Need some advice on molded plastics and metals...

[nimblejack]

Hello

I have a question for any engineers skilled in plastics molding or metals. I need to know if it's possible to manufacture a needle-like device that would be 12 to 18 inches in length with a diameter of no more than 3/64th of an inch. The tip would need to be blunt (as opposed to sharp) and the other end would have to have a hole that could accomodate some thread. Can something something like this be made of fexible plastic such as polyethylene and meet those dimensions? Alternatively, could something like that be made of flexible stainless steel? My crude rendering is attached. Any input would be most appreciated!

Jack

 

[MikeHalloran]

When you say 'some thread', do you mean a helical screw thread, or sewing thread?

Either way, it's possible, so far, to meet your spec in plastic or metal.




Mike Halloran
Pembroke Pines, FL, USA

 

[plasgears]

Suggest nylon without reinforcement. Very flexible. Your rendering shows a hole same dia as shaft?

This could be fabr with extruded nylon filament. Cut off tip on a bias like a surgical needle. The hole end could be upset with a simple piercing die. It will look similar to a sewing needle.

 

[nimblejack]

Thanks for the responses! Mike, to answer your question, I meant sewing thread. I should have been more clear on that.

Plas, I hadn't thought of nylon but I'm not an engineer. Ideally, the tip would be as blunt as possible because it's for an application that would be used by kids.

As far as plastic vs. metal is concerned, are there any advantages of one over the other? Also, assuming I was producing several thousand can you give me any sense of what I might be looking at for a per unit cost? Thanks!

Jack

 

[MikeHalloran]

You need to mock up the item to get a better feel for what you actually require of it. You can get music wire and monofilament at a hobby shop in approximately the size you need. Music wire is not stainless, and monofilament is not usually polyethylene, but the stiffnesses are about right.

Plastic will be much more flexible than stainless steel.

The cost will be sensitive to details that you haven't defined yet, but in general the plastic will be cheaper.



Mike Halloran
Pembroke Pines, FL, USA

 

[nimblejack]

Mike

Thanks again for the input! I was mistaken when I said the tip would be blunt, it actually needs to be sharp. With that in mind, it seems as though plastic would probably not be the way to go. Would you agree?

Jack

 

[MikeHalloran]

In the USA, you can't give kids a giant needle and expect to keep your house.



Mike Halloran
Pembroke Pines, FL, USA

 

[ornerynorsk]

Sounds like you might be looking for a knitting needle, or variation therof. Have you tried a local fabric or hobby store?

 

[nimblejack]

LOL Mike! It seems to me that it depends entirely on the age specified for the product. They do sell sewing kits for kids but they're not marketed to very young ones. My daughter is 12 and she can handle a needle and thread quite well so I would imagine a product rated for kids 12 and up.

Jack

 

[nimblejack]

ornery

Ideally I'm looking for something that might be as long as a knitting needle but is has to be MUCH thinner, more like a regular needle. They have to be less than 1/16 inch in diameter.

Jack

 

[ornerynorsk]

GTAW and Oxy-fuel welding rod can be purchased in many different materials in .045 diameter. Many plastics are available stock off the shelf in 1/16th, which may be a bit on the large side according to your original post. Good luck.

 

[MadMango]

Can you live with a metal part with a kink in it? If not, then plastic may be your best bet, though the plastic will get bent ans twisted as well.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[nimblejack]

ornery

I really can't exceed 3/64ths on the diameter and have it work.

Mad

Not sure what you're referring to when you say "kink" but the diameter requirement remains. This object which looks as though it would best made of metal, must be able to pass through an opening no wider than 1/16th. For all intents and purposes you could think of it as a VERY long sewing needle, although it would be desirable if it had a bit of flexibility to it.

Jack

 

[KENAT]

nimble, look at sewing needles.

Most of them 'swell' quite a bit where the eye is.

Something like a mattress needle might be close to what you need.

http://en.wikipedia.org/wiki/Sewing_needle

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[nimblejack]

Ken

That sounds a lot like something I just ordered called a "Doll Needle":

http://www.amazon.com/gp/product/B000YZ1XCK/ref=oss_product

I think that's probably the longest commercially available needle I'll be able to get. I won't know just how wide it is at the eye until I get my hands on one and put a pair of calipers on it. If it's not too wide I may be able to get it to work...

Jack