatly appreciated

 

[patprimmer]

Maybe acetal, (Delrin or Celcon) might do the job

Regards
pat

 

[Correy]

Thanks for the input Pat

I forgot to mention in my first post that the material must be FDA approved as the rolls are a food contact product. Do you know if I can aquire Delrin or Celcon Acetal approved by the FDA? If so, any ideas as to where I can purchase an appropriate blank for machining(1" to 3" thick, 3' x 3')?

Thanks again
Correy

 

[FredEvans]

If you are looking for impact absorption have you thought of polyurethane? the material, being elastic , will absorb a certain amount of the impact as maybe the "Bounce" is caused by the cardboard roll rather than the starwheel.

In a similar aplication that I once saw the star wheel actually clamped the roll of cardboard while picking it up and then the roll was stripped from the star wheel by an internal cam. I cant remember where I saw this applic? I think is was in an machine rolling phenolic electrical insulators or it might have been a a cigarette factory.

 

[djw2k3]

Hi Correy,

Further to Freds comments,

Am by no means a polymer expert but we have had discussions about impact absorbtion for our particular application. During some research we found polyurathanes are widely used in sawmills, basically stopping logs travelling at rediculous speeds without rebound.

Not sure about the FDA side of things though.

 

[JimMetalsCeramics]

UHMW is polyethylene. I would recommend Delrin or Nylon 6,6. If you can afford it, try Teflon.