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Walking on the Moon

General enquiry

Starlight 1

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My preference is for Delrin ( Acetal) which will machine to a better finish than nylon..

Nylon is also hygroscopic and will absorb moisture and dimensions of the part will change  - some times so much that bearing that was tuning smoothly will bind solid
or a nice fitting adaptor that once fitted snugly won't go in where it once did.

No such problems with delrin.

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Do you know why when using this Computer it automatically put quote in so forget this bit.

I was looking at 3-D printer in making some small parts  but decided the quality would not be acceptable, and as its only  small items which you cannot obtain and not having any background on these materials it's making a interesting read, thank you for your replies.

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Nylon is stronger and more flexible than ABS but as has been said, absorbs water easily and changes dimensions.  I wouldn't consider it suitable for astro projects.  As you mention 3D printing, also consider PLA.  This is stiffer than ABS and doesn't stink when printing unlike ABS.  It's more brittle and will break rather than bend under excessing stress.  Many find it easier for 3D printing.  I mainly use ABS.

Edited by Gina
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All material have their pro's and con's. You must be careful to chose a suitable material for the application.

I have spent a number of years explaining to people why replacing their metal objects with plastic has resulted in failures because they assumed that plastics are direct replacements for metals. They are not. Nor can you lump all the plastic types under one term and assume that they will all perform the same way. There is more than one Nylon just as there is more than one steel. Not only do the various Nylon's have differing properties they can have additives that modify those properties. As an example, a product was made with Nylon 6:6 that met the engineering specifications and production was given the go-ahead. But the customer wanted it black so a black pigment was added to it during the manufacture. It then failed the tests because the black additive also had the property of changing the friction of the Nylon which changed the way the item behaved in the tests.

Probably the most mis-understood property of plastics is Creep. Apply a load to any plastic and it will slowly change shape. Crates to hold bottles cannot be made from low density polyethylene (LDPE) as the bottom ones will creep quite quickly when they are stacked while Polypropylene (PP) will perform satisfactorily.  Therefore it is unwise to use plastics for dimensionally critical items that will be under load such as extension tubes for imaging set-ups.

Otherwise for items that are not critical such as thin washers or adaptors as used by the OP then Acetal is probably the first choice. 

And Acetal is not Nylon.



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