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I'm designing, for want of a better word, a 'widget boss' that is going to be trapped inside a vacuum forming, it will essentially be a boss that a self tapping screw will form a thread in.
It probably sounds massvely over eleborate to all of you, but we have our reasons for wanting to do this!
It will be an injection moulded part. As the part will be trapped inside the vacuum forming I have no environmental degredation worries.
The question is; what plastic will make the strongest thread?
Thanks
Jus
I know little about engineering, but whenever I see plastic nuts and bolts they are made of nylon.
Nylon is fairly inexpensive and has a reasonable range of properties. Something like a PBT or PPS would be stronger, but more expensive. Up to 20% glass would help, much more than that and and the threads can become brittle.
Hi, I work as a mould/component designer in the plastics industry & would suggest a nylon 6 as a good choice. Its very tough & should take a self tapping screw with the correct size pilot hole. I would think you could also try other materials at the tool trials to find the most suitable material for your application (ie perhaps a glass filled nylon).
Without going exotic Nylon 6.
Glass filled nylon wouldn't be as good as the glass would make the tread brittle. If you need the component stiffness of GF Nylon then the tread should be a ultrasonic or heat welded brass insert.
ABS is much better than nylon to take a thread but as you are being so vague i can't help lol!!
Depends on the application (strength, size etc) Nylon 6 as recommended would be my choice, but the range of engineering grade plastics runs into the thousands. Prices can be very exspensive too with some (PEEK) running over ten grand a ton!
Thanks for the advice guys. Was thinking Nylon 6, and have used PEEK before [but was worried about cost] but wanted to see if there is anything else I was missing. I hadn't realised GFN and a high glass content would make the threads brittle.
We use PEEK alot with M2 and M3..tbh Nylon is better for the durabilty of the threads..
ABS?
The type of screw used will be a factor in the strength of the thread.
Although not for selftapping screws there are Dodge® Threaded Inserts For Plastics.
http://www.emhart.com/products/dodge.asp
We manufacture 'plastic' covers for car and truck engines. These are mainly Nylon 6 with a glass filler up to 35%. For mounting off these we either hot imbed a brass insert for parts that may need to be 'serviced' during the life of the vehicle or use a self forming screw into a plain hole. Re-use may be OK but not recommended with the self forming screws.
We also weld parts into the covers. So a Nylon with glass filler should be OK.
We use PC with Plastech self tapping screws, pretty succesful but you need to get the boss dims spot on.
For ease of recycling of course you should try and use the same material as the vac form 😉
Pick a subject, any subject, and there's always 15 people on here who do it for a living.
Pick a subject, any subject, and there's always 15 people on here who do it for a living.
underwater basket weaving? anyone?
When weaving underwater, I suggest a willow based material and a good pair of thin neoprene gloves.
I've been making baskets underwater for five years now and we are now the market leaders in sub aqua baskets.
[i]underwater basket weaving?[/i]
been there, got the t-shirt.
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I have used this before, Nylatron, in my spearfishing gun, the part i remade carries an m3 thread and hasn't failed after 7 yrs of occasional use. it has good mechanical properties and is around £400 for a 300mm long 1.5'' bar, BUT i have some kicking around i think, how much do you need ?
http://www.gcip.co.uk/EP/materials/nylatron.htm