What rubber insulator can be attached to hot aluminum alloy? 1

[JHmechanics]

The scenario: the aluminum alloy nose cone of an impact driver (in mass production) reaches too high of temperatures. To deal with this, I am redesigning the nose cone to have fins. At the peak of each fin, I would like to put some type of insulator that will protect the user from being burned if they would like to touch the nose cone after long periods of operation.

I am looking for a type of rubber or plastic that could be attached to the peak of each fin that will act as this insulator without losing its integrity at temperatures as high as 80ºC. What material could do this job (low conductivity, high service temp) and last for upwards of 10 years? The follow up question is: by what method can I properly attach the material to the fins? Overmolding, glue, or some other process? This process/binding material cannot lose its binding properties at extreme temps or after long periods of time either.

Materials currently being looked at: butyl, EPDM, and different types of insulation tapes (such as butyl)
Binding methods currently being looked at: overmolding and Masterbond EP21LV

Please help and thank you in advance!
(There is a picture attached of the nose cone with fins and rubber attached to the top of each one)

 

[btrueblood]

Bonding rubber to metals is typically best done by using curing agents (primers) applied to the metal and overmolded by the rubber. Lord Chemicals has a lot of background and experience in metal-rubber bonding, as will a typical rubber molding shop that deals with aerospace stuff (try Rainier Rubber in Tukwila, WA).

Butyl will not hold up as well to handling/weather/abrasion as EPDM, and nitrile rubber would likely outlast EPDM unless there is some ozone source nearby (brushed motor?). I'd think nylon or PBT would also work if you added a mechanical retaining means. If you shape a round rib on the rubber/plastic fins that slipped into a similar slot on the aluminum body, then you could use cheaper extrusion runs of the rib material and cut them to length (might be more assembly time and more expensive in the long run, dunno).

 

[JHmechanics]

btrueblood: Thank you for the help! Could you go into more detail about how shaping a round rib could allow for cheaper extrusion runs?

 

[btrueblood]

After thinking about the idea a bit more, I'm not sure how well you could hold tolerances on the cast housing. But, the idea would be to mold slots in the fins with a bulb or similar shape at the root (see the attached file for a cross section of what I was thinking), and to extrude the rubber/plastic filler with a similar cross section. The fillers would be cut/trimmed to length, and slid into the slots at assembly. Rubber would be trickier, as it would have to be pulled into the slots (try pushing a rubber band). Both methods might need some thought on how to ensure the fillers don't slide back out (maybe peen the ends of the slot after installing the fillers). Either way, depending on the amount of fiddling around, the assembly cost might be more than the cost to tool up the overmolding, really would depend on the quantitites.

 

[IRstuff]

Seems to me that this question ought to have been posted in the polymer engineering forum

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[chicopee]

Instead of looking at polymers, I would explore designs that involve perforated metal sleeves which could be offset from the fins and provide protection. Any polymer in contact with the nose cone will increase the fins surface temperature.

 

[dvd]

If you insulate to prevent exposure to high surface temperatures, you will most likely have a higher internal operating temperature, which will probably contribute to a shortened tool life. What is getting hot inside? How about re-designing the cooling? Can you leak some compressed air into the housing? I understand that you are trying to re-design one part and not the whole contraption, but your approach seems to be masking the problem, not solving it.

 

[MisterE2]

I was thinking of just attaching a refractory material... but then i remembered a easier solution, make some carbon fiber parts w/ glue

It looks pretty easy to put an intern up to

Link

 

[Tmoose]

Electric or pneumatic impact driver ? Rotary/torque or hammer ?

 

[MisterE2]

Ah wait, there may be easier solutions. Some important questions I've run across this a lot of times before. Is the impact driver; a one time use for your company only, a mass production model for sale and more importantly are employees required to regularly handle it and on what frequency?