Need info or supplier directions on teflon molding.

[JesperMP]

Hi,

I am an electrical engineer with an idea for a new type of sensor. For this I need to have a specially designed cup with smooth rounded surfaces that are electrically isolating and as non-sticking as possible. Teflon (PTFE) comes to mind.
I would like to avoid to have to machine a block of Teflon as it creates a somewhat more rough surface. I prefer to have it molded into the desired shape.

Anyone knows suppliers in this area that would be interested in manufacturing such teflon parts in relatively small numbers ? Not more than 50-100 pcs. per year.
Anyone have even a crude idea of what the price range is for parts in such small numbers ?

Thanks for any tips on this matters.

 

[Pud]

Contact your local DuPont representative - he/she will know local supply sources.

Moulding/processing PTFE is a bit specialised and they will need custom made equipment.

Material supply companies are often a good source as they will not recommend anyone who is not good!!

Cheers


Harry

 

[Pud]

Forgot to mention: assuming you really need "Teflon" (which cannot be moulded - it is usually sintered and the machined)


Cheers

H

 

[dvd]

Silicone might do the job as well, it is relatively non-sticking and has higher temperature capability that teflon. You could get a mold made at your local machine shop (ideally you could adapt some common shape for use as a mold) and use RTV silicone caulk from a tube and your caulking gun to fill the mold. It would be a low-tech approach.

 

[unclesyd]

You might want to contact these people as they do a lot of work in encapaulation and coating using Silicones.

http://www.nusil.com/index.aspx

 

[Heckler]

I've used this process on several designs...it's Electroless Nickel with a teflon codeposit. It creates a really tough surface with low friction

http://www.coatingtechnologiesinc.com/services_plating_np3.html

Heckler
Sr. Mechanical Engineer
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(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right." -- George Best

 

[btrueblood]

Umm, "electrically isolating as possible" - means exactly what? High DC resistance and high dc arc-breakdown voltage? Low AC permittivity (e.g. for filter capacitors)? Almost all pure polymers work equally well as insulators at room temperature, and for low voltages. They are all a bit different in terms of dielectric properties. There are lots of plastics with non-stick properties, the polyethylenes and polypropylene come to mind. These are much more moldable than fluoropolymers.

If you've got to have fluoropolymers, and there is any complexity to the part, you'll need to look at injection-moldable polymers, such as ETFE and FEP. There are some new grades of PTFE (teflon) that are advertised as "injection moldable", but the equipment for these is not cheap (high temperatures, high pressures, corrosive melt).

Low-quantity injection molding - see

http://www.protomold.com

(but they don't stock, and I think just don't do, the fluoropolymers, thus the first set of questions above).

 

[JesperMP]

Coating in stead of having the cup made completely out of teflon sounds like an interesting alternative.
I could have the cup machined in the "normal" way and then have it coated.
Because of the measurement samples conductive and capacitive properties of the material in the cup, I dont want the cup made out of any electrically conducting material. Plastics seems like the way to go.
Can a teflon coating bond onto some type of plastic ?

Quoting Pud:
"Forgot to mention: assuming you really need "Teflon" (which cannot be moulded - it is usually sintered and the machined)"
Well that only goes to show my ignorance in this area. I have seen Teflon parts that have an extremely smooth surface, and I jumped to assuming they were molded.

We have had good experience with Teflon in other aspects with the material being measured. Some use silicone, but with not so good results as teflon.

Quoting btrueblood:
"Umm, "electrically isolating as possible" - means exactly what? "
I didnt say that.
It has to be electrically isolating, and to be as non-sticking as possible. The non-sticking part is the real kicker here.
It only has to be as electically isolating so that the influence on the measurements are neglible or compensatable.

Thanks for the advices so far.

 

[Heckler]

I know you can apply electroless Nickel to ABS & PC but I am not sure about the NP3 process. You might want to do some google searches on that one.

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
XP Pro SP2.0 P4 3.6 GHz, 1GB RAM
NVIDIA Quadro FX 1400
o
_`\(,_
(_)/ (_)

(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right." -- George Best

 

[btrueblood]

Teflon coating on metal parts is much simpler - google Whitford coatings. The process is to spray teflon particles and a binder onto your parts, then bake out the binder and sinter the Teflon in an oven.

If non-stick is the only concern, can you not use polyethylene, the stuff is pretty darn non-stick at room temp? Silicone-impregnated plastics would do well too, and/or buy a can of silicone oil spray (mold release) and recoat the cup as required. Works great on just about any metal/plastic except silicone.

 

[JimCasey]

We do a lot of "Fluorocarbon" molding here where I work.
PTFE is molded by first making essentially a snowball from PTFE powder, compressing it hydraulically. Then sintering the material. Machine the critical surfaces to final dimension.

PFA and FEP are melt-processable, so we injection-mold those. There are a lot of small injection-molding shops that may be able to help you with FEP or PFA. Your big cost will be in fabricating the tooling.

For really small lots oo prototyping you could always make molds of easily-shaped materials and make prototype parts of binary polymers such as epoxy or polyester resin.

 

[plasgears]

Teflon may not be the right choice in this application. A moldable plastic designed for multiple cavity with built-in details for wiring accommodation, etc. may be more realistic.