Bushing, Alluminum to Plastic

Hi I would like to know if there is a better solution on bushing between plastic tubing and Aluminum tubing.

Better than what? What is your application (size, temperature, pressure, environmental conditions, cycle speed, rotational, linear or both, presence of a fluid), what are you using now and what is your current failure mode?

Also if any one would know how to creat a mechanical seal for plastic molded inclosure?

Without additional information, I would say a simple o-ring gasket like NEMA 12 enclosures use.

Am building a rehabilatation device to help victims of Stroke the size of a Joystick. that the person will be able to grabe in their hand and move around with.

I have created a prototype for testing (CNC Polycarbonate and Aluminum tubing) the parts inclose electronics, the parts are in constance rotational movent and friction to each other. For the part that Plastic was rubbing against the Aluminum I though I don't need to but bushing and putted only Nylon bushing on plastic to plastic rubing.

Do I need to put bushing between the PC and Aluminum?
and after a while does the plastic wearer against the aluminum and is there a way to improve that?

For the seal It was to protect the ellectronics from the cleaning mosture of the exterior of the device. Is there any way to design the plastic to prevent the water to slip in between the moving part, without preventing the degree of movent of those parts?

thanks

Shoko
Rehabtronics

I would definitely design in a nylon bushing as a replaceable wear-part so that you do not damage either principle component. I'm not sure if you will see any static build-up from the nylon-PC rubbing, though. You could try the PC against powder-coated aluminum to prevent wear, but I don't have any direct experience with such an application. For the electronics enclosure, I would still mold in a o-ring groove to seal against cleaning moisture. You can also place an o-ring between your PC and Al parts to prevent moisture ingress there, as well. An o-ring in that location could also be used to tune the rotational resistance and thus the "feel" of the device.

Goshhhh... I don't sure probably a glass or a ceramic or brass composite material will help you out there. Or who know's probably titanium at most. You will get it eventually plus with this CR-4 forum I'll bet it will come to Ya' down the road...!

Nice Job...

MC

If the Aluminum is "Hard Anodized" it should resist wear against soft plastics, and exhibit low friction.

A nylon (PA6 or PA66) or acetal (POM) bushing, either injection molded or machined from rod stock should work fine. The Acetal will give a little better dimensional stability due to less moisture absorption.

I would recommend Powder Metal Bush which has advantage of being self lubricated and will not cause any wear on alluminum or plastic tubing.

Thanks you for the comments.

Here is the image of the device to bether explain the mosture problem I have.

When I clean it with alchool, I get a capillary reaction that get the alchool and the sediment inside the device (see images bellow).

Cross section

Will this solution work

Check out "Turcite". It is made by Shamban Plastics in Newbury Park Ca. This material is very hard and more slipery than Teflon. It is often used in bearing applications. It is also used as a liner for the ways in CNC milling machines and lathes.